Pregnancy rate in Bulgarian White milk goats with natural and synchronized estrus after artificial insemination by frozen semen during breeding season

ObjectiveTo determine the pregnancy rate (PR) in goats with natural and synchronized estrus after artificial insemination (AI) by frozen semen during breeding season.MethodsThe experiment was carried out with 89 Bulgarian White milk goats divided as follows: group I (n = 54) animals with natural estrus (NE), allocated in two subgroups treated with or not with GnRH after the last insemination and group II (n = 35) goats with synchronized estrus by intravaginal sponges and injection of PMSG after the sponges withdrawal. Both groups were also divided according to number AI – single or double. All animals in group I were inseminated by frozen semen after proved standing estrus as a part of goats received second insemination 8 h later. Single insemination in synchronized goats was done 48 and double at 48 and 56 h after the sponge removal. Ultrasound pregnancy diagnosis was performed on day 30 post insemination.ResultsThe pregnant animals in both subgroups with natural estrus and single AI (33.3% and 45.2%) were less than those (58.3%) after estrus synchronization (ES). The pregnancy rate in synchronized goats with double insemination was 63.6%, whereas in animals with natural estrus varied from 40 to 50%. Overall pregnancy rate in group I (60%) was significantly (P < 0.05) higher than (37%) in goats without GnRH treatment.ConclusionThe goats with natural estrus and GnRH treatment tend to enhance pregnancy rate after double artificial insemination 8 h apart. The insemination number has no significant impact on pregnancy rate in synchronized goats as the overall pregnancy rate is better than in animals with natural estrus without GnRH administration.