Effect of the anticipation of the of application of prostaglandin on the reproductive performance of beef cattle cows submitted to artificial insemination in fixed time

Abstract

The effect of the anticipation of the application of prostaglandin F2alfa (PGF2a) was evaluated for the use of fixed time artificial insemination (FTAI). Three hundred and six Aberdeen Angus cows, aged between 3 and 6 years old, with calves at side had been used. The animals were randomly distributed in 4 groups. All animals were synchronized through intravaginal device with progesterone for 8 days (CIDR®), estradiol and PGF2a. The treatments was designed in a factorial arrangement 2 x 2 (CIDR® 1º x 2º use) and the day of the PGF2a application (6.5th x 8 th day). Seven days after the FTAI clean up bulls were joined until the ending of the breeding season. The conception rate to the FTAI and final pregnancy rate were evaluated. The anticipation of the application of the PGF2a (6.5th day) had significant effect (P<0.05) on the conception rate at the FTAI and final pregnancy rate, respectively of 60.9% and 89.1% when compared with the animals that had received PGF2a in the 8 th day, respectively of 49.3% and 76.7%. The 1th or 2th use of the intravaginal device had presented differences (P<0.05) in the conception rate (61.1% and 49.7%), however without effect in the final pregnancy (P>0.05), respectively of 82.6 and 83.4%. The anticipation of the application of the PGF2a increased the pregnancy rate significantly at the FTAI and the final pregnancy. The previous use of the CIDR® affected the percentage of pregnancy at the FTAI, but it did not affect the final pregnancy. The cow’s age and the body condition score had not effect on the conception rate to the FTAI and the final pregnancy.