Abstract

Stagnant early growth and poor lamb survival are the major constraints of sheep production in Ethiopia. The aim of this study was to evaluate early growth and survival rate of crossbred lambs (Dorper × indigenous, Adilo) under semi-intensive conditions. Body weight (BW, kilograms) at 0-180 days, average daily gain (ADG, g/day), pre- (0-90), post (90-180) and overall (0-180 days), and pre-weaning survival rate (PSR) of crossbred (50%) lambs (n=305) were evaluated. The non-genetic factors (season, parity, sex of lambs, litter size) were also determined. The least squares means (±SE) of BW at birth, 30, 60, 90, 120, 150 and 180 days of age were 2.6± 0.63, 5.6± 0.12, 8.7± 0.18, 11.6±0.23, 15.0±0.46, 17.2± 0.31, and 18.4±0.26 kg, respectively. The crosses were higher by 11.9% and 9.3% at 90 and 150 days, respectively, than indigenous Adilo lambs. There was clearly evident effect of season on body weights at various ages, pre- and post-weaning and overall ADG. Parity influenced weight at 30, 60, and 90 days, and ADG (pre, post and overall). The litter size (1.68 ± 0.6) consistently affected BW at all ages, pre-weaning and overall ADG. Weight at birth, 30 and 90 days, and ADG from 30-60, 60-90 and 120-150 days were affected by parity-by-litter size interaction. The PSR rate (90.2%) was influenced by all non-genetic factors except sex. The improvement in litter size, body weight, and survival represents potentially significant economic advantage of crossbred over local sheep. Managing dam age through replacement ewes, and improving nutrition and litter size would improve lamb survival and growth that enhances total lamb output per ewe per year.

Key words: Growth rate, market weight, crossbred lamb, fixed factors.