Mating behaviour and testis growth of Finnish Landrace, Tasmanian Merino and crossbred rams

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Abstract
SUMMARY: Twenty-one of 23 Finn and 23 of 28 Finn-Merino crossbred springborn males mated at about 6 mo of age during their first breeding season, whereas all of nine Merino males did not do so until the second breeding season at about 18 mo of age. The diameter of the testes of Finn and crossbred males at 6 mo of age was a higher proportion of their diameter at 18 mo than was that of the Merinos. Seasonal studies showed an earlier increase in the testis diameter of Merino males than that of the Finns or crossbred. At all seasons, the intensity of mating behaviour of Merinos was lower than that of the other breed types.The results support the hypothesis that the reproductive activity of males is correlated with that of related females, and the use of male reproductive activity as a criterion for genetic selection for that of the female is discussed.