Article

Comparison of the effects of gonadotropin-releasing hormone, human chorionic gonadotropin or progesterone on pregnancy per artificial insemination in repeat-breeder dairy cows

Department of Clinical Sciences, School of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, P.O. Box: 91775-1793, Iran.
Research in Veterinary Science (Impact Factor: 1.41). 04/2011; 90(2):312-5. DOI: 10.1016/j.rvsc.2010.05.025
Source: PubMed

ABSTRACT

Three different treatments were compared to improve pregnancy per artificial insemination (P/AI) in repeat-breeder (RB) dairy cows. All cows (n=103) were assigned to one of four groups: (1) gonadotropin-releasing hormone (GnRH); (2) human chorionic gonadotropin (hCG); (3) once-used controlled internal drug release (CIDR) device; and (4) control. All treatments performed 5-6days after artificial insemination (AI) and milk samples were collected just before treatment for progesterone assays. There were no significant differences in milk fat progesterone concentration among trial groups. Cows were observed for estrus signs thrice daily. Pregnancy per AI on day 45 in hCG and CIDR groups were significantly higher than GnRH and control groups (60.0% and 56.0% vs. 26.9% and 29.6%, respectively), but there were no differences in P/AI between GnRH and control groups. There were also no significant differences between hCG and CIDR groups. Milk fat progesterone concentrations were compared between pregnant and non-pregnant cows in each group and only in the hCG group it was significantly lower in pregnant cows. In conclusion, treating repeat-breeder cows with hCG or once-used CIDR 5-6days after AI improved P/AI.

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    • "Recently, Khoramian et al. [24] showed in a small number of animals that treatment with human chorionic gonadotrophin or intravaginal progesterone devices during the very early stages of pregnancy improved fertility in repeat breeders compared with control cows, in agreement with prior reports [25]. Such treatments are thought to rescue cows with poor luteal activity [26]. "
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