Studies on reproductive endocrinology and factors influencing fertility in dairy and draught buffaloes in Sri Lanka

Analysis of calving data on state farms and a field survey in village herds were used in conjunction with radioimmunoassay for plasma and milk progesterone, rectal palpation and other clinical observations to study reproductive functions of river type (Murrah) and indigenous (Lanka) buffaloes. A marked seasonality of calvings and conceptions was observed in both types, with the highest percentage of conceptions occurring 2-5 months after the annual peak in rainfall. In Murrah buffaloes on two state farms the mean ages at first calving were 51.0 and 52.1 months, and the calving interval 17.5 months. Progesterone profiles during the postpartum period showed ovarian inactivity to be the major problem. Most animals remained anoestrous for 100-200 days, but conceived at the first or second postpartum ovulation. Treatment with GnRH during anoestrus had no beneficial effect. Hormonal changes during normal and prostaglandin-synchronized oestrous cycles, pregnancy and the peripartal period were basically similar to those in cattle, with some differences in absolute values. Gestation length (mean+-SD) was 309.9+-8.8 days. In Lanka buffaloes under village conditions marked differences in fertility were evident between certain districts and agro-ecological zones. Mean ages at first calving ranged from 41.4-49 months, calving intervals from 13-23.5 months, and annual calving rates from 42-75%. Ovarian inactivity was the major problem in areas with poor fertility, and was influenced by suckling management and usage for draught and milk. At one village location with high fertility 70% of the animals had calving to first service intervals less than 60 days, first service conception rate of 65.5% and 1.4 services per conception. The mean (+-SD) interval from calving to first elevation of progesterone in milk was 55.2+-18.6 days, the calving interval 393.7+-79.8 days, and the gestation length 316.9+-9.9 days. (author)