Studies on west African dwarf sheep: incidence of perinatal mortality in Nigeria.

A study was conducted on the incidence of perinatal lamb mortality with extension up to 30 days of age (PMR 30) in West African Dwarf sheep in Ibadan, Nigeria, over a three year period. An overall PMR 30 of 19.9% was recorded. This consisted of an abortion rate of 3.0%, a still-birth rate of 2.7% and a neonatal lamb mortality rate of 15.6% up to 30 days of age (LMR). Abortion rate was significantly higher in pregnancies with multiple foetuses and during the dry sea son (P less than 0.01 and P less than 0.05 respectively). Conversely, the still-birth rate was slightly higher in single lambs (P less than 0.05). The LMR for males (17.1%) and that for females (13.4%) were not significantly (P greater than 0.05) different. Also the LMR for single-born (14.4%), twin-born (15.4%) and triplets (26.7%) did not significantly differ (P greater than 0.05). The optimum birth weight for survival of the breed appeared to be 2.6 to 3 kg. Regression analysis showed a 28.3% increase in birth weight and all live-born lambs with birth weights of 0.9 kg or less died during the neonatal period. About two-thirds (67.2%) of all neonatal deaths occurred during the first week of life. There was no significant effect of season on LMR. The perinatal mortality rates recorded among West African Dwarf sheep in this study do not seem to significantly differ from corresponding figures recorded in other parts of the world.