TQDOC Z TA245.7 B873 8-1589 NO.1589 L,’ ‘ LIBRARY SEP 2 7 1988 Jisxas MMTT "niveaaiti, Operational Characteristics and Herd Health Management Practices Associated with Brucellasis Quarantined Cattle Herds, U.S., 1980-82 t TEXAS AGRICULTURAL EXPERIMENT STATION/Neville P. Clarke, Director The Texas A&M University System/College Station, Texas [Blank Page in Orfinfl Bulletin] ' r4‘ u Operational Characteristics and Herd Health Management Practices Associated with Brucellosis Quarantined Cattle Herds, U.S., 1980-82 Raymond A. Dietrich Associate Professor Texas Agricultural Experiment Station Department of Agricultural Economics Texas A&M University Stephen H. Amosson Extension Economist— Management Texas Agricultural Extension Service Department of Agricultural Economics Texas A&M University Richard R Crawford Professor Texas Agricultural Experiment Station Department of Veterinary Public Health Texas A&M University Preface This report analyzes herd health management practices and operational characteristics of the owners of newly quaran tined beef and dairy herds in the contiguous 48 states during 1980-82. Data for this study were obtained via a nationwide questionnaire from Veterinary Medical Officers, Animal and Plan‘ Health Inspection Service (APHIS), U.S. Department of Agriculture. Information was collected on herd health manage ment practices and characteristics of quarantined herds; methods of identifying infection; the origin of cattle in quaran tined herds; adjacent herd testing; relationship of vaccination level to reactor rate; reactors removed; length of quarantine and number of tests; disposition of quarantined herds; and associated epidemiological data. In addition to the regionaj demarcation, which consisted of the South Central states, the Southeast, the Northeast, the North Central states, and the West, the data are also assembled by subgroups such as herdsize, cattle type, and vaccination status. Funding for this study was provided by Veterinary Services, APHIS, U.S. Department of Agriculture, and the Texas Ag ricultural Experiment Station. Table of Contents \. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Regional Demarcation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Completed Questionnaires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Characteristics of Quarantined Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Herdsize Distribution of Quarantined Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Calving Season by Month and Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Grazing and Calving Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Past History of Quarantines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Origin of Cattle in Quarantined Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Origin of Purchased Cattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Frequency of Cattle Purchases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1O Type of Female Replacements Purchased . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Identification and Source of Infection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Method for Identifying Infected Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Adjacent Herd Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Probable Source of Brucella Infection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Data to Support Most Probable Source of Brucella . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Relationship of Vaccination Level and Reactor Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Utilization of Calfhood Vaccination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Herd Vaccination Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Initial and Cumulative Beef Cattle Reactor Rate by Vaccination Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Initial and Cumulative Dairy Cattle Reactor Rate by Vaccination Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 \ Initial and Cumulative Beef Herd Reactor Rate by Herd Vaccination Level and Region . . . . . . . . . . . . . . . . . . . . . . . . 15 Initial and Cumulative Beef and Dairy Herd Reactor Rate by Herd Vaccination Level . . . . . . . . . . . . . . . . . . . . . . . . . 16 Length of Quarantine and Number of Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Length of Quarantine and Number of Tests for Quarantined Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Length of Quarantine and Number of Tests by Herd Vaccination Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Relationship of Herdsize to Length of Quarantine and Number of Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Disposition of Quarantined Herds and Selected Characteristics of Depopulated Herds . . . . . . . . . . . . . . . 18 Disposition of Quarantined Herds by Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Disposition of Quarantined Beef Herds by Herd Vaccination Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Disposition of Quarantined Dairy Herds by Herd Vaccination Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Initial and Total Herd Reactor Rate of Depopulated Herds and Herds Released from Quarantine . . . . . . . . . . . . . . . . 20 Disposition of Quarantined Beef Herds by Herdsize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Selected Statistics Per Depopulated Herd and Disposition of Calves in Quarantined Herds . . . . . . . . . . . 22 Disposition of Heifer Calves During 1977-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Disposition of Vaccinated Heifer Calves During 1977-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Characteristics of Quarantined Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Origin of Cattle in Quarantined Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Identification and Source of Infection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Relationship of Vaccination Level and Reactor Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Length of Quarantine and Number of Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5‘ Disposition of Quarantined Herds and Selected Characteristics of Depopulated Herds . . . . . . . . . . . . . . . . . . . . . . . . 24 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 [Blank Page in 0%»! Bulletin] ' P4 ' x" 5a» Introduction A recent economic and epidemiologic analysis of U.S. bovine brucellosis programs (Dietrich, Amosson, and Craw- Qford 1985) required the acquisition of data concerning herd health management practices and associated epidemiologi- cal information of newly quarantined beef and dairy brucel- losis herds in the contiguous 48 states during 1980-82. De- tailed information was obtained from Veterinary Medical Officers, Animal and Plant Health Inspection Service (APHIS), U.S. Department of Agriculture, via a nationwide questionnaire of newly quarantined herds. Information was collected on such factors as herd health management practices and characteristics of quarantined herds; methods of identifying infection; cattle sources in quarantined herds; adjacent herd testing; relationship of vaccination level to reactor rate; reactors removed; length of quarantine and number of tests; and disposition of quarantined herds. The original purpose for the collection of this data was to update and/or develop epidemiologic coefficients for analyz- ing alternative U.S. bovine brucellosis programs. However, the data reveals considerable basic information and statis- tics relating to quarantined beef and dairy herds which are not available to the livestock industry, government agencies, and other personnel concerned with animal health. There- fore, these data were assembled and analyzed as presented in this report. Regional Demarcation Regional delineations for the purpose of assembling data from the national brucellosis questionnaire of newly quaran- tined herds was based on such factors as herd health man- agement practices, geographic considerations, and inci- dence of disease, as shown in Figure 1. In addition to the regional demarcation, which consisted of the South Central states, the Southeast, the Northeast, the North Central states and the West, the data were also assembled by sub- groups such as herdsize, cattle type, vaccination status, and disposition of quarantined herds. U.S. averages, when applicable, were obtained by weighing the regional coeffi- cients developed from the questionnaires by the regional number and/or proportion of newly quarantined beef and dairy herds in the contiguous 48 states during 1982. WEST j NORTH I CENTRAL NORTHEAST @111“ CENTRAL $OUTHEA5T Figure 1. Regional delineation of herd health management—epidemiological survey of newly quarantined brucellosis herds, contiguous 48 states, 1980-82. Completed Questionnaires Completed and usable questionnaires numbered 1,455 and represented about 15 percent of newly quarantined herds in the contiguous 48 states for Fiscal Year (FY) 1981 as shown in Table 1. The two regions with the largest num- bers of newly infected herds, the South Central and South- east, were represented by the largest number of completed questionnaires, and, at the same time, by the lowest comple- tion rate compared to the number of quarantined herds dur- ing FY 1981. These results were anticipated because of [l) large regional variations in the numbers of newly quaran- tined herds, (2) workload associated with completing the ~ questionnaire with limited available resources, and (3) reg- ional differences in personnel required for conducting the on-going state/federal programs in each region. All ques- tionnaires were edited for completeness and questions were resolved by telephone or were returned by mail with instruc- tions for completion. " w Table 1. Number of completed questionnaires for newly quarantined beef and dairy herds, newly quarantined cattle herds FY 1981, and percent completion rate, by region, U.S., 1980-82. Completed and Usable Questionnai res FY1981 Newly Questionnaire Region Beef Dairy Total Quarantined Herds Completion Rate Number ------- -- Percent ------- -- Northeast 87 47 134 229 58.5 Southeast 526 69 595 3,709 16.0 North Central 276 26 302 735 41 .1 South Central 353 4 357 4,946 7.2 West 5O 17 67 188 35.6 U.S. Total 1,292 163 1,455 9,807 14.8 \- Characteristics of Quurcmtined Herds Basic characteristics of quarantined herds such as herdsize, calving season, maximum grazing and calving density, and past history of infection, varied by region in the U.S. during 1980-82. Herdsize is an important variable be- cause the number of tests required to clean up quarantined herds are generally related to herdsize. Calving season is an important variable in herd health management because the potential transmission of the Brucella organism is generally at the highest level immediately prior to and after parturi- tion. References to the U.S. in this study are the contiguous 48 states. Herdsize Distribution of Quaranlined Herds More than 90 percent of the quarantined beef herds con- sisted of herds with less than 99 head during 1980-82 (Table 2). Almost all of the remaining l0 percent included beef herds with 100 to 499 head. The beef and dairy herdsize dis- tribution patterns of newly quarantined herds in Table 2 closely coincide with the herdsize distribution of quaran- tined beef and dairy herds in the U.S. during 1978 according to U.S. Department of Agriculture APHIS Forms 4-35. Data reported on APHIS Forms 4-35 reveal that the herdsize dis- tribution of quarantined beef herds in the U.S. during 1978 was as follows: 1-99 head, 88.3 percent; 100-499 head, 9.7 percent; and 500 head or more, .5 percent. The herdsize dis- tribution for quarantined dairy herds during 197 8 was 1-99 head, 59.6 percent; 100-499 head, 31.1 percent; and 500 head or more, 9.3 percent. More than 90 percent of the quarantined dairy herds were represented by herds with 199 head or less (Table 2). Among herdsize groups, herds consisting of 20 to 49 head ac- counted for higher percentages of quarantined herds in both the beef and dairy sectors than did other groups. Further- more, comparisons of quarantines among herdsize groups reveal that beef herds of 1 to 19 head and 20 to 49 head ac- counted for almost 71 percent of the quarantined beef herds. Among dairy herds, the top 2 herdsize groups representing the largest percentage of quarantined herds were the 20 to 49 head and 50 to 99 head groups with 62 percent of the total. Calving Season by Month and Region w More than two-fifths of the quarantined herds relied on year-round calving practices during 1980-82 [Table 3). Year- round calving was most prevalent in the Southeast and South Central states, whereas seasonal calving was more pronounced in the West, the North Central states, and the Northeast. For producers not using year-round calving prac- S; tices, March and April were the most prominent calving months, followed by May and February [Table 3). Table 2. Herdsize distribution of quarantined beef and dairy herds by region, U.S., 1980-82. NR = None reported. Region Herdsize North South U.S. @ (head) Northeast Southeast Central Central West Average Percent Beef: 1-19 28.2 35.7 17.2 31.5 11.1 31.8 20-49 38.5 42.8 41.4 36.4 22.2 38.8 50-99 26.9 16.2 29.3 20.7 11.1 19.6 100-199 3.8 3.5 9.4 6.5 27.8 5.9 200-499 2.6 1.6 2.7 4.6 16.7 3.6 500-999 NR NR NR .3 5.6 .2 1,000 or more NR. .2 NR NR 5.5 .1 Total 100.0 100.0 100.0 100.0 100.0 100.0 Dairy: 1-19 NR 11.1 31.6 ID 13.1 12.2 20-49 33.3 34.9 36.8 ID 26.1 34.2 50-99 60.0 28.6 5.3 ID 13.0 28.1 100-199 6.7 19.0 26.3 ID 34.8 19.8 200-499 NR 4.8 NR ID 8.7 4.1 500-999 NR NR NR ID 4.3 .4 1,000 or more NR 1.6 NR ID NR 1.2 Total 100.0 100.0 100.0 ID 100.0 100.0 NR = None reported. ID = Insufficient data to report separately. Table 3. Calving season of quarantined herds by month and region, U.S., 1980-82. Region North South U.S. Month Northeast Southeast Central Central West Average Percent January 3.3 5.2 2.4 6.4 2.7 5.6 February 8.2 5.8 6.2 8.6 11.4 7.5 March 17.7 9.8 22.3 12.0 23.5 12.1 April 16.5 7.8 22.6 9.2 19.5 9.8 May 11.9 6.2 14.0 5.8 14.1 6.7 June 4.9 1.2 4.9 1.4 2.7 1.6 "July 2.1 .7 1.9 NR 2.0 .5 August 2.5 .9 1.2 NR 1.4 .5 September 2.9 3.1 2.1 .5 1.3 1.6 October 1.2 4.0 2.4 1.6 1.3 2.5 November .8 4.8 2.5 2.8 1.3 3.4 "December .8 4.3 1.6 3.9 NR 3.8 Year-round 27.2 46.2 15.9 47.8 18.8 44.4 Total 100.0 100.0 100.0 100.0 100.0 100.0 Grazing and Calving Density Maximum grazing density varies by region and within re- gion depending upon such factors as rainfall, geographic lo- cation, soil type, range and grass (forage) production, and grazing practices. The maximum grazing density for newly U.S. quarantined herds during 1980-82 averaged 6 acres per cow (Table 4]. Producers in the Northeast reported the high- est grazing density at almost 3 acres per cow in contrast to the West which reported about 30 acres per cow. Maximum calving densities or acres per cowwere slightly higher than maximum grazing densities in all regions ex- cept the West, where calving densities were about twice that of grazing densities. However, the pattern of maximum calv- ing density in all regions was similar to the regions maximum grazing density. Past History of Quarantines More than 15 percent of the newly quarantined herds were previously quarantined and 14 percent cited the cause \ of the current infection as past quarantines (past infection] [Table 5]. The South Central and Southeastern states re- ported the highest percentage of previous quarantines and also attributed the cause of the current infection more fre- _ quently to past quarantines than did other regions. The,“ Northeast reported the highest proportion of herds not previ- ously quarantined and also most often cited the cause of the current infection as newly introduced disease. Table 4. Maximum grazing and calving density for quarantined herds by region, U.S., 1980-82. Region North South U.S. Month Northeast Southeast Central Central West Average Acres/Cow Maximum grazing density 2.9 3.4 4.2 7.3 29.4 6.0 Maximum calving density 2.7 3.3 3.5 7.0 12.9 5.4 \ Table 5. Percent of herds previously quarantined during last 5 years and cause of current disease, quarantined herds by region, U.S., 1980-82. Region Herd North South U.S. Data Northeast Southeast Central Central West Average Percent Previously quarantined 2.2 14.7 11.4 16.8 11.6 15.4 Not previously quarantined 97.8 85.3 88.6 83.2 88.4 84.6 Total 100.0 100.0 100.0 100.0 100.0 100.0 Cause of current infection: Newly introduced disease 97.0 88.7 91.6 82.8 89.6 85.9 " From past W quarantine 3.0 11.3 8.4 17.2 10.4 14.1 Total 100.0 100.0 100.0 100.0 100.0 100.0 Origin of Cattle in Quaroniined Herds Fifty-four percent of the cattle in newly quarantined herds were introduced into the herd (purchased, leased, or bor- rowed) (Table 6). Regionally, quarantined herds in the South Central region and the West contained the highest propor- tion of introduced cattle, while herds in the Northeast con- tained the lowest percentage of introduced cattle. The proportion of purchased (introduced) cattle in these newly quarantined herds was substantially higher than the U.S. beef-dairy cow and replacement heifer purchases dur- ing 1977-79, which were equivalent to 6.1 percent of the fol- lowing Ianuary l inventory, according to Doane Agricultural Services. Earlier data, as reported in the 1969 Census ofAg- riculture, l/blume l/f Special Reports, revealed beef and dairy cow purchases which were equivalent to 4.8 percent of the January 1, 1970, beef and dairy cow inventories. These data suggest that owners of newly quarantined herds during 1980-82 were purchasing substantially higher proportions of beef and dairy test-eligible cattle than other buyers in the U.S. cattle industry. In addition, more than 40 percent of the newly quarantined herd owners during 1980- 82 reported that 80 percent or more of the cattle in their herds were introduced into such herds. These data also suggest the importance of maintaining closed herds and/or isolation and pre-purchase and post-purchase testing of purchased cattle as a herd health management practice. Origin of Purchased Cattle More than one-third of the purchased cattle in quaran- tined herds were bought at public markets, while another 29 percent were purchased from other individuals (Table 7). Public markets and other individuals were of almost equal importance as a source of purchased cattle in the Southeast and North Central regions while public markets were most prominent in the South Central region. Other individuals were the most important source in the Northeast and West. Livestock dealers, the third most important source of purch- ased cattle, provided about 9 percent of the purchased cattle in quarantined herds. Approximately one-fourth of the purchased cattle were obtained from two or more market sources. Table 6. Origin of cattle, quarantined herds by region, U.S., 1980-82. NR = None reported. \ Region North South U.S. Source Northeast Southeast Central Central West Average Percent Introduced‘ 38.9 49.9 51.5 57.5 55.0 54.0 Born/raised in herd 61.1 50.1 48.5 42.5 45.0 46.0 Total 100.0 100.0 100.0 100.0 100.0 100.0 ‘ Purchased, leased, or borrowed. Table 7. Source of purchased cattle, quarantined herds by region, U.S., 1980-82. Region Source of North South U.S. Purchase Northeast Southeast Central Central West Average Percent Otherindividuals 30.1 29.0 25.9 28.7 28.6 28.7 Livestock dealers 15.6 11.9 8.9 6.9 12.5 9.1 Public markets 14.5 31.7 29.2 36.7 16.1 33.7 ,QDlSp6l'S8| or consignment , 4.9 3.3 2.9 3.4 3.6 3.4 Combination of above sources: Twocombinations 29.1 18.6 25.9 18.1 26.7 19.1 Three combinations 5.8 4.2 4.1 4.5 9.0 4.4 \ Allcombinations NR .2 .3 .7 3.5 .5 Other NR 1.1 2.8 1.0 NR 1.1 Total 100.0 100.0 100.0 100.0 100.0 100.0 Frequency of Cattle Purchases Fifty-three percent of the quarantined herd owners who introduced cattle into their herds purchased cattle two or more times a year, whereas 47 percent purchased cattle once a year (Table 8). Approximately l0 percent of the quarantined herd owners purchased cattle more than five times per year. The pattern relative to frequency of cattle purchases for quarantined herd owners was relatively stable on a regional basis with the West reporting the highest per- centage of multiple purchases per year in contrast to the Northeast which revealed the lowest percentage of multiple purchases per year. Iype of Female Replacements Purchased Type of female replacements purchased by owners of quarantined herds reveals some important herd health man- ‘ agement practices (Table 9). Almost 40 percent of these owners purchased pregnant heifers; 30 percent purchased unbred heifers, either occasionally or more often; and more than 80 percent also purchased adult cows, either occasion- ally or more often. - g Only ll percent of the owners of quarantined herds who purchased cattle made it a general practice to buy strain 19 vaccinated cattle (Table 9]. Most of the remaining 89 per- cent never purchased strain 19 vaccinated cattle. Approximately 45 percent of the owners of quarantined herds purchasing cattle made it a general habit to obtain proof of Brucella test negative status when buying cattle. Two-thirds of the remaining 55 percent never required proof of Brucella test negative status for their purchased cattle. Table 8. Frequency of cattle purchases during 1976-80, quarantined herds by region, U.S., 1980-82. Region Frequency North South U.S. of Purchase Northeast Southeast Central Central West Average Percent One time only 52.8 43.7 50.1 48.7 36.7 46.8 2-5 times/year 38.5 46.1 40.0 42.0 58.7 43.6 , More than 5 \ times/year 8.7 10.2 9.9 9.3 4.6 9.6 Total 100.0 100.0 100.0 100.0 100.0 100.0 Table 9. Type of female replacements purchased during 1976-80 by producers of quarantined herds, U.S., 1980-82. Item Always Generally Occasionally Never Total Percent Unbred heifers 8.3 7.4 13.9 70.4 100.0 Pregnant heifers 6.5 9.1 24.0 60.4 100.0 Adultcows 37.8 24.5 19.7 18.0 100.0 Strain 19 vaccinated cattle 5.0 6.0 36.7 52.3 100.0 Proof of test negative status received 25.5 20.4 18.9 35.2 100.0 u l0 ldentificotion ond Source of Infection Methods used for identifying infected herds, adjacent herd testing practices, and data to support the most proba- a ble source of Brucella varied by region. Factors cited as the probable source of Brucella were fairly consistent through- out all regions. Method for Identifying Infected Herds Testing at livestock markets was cited as the most fre- quent method for identifying infected herds in all regions ex- cept the Northeast, where brucellosis ring tests were cited most often in conjunction with the relatively large dairy population in that region (Table l0). Testing at livestock markets identified 48 percent of the newly quarantined herds during 1980-82. The second most important method for identifying infection was testing at diagnostic laboratories, fol- lowed by adjacent herd testing, testing at slaughter plants, pri- vate tests, and brucellosis ring testing. Among regions, newly quarantined herds in the Northeast were identified most often through brucellosis ring tests, fol- lowed by testing at slaughter plants, livestock markets, and diagnostic laboratories (Table l0). Livestock markets were highly important in the Southeast, followed by adjacent herd testing, diagnostic laboratories, and brucellosis ring tests. The North Central region ranked livestock markets first, fol- lowed by diagnostic laboratories, slaughter plants, adjacent herd testing, and private tests. Livestock markets were cited as the predominant method for identifying newly quarantined herds in the South Central region, followed by diagnostic tests, slaughter plants, and adjacent herd test- ing. Livestock markets also ranked first for identifying infec- tion in newly quarantined herds in the West, followed by slaughter plants, brucellosis ring tests, diagnostic tests, and private tests. Adjacent Herd Testing Research has revealed that testing of herds adjacent to newly quarantined herds is a highly effective tool in identify- ing additional infected herds, thereby reducing the preva- lence of brucellosis infection and the costs associated with the disease (Amosson 1983]. More than 52 percent of the herds adjacent to newly quarantined herds were tested (Table ll). The Northeast and West reported the highest proportion of adjacent herd testing followed closely by the Southeast. The lowest levels of adjacent herd testing occur- red in the South Central region which also reported a sub- stantially higher percentage of adjacent herds with reactors than did other regions. The average number of herds adja- cent to quarantined herds ranged from 1.8 in the South Cen- tral region to 2.5 in the Northeast. Nationally, about 38 percent of the herds adjacent to newly quarantined herds were found to be infected (Table 11). The South Central and Southeast regions revealed the highest percentage of adjacent herds with reactors, while the more sparsely populated West reported the lowest rate of adjacent herds with reactors. Table 10. Method for identifying infected bovine brucellosis herds by region, U.S., 1980-82. Region Method of North South U.S. Identification Northeast Southeast Central Central West Average Percent Slaughter plant 14.6 4.5 12.3 12.6 14.5 9.6 Livestock market 13.1 45.5 32.7 53.6 21.7 48.1 Brucellosis ring test 24.1 7.1 3.9 .8 13.0 3.9 Diagnostic I (abortion,etc.) 12.4 8.9 16.2 13.7 11.6 12.0 I Private test-sale orshow 4.4 5.4 10.3 5.0 10.2 5.6 Herd recertification 2.9 .2 NR .8 NR .6 Area recertification NR 1 .0 NR NR NR .4 Q Post-movement test _, 2.2 1.2 2.9 1.1 8.7 1.4 Area-community test l; 7.3 5.8 1.9 .8 5.8 2.9 Purchase from infected herd 7.3 1.5 3.2 1.1 NR 1.5 Adjacent-neighborhood herd 6.6 15.8 11.0 7.0 5.8 10.5 Common pasture test .7 .3 .7 1.1 5.8 .8 Other 4.4 2.8 4.9 2.4 2.9 2.7 Total 100.0 100.0 100.0 100.0 100.0 100.0 NR = None reported. l1 Table 11. Average number of herds adjacent to quarantined herds, percent of adjacent herds tested, and percent of adjacent herds with reactors by region, U.S., 1980-82. Region North South U.S. Item Northeast Southeast Central Central West Average Number Average number . of adjacent herds 2.5 1.9 2.3 1.8 2.0 1.9 Percent Adjacent herds tested 79.9 71.9 61.6 35.8 79.7 52.2 Adjacent herds with reactors 20.3 29.3 24.3 46.3 12.7 37.7 Probable Source of Brucella Infection Fifty-five percent of producers with newly quarantined herds reported purchased cattle as the probable source of infection [Table 12). These statistics appear to lend cre- dence to the often repeated phrase that “more infection is introduced into herds via trailers/trucks than any other means.” Twenty-seven percent of the respondents reported that the second most cited probable source of infection was adjacent pastures. Purchased cattle and adjacent pastures ranked first and second in all regions as the probable source of infection. “Other” sources, which were generally not identified, and “unknown” sources ranked a distant third or fourth in all re- gions. Environmental factors and borrowed cattle were cited in only a few instances as a probable source of infection. Data to Support the Probable Source of Bnzcella Three-fourths of the respondents did not indicate the avail- ability of data to support the probable source of Brucella in- fection (Table 13). For example, almost 45 percent did not indicate the availability of any data or information to sup- port the probable source of infection. Another 6 percent indi- cated that the probable source was unknown, and about 25 percent indicated “other,” which consisted of various opin- ions about the probable source. Less than 3 percent of the respondents revealed an isola- tion of the Brucella biotype [Table 13). Although 97 percent of the respondents reported no biotype isolation, more than 21 percent reported that either direct contact with the source was observed or community spread was postulated. Table 12. Probable source of Brucella infection, quarantined herds by region, U.S., 1980-82. Region Source of North South U.S. Infection Northeast Southeast Central Central West Average Percent Borrowed cattle 1.1 1.3 1.5 1.2 NR 1.2 Adjacent pasture 20.8 31.5 30.9 23.0 21.6 26.6 Environmental 3.1 3.0 1.5 1.8 1.7 2.3 Purchased cattle 55.2 48.1 50.7 60.1 63.3 55.0 Other 11.5 8.2 7.0 6.6 11.7 7.4 Unknown 8.3 7.9 8.4 7.3 1.7 7.5 Total 100.0 100.0 100.0 100.0 100.0 100.0 NR = None reported. 12 k Table 13. Data to support the probable source of Bruce/la for quarantined herds by region, U.S., 1980-82. Region North South U.S. Item Northeast Southeast Central Central West Average Percent Biotype isolated: Biotype 1 2.9 2.5 2.6 1.4 27.5 2.3 Biotype2 NR NR NR NR 1.5 * Biotype4 1.5 .2 NR NR NR .1 No isolation: Directcontact 3.6 7.1 8.1 8.1 11.6 7.7 Communityspread 8.8 18.3 15.5 11.5 1.5 14.1 Other 16.1 25.4 26.5 25.1 24.6 25.2 Unknown 3.6 4.6 6.2 7.0 1.4 5.9 Not specified 63.5 41.9 41.1 46.9 31.9 44.7 Total 100.0 100.0 100.0 100.0 100.0 100.0 NR = None reported. * = Less than .005. Relationship of Vaccination Level and Reactor Rate Utilization of calfhood vaccination (CV) and herd vaccina- tion level in newly quarantined herds during 1980-82 re- vealed substantial differences in initial and cumulative reac- tor rates. Utilization of Calfllood Vaccination Eighty-one percent of the owners of newly quarantined herds did not use calfhood vaccination (Table 14). Calfhood vaccinations comprised 12.4 percent of the cattle tested on the initial test among quarantined herds during 1980-82. This is substantially lower than the 30.2 percent and 20.1 percent calihood vaccination rate reported by Veterinary Services, APHIS, U.S. Department of Agriculture, for U.S. cattle producers during 1980-82 and 1976-80, respectively The lowest percentage of quarantined herd owners using calfhood vaccination occurred in the Southeast followed by the South Central and North Central states. More than 40 percent of the owners of newly quarantined herds in the West reported using calfhood vaccination in their herds. Herd Vaccination Levels More than 84 percent of the newly quarantined beef herds and 68 percent of the newly quarantined dairy herds did not contain vaccinates [Table 15). Among beef herds, the South- east and South Central states contained the highest propor- tions of non-vaccinated beef herds. Among newly quaran- tined dairy herds, the Southeast also had substantially higher proportions of non-vaccinated herds than did other regions. Table 15 also reveals that quarantined dairy herds with 80 to 100 herd vaccination levels represented about ll _ percent of the quarantined dairy herds compared to less than 2 percent of the quarantined beef herds. 13 Initial and Cumulative Beef Cattle Reactor Rate by Vaccination Status Although calfhood vaccination does not provide 100 per- cent protection against brucellosis, initial tests of vacci- nated and non-vaccinated cattle in newly quarantined beef herds revealed that initial reactor rates in vaccinated cattle were about two-fifths the rate for non-vaccinated cattle (Table 16). In addition, the cumulative reactor rate or total proportion of reactors removed from the herds was almost two and one-half times greater for non-vaccinated cattle than for vaccinated cattle. Although the proportion of reac- tors removed from the herd by vaccination status varied by region, the general pattern of reactors removed on the initial tests and on a cumulative basis, by vaccination status, was similar across all regions. Initial and Cumulative Dairy Cattle Reactor Rate by Vaccination Status The proportion of reactors removed on the initial test and on a cumulative testing basis also varied by vaccination status in dairy herds as in beef herds [Table 17). The propor- tion of vaccinated dairy cattle identified as reactors on the initial test was about two-fifths the rate for non-vaccinates, a rate differential for vaccinates versus non-vaccinates that is almost identical to quarantined beef herds. The cumula- tive rate for vaccinated dairy cattle was about one-fourth the rate for non-vaccinated cattle. The total proportion of reac- tors removed from the herd on the initial test and on a cumulative basis in both beef and dairy herds was heavily weighted by the reactor rate in non-vaccinated cattle be- cause non-vaccinates comprised about 90 percent of the beef cattle tested on the initial test, compared to 54 percent of the dairy cattle. Table 14. Percent of herd owners using calfhood vaccination (CV), quarantined herds by region, U.S., 1980-82. Region Using Calfhood North South U.S. Vaccination Northeast Southeast Central Central West Average Percent Yes 27.2 13.3 24.4 21.3 40.3 18.9 No 72.8 86.7 75.6 78.7 59.7 81.1 Total 100.0 100.0 100.0 100.0 100.0 100.0 Table 15. Herd vaccination level, quarantined beef and dairy herds by region, U.S., 1980-82. Region Percent of Herd North South U.S. Vaccinated Northeast Southeast Central Central West Average Percent Beef: No Vaccinates 78.2 91.7 71.5 81.8 56.8 84.3 1°/>-19°/5 10.3 3.7 17.6 12.7 9.1 9.7 20°/o-39°/> 5.1 1.4 4.7 1.9 6.8 2.0 40"/°-59°/5 1.3 1.4 2.3 1.8 11.4 1.8 60%-79% 1.3 .4 1.6 .3 4.5 .5 80°/°-100% 3.8 1.4 2.3 1.5 11.4 1.7 Total 100.0 100.0 100.0 100.0 100.0 100.0 Dairy: NoVaccinates 40.0 77.s 31.6 ID 45.5 68.4 H 1°/>-19°/<> 40.0 9.5 15.8 ID NR 12.8 20"/<>-39% NR 8.0 5.3 ID 9.1 7.1 40"/<>-59% NR NR 10.5 ID NR 1.1 80°/>-100°/5 20.0 4.7 36.8 ID 45.4 10.6 Total 100.0 100.0 100.0 ID 100.0 100.0 NR = None reported. ID = Insufficient data to report separately. Table 16. Initial and cumulative beef cattle reactor rates, quarantined herds by vaccination status and region, U.S., 1980-82. Region Vaccination North South U.S. Status Northeast Southeast Central Central West Average Percent Vaccinated cattle: . Initial 7.0 4.9 5.8 8.9 3.8 7.2 U Cumulative 10.9 8.5 15.4 11.0 6.2 10.3 Non Vaccinated cattle: Initial 21.0 22.8 15.5 14.8 13.6 17.8 Cumulative 28.3 32.2 25.0 20.1 25.9 24.9 Total herd: Initial 19.6 21.4 15.0 14.3 10.3 16.9 Cumulative 26.6 31.6 24.4 19.9 15.8 24.4 14 Table 17. Initial and cumulative dairy cattle reactor rates, quarantined herds by vaccination status and region, U.S., 1980-82. Region Vaccination North South U.$. Status Northeast Southeast Central Central West Average Percent Vaccinated cattle: Initial 4.8 .6 4.8 ID .9 1.7 Cumulative 9.6 .6 5.5 ID 2.5 2.2 Non Vaccinated cattle: lnitial 6.7 4.5 4.8 ID 1.5 4.3 Cumulative 23.0 9.3 11.7 ID 5.5 8.7 Total herd: lnitial 5.7 3.2 4.8 ID 1.0 3.4 Cumulative 18.3 11.2 7.5 ID 2.9 8.8 ID = Insufficient data to report separately. Initial and Cumulative Beef Herd Reactor Rate by Herd Vaccination Level and Region The proportion of reactors removed from newly quaran- tined beef herds on the initial test and the total reactors re- moved on a cumulative testing basis decreased as the herd vaccination level increased [Table 18]. For example, the ini- tial reactor rate for non-vaccinated herds was 18 percent and decreased to a low of less than 4 percent for herds with a 60 percent to 79 percent herd vaccination level. The initial reactor rate then increased to 6 percent for herds with an 8O percent to 100 percent vaccination level. The cumulative reactor rate similarly decreased from a high of 26 percent for non-vaccinated herds to a low of 6 per- cent for herds with a 60 percent to 79 percent herd vaccina- tion level. These data suggest that both the initial and cumulative reactor rates tend to decline as herd vaccination levels increase. The decline in initial and cumulative reactor rates as herd vaccination levels increased was more variable within re- gions than in the regional or U.S. average (Table 18]. While the trend in initial and cumulative herd reactor rates tended to decline as herd vaccination levels increased in the North- east, the Southeast, the North Central region and the West, this relationship was not as stable in the South Central re- gion. For example, quarantined herds with 80 percent to 100 percent herd vaccination levels in the South Central region revealed higher levels of initial and cumulative infection rates than herds with lower herd vaccination levels. This suggests that other factors may also affect initial and cumulative reactor rates. Table 18. lnitial and cumulative beef herd reactor rates by herd vaccination level and region, U.S., 1980-82. Region Percent of Herd North South U.$. Vaccinated Northeast Southeast Central Central West Average Percent No Vaccinates: Initial 19.2 21.7 16.6 15.4 13.0 17.8 Cumulative 26.0 32.0 25.5 21.5 20.6 25.6 170-19701 Initial 34.5 29.0 13.8 10.7 1.3 17.6 Cumulative 48.3 41.5 24.5 14.5 1.3 25.1 20°/°-39°/°: lnitial ID 20.5 11.3 10.5 11.9 14.2 Cumulative ID 33.3 16.3 21.0 13.4 25.1 40"/°-59°/¢: lnitial ID 13.2 9.4 5.6 6.9 8.6 Cumulative ID 21.2 23.2 8.7 8.1 14.1 60"/>-79%: lnitial ID 3.4 4.0 ID 1.2 3.4 Cumulative ID 3.4 21.2 ID 2.6 5.8 80°/<>-100°/>: Initial 1.3 2.1 5.0 10.3 3.7 6.3 Cumulative 2.9 8.4 10.4 13.5 9.1 11.3 ID = Insufficient data to report separately. 15 Initial and Cumulative Beef and Dairy Herd Reactor Rate by Herd Vizccination Level The initial and cumulative herd reactor rates for both newly quarantined beef and dairy herds decreased as herd vaccination levels increased [Table 19]. However, the cumulative reactor rate for quarantined beef herds did not decrease until vaccination levels exceeded 40 percent. Com- parison of initial and cumulative herd reactor rates between quarantined beef and dairy herds, by herd vaccination levels, reveals that initial herd reactor rates for dairy herds were generally about one-third those of beef herds. Cumula- tive herd infection rates for dairy herds, by herd vaccination levels, were about one-half to one-fifth the rate for beef herds, depending on vaccination levels (Table 19) . The lower initial and cumulative reactor rates in dairy herds versus beef herds emphasizes the importance of early detection re- sulting from the more frequent or periodic testing of dairy herds as a result of brucellosis ring testing programs. Table 19. Initial and cumulative beef and dairy herd reactor rates by herd vaccination level, U.S., 1980-82. Beef Dairy Percent of Herd Vaccinated Initial Cumulative Initial Cumulative ------------------------- -- Percent No vaccinates 17.8 25.6 ~3.1 11.8 1°/°-19°/s 17.6 25.1 5.1 18.8 20°/>-39°/> 14.2 25.1 5.6 9.1 40°/o-59°/<> 8.6 14.1 2.2 2.2 60%-79°/° 3.4 5.8 NH NR 80°/>-100% 6.8 11.3 1.4 2.4 NR = Nonereponed. Length of Quarantine and Number of Tests Data revealed that herdsize was positively related to length of quarantine and number of tests required for re- lease from quarantine. Data obtained from the Texas Animal Health Commission for 6,200 herds released from quaran- tine during 1981-84 showed that herds with a history of a high proportion of replacements during quarantine tended to remain on quarantine longer than herds with either no re- placements or a low proportion of replacements. Prelimi- nary results from the Texas Animal Health Commission data also reveal that initial herd reactor rate had little or no effect on number of tests or length of quarantine. Length of Quarantine and Number of Tests for Quarantined Herds Newly quarantined beef herds were under quarantine for an average of 199 days compared to 216 days for dairy herds prior to release from quarantine and/or depopulation (Table 20). Further, quarantined beef herds underwent 3.6 tests prior to release from quarantine and/or depopulation, com- pared to almost 5 tests per herd for dairy herds. Table 2O also reveals that beef herds tended to remain in quarantine longer and undergo more tests in the West and South Central regions than any other region. Dairy herds, in contrast, remained under quarantine for longer periods and underwent more tests in the Northeast and West prior to release from quarantine and/or depopulation. Average quarantine length for beef herds in the U.S. in- creased 2O percent when adjusted for depopulated herds [Table 21). Non-depopulated beef herds or quarantined herds which continued testing until the quarantine was re- leased were under quarantine for 239 days and underwent an average of 4.2 tests per herd. Depopulated beef herds, in Table 20. Average length of quarantine and average number of tests for quarantined beef and dairy herds by region, U.S., 1980-82. Region North South U.S. Item Northeast Southeast Central Central West Average Beefi Average length of quarantine (Days) 134.9 164.1 183.0 220.8 209.3 199.1 Average number oftests 2.7 3.4 2.9 3.8 4.3 3.6 Dairy: Average length of quarantine (Days) 257.9 184.8 181.9 194.0 245.7 215.8 Average number oftests 6.7 5.0 4.0 3.0 7.1 4.7 16 H U Table 21. Length of quarantine and number of tests by method of quarantine disposition of quarantined beef and dairy herds, U.S., 1980-82. Beef Dairy Disposition of Quarantine Number Quarantine Number Herd Quarantine Length ofTests Length ofTests Days Number Days Number Depopulated 120.2 2.3 166.8 4.1 Reactors removed 239.2 4.2 198.8 4.2 Under quarantine‘ 330.3 5.8 364.5 7.7 Total 199.1 3.6 215.8 4.7 ‘Still under quarantine when the survey was completed. contrast, reported quarantine periods of 120 days, or about one-half of the quarantine period for beef herds that con- tinued testing until all reactors were removed. Number of tests for depopulated beef herds averaged 2.3 tests per herd. Newly quarantined dairy herds that continued testing until all reactors were removed remained under quarantine for longer periods and underwent more tests than depopu- lated herds. However, differences in quarantine length and number of tests between depopulated and non-depopulated dairy herds released from quarantine were substantially less in quarantined dairy herds than in quarantined beef herds (Table 21). Length of Quarantine and Number of Tests by Herd Wzccination Level Length of quarantine for newly quarantined beef and dairy herds tended to be longer for vaccinated herds than for non-vaccinated herds (Table 22). The number of tests did not appear to be affected by herd vaccination level in either the beef or dairy sectors. Relationship ofHerdsize to Length of Quarantine and Number of Tests Herdsize had a positive effect on the number of tests and length of quarantine for both quarantined beef and dairy herds (Table 23). For example, length of quarantine for beef herds increased more than 70 percent as the herdsize group increased from l-19 head to 200-499 head. The number of tests for beef herds increased 40 percent as the herdsize group increased from 1-19 head to 200-499 head (Table 23). Quarantined dairy herds depicted a similar herdsize pattern between quarantine length and number of tests. Data obtained from the Texas Animal Health Commission for more than 6,200 beef herds and approximately 200 dairy herds released from quarantine during 1981-84, obtained similar results (Table 24). This information also demon- strated the positive herdsize relationship between length of quarantine and number of tests depicted by newly quaran- tined U.S. beef and dairy herds. Both the number of tests and the length of quarantine for the Texas beef herds released from quarantine more than doubled as the herdsize in- creased from 1-19 head to 200-499 head. Dairy herds re- leased from quarantine in Texas revealed a mixed relation- ship between number of tests and length of quarantine in relation to herdsize (Table 24). A possible contributing fac- tor to this relationship for Texas dairy herds is that more than 57 percent of the Texas dairy herd producers continued adding replacements to their herds while they were under quarantine. Table 22. Average length of quarantine and average number of tests by herd vaccination level of quarantined beef and dairy herds, U.S., 1980-82. Beef Dairy Percent of Herd Quarantine Number Quarantine Number Vaccinated Length of Tests Length of Tests Days Number Days Number No vaccinates 193.7 3.5 182.3 5.2 1%-19°/<> 202.0 3.9 240.0 5.9 20°/°-39°/<> 224.1 4.5 215.7 5.2 40°/>-59°/<> 230.8 4.5 237.0 4.0 600/0-790/0 239.5 4.1 NR NR 80°/>-100°/> 244.0 3.9 221.9 4.8 NR = None reported. 17 Table 23. Average length of quarantine and average number of tests for quarantined beef and dairy herds by herd size, U.S., 1980-82. Beef Dairy Herdsize Quarantine Number Quarantine Number (Head) Length of Tests Length of Tests Days Number Days Number 1-19 163.5 3.0 160.2 3.4 20-49 192.4 3.7 173.6 4.3 50-99 236.3 4.1 227.5 6.0 100-199 249.5 3.8 255.7 6.4 200-499 281 .3 4.2 ID ID 500-999 ID ID ID ID 1,000 or more ID ID ID ID ID = Insufficient data. TabIe 24. Relationship of herdsize to number of tests and days under quarantine per quarantined beef and dairy herd, Texas, 1981-84. Beef Dairy Herdsize Quarantine Number Quarantine Number (Head) Length ofTests Length ofTests Days Number Days Number 1-19 215.9 3.8 297.5 8.7 20-49 282.2 4.7 364.5 7.3 50-99 346.1 5.8 287.2 6.1 100-199 407.9 6.4 363.6 9.2 200-499 440.1 7.7 354.9 8.6 500 or more 690.3 9.5 698.0 8.0 State average 285.0 4.8 336.5 8.0 Disposition of Quurcmtined Herds and Selected Characteristics of Depopuluted Herds The disposition of newly quarantined herds during 1980- 82 varied by cattle type, region, vaccination level, reactor rate, and herdsize. Disposition of Ouarantined Herds by Region Thirty~seven percent of the beef herds quarantined during 1980-82 were depopulated, compared to 11 percent of the dairy herds [Table 25). Approximately two-thirds of the quarantined beef herds in the Northeast and North Central regions were depopulated, as were almost 57 percent of the quarantined herds in the Southeast. The South Central re- gion depopulated the lowest proportion of quarantined beef herds, followed by the West. The Northeast also depopulated the highest proportion of quarantined dairy herds, followed by the Southeast and North Central regions. Disposition of Quarantined Beef Herds by Herd Wzccination Level More than 39 percent of the non-vaccinated, newly quarantined beef herds were depopulated, compared to a de- 18 population rate of almost one-third for vaccinated beef herds (Table 26). Depopulation rates tended to decrease slightly as herd vaccination levels increased. Non-vaccinated beef herds, which represented 84 percent of the total newly quarantined beef herds, accounted for 88 percent of the depopulated beef herds and 82 percent of the herds released from quarantine [Table 27). Regionally, non- vaccinates comprised a higher proportion of the depopu- lated beef herds in the Southeast than any other region (Table 27). Furthermore, non-vaccinates, plus herds with less than 20 percent herd vaccination levels, accounted for 92 percent or more of the depopulated beef herds in all re- gions except the West. Vaccinated beef herds, at the same time, represented a higher proportion of the depopulated beef herds in the West than in any other region. This is not unexpected since the West reported higher proportions of beef herds using calfhood vaccination than did other re- gions. The West was also the only region which reported that vaccinated beef herds represented more than 50 percent of the beef herds released from quarantine (Table 27). Vacci- nated beef herds in the Southeast, in contrast, represented about 12 percent of beef herds released from quarantine. H W Q H" Table 25. Disposition of quarantined beef and dairy herds by region, U.S., 1980-82. Region North South U.S. Disposition Northeast Southeast Central Central West Average Percent Beef: Quarantine released 30.8 38.8 35.1 75.0 52.3 58.7 Depopulated 67.9 56.9 64.1 20.4 40.9 37.0 Still quarantined 1.3 4.3 .8 4.6 6.8 4.3 Total 100.0 100.0 100.0 100.0 100.0 100.0 Dairy: Quarantine released 73.3 65.1 89.5 100.0 63.6 77.0 Depopulated 26.7 14.3 10.5 NR 9.1 10.7 Still quarantined NR 20.6 NR NR 27.3 12.3 Total 100.0 100.0 100.0 100.0 100.0 100.0 NR = None reported. Table 26. Disposition of quarantined beef herds by herd vaccination level, U.S., 1980-82. Percent of Herd Herd Quarantine Still Vaccinated Depopulated Released Quarantined Total Percent Novaccinates 38.6 57.0 4.4 100.0 1%-19% 35.3 60.6 4.1 100.0 20°/°-39°/> 16.4 76.2 7.4 100.0 40%-59°/<> 6.6 93.4 NR 100.0 60°/°-79°/o 17.8 82.2 NR 100.0 80%-100°/> 30.8 69.2 NR 100.0 NR = None reported. Table 27. Herd vaccination level for depopulated beef herds and beef herds released from quarantine by region, U.S., 1980-82. Region Percent of Herd North South U.S. Vaccinated Northeast Southeast Central Central West Average Percent Depopulated: No vaccinates 81.1 93.8 76.2 83.3 72.2 88.1 1°/o'19°/o 13.2 4.5 15.9 15.2 NR 9.1 20°/o-39°/<> 1.9 .7 3.1 NR 5.6 .9 40°/=-59°/¢ 1.9 NR 1.8 NR 5.6 .3 60°/=-79°/° 1.9 NR 1.2 NR 5.5 .2 80°/<>-100% NR 1.0 1.8 1.5 11.1 1.4 Total 100.0 100.0 100.0 100.0 100.0 100.0 Quarantine Released: No vaccinates 70.8 87.8 63.4 81.9 43.5 82.1 1°/o-19°/° 4.2 3.1 20.0 11.5 17.4 9.8 20°/>-39% 12.5 2.5 7.8 2.1 4.4 2.5 40°/°-59°/° NR 3.6 3.3 2.5 17.4 3.0 60°/°-79°/> NR 1.0 2.2 .4 4.3 .7 80°/°-100°/> 12.5 2.0 3.3 1.6 13.0 1.9 Total 100.0 100.0 100.0 100.0 100.0 100.0 NR = None reported. 19 Table 28. Disposition of quarantined dairy herds by herd vaccination level, U.S., 1980-82. Percent of Herd Herd Quarantine Still Vaccinated Depopulated Released Quarantined Total Percent No vaccinates 11.2 73.6 15.2 100.0 1°/>-19°/s 20.4 73.8 5.8 100.0 20°/@-39% 10.6 66.0 23.4 100.0 40"/o-59% NR 100.0 NR 100.0 60°/<>-79°/s NR NR NR NR 80"/>-100°/<> 3.7 91.1 5.2 100.0 NR = None reported. Disposition of Quarantined Dairy Herds by Herd Vaccination Level The proportion of dairy herds vaccinated had little or no effect on the disposition of newly quarantined dairy herds during 1980-82 because approximately the same proportion of non-vaccinated dairy herds as vaccinated dairy herds were depopulated (Table 28). In addition, Table 29 reveals about 63 percent of the total depopulated dairy herds were non-vaccinated herds, whereas 58 percent of the newly quarantined dairy herds consisted of non-vaccinates during 1980-82. However, a comparison of Tables 15 and 28 suggests that as herd vaccination levels increased, the pro- portion of depopulated dairy herds tended to decrease. This conclusion is further substantiated by Table 29, which re- veals that 25 percent of the depopulated dairy herds con- sisted of herds with herd vaccination levels of 19 percent or less, whereas the proportion of newly quarantined herds with less than 20 percent herd vaccination levels comprised less than 13 percent of the total quarantined dairy herds. Table 29. Herd vaccination level for depopluated dairy herds and dairy herds released from quaran- tine, U.S., 1980-82. Percent of Herd Depopulated Herd Released Vaccinated Herd From Quarantine ------------------- -- Percent No vaccinates 62.5 57.7 10/0-190/0 25.0 12.8 200/0-390/0 6.3 5.1 40%-59% NR 3.9 60°/<>-79°/> NR NR 80°/o-100°/° 6.2 20.5 Total 100.0 100.0 NR = None reported. Initial and Total Herd Reactor Rate of Depopulated Herds and Herds Released from Quarantine Both the initial and cumulative reactor rates for depopu- lated beef herds were about twice as high as the initial and cumulative rates for beef herds released from quarantine (Table 30). Initial and cumulative reactor rates were from 6 to 9 times higher for depopulated dairy herds as were initial and cumulative rates for dairy herds released from quaran- tine. The average cumulative reactor rate for depopulated 20 beef herds was 33 percent compared to 32 percent for de- populated dairy herds (Table 30). The cumulative reactor rate for beef herds released from quarantine averaged 16 percent, while dairy herds averaged 3 percent. A comparison of regional cumulative reactor rates for de- populated beef and dairy herds reveals that the highest reac- tor rates were generally reported in the Northeast, the Southeast, and the North Central regions (Table 30). Cumula- tive reactor rates for beef herds released from quarantine were highest in the Southeast and the South Central re- gions, while the Northeast and North Central regions re- ported the highest cumulative rates for dairy herds released from quarantine. Disposition of Quarantined Beef Herds by Herdsize Decisions regarding depopulation of newly quarantined beef herds during 1980-82 were not based on herdsize be- cause the proportion of herds depopulated and/or released from quarantine was distributed evenly throughout all herd- sizes [Table 31). In addition, depopulated beef herds aver- aged almost 53 head per herd, compared to an average size of 52 head per quarantined beef herd on the initial test. How- ever, more than 9O percent of the beef herds depopulated and also released from quarantine consisted of herds with less than 100 head (Table 32). Furthermore, quarantined herds ranging from 20-49 head per herd comprised the largest proportion of herds depopulated and also released from quarantine in all regions except the West, where herds ranging in size from 100 to 199 head predominated. The herdsize distribution patterns of Table 32 generally coincide with the quarantined beef herdsize distribution pat- terns in Table 2. However, industry herdsize distribution pat- terns reported by the 1978 Census of Agriculture revealed higher proportions of herds with 1- 19 head and lower propor- tions of herds with 20-49 and 50-99 head than are shown in Tables 2 and 32. This was not unexpected, because vari- ations exist in herd health management practices within and between herdsize groups and regions. In addition, larger herdsize groups generally contain more purchased cattle than smaller herdsize groups. Depopulation data were obtained on 16 dairy herds. De- populated dairy herds averaged 39 head per herd, whereas newly quarantined dairy herds during 1980-82 averaged 112 head on the initial test. These data suggest that of the dairy herds depopulated, the predominant majority were smaller herds. w) u) U W Table 30. Initial and cumulative herd reactor rate by region for depopulated beef and dairy herds and herds released from quarantine, U.S., 1980-82. Region North South U.S. Item Northeast Southeast Central Central West Average Percent Depopulated: Beef: Initial 26.0 27.0 19.5 21.5 14.6 24.3 Cumulative 35.6 36.6 31.7 26.9 20.1 32.9 Dairy: Initial 13.5 18.0 8.6 NR 4.8 15.9 Cumulative 45.4 26.0 68.6 NR 4.8 31.6 Quarantine released: Beef: Initial 6.4 12.2 5.5 11.6 6.0 11.4 Cumulative 7.8 19.1 8.0 15.9 12.3 16.3 Dairy: Initial 2.8 1.5 4.7 3.3 1.0 2.5 Cumulative 8.4 2.5 5.5 3.3 1.4 3.4 NR = None reported. Table 31. Disposition of quarantined beef herds by herdsize, U.S., 1980-82. Herdsize Herd Quarantine Still (Head) Depopulated Released Quarantined Total Percent 1-19 40.4 57.5 2.1 100.0 20-49 36.6 60.1 3.3 100.0 50-99 32.2 61.1 6.7 100.0 100-199 39.8 52.6 7.6 100.0 200-499 27.2 57.0 15.8 100.0 500-999 87.0 13.0 NR 100.0 1,000 or more 100.0 NR NR 100.0 NR = None reported. Table 32. Herdsize distribution of depopulated beef herds and beef herds released from quarantine by region, U.S., 1980-82. Region Herdsize North South U.S. (head) Northeast Southeast Central Central West Average Percent Depopulated: 1-19 30.2 38.2 17.1 36.4 11.1 34.9 20-49 35.8 41.7 40.2 33.3 22.2 38.6 50-99 28.3 14.9 26.2 16.7 11.1 16.9 100-199 3.8 3.8 12.8 7.6 27.8 6.2 200-499 1.9 1.0 3.7 4.5 16.7 2.6 500-999 NR NR NR 1.5 5.6 .5 1,000 or more NR .4 NR NR 5.5 .3 Total 100.0 100.0 100.0 100.0 100.0 100.0 Quarantine released: 1-19 25.0 34.0 17.8 31.3 13.0 31.2 20-49 41.6 44.7 44.5 38.3 26.1 39.9 50-99 25.0 17.3 33.3 20.6 13.0 20.2 100-199 4.2 2.5 3.3 5.7 34.8 5.2 200-499 4.2 1.5 1.1 4.1 8.7 3.4 500.-999 NR NR NR NR 4.4 .1 1,000 or more NR NR NR NR NR NR Total 100.0 100.0 100.0 100.0 100.0 100.0 NR = None reported. 21 Selected Statistics Per Depopuloted Herd and Disposition of Calves in Quorontined Herds The number of total cattle and breeding cattle sold for slaughter per depopulated herd generally varied on a re- gional basis in relation to the herdsize structure within each region. Owners of depopulated herds averaged selling al- most 5O head per herd for slaughter, with breeding cattle accounting for about 40 head per herd or almost 80 percent of the total cattle sold for slaughter (Table 33). Producers of depopulated herds also averaged selling about seven calves per herd for slaughter. The remaining cattle sold for slaughter from depopulated herds, about 5 percent of the total, were test eligible cattle that were not classified as breeding cattle or calves. A comparison of depopulated herdsize groups on a reg- ional basis shows that the largest depopulated herds were in the West, while the Southeast reported the fewest number of cattle per depopulated herd (Table 33] . The South Central and North Central regions reported the smallest number of calves sold per depopulated herd. Disposition of Heifer Calves During 1 97 7-80 An analysis of the disposition of heifer calves during 1977-80 by herds which were quarantined during 1980-82 reveals that more than 41 percent of the heifer calves were retained in such herds [Table 34). The U.S. Department of Agriculture reported a retention rate of 45 percent during 1977-80, suggesting that pre-quarantine retention rates were similar to those of average U.S. cattle producers. Table 34 also reveals that more than 86 percent of the heifer calves sold during 1977 -80 were 6 months old or older. Quarantined herds in the West reported the highest heifer retention rates, followed by the Southeast. Lowest heifer re- tention rates were reported by the North Central and South Central regions. Table 33. Number of cattle, breeding cattle, and calves sold for slaughter per depopulated herd by region, U.S., J W 1980-82. Region “ North South U.S. Item Northeast Southeast Central Central West Average Number/Depopulated Herd Cattle sold for slaughter 55.8 37.3 51.4 44.2 169.7 48.6 Breeding cattle sold forslaughter 38.1 29.1 46.5 39.7 134.2 39.8 Calves sold for slaughter 16.6 8.3 3.6 2.1 11.1 7.3 Table 34. Disposition of heifer calves during 1977-80, quarantined herds by region, U.S., 1980-82. Region North South U.S. Disposition Northeast Southeast Central Central West Average Percent Retainedin herd 41.1 45.6 25.6 29.3 70.3 41.1 ~ Sold at age: Lessthan 6monthsold 8.2 11.9 4.0 10.4 2.3 8.0 6to12monthsold 32.3 35.4 53.4 55.1 23.7 41.8 More than 12 months old 18.4 7.1 17.0 5.2 3.7 9.1 p Total 100.0 100.0 100.0 100.0 100.0 100.0 22 \ . —~. Disposition of Vaccinated Heifer Calves During 1977-80 More than two-thirds of the heifer calves vaccinated dur- ing l977-80 were retained by quarantined herd owners [Table 35). Another 5 percent were sold to other producers for herd additions with the remainder, about 27 percent, sold for non-breeding purposes. Quarantined herds in the West and Southeast reported the highest retention rate for vaccinated heifers during 1977 -80, followed by the South Central and Northeast. The lowest vaccinated heifer retention rate was reported by the North Central region with less than 40 percent. Table 35. Dispositon of vaccinated heifer calves during 1977-80, quarantined herds by region, U.S., 1980-82. Region Disposition North South U.S. of Vaccinates Northeast Southeast Central Central West Average Percent Fietainedin herd 61.2 70.4 39.2 61.2 88.6 68.0 Sold for breeding 6.8 2.3 7.1 3.7 8.1 5.3 Sold for other purposes 32.0 27.3 53.7 35.1 3.3 26.7 Total 100.0 100.0 100.0 100.0 100.0 100.0 Summary This report presents information and data concerning op- erational characteristics, herd health management prac- tices, and related epidemiological information regarding , newly quarantined beef and dairy brucellosis herds in the contiguous 48 states during 1980-82. Detailed information was obtained through Veterinary Medical Officers, APHIS, U.S. Department of Agriculture, via a nationwide questionnaire on herd health management practices and characteristics of quarantined herds; methods of identifying infection; source of cattle in quarantined herds; adjacent herd testing; relationship of vaccination level to reactor rate; reactors removed; length of quarantine and number of tests; and disposition of quarantined herds. The following information provides selected findings of this report. Characteristics 0f Quarantined Herds 0 More than 90 percent of the newly quarantined beef herds consisted of herds with less than 100 head. O More than 94 percent of the quarantined dairy herds were represented by herds with 199 or fewer head. I Herds ranging from 20 to 49 head accounted for higher percentages of quarantined herds in both the beef and dairy sectors than any other group. The group with the second highest proportion of quarantined herdsize in the beef sector were herds with 1-19 head, compared to dairy herds with 50-99 head. 0 More than 44 percent of the quarantined herds relied on year-round calving practices. 0 Approximately 15 percent of the newly quarantined herds were previously quarantined. 23 Origin 0f Cattle in Quarantined Herds 0 Fifty-four percent of the cattle in newly quarantined herds were introduced into the herd via purchases and/or leasing and borrowing arrangements. This was substantially higher than for the U.S. beef-dairy industry during 1977-7 9. I Public markets were the source for 34 percent of the cattle purchased, followed by other individuals with 29 percent, livestock dealers with 9 percent, and dispersal or consignment sales with 3 percent. Various combinations of these sources accounted for the remaining 25 percent. 0 Fifty-three percent of the quarantined herd owners who introduced cattle into their herds purchased cattle two or more times per year. O Almost 40 percent of the quarantined herd owners purchased pregnant heifers, 30 percent purchased unbred heifers, either occasionally or more often, and more than 80 percent purchased adult cows, either occasionally or more often. I Eleven percent of the quarantined herd owners who purchased cattle made it a general practice to buy strain 19 vaccinated cattle. Identification and Source 0f Infection 0 The most prevalent method of identifying newly infected herds was through testing at livestock markets, where 48 percent of the newly quarantined herds were identified. The next most important method included diagnostic laboratories, followed by adjacent herd testing, testing at slaughter plants, private tests, and brucellosis ring testing. O More than 52 percent of the herds adjacent to newly quarantined herds were tested, with 38 percent of these herds found to be infected. O Purchased cattle were cited by 55 percent of the quarantined herd owners as the probable source of infection. Adjacent herds were cited by 27 percent as the probable source of infection. Relationship of Vhccination Level and Reactor Rate O Eighty-one percent of the newly quarantined herds did not use calfliood vaccination. O Approximately 84 percent of the newly quarantined beef herds and 68 percent of the newly quarantined dairy herds did not contain vaccinates. O Reactor rates on initial tests in vaccinated beef and dairy cattle were about two-fifths the rate of non- vaccinated cattle. O The cumulative reactor rate for quarantined beef herds did not decrease until vaccination levels exceeded 40 percent. However, total cumulative beef reactor rates were about two and one-half times greater for non- vaccinated cattle compared to vaccinated cattle. O The cumulative reactor rate for vaccinated dairy cattle was about one-fourth the rate for non-vaccinated cattle. o The initial and cumulative herd reactor rates for beef and dairy herds decreased as herd vaccination levels increased. Length 0f Quarantine and Number of Tests O Beef herds were under quarantine for an average of“; 199 days compared to 216 days for dairy herds. O Owners of beef and dairy herds, who continued testing until all reactors were removed, averaged 4.2 tests per herd. O Length of quarantine for both beef {and dairy herds‘ tended to be longer for vaccinated herds than for non- vaccinated herds. O Herdsize had a positive effect on the number of tests and length of quarantine for both beef and dairy herds. Disposition of Quarantined Herds and Selected Characteristics 0f Depopulated Herds O Thirty-seven percent of the beef herds were depopu- lated compared to 11 percent of the dairy herds. O Higher proportions of non-vaccinated beef herds were depopulated than vaccinated herds. Among dairy herds, vaccination status had little or no effect on depopulation. O Both initial and cumulative reactor rates for depopu- lated beef herds were about twice as high as initial and cumulative rates for beef herds released from quarantine. O Initial and cumulative reactor rates were from 6 to 9 times higher for depopulated dairy herds as were initial and cumulative rates for dairy herds released from, \ quarantine. W RGTGlGHCGS Amosson, Stephen H. 1983. Economic and epidemiologic implica- tions of national bovine brucellosis programs-a case study. Ph.D. Dissertation. Texas A&M University. Dietrich, Raymond A., Stephen H. Amosson, and Richard P. Craw- ford. 1985. Economic and epidemiologic analysis of U.S. bovine brucellosis programs-Volume 1. Veterinary Services, APHIS, U.S. Department of Agriculture. Hyattsville, MD. 24 Doane Agricultural Service. 1980. Disease incidence package. Doane Agricultural Service. St. Louis, M0. U.S. Department of Commerce, Bureau of The Census. 1973. 1969 Census of Agriculture — Cattle, Hogs, Sheep, Goats. Vol. V, Part 9 — Special Reports. Washington, D.C. U.S. Department of Commerce, Bureau of The Census. 1981. 1978 Census of Agriculture. Vol. I, Part 51. Washington, D.C. [Blank Page in Original Bulletin] ' Q Mention of a trademark or a proprietary product does not constitute a guarantee or a warranty of the product by The Texas Agricultural Q Experiment Station and does not imply its approval to the exclusion of other products that also may be suitable. All programs and information of The Texas Agricultural Experiment Station are available to everyone without regard to race, color, religion, sex, age, handicap, or national origin. 2.5M, 5-88