Application of synthetic estrogen in sheep.

Abstract

Thirty castrated crossbreed lambs of 4 months age were divided into three groups. DES pellets (6 mg) were implanted subcutaneously in lambs of groups II and III, respectively at 4 and 7 months of age whereas those in group I served as controls. The lambs were fed on a dry fattening ration during a period of 29 weeks after which two lambs of each group were slaughtered and three lambs were also used in nitrogen balance studies. The body gains of lambs implanted with DES at 4 months of age were the highest. The growth promoting effect of the hormone in these lambs was significant during a period of 13 weeks after the implantation. The dietary nitrogen retained by treated lamb was significantly higher. The dressing percentage and weights of wholesale cuts in lambs implanted with DES were similar to those of control lambs. However, the percentage of meat in the lambs treated at 4 months of age was the highest. The protein and moisture contents of the tenth rib of these lambs were greater and the fat contents were lower than in the control animals. No DES residual activity was ever noted in the livers of slaughtered lambs. Effect of DES Implantation on Body Components. Six 2 year old Egyptian rams were used in a 2-month experiment, the duration being divided into three successive intervals. The 1st period served as a control. At the beginning of the 2nd period, DES was implanted subcutaneously. Total body water was measured using tritiated water, total muscle mass was determined by the creatinine excretion during 24 hrs, lean body mass, body rat, and nitrogen balance, were measured during the last 5 days of each experimental period. DES implantation increased the body weight of the ram by 10.4% and caused no significant change in total body water, body ash, or total muscle mass. However, body fat increased significantly. The efficiency of nitrogen utilization also increased significantly although nitrogen intake did not change. The maximum effects of DES were observed at the end of the second experimental period. Effect of Some Estrogens on Rumen Metabolism. Three DES treated and three untreated cross bred Egyptian rams were used for studying the effect of DES on rumen microorganisms. Ruminal activity, judged by the diurnal concentrations of volatile fatty acids (VFA) and ammonia-N determined 3 and 6 weeks after DES implantation, was greater in treated animals. When rumen contents from fistulated sheep were incubated in vitro with stilbestrol dipropionate (SDP), DES, and Estradiol dipropionate (EDP), a significant increase in the number and size of rumen ciliate protozoa was observed. The extent of increase varied according to the type and concentrations of added hormones and type of rumen protozoa. Further in vitro experiments indicated that the addition of DES, SDP, and EDP promoted the fermentation of starch by washed suspensions of mixed populations of ciliate protozoa. EDP seemed to show the greatest effect in stimulating VFA production by the protozoal cells.