A short note: lack of effect of post-AI hCG or GnRH treatment on embryonic mortality in dairy cattle

The aim of the present trial was to test the effects of two treatments in dairy cows, in an attempt to sustain the circulating progesterone levels and hence possibly reduce the embryonic mortality rates. Treatment 1 consisted of a 3000 IU hCG i.m. injection at day 4 (D4) after artificial insemination (AI) and treatment 2 of a GnRH i.m. injection (Buserelin, 10 mug) on day 12 after AI (D12). A set of 156 Holstein females from the same herd were assigned to one of the four treatments: hCG D4 (n = 52), placebo D4 (n = 25), GnRH D12 (n = 52), placebo D12 (n = 27). They were served for the first. second or third time or more and monitored regularly via a herd fertility survey. Pregnancy status was assessed by rectal palpation at day 45 after Al. The overall mean pregnancy rate (PR) was 42% and there was no significant difference between treatment groups or between ranks of Al (P > 0.05). These data show that stimulation of luteal function following ovulation and Al did not result in any reduction of the embryonic mortality rates. (C) 2001 Elsevier Science BY. All rights reserved.