EFFECT OF SEASON OF BIRTH ON SEASON OF CALVING AND AGE AT FIRST CALVING IN BUFFALO HEIFERS

摘要

Records for 589 Bulgarian Murrah heifers from the buffalo herd of Agricultural Institute - Shumen, borne within the period 1982-2010, were processed using the software products LSMLMW and MIXMDL (Harvey, 1990) with the aim to study the effect of season of birth on season of calving and age at first calving (AFC). The operational model also included the factors period of birth, season of conception, and period of conception. It was established that the factor season of birth has significant effect onthe variation of the trait AFC (P=0.0025), expressed in lower calving age in the heifers borne in summer and autumn. The influence of season of calving on AFC has shown to be more pronounced in the winter-borne heifers, the age of the autumn calvers being significantly lowest; as well as in the spring-borne ones, where the age of the summer calvers is highest. The heifers borne in summer are characterized by the typical for the breed spring-summer seasonality of calving, those borne in spring calve chiefly in spring, while the calvings of those borne in autumn and winter are mostly in summer.