REPRODUCTIVE EFFICIENCY OF BOS-INDICUS (ZEBU) COWS UNDER ARTIFICIAL-INSEMINATION MANAGEMENT IN ETHIOPIA

Data on 4123 inseminations from 1237 Ethiopian Arsi (Bos indicus) cows were analysed. Data were obtained from the Gobe ranch of the Ethiopian Ministry of Agriculture where cows were kept under similar management. Calving and postpartum anoestrous intervals averaged 620.9 +/- 3.8 (SEM) and 304.1 +/- 3.5 days respectively and were affected by year of calving and parity (P < 0.001). Mean service period was 58.6 +/- 2.7 days and influenced by season of first oestrus (P < 0.05). Calving interval was significantly (P < 0.001) correlated with the duration of postpartum anoestrus (r = 0.93) and length of service period (r = 0.12) but there was no significant relationship between postpartum anoestrous interval and service period duration. Only 1.6% of cows calved annually, 31.6% calved after 13-18 months, 45.6% between 19 and 24 months, and 21.2% calved over 24 months. About 47.5% of cows conceived on first service, 29.3, 21.0, 1.7 and 0.4% conceived after two to five services, respectively. Mean interval between services was 53.0 +/- 39.7 days and number of services per conception averaged 1.8 +/- 0.8. Gestation length was 280.5 +/- 3.3 days. It was concluded that long postpartum anoestrus, poor oestrus detection and low conception rates contributed to extending calving intervals.