Effect of Human Chorionic Gonadotropin on Late Embryonic Death in Holstein Dairy Cows

The objective of this study was to determine whether administration of 1500 IU of hCG on Day 29±1 after artificial insemination (AI) would reduce pregnancy loss by inducing accessory corpora lutea and increasing serum progesterone concentrations in dairy cattle.

Three hundred and seventy lactating Holstein dairy cows from a farm with 1200 lactating cows were randomly assigned to a treatment and a control group. The animals of the treatment group (n=185) received hCG 1500 IU (IM), while in the control group they received the control group (n=185) received no treatment. Ovarian structures, serum progesterone levels and pregnancy status were determined on days 29±1 and 42, respectively.

The Progesterone concentration on day 42 was higher (P=0.005) for cows in the hCG group (14.9±0.7 mg/ml) compared to the control group (12.1±0.7ng/ml). On day 42, the number of accessory CLs  for cows in the hCG group (1.6±0.04) were higher (p˂0.0001) than cows in the control group (1.2±0.04). A Positive correlation was detected between the circulating progesterone and CL volume in the hCG group (r=0.47, p=0.001). Pregnancy losses did not differ between days 29±1 and 42 both in the control (7.6%) and in the hCG group (5.9%).

It was concluded that the administration of hCG (1500 IU) on day 29±1 of pregnancy in lactating dairy cows increased the number of corpora lutea and serum progesterone concentration but did not have any effect on pregnancy loss rate or pregnancy losses.