Social dominance of female dairy goats and response to oestrous synchronisation and superovulatory treatments

Abstract

Two experiments were performed to determine if there is a relation between the goat's hierarchical position, and (1) the conception rate and litter size obtained with hormonal oestrous synchronisation treatments and fixed timed artificial insemination, and (2) the number of corpus luteum (CL) and the embryo quality obtained in superovulatory treatments during the breeding and the non-breeding seasons. In the first experiment, the success index of goats from four herds was determined, and was related to the reproductive results after oestrous hormonal synchronisation and fixed time artificial insemination. There were no significant differences in fertility ( n = 253; 49.5, 50.7 and 43.2%) or litter size ( n = 185), which was 1.6 ± 0.1, 1.8 ± 0.1, and 1.8 ± 0.1 (mean ± SEM) for Low, Medium and High ranked goats, respectively ( P > 0.1). In the second experiment, 37 and 34 superovulatory treatments were performed during the breeding and the non-breeding season, respectively. There was a link between hierarchical position and the number of corpus luteum in the non-breeding season and between dominance hierarchy and transferable embryos/fertilised embryos in the breeding season. We conclude that probably the social rank is not related to the conception rate or the litter size obtained after oestrous synchronisation treatments and fixed time artificial insemination in dairy goats under intensive reproductive management. Social hierarchy does not affect the response to superovulatory treatments in terms of the number of corpus luteum or the embryo quality during the breeding season. However, during the non-breeding season, hierarchical position may influence on the number of corpus luteum obtained.