Fertility in zebu cattle (Bos indicus) after prostaglandin administration and artificial insemination

A total of 137 cycling zebu cows, each receiving a single dose of prostagla ndin PGF(2 alpha) were used in an oestrus synchronization programme on thre e different farms. Of the cows on the three farms, 60.6 and 90.5% showed ov ert oestrus and luteolysis, respectively. Pregnancy rate to fixed time inse minations following single injection of PGF(2 alpha) was 61.4% for farm 1, significantly higher than the values of 45.7 and 46.9% for farms 2 and 3, r espectively The pregnancy rates to second service of rebred cows were 53.3, 50.0 and 50.0% for the three farms, respectively, with no significant diff erences between each. Fertility classification of the cows based on progesterone (P-4) concentrat ion showed that 6.6% of cows on the three farms were incorrectly diagnosed as having corpora lutea; 2.9% of them had incomplete luteolysis and 5.1% ma y have lost their embryos between days 21 and 45 post-insemination, The pre gnancy rate was 10% higher in the rainy season than in the dry season. Cows with body condition scores of 3 and 4 had a higher overall pregnancy rates than those with a body condition score of 2. The findings of this study further confirm the luteolytic efficacy of prost aglandin in inducing oestrus in zebu cattle and indicate that the nutrition al status of the cows must be satisfactory before embarking on oestrus sync hronization programmes.