Using an on-farm progeny testing scheme developed on the Lacaune Milking Breed, we have studied the relationship between testis size of young males tested on individual performance, and natural or induced prolificacy of their daughters. In the first case <GG to 219 sires with an average of 10 daughters fecundated on natural oestrus), phenotypic sire-daughters correlations are never significant. In the second case (83 to 302 sires with 10 to 13 daughters), the daughters’ induced prolificacy shows a significant correlation (phenotypic and genetic) with testis diameter on day 140 or at 45 kg, and testicular growth between days 80 and 140. Heritability of testis diameter (TO) is rather high (0.20 on day 80; 0.48 on day 140) and is comparable to that of live weights (LW ) (0.30 to 0.36). Genetic correlation between TO and LW increases with age: 0.39 on day 80; 0.81 on day 140.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XI. Genetics of reproduction, lactation, growth, adaptation, disease, and parasite resistance., , 72–77, 1986
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