Effect of pre- and post-partum dietary crude protein level on the performance of ewes and their lambs

Abstract

In a block randomized design, fifty-one Barki ewes weighing 38.0 kg in average and 2–4 years old, were used to study the effect of pre- and post-lambing dietary crude protein level (CP) of concentrates on the milk yield, milk composition and weight of ewes, and performance of their lambs. The treatments comprised supplementary concentrate containing (g/kg dry matter (DM)): (1) 110 CP (low), (2) 130 CP (medium) and (3) 150 CP (high), while Egyptian berseem hay (Trifiolium alexandrinum) was the basal diet. Ewes were weighed individually biweekly, and the number of lambs dropped and nursed by ewes was recorded within 24 h after birth and biweekly subsequently. New-born lambs were left to suckle their dams freely, except for the period when milk yield was recorded by weighing lambs before and after suckling. Milk yield was estimated once a week. Ewes were fed the experimental diets during the last two months of pregnancy and throughout the lactation period. Ewes fed 110 g CP/kg DM attained peak of milk yield earlier than those fed 130 and 150 g CP/kg DM. Total milk yield, milk fat and milk total solids, and weaning weight, average daily gain and relative growth rate of lambs were higher (P < 0.05) for ewes fed medium and high protein levels compared to those fed low protein level. Suckled milk was affected by protein level (P < 0.05); the rank order was: 110 CP < 130 CP < 150 CP. Milk protein and extractable milk were higher (P < 0.05) for high protein level compared to low protein level but solids-not-fat (SNF) and lamb birth weight were not affected (P > 0.05) by protein level. Lamb sex, and parity and weight atlambing of ewes had no effect (P > 0.05) on suckled milk, extractable milk and milk yield. Whereas lamb sex and parity of ewe had no effect (P > 0.05) on milk composition, ewe lambing weight affected (P < 0.05) milk fat and SNF but not milk protein and total solids (P > 0.05). Weights of ewes during gestation, after lambing (post-partum weight loss) and during lactation were not affected (P > 0.05) by protein level, except at the 3rd month of lactation. Lamb sex, parity and lambing weight had pronounced (P < 0.05) effects on lamb birth weight and weaning weight. It is concluded that 150 g CP/kg DM level pre- and post-partum could be used for improved performance of ewes and their lambs while parity and weight of ewe at lambing should also be given consideration.