Effects of plane of nutrition in late pregnancy on lamb birth weight and milk yield in early lactation of Chios and Awassi sheep

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Abstract
SUMMARY: Two trials were conducted using two breeds of sheep varying in prolificacy but producing high commercial milk yields. In the first, 85 Chios ewes were assigned at 10 weeks before lambing to one of three planes of feeding: L, straw ad libitum; M, straw ad libitum + 0·5 kg concentrates; and H, straw ad libitum +1·0 kg concentrates. Six weeks prior to lambing, treatment L was stopped and all 85 ewes were re-randomized to treatments M and H. They were kept on these treatments until 14 days after lambing. In the second trial, 54 Chios and 56 Awassi ewes were allocated to the M and H treatments 6 weeks prior to lambing. After lambing they were fed ad libitum on straw and concentrates for 28 days.The mean metabolizable energy intake (Meal/day) over the 6-week period before lambing was 2·78 and 3·96 for Chios ewes in Trial 1, 2·39 and 3·51 for Chios ewes in Trial 2 and 2·66 and 3·72 for Awassi ewes in Trial 2, for the M and H treatments respectively.In both trials the treatment of the ewes affected the birth v/eight of twin and triplet lambs but not that of singles. In Trial 1, the differences in 14-day milk yield between treatments M and H were highly significant. In Trial 2, however, in which the ewes were fed ad libitum during lactation, no differences in the 14-day or the 28-day milk yields were observed for either breed. It is concluded that milk yields in early lactation are closely related to actual plane of nutrition in lactation but may also be affected by the body condition of the ewe at lambing, which may in turn be influenced by a low level of feeding in pregnancy.