INFLUENCE OF BIRTH WEIGHT, YEAR AND PARITY ON PREWEANING MORTALITY IN YANKASA SHEEP

Résumé

The influence of lamb birth weights, year of

birth, and parity on pre-weaning death were observed in Yankasa sheep over a period of 4 years (1989-1992) in Misau, Bauchi State, Nigeria. Of the 150 lambs observed, birth weight fell into 4 categories; upto 1.5; 1.6-2.0; 2.1-23 and 2.6 -3.0 Kg, with percentage deaths in each being 33, 34,16 and 0, respectively. The overall mean birth weight was 23±0.03, and overall percentage mortality was 18%. Significant correlation (p < 0.05, r = 0.49) was observed between birth weights and deaths incidence. Significant year and parity differences existed in lamb birth weights (P.< 0.05). 90% of the ewes lambing were in their 1st parity, while 6% and 4% respectively were in the 2nd and 3rd parities. Mean birth weights were heaviest for lambs with ewes in their 2nd parity 2.6 (0.46), followed by those in their 1st parity 23 (0.27) and those in their 3rd parity 2.2(0.27). Percentage mortality increased with parity, being 14,27 and 50 for 1st, 2nd and 3rd parities respectively. Chi-square analysis showed no significant differences between the ratio of ram to ewe lambs, though ram lambs were significantly heavier than ewe lambs. Low lamb birth weight was found to be a major cause of pre-weaning mortality in Yankasa sheep in Misau, Nigeria.