WINTER-SPRING NUTRITION AND MANAGEMENT EFFECTS ON EWE AND IAMB PERFORMANCE

Aspects of the above theme were investigated in 5 trials. Trial 1 compared the effects of high and low nutrition during pregnancy and lactation on ewe and iamb production. Ewe live weight was substantially affected by nutrition treatment during pregnancy but carry-over effects on live weight at weaning were small. Nutrition during lactation strongly affected both lamb and ewe weaning weights. Ewe and lamb losses were not affected by nutrition at any stage. The results implied that ewes can be quite severely restricted on pasture during pregnancy in order to save feed for the much more important lactation period. Trials 2 and 3 investigated the management of ewes fed at maintenance levels in mid-pregnancy. The treatments consisted of various grazing durations where the ewes were shifted from one pasture break to another after a specific grazing duration, as defined by their treatment. These treatments consisted of grazing durations ranging from 3 to 56 days. Liveweight differences occurred during the 56-dav trial period but at the end there was only 2.5kg difference between extreme treatments. This suggests that where ewes are on restricted feeding during pregnancy to conserve pasture reserves, grazing duration has little consistent impact on final ewe live weight and performance. However, for several reasons, a shorter duration (3-7 days) is preferred. Trials 4 and 5 compared several winter-spring management treatments. Ewes on a 35day (short) rotation during pregnancy versus those on a 70day (long) rotation had less pasture on their farmlet at lambing (930 V. 1030 kg/ha). As a consequence the short rotation ewes were 1.5 kg lighter at weaning. Their lambs ware 2.3 kg lighter. In another comparison, set-stocking ewes 4 weeks before lambing compared with at lambing disadvantaged the ewes and lambs by 2-3 kg at weaning. The ewes set-stocked 4 weeks before lambing had consumed most of their winter reserves by lambing. In Trial 5, rotational grazing after lambing until weaning versus set-stocking, disadvantaged the ewes and iambs by 4 and 3 kg respectively at weaning. This was probably because the rotation length of 21 days in the rotational group was too long. Management implications from these results are discussed.