Eventos reproductivos de vacas con diferente porcentaje de genes Bos taurus en el trópico mexicano

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.