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The Effects of Diethylstilbestrol, Testosterone, and Progesterone on Growth and Fattening and Certain Carcass Characteristics of Western Lambs^{1, 2,}

University of Wisconsin

Abstract

Two experiments involving 400 western lambs, 100 ewes and 100 wethers in each experiment, were conducted to determine the effects of stilbestrol, testosterone, and progesterone on growth and fattening and on certain carcass characteristics when each lamb was taken to the same final weight of 100 pounds. The following effects of stilbestrol treatment were indicated when all animals were fed to this same final weight.

1. Greater rate of gain either when controls and treated animals are both self-fed or when feed consumption is limited to the amount that either will consume.
   
2. Greater feed consumption when self-fed.
   
3. Greater economy of gain; shorter period of time on feed to reach market weight.
   
4. Lower live grade but not consistently detectable by the grader.
   
5. Lower carcass grade.
   
6. Lower dressing percentage.
   
7. Smaller amount of external fat.
   
8. Greater moisture content of external fat.
   
9. No difference in muscle or internal fat.
   
10. Greater amount of bone and connective tissue when considered together.
    
11. Lower feed cost and slightly lower selling price but a greater profit per lamb.
    

Testosterone tended to inhibit the action of stilbestrol on bone and connective tissue when administered simultaneously with stilbestrol. Neither testosterone nor progesterone tended to modify the other actions of stilbestrol.

The slight effects of testosterone on growth and fattening and certain carcass characteristics were qualitatively of the same character as those of stilbestrol but were much less marked. Progesterone had no detectable effects on these characteristics.

A comparison of the performance of wether and ewe lambs shows for the former:

1. Greater daily feed consumption.
   
2. Greater daily gain.
   
3. Greater economy of gain.
   
4. Lower live grade.
   
5. Lower carcass grade.
   
6. Less finish on carcass.
   
7. Less external fat.
   
8. Greater water content in external fat.
   

¹ Paper from the Department of Genetics and Animal Husbandry (Genetics No. 494). Published with the approval of the Director of Wisconsin Agricultural Experiment Station.

² The authors are grateful to Oscar Mayer and Company for their cooperation in making this study possible.

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