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Estimates of genetic correlations between sire scrotal circumference and offspring age at first calving in nellore cattle

R. Martins Filho^I; R.B. Lôbo^II

^IDepartamento de Zootecnia, Centro de Ciências Agrárias, UFPi, 64000 Teresina, PI, Brasil
^IIDepartamento de Genética, Faculdade de Medicina de Ribeirão Preto, USP, 14049 Ribeirão Preto, SP, Brasil. Send correspondence to R.B.L.

ABSTRACT

The scrotal circumference (SC) of 3,393 young bulls and the age at first calving (AFC) of 703 daugther cows, were recorded during 1984 to 1989 in Nellore cattle in Northwest São Paulo State, Brazil. The least-squares means and standard errors were 31.03 ± 0.93 cm and 35.81 ± 0.17 months for SC and AFC, respectively. Heritabilities, estimated from paternal half-sib correlations were 0.36 ± 0.07 for SC and 0.19 ± 0.09 for AFC. The genetic correlation between SC and AFC estimated by Yamada's (Jpn. J. Gen. 37: 498-509, 1962) formula was -0.44. This suggests the possibility of earlier selection for female fertility based on the scrotal circumference of the sire.

Keywords: Size scrotal; Nellore cattle.

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