Altering ewe nutrition in late gestation: I. The impact on pre- and postpartum ewe performance

The present study was conducted to examine the effects of offering a single diet rationed to 80% (80% ME), 100% (100% ME), or 120% (120% ME) of recommended ME requirements from d 119 of gestation to lambing, with concurrent changes in other dietary nutrients. The effects on pre- and postpartum ewe performance, including estimated milk yield and milk fatty acid concentrations, were monitored. Sixty twin-bearing ewes were allocated to 1 of 3 dietary treatments ( = 20 per treatment) and individually fed for the final 4 wk of gestation. Metabolizable energy requirements were individually calculated for each ewe and amended according to treatment. Ewes were rationed daily on the basis of their treatment ME allocation, which led to concurrent alterations in other nutrient intakes. Diets were grass silage based and supplemented with concentrates to meet treatment ME allocation on an individual ewe basis. Ewes offered the 80% ME treatment had a lower liveweight ( = 0.04) and BCS ( = 0.03) at 24 h postpartum when compared with ewes offered the 120% ME diet. Although there was no difference in liveweight at either d 40 ( = 0.18) or 98 postpartum ( = 0.20), the difference in BCS persisted until d 40 postpartum ( = 0.02). Colostrum yield at 1 h postpartum ( = 0.03) and total yield up to 18 h postpartum ( = 0.04) was greater for ewes offered the 120% ME diet than either of the other treatment groups. Similarly, these ewes had a greater estimated milk yield during wk 3 of lactation ( = 0.04) and elevated concentrations of short-chain SFA ( = 0.02) and long-chain SFA ( ≤ 0.05) from wk 2 through 6 of lactation. In summary, the negative impact of applying a dietary insult to ewes in late gestation is reflected in colostrum and estimated milk yield and fatty acid composition, thus potentially influencing postpartum growth and development of the offspring.