Comportamiento reproductivo de un hato Angus en el Bajío mexicano.

The objective of the present study was to evaluate some environmental factors on the reproductive performance of an Angus herd under grassing conditions in the Mexican Bajio. Data of a pure breeding exploitation of the municipality of Leon, Guanajuato were used. The region has a temperate sub-humid climate with rains in summer; the animals used were fed in a free range pasture. Breeding takes place during two periods, one from May to July and another from December to January and weaning occurs approximately at seven months of age. The data were analyzed using the method of least square to determine the effect of parity year (PY= 1991-2007), parity season (PS = cold: December-March; dry: April-June; and rain: July-November), and parity number (PN = 1, 2,…≥9). The response variables studied were age at fist calving (AFC), and calving interval (CI). The overall means and standard deviations for AFC and CI were 793.5 ± 165.8 and 407.5 ± 83.5 days. The PY, PS and PN affected (P < 0.01) the CI. From these results it might be concluded that the year, season and parity number are important in the reproductive performance of the Angus cows under range management conditions. [ABSTRACT FROM AUTHOR]