'59 b flullem 21.2 ' Plzotosenxitiza tian 0 f Ca tile ' in Texan Right—A case oi winter photosensiti- zation. The eye, nose and mouth are inflamed. The brisket has ac- cumulated a large amount of serous fluids. Leit — The same animal 15 days later. The areas around the eyes and nose have peeled and some skin is sloughing from the dewlap. July /955 TEXAS AGRICULTURAL EXPERIMENT STATIUN - - - TEXAS AGRICULTURAL EXTENSIUN SERVICE College Station, Texas SUMMARY Photosensitization in South and East Texas has been under study for 3 years. More than 50 past in 30 counties were included. The area studied most intensively extends from Atascosa county to Wh 5 county. Experimental feeding was done in DeWitt and Wharton counties. Outbreaks have occurr , Brazos, Polk, Jasper and Newton counties in East Texas and several counties on the Rio Grande Pt These outbreaks occurred during all seasons but mostly during the spring and early summer. All outbreaks of the disease studied occurred on pastures with a high percentage of annual gr 4 and weeds and a low percentage of good perrennial grasses. . Each outbreak studied fitted in a definite climatic-plant growth cycle. A fair amount of :5‘ and growth of the vegetation was followed by a dry period. The dry periods were broken by rain then by seasonable warm or hot weather. Large quantities of the revived, often lush growth, of‘ annual vegetation were consumed by cattle. Photosensitization occurred from 1 to 15 days after, rainy period. Feeding experiments, pasture analyses and relat-ed studies indicate annual grasses, , native and cultivated, are the primary causal agents. l The following recommendations for the management of photosensitized animals are based on studies, reports of oth-er workers and treatment records: as soon as possible and provide shade. Consult a qualified veterinarian for proper diagnosis of the d’ Follow his recommendations. Paint or spray the affected parts with methylene blue or some ‘i nontoxic dye; this will speed recovery and reduce the overall damage from the disease. Provide = dry feed such as hay, straw or fodder. Mixed feeds containing leaf meal and bran also are bene Anticipate outbreaks by maintaining a reserve range or pasture for rotating livestock durin dangerous period. A reserve of roughage, in the field or in storage, is valuable for emergencies 1 supplemental feed. ACKNOWLEDGMENTS The research reported in this bulletin was supported in part by federal-grant funds made available to the Texas Agricultural Experiment Station by the 1946 amendment of the Bankhead- Jones Act; and local expense funds provided by the DeWitt County Cattlemen’s Association. Cattle fed on the Will Rob Miller ranch were furnished by the DeWitt County Cattlemen’s Association. Those fed on the John Ferguson ranch in Wharton County were obtained from the Ferguson herd. REFERENCES Britton, N. W. and T. B. Paltridge. 1941. Preliminary role on photosensitization of sheep grazed on Brachiaria brizantha. Proceedings of the Royal Society of Queens- land, 52 (2): 121-129. Clare, N. T. 1952. Photosensitization in diseases of domestic animals. Commonwealth Agricultural Bureaux, Farnham Royal, Bucks, England. 58 pps. Cooper, E. R. and D. Walker. 1940. Climatic factors relating to outbreaks of facial eczema in New Zealand. New Zealand Journal of Science and Technology, 22:30A-41A. Cunningham, I. J., C. S. Hopkirk and J. F. Filmer. 1942. Photosensitivity diseases in New Zealand. New %ea‘lkaind Journal of Science and Technology, 24: 185A- 98 . Gibbons, W. J. 1953. Photosensitivity in cattle. The Auburn Veterinarian, 9 (3): 177-179. Hoffman, G. O. 1954. A study of photosensitization of cattle in Southeast Texas during 1953. M. S. thesis, Texas A. & M. College, unpublished, 78 pps. 2 Remove affected animals from the p 5 Practicing veterinarians who coopera this project were: Drs. R. R. Childress, J 1; V. H. Driscoll, Wharton; W. W. Green, t, A. C. Kaltwasser, El Campo; V. R. Pa A Floresville; H. H. Payne, El Campo; C. R. < Cuero; and C. F. Wallace, Cuero. i The cooperation of personnel of the Agricultural Extension Service, veterinaria ranchmen throughout the area, and all othe contributed in many Ways, as well as all, mation from the literature, included or c' gratefully acknowledged. l Howarth, J. A. 1931. Sudan grass as a photos agent causing dermatitis in sheep. North V Veterinarian, 12:29-23. . Hurst, E. 1942. Poisonous plants of New Sou -l Sydney, N. S. W. Poison Plants Gommittee,"4 Levy, E. B. and P. s. Smallfield. 1942. Thei if soil, climate, pasture composition of facial ecze" gleikaind Journal of Science and Technology, _ Quinn, J. I. 1933. Studies on the photosensi' animals in South Africa. I. The action of n; dye stuffs. Onderstepoort Journal of Veterin " and Animal Industry, 1 (2) 459-468. Steyn, D. G. 1934. The toxicology of plants Africa. Cape Town Central News Agency, .' Stroud, F. B. 1955. A study of photosensi cattle in Southeast Texas during 1954. M." Texas A. & M. College, unpublished, 101 pps. * a Photosensitization of Cattle in Texas O. E. SPERRY, R. D. TURK, G. O. HOFFMAN and F. B. STROUD* PHOTOSENSlTIVE—Sensiti1/e t0 the action of radiant energy, especially light. system. OTOSENSITIZATION OF CATTLE HAS BEEN A stant menace to stockmen in Texas for more 40 years, and losses from this disease appear ‘v increasing steadily. The disease is known several local names, the most common being ” or “Weed” trouble. Many conditions called E-dburn undoubtedly are photosensitization. The se is produced as the result of the abnormal ion of light-colored skin to sunlight after a todynamic substance or agent has been ab- h- through the animal’s system. This sub- cc is obtained from certain vegetation under ‘ ific conditions. After the toxic principle has been system- absorbed and has moved to the subdermal l, s of the skin, reddening of the light-colored appears. Conjunctivitis usually is appar- particularly in cattle with light-colored eyes. i. e reaction progresses, the skin may exude rous fluid, erupt into watery blisters and m e yellowish, indicating jaundice (icterus). r this initial reaction, the blistered or affected “usually sloughs, leaving raw areas which are y susceptible to secondary infections, espe- v by screwworms. At the outset of the dis- y. the cattle are extremely sensitive to sunlight pend most of the daylight hours under shade. 'ng, scratching, rubbing against objects and the affected parts are shown in varying ities at this time. Internal disturbances, "rily in the liver, apparently are present in rly stages of the disease. attle of all breeds, crosses and sexes are y susceptible to the blistering and peeling. g calves usually are not affected although ms have been observed in animals as young onths. Fat cattle are as susceptible as those 3.. condition. The udders of cows with S; calves are subject to greater damage than of heifers or dry cows. Predominately red ~ k animals become listless and show signs turbance, but do not blister or slough cept on white and lighter-colored areas. ' of all colors may develop acute laminitis T 'vely, professor, Department of Range and For- head, Department of Veterinary Parasitology; "on range specialist; and research assistant, De- l» of Range and Forestry. PHOTOSENSITIZATION ——A disease produced as the result of the reaction of light-colored skin to sunlight after a photodynarnic (sensitizing) substance or agent has heen ahsorhed through the anirnal’s (founder) with resultant swelling of the coronary band. The animals appear reluctant to move, and when forced, walk with a high-stepping gait. Occasionally hooves may be sloughed and the animals must be destroyed. Susceptibility and severity of the disease vary among individuals. Cattle seldom die from photosensitization. The chief monetary losses are due to loss of weight, damaged udders and secondary infections. Screwworms frequently cause secondary eye damage. If not treated, or when certain screw- worm remedies are used in the eyes, the animal may become blind temporarily and sometimes suffer complete loss of eyesight. Mother cows frequently do not allow their calves to nurse because of blistered teats and painful udders, and the calves may be undernourished and prema- turely weaned. Horses, sheep and goats also have been re- ported with photosensitization. Photosensitization may occur at any season of the year, but the larger and more serious out- breaks occur in the spring and summer. Most of the known outbreaks have occurred within 2 weeks following rain and during periods of rising temperature. The onset of the disease is quite sudden; few animals or the entire herd may be affected. CONTENTS Page Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .. 2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Review of Literature . . . . . . . . . . . . . . . . . . . . . 4 Problem Area . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Study Procedure . . . . . . . . . . . . . . . . . . . . . . . . 5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Prevention and Treatment . . . . . . . . . . . . . . . . 8 Figure 1. Crossbred Hereford cow showing poor physi- ' cal condition, sloughed skin on white areas. loss oi eye and a ruined udder from a severe attack of photosensitization. REVIEW OF LITERATURE New Zealand, Australia and South Africa pioneered much of the research in photosensiti- zation of range animals which occurred under conditions similar to those in Texas. The vege- tation, climatic conditions and animal symptoms found in many regions in Texas are similar to those recorded for these countries. Clare (1952) classified a type of photosensi- tivity as hepatogenous photosensitivity. This most nearly fits the type encountered in this study. In hepatogenous photosensitivity, the toxic agent is a substance normally absorbed and ex- creted, which is diverted to the peripheral circu- lation through the failure of the liver or detoxi- eating mechanism. Jaundice usually is present in this type of photosensitivity. Symptoms of photosensitized cattle in New Zealand described by Cunningham, Hopkirk and Filmer (1940) were similar to those shown by cattle in the present study. After post-mortem examinations, these authors reported that the liver may be swollen to several times its normal Figure 2. Dairy cows with peeling skin on white areas. udder and teats. 4 Figure 3. A Iersey cow reacting to udder irrit the early stages oi photosensitization. Loss of body was pronounced. The milk flow was reduced approxij 85 percent in 48 hours and did not return to normal - the 1953 and 1954 lactation periods. A size. The left lobe usually received the damage and sometimes atrophied and the i lobe often assumed a bulbous shape. l Many meteorological factors were studi Cooper and Walker (1940) during outbre i; photosensitization in New Zealand. Abno high air and soil temperatures were corr with the time of the occurrences. Relative r" ity, rainfall on a yearly basis and hours 0f ~~ sunshine could not be correlated. The _ serious outbreaks, according to these au occurred after rains which ended abnormall periods and were followed by rising tempera; The research of Levy and Smallfield ( on the effects of soil, botanical compositio pasture management practices on Olllibl‘, Figure 4. Scar tissue on a Brahman cow dull blistering and peeling oi the skin on a typical phop zation case. ' T‘ New Zealand showed the more serious years for g; the disease were associated with lush feed after drouth-breaking rains. The capability of the soil to promote rapid plant growth after rain was ‘ considered more important than soil structure or texture. Soil fertility and climate were the main " factors in determining when a particular soil type was dangerous. The stage of growth of the vege- - tation was more important than the plant species. " This was apparent as the disease occurred on t pastures of widely different species composition. - Many plants produce photosensitization, and l. grasses are reported as the causal agents by several writers. Weather conditions, including a sequence of drouth and rain, were associated with the reported cases. Many of the same or ; related species of grass are common throughout i the world in areas where photosensitization has occurred. Two panicgrasses, Panicum coloratum and P. laevifolium, produced photosensitization in r sheep in South Africa following good rains, according to Rimington and Quinn (1937). ; Howarth (1931) reported the disease in Cali- fornia was caused by Sudangrass after it had . been irrigated during hot, clear weather condi- i tions. Britton and Paltridge (1941) concluded . that a signalgress, Brachia/ria brizantha, in Au- . stralia was dangerous only in a particular stage of growth and only under certain weather condi- 1 tions. Guineagrass, Panicum maximum, accord- a ing to Hurst (1942) in New South Wales, was idangerous to sheep shortly after rains. Feeding ; of Guineagrass by Hurst in the fieldproduced photosensitization in sheep and guinea pigs. Many 11> other grasses are recorded as photodynamic, but specificweather conditions are required before they become toxic. PROBLEM AREA , The part of Texas where photosensitization is known to occur is 50 to 100 miles wide and extends from Atascosa county on the west through fDeWitt, Jackson, Wharton and Brazoria counties ‘on the east. Outbreaks also have occurred in Brazos, Polk, Jasper and Newton counties. Rec- ‘ords of outbreaks are known for the Rio Grande giPlain counties of Live Oak, Brooks, Kleberg, ‘Kenedy, Jim Hogg and Starr. The disease may occur over much more of East and South Texas ‘han has been reported to date. 1 Photosensitization reported in cattle in Flo- rida, Georgia and Alabama probably is of the ;.. me type as experienced in Texas. Isolated cases which may be of a similar nature also have it curred in the Midwestern States and in Cali- ornia. v Outbreaks of photosensitization have been eported from all continents and most of the rger islands. The consequences of large out- reaks of this malady are felt more keenly in reas where grazing is of major economic im- ortance. Australia, New Zealand and Africa have been plagued with serious occurrences for many years. STUDY PROCEDURE In this study, four conditions were considered necessary before photosensitization would occur: natural sunlight, light-colored or nonpigmented skin, a responsible plant or plants and specific weather conditions. Therefore, the investigation of this malady revolved around the determination of the toxic plant or plants and the weather and soil conditions, and their correlation with period- icity of the outbreaks. Rainfall and temperature data were obtained from weather stations in the areas where photo- sensitization had occurred and were analyzed to determine the factors which might be correlated with the outbreaks. Soil moisture and soil tem- perature also were taken on selected pastures which had produced photosensitization. The vegetation of pastures producing photosensitiza- tion was classified to determine the most common species. The vegetative cover and the percentage composition of the grasses were obtained by the line-transect method. Stem counts of forbs (weeds) by species were taken from 3-inch belts paralleling the transects. Studies were made of cattle as they grazed undisturbed on ranges that had produced photo- sensitization. The amount of each plant grazed was recorded. Information on the life span, abundance and relative utilization was recorded for each species of the plants grazed. Experimental feeding trials were conducted in DeWitt and Wharton counties. Animals with large areas of light-colored skin and nonpigmented eyes, udders and teats were used so that any external symptoms produced could be observed readily. The beginning and ending weights were recorded for each animal and the percentage intake of each plant fed was determined in rela- tion to the beginning weight of the animal. All animals were placed in open, unshaded pens with fresh water available at all times. Control animals were used for all experiments and were subjected to the same treatments but were fed different rations. Practicing veterinarians in the area examined the animals at the beginning and end of each feeding period. DISCUSSION Cases of photosensitization on a large number of pastures were studied during 1952-54. Rainfall and temperature records, and the vegetational composition and growth were examined for each outbreak. These records indicate that the out- breaks occurred from 1 to 15 days after rain. The rain was preceded by a period of dry weather. The length of the dry periods varied with the soil type but they were long enough fo-r the growth of the vegetation to become retarded and usually 5 somewhat wilted during the daytime. The rains were followed by increasing temperatures. All of the native and improved pastures concerned showed a high percentage of annual grasses and weeds. The annual type of vegetation reacted readily to climatic changes and showed a marked rejuvenated growth following rains. It is under this combination of drouth, rainfall and temperature that»the pasture vegetation of South and East Texas causes photosensitization. Photosensitization apparently is not limited to a particular soil type. The disease has occurred on soils ranging from deep, highly leached sands to fertile, heavy clays. It has not been possible to correlate soil temperatures and soil moisture with the outbreaks studied to date. However, it is apparent that the soil serves as a medium for expressing the weather. Therefore, the ability of the soil to induce a period of quick growth appears to be more important than a particular type of soil. Annual and other grasses of low grazing value made up a large percentage of the vegetation of the native pastures in this study. The amount of weedy vegetation other than grasses on the photodynamic pastures also was high. A One of the unexplained conditions is that not all pastures with apparently the same vegetation produce photosensitization. Nor do all pastures concerned have pohtosensitization every year. It is obvious that a definite combination of the conditions nec- essary to produce the disease are associated with the grazing behavior and possibly the physiologi- cal nature of the animal. Native pastures with a high percentage of perennial grasses and abun- dant forage normally do not produce photosensi- tization. Apparently, the carryover perennial grass furnishes considerable roughage which is used by the animal to offset the toxic condition produced by the lush growth of the annuals. Perennial grasses do not respond as rapidly in growth to moisture and temperature as annual grasses. Perennial grasses also produce more fiber than short-lived annuals. It is apparent that roughage is needed with the green feed f0 proper rumination. These explanations requir further study. Photosensitization has occurred on improv pastures where bur clover, annual ryegrass, oat Sudan and rescuegrass alone, or in combinatio made up the bulk of the vegetation. Y Grazing studies conducted during the spri = and summer of 1953 and 1954 indicated t =, cattle are selective in their grazing habits. Weat t. er conditions, availability and abundance of th plants, the palatability of the plants and th‘ physical condition of the animal appear to infl ence the amount of each species grazed. T grazing day—that portion of the day betwee first getting up in the morning and bedding do, at night—was approximately 16 hours. The typ cal grazing day began at dawn, continued un l about 10:00 a.m., began again about 4:00 “j and lasted until dark. Grazing continued long in the mornings and began earlier in the afte noons on cloudy, cool days. Grazing also continu after dark on moonlit nights. Cattle drank in t‘ morning before going into the shade and early ' the afternoon before resuming grazing. Most j the ruminating was done when the animals we-Ti in the shade. Photosensitized cattle grazed mos i in the shade of trees during the sunlight hou and at night, regardless of moonlight conditiof Forbs made up a larger part of the diet in r spring than at any time during the period studi - However, they did not constitute more than abo 10 to 15 percent of the diet. The diet of t cattle was altered by rain. This is partia explained by the fact that certain grasses a other plants that show a quick response to mo ture were selected after rain. Field observatio and observations of ranchmen were the basis i, selecting certain species for experimental feedi A variety of forbs and grasses were fed DeWitt and Wharton counties (Table 1). All for were ground and force-fed to the cattle with, balling gun, while the grasses were fed f 1 choice. Supplementary feed was given the anim TABLE I. EXPERIMENTAL FEEDING OF CATTLE IN DEWITT AND WHARTON COUNTIES DURING 1953-54 PMS ‘ed 3231's anfiliied A13.“..“§.§°d' fivéifiiigi/i’. Philiillfi Violet ruellia. Ruellia nuditlora 14 1 508 7.05 None *7 Whitebract woollywhite, Hymenopappus caroliensis 14 2 1268 5.66 None ; Greater ammi, Ammi maius 1U 1 337 2-30 NW9 l: Texas skeleton plant, Lygodesmia texana 14 2 1414 9.81 None i? Prostrate euphorbia. Euphorbia prostrata 4 2 208 2.00 None Snow-on-the-mountain, Euphorbia marginata 4 2 200 1.72 None J , Fringeleat paspalum. Paspalum ciliatiiolium 10 2 2832 26.41 Mild Iunglerice. Echinochloa colonum 1o 2 3616 34.76 None f Prairie cupgrass, Erichloa contracta 10 2 3632 36.32 Mild 5 Southern sandbur. Cenchrus pauciflorus 5 3 4368 12.55 Mild 5 Annual grass mixturel 9 4 20720 ‘ 71.23 None § lApproximate composition: Texas panicgrass, Panicum texanum. 80 percent; prairie cupgrass, Erichloa contracta, 5 peril signalgrass. Brachiaria extensa, 10 percent; iunglerice. Echinochloa colonum. 5 percent. - 6 Figure 5. Animal ied prostrate euphorbia. The ab- normal stance and digestive disturbance became more pro- nounced as the feedings oi the spurge continued. that were fed forbs. Various disorders, ranging from severe digestional disturbances to bleeding from the intestinal tract, were produced from the forbs, but no observable photodynamic reactions were obtained. Two Hereford heifers fed Texas skeleton plant for 14 days developed watery eyes, scours and extreme nervousness. After the fifth feeding, when 48 ounces or more were fed at one time, the animals apparently became “loco,” ran into fences, pawed the earth and bucked violently. This con- dition subsided after a brief interval. Two heifers were fed 104 ounces each of prostrate euphorbia (a spurge) in four successive daily feedings. Both animals salivated profusely during each feeding, apparently because of the irritating effect of the plant material. Twenty- four hours after the first feeding of 24 ounces. both animals showed arched backs, severe scours and a jerking or “thumps” of the abdominal muscles, indicating pain in the digestive tract. The reactions became more severe with each suc- cessive feeding. No material was fed after the Figure 6. The types of animals, pens and feeding ar- rangements used in the grass ieeding experiments. The watery and matted eyes are symptoms typical of early i, photosensitization. fourth day. Scours continued for 10 days and the animals lost 35 and 50 pounds, respectively. Two heifers fed a total of 200 ounces of snow-on-the-mountain developed similar but more severe symptoms than those fed prostrate euphor- bia. The juice of snow-on-the-mountain was rubbed on the udder and teats of one of the animals but no ill effects were noted. The scours subsided after 12 days. These heifers and those fed prostrate euphorbia apparently were normal approximately 1 month after the feeding was discontinued. Whitebract woollywhite fed to Hereford heif- ers produced scours. However, these animals gained in weight and developed smooth, glossy hair. Violet ruellia caused watery eyes, a scabby nose and scours after the fifth feeding. Greater ammi caused mild scours. Four species of grass were fed to nine selected animals and an annual grass mixture was fed to four heifers. The two animals fed fringeleaf paspalum developed watery eyes, harder than normal droppings and stood with arched backs and moved about sluggishly. Two heifers fed prairie cupgrass developed extremely watery eyes, stood with arched backs and moved sluggishly. The eyelids of both animals became inflamed and one heifer developed an abnormally wrinkled, hard and dead-looking neck skin and the brand scar became inflamed and peeled off. Animals fed junglerice lost weight but showed no photo- sensitization reactions. Three selected cows were fed southern sand- bur. The light-colored skin area oozed a notice- able amount of serous fluid, the nictitating mem- brane became inflamed and mild conjunctivitis developed in one animal. The feeding was stopped at the end of 5 days because of dry weather and the drying of the grass. By July 1954, our experiments and observa- tions led us to the conclusion that annual plants, primarily grasses, that showed an early response to rainfall were the causal agents of photosensi- tization in the study area. Plant collections from more than 50 pastures which produced photosensitized animals showed that annual species, pri- marily grasses, were the only plants common throughout. Photodynamic reactions were ob- tained from three grasses fed during 1953 and 1954. Several grasses and forbs determin- ed as photodg/namic by investigators in other areas were present or had related species in the pastures studied. A feeding experiment was planned in Whar- ton county for July 1954 to include several of the annual grasses prominent at the time. Four 7 cows were selected and arrangements were made to start feeding immediately following the first rain. Since July was without rain in Wharton county, annual grasses were collected in cultivated fields. Although the grasses were quite mature, large amounts were fed without other forage. The animals gained weight during the feeding period but showed no symptoms of photosensi- tization. Certain facts became evident following the feeding experiments. It is extremely difficult to collect a quantity of a given species of grass and keep it in a turgid state long enough to feed as representative of range conditions. Although the grasses were sprinkled before the feeding time, normal wilting changed their conditions so that they were not in the state naturally grazed. Fur- thermore, annual grasses mature rapidly and toward the end of all feeding periods, the grasses had passed the lush stage of growth normally assumed following rain. Even though some pre- liminary symptoms were obtained, the growth stage which produces photosensitization had passed before a feeding period could be completed. PREVENTION AND TREATMENT The prevention of photosensitization among cattle is difficult since its occurrence cannot be predicted accurately. A study of the general pasture conditions, rainfall and temperature shows a definite pattern in relation to outbreaks. Spring and summer are more prone to have large- scale outbreaks than fall and winter. An intensive range improvement program should be started on native grass problem pastures. Such a program would include reduced stocking, deferred or rota- tion grazing and other soil conservation practices designed through careful planning to develop a good percentage of desirable perennial grasses A in the pastures involved. Several practices may be used as temporary precautionary measures on pastures which pro- duce photosensitized animals. After heavy rains that break dry periods, one of the simplest prac- tices is to exchange animals in certain pastures or to move them to a reserve pasture. When cattle are moved into new pastures, the grazing pattern is changed and consequently the diet for that period concerned is altered. Dry roughage on lush, green pastures should be an essential part of the cow’s diet. This can be provided by reserve pastures of old grass or stubble which are used in connection with the green grazing. If standing roughage is not avail- able, hay, straw or fodder can be fed in the pasture or in drylot. Drylot feeding is advisab a when outbreaks have occurred repeatedly on ce tain pastures. Three to 10 days of drylot feedin will get the animal through the critical period an allow the vegetation to advance in maturity. ' If animals are not normally grazing parts o a pasture which have some coarser grasses o, roughage, they can be attracted to the unde j utilized areas with salt. Since salt is commonl placed near water, these areas usually are ove } grazed and weedy, thus potential hazard si w» Changing the location of salt from time to ti helps to obtain a more even grazing pattern. N0 specific treatment for photosen- sitization is known and symptoms mast be treated as they appear. Steyn (1934), in treating sheep for pho I sensitization in South Africa, recommended pr, viding shade for animals as soon as the sympto appear. Treating the affected areas with astri“ gents, such as tannic acid, zinc oxide ointment _'_ alum, was recommended. Steyn also consider that changing the grazing routine was essenti in the prevention of photosensitization. Staini the unprotected or nonpigmented parts with no toxic dyes such as bismark brown or potassiu permanganate was suggested as a possible meal of preventing skin lesions. .i Gibbons (1953) applied carron oil or zit oxide in oil to the skin lesions. The udder lesi _ were treated with various astringent salves. Quinn (1933) prevented photosensitizat in sheep and goats by painting them with e throsin, rose bengal, methylene blue and met lene violet. He found that placing the unpain - animals in the sun after injecting them ' certain of these dyes produced photosensitizati Many treatments were tried throughout t study area. Some retarded healing. Applyi various oils, greases and smears to the affec, parts maintained the lesions in a moist conditi’, and increased the susceptibility to flies and ondary infections. While subjected to these tr l, ments, cattle were extremely hypersensiti? grazed very little and consequently lost weigh Favorable results were obtained from sp 4 ing or painting the affected parts of the ca with a solution of methylene blue and wa Methylene blue in nonirritating and appare J nontoxic. It also has an astringent effect on 1 skin lesions which is valuable in promoting ; ing and in discouraging flies and the resul screwworm infestations. Texas Agricultural Experiment Station, R. D. Lewis, Director, lCollelge l l l