Synchronization of oestrus cycle in cattle with prostaglandin F2 alfa. III. Breeding at a predetermined time following PGF2 alfa in a Nelore herd

Abstract

60 Nelore cows, without previous control regarding oestrous cycle, were assigned randomly to two treatments. Treatment 1 (n =30) consisted in an injection of 4 mg PGF2 alfa in 2 ml o f Phosphate-Buffer into the uterine horn ipsilateral to the corpus luteum, followed by A.I. at 72 and 80 hs postPGF2 alfa. Treatment 2 (n = 30) serving as control was double A.I. also with an interval of 8 hs at standing estrus during a 60-day period. Conception rate, through rectal palpation was 20.0% (6 pregnant cows) in treatment I and 26.6% (8 pregnant cows) in treatment 2. These results, although too low, seems to indicate the similarity in fertility between control animals and those inseminated at a predetermined time, without estrus detection. The time taken for treatment of Nelore cows and of European crossed cows with zebu (in a previous paper) was recorded. Prostaglandin infusion including ovarian palpation took 7.5 Nelore cows per hour and 12 crossed cows per hour, respectively.