Environmental and genetic factors affecting Bos indicus pre-weaning performance and calving interval in southeast Mexico

Data on pre-weaning performance and calving in a ranch In Yucatan, Mexico w ere analyzed. The objective was to study the effect of the breed, calf or c ow, as well as certain environment factors of birth weight (BW), weaning we ight adjusted at 249 days (AWW), pre-weaning daily gain (PDG) and calving i nterval (CI). The climate in the region is tropical sub-humid. Animals graz ed zacate Panicum maximum during the night. The statistical model included the effect of birth or calving period (1973-1976, 1977-1980, 1981-1984 and 1985-1987), season (February-April, May-July, August-October and November-J anuary) sex of calf, parity (1,2... 5), breed group of the calf (Brahman (B ), Indubrazil (I), Gyr (G), Commercial Zebu (Z) and their inbreeding, and f irst-order interactions. For calving interval(CI) the effect of calf sex an d breed of (B, I, G and Z) cow were also considered. The average and standa rd deviations were 32.09 +/- 3.52 kg, 202.84 +/- 27.19 kg, 686 +/- 105 g an d 442.98 +/- 74.46 days, for BW, AWW, PDG and CI, respectively. The period affected PWW and PDG (P < 0.01), while the season affected PWW, PDG and Ci (P < 0.01). The sex of the calf and parity affected all the variables studi ed (P < 0.05). Breed group only affected BW.