Enhancing the rate of recovery and quality of the embryos in repeat breeding cows by using a GnRH analogue injection at mid-luteal phase prior to breeding

Abstract

Nonsurgical embryo collections were made 11 days after AI from a total of 101 repeat breeding dairy cows over two complete years. The 101 cows were randomly assigned to 1) control (n =52) or 2) treated (n= 49) groups. After a third unsuccessful AI or more (with previous regular intervals between AI), no insemination took place at the following heat. Then at Day 12 (day 0 = estrus), the former received 5 ml injection i.m. of a saline solution (placebo) and the treated group was injected with 20 μg of a GnRH analogue (Buserelin, Hoe 766). The cows were inseminated on the following estrus with semen of average or above fertility. The GnRH analogue-treated group had a much higher recovery rate of embryos than the controls (65% vs 32%, p<0.005). Similarly the treated group had 91% good embryos (fertilized ova with the appropriate stage of development) out of those recovered; this rate was much higher than that of the controls (57%; P<0.05), resulting in 59% of good embryos per collected treated cows versus 19% in the controls (p<0.001). Practically, these data prove the benefits of this GnRH analogue therapy at mid-luteal phase before AI in nonsuperovulated repeat breeding bovines.