Age related effect on pregnancy rate and pregnancy wastage in thoroughbred mares bred during different heat cycles postpartum under subtropical conditions

Abstract

This investigation reports the correlation of age and heat cycles on the pregnancy rate and pregnancy wastage in Thoroughbred mares bred during foal heat (FH), second heat (SH) and third heat (TH) in a commercial stud farm in Kunigal, Karnataka, India. The pregnancy rate was not influenced by the different heat cycles post partum. The correlation of mare’s age on the pregnancy rate and heat cycles showed that the age of the mares significantly influenced the conception rate in mares bred during FH and TH postpartum, while it was not significant in SH. The mare’s age did not influence the pregnancy wastage significantly in mares bred during FH, SH or TH, but the FH bred mares showed significantly higher early embryonic mortality rate than SH and TH bred mares. While the abortion rate was not influenced by the different heat cycles postpartum. In conclusion, the reproductive efficiency with respect to pregnancy rate was age dependent, while pregnancy wastage looked independent of age in Thoroughbred mares bred on FH, SH and TH. The optimum age for better pregnancy rate was between 6 and 13 years in all the heat cycles and aged mares (>18 years old) showed reduced pregnancy rate due to increased pregnancy losses.