EFFECT OF POSTWEANING LEVEL OF NUTRITION ON THE EARLY REPRODUCTIVE-PERFORMANCE AND PRODUCTIVITY INDEXES OF MENZ SHEEP

Weaner ewe lambs (92 +/- 4 days, SD) of the Ethiopian Menz breed (n=11 5) were used to assess the impact of level of nutrition before and aft er first lambing on subsequent productivity. Lambs were raised either on pasture grazing only (P) or grazing with low (L), medium (M) or hig h (H) levels of a concentrate supplement containing 125 g/kg DM digest ible protein and 25 Mcal/kg DM. Postweaning mortality was 13.9%, being substantially higher for P animals (33%) than better fed counterparts (7%). Lamb weaning weight was affected by lambing season (P<0.01) and ewe postpartum level of nutrition (P<0.05). Both factors also affecte d the three productivity indices expressed as (1) the weight of a 90 d ays old lamb produced per ewe per year (Index I), 2 per kg of breeding female per year (Index II) or (3) per kg0.73 of breeding female per y ear (Index III), and respectively averaging 11.0 +/- 0.87 kg, 520 +/- 41 g and 1.18 +/- 0.09 kg. The productivity index for ewes that only g razed was estimated as 60 and 50% that of contemporaries on L and M di etary levels because of lower lamb weaning rates, slower growth and ex tended lambing intervals. A possible approach to improve productivity of Menz sheep is suggested.