Evaluation of Synchronization of Oestrus Based on Gonadotrophin-releasing Hormone and Its Potential Use for Fixed-Time Breeding in Tuli Beef Cows

Author： Muruvi W.

Publisher： Springer Publishing Company

ISSN： 0049-4747

Source： Tropical Animal Health and Production, Vol.33, Iss.5, 2001-10, pp. : 431-440

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

The objective of the experiment was to compare the reproductive post-partum performance of beef cows synchronized for oestrus using prostaglandin F_2α (PGF_2α) alone or with a gonadotrophin-releasing hormone (GnRH)-based drug. Fifty-five post-partum lactating Tuli cows were randomly allocated to three groups. Two groups were synchronized using either two injections of PGF_2α (500 μg Prosolvin per injection) given 11 days apart (group 1), or GnRH (12.5 μg Receptal per injection) followed 6 days later by an injection of 500 μg PGF_2α (group 2). The cows were bred by artificial insemination 12 h after they were observed in oestrus. Group 3 was synchronized as for group 2, but a second injection of GnRH was given 54 h after the PGF_2α injection, at which time the cows were bred by artificial insemination (AI) without detection of oestrus. Blood samples were taken from the cows in group 3 and analysed for progesterone concentration to establish which cows were cycling and in oestrus before and at the time of breeding. Detection of oestrus and breeding by AI was done over 60 days. There were no significant differences (p>0.05) among the three groups in the first service and total conception rates. The percentage of cows in oestrus within 10 days of the synchronization treatment was not significantly different (p>0.05) between groups 1 and 2. The progesterone concentrations in the cows in group 3 showed that only those that were cycling at the start of the experiment responded to the synchronization treatment and conceived after fixed-time breeding. These results suggest that combinations of PGF_2α and GnRH may be of value in synchronizing oestrus and controlling breeding in Tuli cows. However, the benefit might be greater if only cows that are known to be cycling are bred in this way.