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Reproductive development of Gyr young bulls selected for milk production

This study aimed to identify precocious and non-precocious Gyr young bulls according to puberty and evaluate differences during their reproductive development. Live weight and scrotal circumference were measured monthly with collection and evaluation of semen samples from 16 animals, from 13 to 23 months of age. Precocious animals were lighter at the pre-puberty period and younger at puberty and sexual maturity, 17.0 and 18.7 months, respectively, regarding non-precocious, 19.2 and 20.5 months, respectively. Sperm motility increased during pre-puberty two months earlier for precocious animals, 1.75% to 18.4% from 14 to 17 months, regarding non-precocious, 2.5% to 12.4% from 16 to 18 months. Sperm concentration increase occurred earlier in precocious animals, and was higher, 669 million/mL, at 23 months of age in relation to non-precocious animals, 66.7 million/mL. The differences in reproductive development of both groups were favorable for precocious animals and indicate that the selection for precocious sexual maturity is advised to anticipate the reproductive phase of Gyr bulls.

bovine; precocity; puberty; semen evaluation; zebu

Universidade Federal de Minas Gerais, Escola de Veterinária Caixa Postal 567, 30123-970 Belo Horizonte MG - Brazil, Tel.: (55 31) 3409-2041, Tel.: (55 31) 3409-2042 - Belo Horizonte - MG - Brazil