The effects of GnRH and hCG used during and after artificial insemination on blood serum progesterone levels and pregnancy rate in cows

In dairy cattle farming, it is very important to have a calf from a cow within a year and provide it to remain pregnant at first insemination after parturition. For this purpose, there should not be any problem in the herd regarding reproductivity. Many diseases and environmental factors can decrease fertility in postparturient cows. Recently, different techniques have been used to increase the fertility rate in lactating dairy cows. GnRH and hCG hormone administrations are most commonly used method to arrange maternal and fetal relationship, retard or inhibit luteinization, increase the concentration of progesterone hormone released by corpus luteum and to stimulate the formation of accessory corpus luteum. These applications are performed before the insemination, during insemination or between 1-15 days post-insemination.In this study, it was aimed at evaluating the effects of the administrations of GnRH or hCG?s alone and together during and at the 12th day of insemination on pregnancy rates and serum progesterone in cows. As the materials of this study, 73 Holstein and 2 Brown Swiss cows of 2-3 years old with no reproductivity problem were used.All animals were divided randomly into five groups and inseminated in the first oestrus period between the postpartum 40th ? 80th days. The first group cows received 10 µg buserelin acetate both following and the 12th days of the insemination. The second group was given 10 µg buserelin acetate during the insemination and 1.500 IU hCG at the 12th day after the insemination. In the third group, hCG was applied immediately after and on the 12th day of the insemination. The fourth group cows were administered hCG immediately after and GnRH on the 12th day of the insemination. The last group was left as control.The gestation of the cows was diagnosed between 45- 60 after insemination through rectal examination. Six cows from each of the first, fourth and fifth groups and 7 cows from each of the second and third groups were pregnant while the remaining 9 in the first three and 8 in the last two groups were not pregnant.As a result, in this study, it is identified that GnRH and hCG administration during and at the 12th days after insemination period had no effect on pregnancy rate and caused no statistically significant alteration in progesterone level.