- W TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS, Director. College Station, Texas 76a i Phennthiazine-Salt Mixture, Free Choice, tor the [Inntrnl 0t the t 1 Large Stomach Worm in Range Sheep An H-gear Stndg Conducted Under the Naturat Range Conditions of the Edwards Plateau 11%;» a 95a The TEXAS AGRICULTURAL AND MECHANICAL COLLEGE SYSTEM GIBB GILCHRIST, Chancellor DIGEST An 8-year study conducted under practical range condit typical of the Edwards Plateau of Texas indicates that the ‘ stomach worm of sheep can be» controlled satisfa-ctorily through? continued use of a 1-to-9 phenothiazine-salt mixture supplied choice as a method of treatment. a Two groups of sheep were used. One group had access, choice, to the phenothiazine-salt mixture for the entire period? control group had access, free choice, to white salt only. ’ No apparent toxic effects were noted in any of the ani having continued access to the medicated mixture despite the I" period of treatment. ~ Comparison of worm-egg counts, larval development in t. samples, and actual worm counts at autopsy indicate that the 1-, phenothiazine-salt mixture satisfa-ctorily controlled the large s ‘ ach worm in range sheep. " While these findings may be applicable to similar or more regions, they may not lend themselves to practical applicati ' areas of greater rainfall and different topography. Phenethiazine-Salt Mixture, Free Choice, for the Control at the Large Stomach Worm in Range Sheep .,-_ A» xv» _ D. A. Price, W. T. Hardy and I. B. Boughton* HE SHEEP INDUSTRY is by far the most important phase of ;- agricultural economy of the Edwards Plateau of Texas, and it ' in this area that most of Texas’ sheep population is located. This teau lies in West-central Texas -east of the Pecos River, and p ends eastward nearlyto Austin. Its northern extent is marked the city of Big Spring, and the southern limit corresponds ¢ ghly to a line between the cities of Austin and Uvalde. The re- on contains more than 34,000 square miles. . The annual rainfall is relatively light, the average recorded at e Sonora station for a 30-year period being approximately 24 ches. Elevation at the Sonora station is approximately 2,400 above sea level. This combination of light rainfall and rela- ely high elevation is favorable for sheep raising, and the general e of range vegetation, too, is excellent for the purpose. v Generally, mixtures of bunch and turf grasses, weeds and wse occur on each ranch. When the grasses and weeds become pleted during Winter and in periods of drouth, sheep can subsist ‘n ost entirely on low-growing trees and shrubs. It is generally lieved that the bunch grasses common to many pastures fail to ovide adequate protection for parasite eggs and larvae against ,e strong sunlight, but the turf grasses do provide a protective ilvironment for them. The sparsity of the range vegetation neces- tates the grazing of limited numbers of sheep in large pastures, a tactice which contributes greatly to the natural control of para- ; es. The large stomach worm, Haemonchus contortus, is the most portant internal parasite of sheep on the Edwards Plateau. Be- j: the use of phenothiazine drench became general in the early 407s, losses due to the stomach worm had made serious inroads i the local sheep industry. During these and subsequent years, ere came about the general acceptance of the routine use of phen- “hiazine drench and one of the major obstacles to profitable sheep aising was overcome. i espectively, veterinarian and superintendent, Ranch Experiment Station, onora, Texas; and dean, School of Veterinary Medicine; Texas A. & M. » ollege, College Station, Texas. ' provide good control without supplemental drenching. __4_ The several disadvantages associated with drenching l, flocks of sheep were in part responsible for the establishment the long-term trial described herein. The disadvantages incl labor and the time required for gathering sheep, weight lossf sulting from holding in pens, and occasional injuries with su quent screwworm infestation. Although the authors believe the regular use of phenothiazine-salt mixture is more econo than the practice of drenching, the factors mentioned are so t tremely variable that an attempt to estimate the actual mo saving is almost impossible. When these factors are not conside j the cost of each of the two methods is approximately the same. f Since the beginning of the experiment in 1945, many of j, Edwards Plateau sheep raisers have become acquainted with administration of phenothiazine in salt as described in this bull and endorse it enthusiastically. They have found that it is p ticable and that it controls the stomach worm satisfactorily. REVIEW OF LITERATURE Since the discovery, in 1938, that phenothiazine is of valu an anthelmintic, or worm medicine, an impressive amount of “ ature dealing with the subject has accumulated. Phenothiazi generally conceded to be the most effective, the least toxic and most widely used medication for the control of round-worm Oi sitisms of sheep. ' Some of the first work with phenothiazine-salt mixtures control of parasite infestations was conducted late in 1939, and, ensuing years produced many experiments in which such mixt were used in various concentrations. and under many different ’ ditions, both in this country and abroad. Most of the wor carried out short-term experiments, some for only 3 or 4 mon A few studies have extended a year or more, however, and “ longest study heretofore published covered the 4-year use of f mixture in West Virginia, where a 1-to-14 mixture was reporte PURPOSE OF THE EXPERIMENT The purpose of the study reported in this bulletin has ~. to determine whether a 1-to-9 phenothiazine-salt mixture coul used as the sole means of controlling stomach worms in sheep _ tained under practical range conditions on the Edwards Platea PROCEDURE Although preliminary trials with phenothiazine-salt mixt of varying concentrations were conducted in 1941, the work; ported in this bulletin did not begin until May 1945. Unpubli tests conducted from 1941 through 1944 indicated the possi of controlling stomach-worm infestations by such a method. AVERAGE ANNUAL EGG COUNT PLAIN WHITE SALT GROUP PHENOTHIAZINE - SALT GROUP PM,“ W”; SALT COUNTED AT AUTOPSY PHE NOTHIAZ I N E - SALT GROUP AVERAGE ANNUAL . ESTIMATE LARVAL DEVELOPMENT PLAIN WHITE SALT GROUP PHENOTHIAZINE-SALT GROUP “nu-u... "n..."- ,// l945-46 I946-47 I947—48 I95I-52 I952-53 Figure 1. A comparison of the treated and control flocks of sheep based j worm-egg content of dung samples, larval development in the dung and a al worm counts at autopsy. v The sheep used in this study were purebred Rambouillet ewes § ich were bred to lamb in November and December of each year. ey were maintained under conditions typical of the local ranches. 9 shelter was needed because of the mild winters. The ewes ’_ bed in the pasture without special attention, and the lambs were pereafter kept in those same pastures for the duration of their es, except for the brief periods when they were penned for the Ilection of dung samples. When the ewes became too old for eding, they were sent to market. Two adjoining pastures were used for the experiment. One, EAOO-acre pasture, was stocked with 60 to 75 breeding ewes which f: continued access, free choice, to the phenothiazine-salt mixture. furteen to 18 ewes in a 100-acre pasture constituted the controls. ,_th pastures were adjudged to be similar in their vegetative cov- _6-_ Phenothiazine N. F. powder was purchased 0n the open m ket, usually in drums of 150 pounds each. Eleven pounds of t powder were thoroughly mixed with a 100-pound bag of grou stock salt to give approximately a 1-to-9 mixture. The mixtu. was kept in a covered salt trough and was not allowed to beco’ depleted. The supply was replenished at monthly intervals. control animals were supplied with the same stock salt, withoi the phenothiazine powder. At regular intervals, the sheep in ea pasture were penned for the collection of dung samples. One p0 tion of each sample was subjected to routine microscopic exami i tion to determine the number of worm eggs present. Another poi tion was incubated to allow the development of larvae, which We counted. Samples were taken from the new lambs beginning May of each year and this procedure was repeated periodically unp May of the next year, when the male lambs were slaughtered autopsied for the purpose of making actual worm counts. fin: Figure 2. When sheep and cattle are pastured together, the phenothiazi salt mixture can be placed in a low-style, covered salt trough for the sh‘ but plain white salt should be provided for the cattle in troughs so high ti the sheep cannot reach them. . T? RESULTS No evidence of phenothiazine toxicity was observed. Thisél in accordance with the observations of others who have conduc, studies on the use of phenothiazine-salt mixtures. Many of , animals in the treated flock attained the age of 6 to 8 years bef, being marketed and had never received any salt except that i tained in the phenothiazine-salt mixture. " The rate of phenothiazine-salt consumption was slightly 1 than one-third pound per sheep per month. This rate varied c ierably from month to month and from year to year, and was bably due to the presence each year of growing lambs in the ‘ture and to variations in the annual rainfall. a The accompanying graphs present a comparison of the treated »» control flocks of sheep, the bases for comparison being worm- 4: content of dung samples, larval development in the dung and i ual Worm counts at autopsy. Studies on larval development were de only during the last 5 years of the study. v A reflection of the most severe drouth ever recorded in West ixas is apparent in the zero value of egg counts in 1951-53. Al- pugh a few Worms were counted at autopsy at the end of that 'od, the method used for egg“ counts was not sensitive enough a reveal their presence in such small numbers. ACKNOWLEDGMENTS A The Work reported in this bulletin was conducted by I. B. ughton and W. T. Hardy the first 3 years; by W. T. Hardy : ing the following 2 years; and subsequently by D. A. Price.