Resumo

LOPEZ ORDAZ, Rufino et al. Effects of Bos taurus gene percentage on reproductive performance of crossbred cows in the humid tropics of Mexico. Rev. mex. de cienc. pecuarias [online]. 2010, vol.1, n.4, pp.325-336. ISSN 2448-6698.

The objective of the present study was to determine the best possible percentage of Bos taurus (BT) genes on age-at-first-calving (AFC), days to first post-partum service (DFPS), days open (DO) and calving interval (CI) in crossbred cows. Data was collected in a typical commercial dairy farm of Tabasco on 1,704 full lactations (270-d) from 677 cows ranging between 100 % Bos taurus (BT) and 100 % Bos indicus (BI). Data analysis was carried out through a mixed model which included the following unchanging effects: calving number, calving year and season and the random effects of sire, cow within sire, with BT gene percentage effect as covariable. Fourth calving cows showed a lower DFPS (P<0.05) than second and third calving animals and these were different to primiparous. Correspondingly, second or more calving cows showed shorter DO and CI (P<0.05) than first calving cows. AFC was shortest in 49 % BT genes, increasing to 36 mo as this percentage increased. Cows having 100 % BI genes showed 106 d DFPS, 166 d DO and 14.6 mo CI, all of them shorter than in crossbred cows. As a conclusion, it can be stated that cows having 50 % BT genes show longer DFPS, DO and CI and shorter AFC, therefore being the best genotype for dairy herds in the humid tropics.

Palavras-chave : Crossbreeding; Tropical bovines; Reproductive performance.

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