Effect of GnRH treatment at embryo transfer on pregnancy rate and early embryonic death of Holstein-Friesian cows
Journal of Kerbala for Agricultural Sciences,
2018, Volume 5, Issue 5, Pages 690-696
AbstractThis study was undertaken to explore the influence of gonadotropin-releasing hormone; GnRH treatment at embryo transfer on pregnancy rate and early embryonic mortalities of Holstein-Friesian cows. This study was executed at the Department of Artificial insemination, Directorate of Animal Resource, Ministry of Agriculture using 58 Holstein-Friesian cows prepared for embryo transfer. The cows were randomly distributed into two groups following their normal estrus cycle. The first group (n=21) was left without any treatment and regarded as control (T1), while the second group (n=2) was injected with GnRH (10 µg per cow; T2) at the 7th day of their normal estrus cycle, and the estrus was monitored for 6 sequential cycles. The pregnancy was checked at days 45, 60 and 120 post-mating (PM) using rectal palpation. Pregnancy and calving rates as well as early embryonic mortality percentage were estimated for all cows. The bulls that born for the embryo transfer (n=5) was used for artificially inseminated of cows following evaluation of their semen. Greater pregnancy rates were observed for the GnRH-treated cows (T2) at days 45 (43. 24%) and 120 (37.84%) PM as compared with T1 group (33.33 and 28.57% respectively). Concomitantly, the early embryonic mortality percentage was reduced in T2 groups (56.76%) in comparison with the T1 group (66.76%) at day 45 PM. Greater (P≤ 0.05) calving rate was recorded for T2 group (37.84%) as compared with T1 group (28.57%). Using of GnRH treatment at embryo transfer has positive economic return resulting from higher pregnancy and calving rates as well as reducing early embryonic mortality percentage. Four bulls from the T2 group were born versus one bull born from T1 group. These bulls was used currently for semen collection and cryopreservation at the Department of Artificial Insemination, and produced 158,016 and 39,504 semen straws respectively with net profit of US$ 701,227 for T2 group and US$147,228 for T1 group.
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