Resumo

LOPEZ-ORDAZ, R.; VITE-CRISTOBAL, C.; GARCIA-MUNIZ, J.G.  e  MARTINEZ-HERNANDEZ, P.A.. Reproductive and milk yield performance of crossbred cows with different proportions of Bos taurus genes. Arch. zootec. [online]. 2009, vol.58, n.224, pp.683-694. ISSN 1885-4494.

The objective of this study was to evaluate the effect of environmental factors, and to determine the optimum proportion of Bos taurus (BT) genes on milk yield (MY) and reproductive traits of ¾ Holstein (H) x ¼ Zebú (Z), 3H1Z; ¾ Swiss (S) x ¼ Z, 3S1Z; ½ H x ½ Z, HZ; y ½ S x ½ Z, SZ; crossbred cows. Lactation records (n= 276) of 69 cows in three commercial dual-purpose farms of Veracruz, Mexico, were used. Total MY (TMY), daily MY (DMY), calving interval MY (CIMY), MY at lactation peak (PMY), days to peak MY (DPMY), lactation length (LL), age at-first calving (AFC), days open (DO), and calving interval (CI), were analyzed. The obtained results showed that the racial group affected (p<0.05) TMY and LL solely; cows 3H1Z did produce 12, 12, and 34% more milk than 3S1Z, HZ and SZ, respectively. Likewise, HZ cows had better reproductive performance (p<0.05) than 3H1Z, 3S1Z, and SZ, with earlier AFC, and shorter DO and CI. In addition, cows did reach maximum TMY (4859 kg), DPMY (39.6 d), LL (376.8 d), DO (180.7 d) and CI (463.4 d) when the proportion of Bos taurus gene was 75%. In conclusion, cows 3H1Z fed tropical forages and supplemented with 18% CP concentrates had better performance in TMY and moderate LL, DO and CI than 3S1Z, HZ and SZ. Holstein x Zebu crossbreeding cows had higher reproductive ability than those with genes of Swiss. Results from this study suggest crossbred cows with 75% BT genes as the most appropriate to produce milk in the tropical conditions of Northern Veracruz.

Palavras-chave : Dual-purpose cattle; Crossbreeding; Supplementation.

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