Influência da época de estação de monta e idade à cobrição sobre características reprodutivas de novilhas nelore criadas em regiões semiáridas

Abstract

The breeding season is one of the steps to increase the productive efficiency of beef cattle breeding systems. When defining a specific period for the breeding season, it is possible to discipline and strategically concentrate the execution of the different managements of the herd, according to the objectives and directions of the property. The objective was to verify the effect of the breeding season and age on the breeding on reproductive characteristics of Nellore heifers, raised in conditions of the semi-arid region of Minas Gerais. Reproductive characteristics of heifers submitted to two breeding seasons at different times were evaluated: conventional, in which two groups of heifers aged 14 to 17 months and the second over 24 months were evaluated; in the second breeding season, two groups of heifers, the first aged 14 to 16.9 months and the second aged 17 to 19 months. When compared the breeding seasons, it was observed that the breeding season 1 in the first delivery was superior with an average of 111, 58 days (3.7 months), while in the breeding season 2, 271.31 days (9 months). And, when observing the service period in the second delivery, no difference was observed between the seasons, with an average of 80 to 100 days. The service period of the first delivery in the conventional breeding season was shorter (P<0,05) in relation to the service period of the first delivery in the additional breeding season. This difference can be attributed to the different ages that were subjected to mating. The deleterious effects on the reproductive efficiency of the youngest mated heifers and in an unconventional breeding season are only manifested in the beginning of the reproductive life.