To assess the effects of selection fo r high and low p ro lific a c y on scrotal circu m feren ce(S C ) and lib id o in R a m b o u illet rams two t r i a l s were conducted. Three lin e s , a high lin e (H ), low lin e (L ) and random bred c o n tro l lin e (C ) were e s ta b lis h e d in 1968. P rim ary s e le c tio n c r ite r io n fo r rams used in H and L lin e s was t h e ir dams re p ro d u ctive perform ance. In t r i a l I , 4 se lecte d rams from each lin e were penned in d iv id u a lly w ith 4 ovarectomized estrogenized(OE) ewes fo r 30 m inutes and number o f m ounts(M), and number o f se rv ic es (S ) were recorded and SC was measured. Rams were tested every 2 weeks fo r a year. Line affected SC(P<.01), M(P<.01) and S(P<.10). Least-squares means+SE fo r H, L and C, re s p e c tiv e ly , fo r SC were 33-2±.2, 35.5±.2 and 33-7±2 cm, fo r M were 18.1±1, 9.9±1 and 14.2±1, fo r S were 3-0±.2, 2.4±.2 and 2.6±.2. T r ia l I I used 96 ram lam s to e v a lu a te the e ffe c t o f s e le c tio n on SC, M, and T. Ram lambs were in d iv id u a lly penned fo r 15 minutes w ith 4 0E ewes, M, S and SC were recorded. Ram lambs were tested every 2 weeks fo r 20 weeks (10 periods). High lin e rams had la rg e r (P<.05) SC a t periods 3, 4, 5 and 8 more M(P<.05) a t p eriod 3 through 7 and 9 than did the L or C ram lambs which were not d iffe re n t. L rams had fe w e r S (P<.05) than H or C rams fo r p erio d s 6, 9 and 10, which were not d iffe re n t.

P. J Burfening, D. Tulley

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 7. Symposia (1), , 536–542, 1982
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