Effects of nutrition in pregnancy and in lactation on milk yield in ewes

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Abstract
SUMMARY: 1. Dorset Horn ewes were fed individually to make high (H) and low (L) gains in weight in the last 6 weeks of pregnancy. The gains were 20% (H) and 10% (L) of the live weight in week 14 of pregnancy for ewes with twin foetuses, and 16% (H) and 6% (L) for ewes with a single foetus. Three levels of intake imposed during lactation were denned as low (L) 15·0, medium (M) 22·5, and high (H) 30·0 g of feed dry matter/kg of ewe live weight in week 14 of pregnancy. The lambs were removed 12 to 16 hours after parturition and the ewes were machine-milked twice daily for the first 6 weeks of lactation.2. Ewes making low gains in pregnancy produced lambs with slightly lower birth weights but the difference was not significant for either twins or singles. Pregnancy treatment had no effect on milk yield or live-weight change in lactation, but fat content was increased in milk from ewes on the H treatment in pregnancy (8·06% v. 7·46%).3. Level of feeding during lactation did not significantly affect milk yields. The total yields in the first 6 weeks of lactation were (L) 49·4 kg, (M) 60·8 kg and (H) 62·7 kg. However, there were significant effects on milk composition. The treatment means for fat content were (L) 8·34%, (M) 8·05% and (H) 6·84% and for solids-not-fat content were (L) 10·04%, (M) 10·37% and (H) 10·82%.4. Live-weight losses in lactation were (L) 9·1 kg, (M) 6·3 kg and (H) 3·2 kg.