Effect of lecirelin acetate, hCG or progesterone administration on day 7 post-insemination on conception rate and progesterone concentration in cross-bred cattle

The present study was designed to evaluate the effect of administration of lecirelin acetate, hCG and progesterone after AI on ovarian picture, serum progesterone concentrations and first service conception rate in cross-bred cattle. A total of 160 lactating cross bred (Friesian x Sahiwal) cattle were divided into 4 groups after AI. The groups were treated as follows: control (injected i.m with normal saline 2ml, n=40), d 7-LA (injected i.m with lecirelin acetate100 μg, n=40), d 7-hCG (injected with hCG 3300 IU, n=40) and d 7-P4 (injected i.m with Progesterone 0.5 mg daily for 4 days, n=40) group. The hormonal treatments were given to animals on day 7 after AI. The ultrasonography and blood sampling was done before treatment and then 7 days later. All animals were examined for pregnancy through ultrasonography at 40 ± 1 day after AI. The diameter of SCL on 7 days after treatment was higher (P < 0.01) in group d 7-LA and d 7-hCG group cows as compared to control cows. In contrast, the diameter of SCL in d 7P4 treated cows did not differ from control cows. Formation of ACL was observed only in 50 % & 80 % cows in d 7-LA and d 7-hCG group respectively. No ACL was observed in control and d 7P4 cattle on day 7 after treatment. The P4 concentrations were significantly higher (P < 0.01) in d 7-hCG treated cattle as compared to control at 7 days after treatment. As compared to 10 percent First Service Conception Rate (FSCR) in controls, an increase (P < 0.05) of 50 percent and 40 percent was observed in each treatment group (d 7-hCG & d 7-LA), non-significant (P > 0.05) difference in FSCR was observed between control and d 7-P4 group. It was concluded that the use of hCG or LA, 7 days after AI is a beneficial tool to improve conception rate in cross-bred cattle whereas use of parental P4 post-breeding has no effect on SCL diameter and conception rate.