Rape and sunflower seed meals as supplements for sheep grazing cereal stubbles

Abstract

In 2 experiments, Merino sheep aged about 18 months grazed cereal stubbles for 12 weeks and were either: (i) given no supplement; (ii) given free access to blocks containing 30% urea; or received daily about 300 g DM sheep-1 of (iii) rapeseed meal (RSM); (iv) formaldehyde-treated RSM (FRSM); (v) sunflower meal (SFM); or (vi) formaldehyde-treated SFM (FSFM). In experiment 1, wethers grazed a barley stubble at stocking rates (SR) of 18 and 36 sheep ha-1, and in experiment 2, mixed flocks of wethers and ewes grazed wheat stubble at 10 and 20 sheep ha-1. Mean daily intakes of urea were about 8.5 and 11.5 g sheep-1 for experiments 1 and 2 respectively. Both forms of SFM were readily eaten throughout, but in both experiments, intakes of RSM and FRSM were low and were characterised by high variability from day to day, and among individual sheep within groups. In both experiments, all sheep gained some weight during the first 2-3 weeks; thereafter control and urea fed sheep lost weight at mean rates varying from about 96 to 180 g day-1 depending on SR. Feeding SFM or FSFM reduced this loss to about 20 g day-1 at SR of 10-20 ha-1, and to 60 g day-1 at a SR of 36 ha-1, while losses were intermediate in sheep fed RSM or FRSM. In experiment 1, daily wool growth rates varied from about 5.5 g clean dry wool (CDW) sheep-1 for control and urea-fed sheep to about 11 g CDW sheep-1 for sheep fed SFM and FSFM; respective daily rates in experiment 2 were 3.6 and 8.2 g CDW sheep-1. Wool growth of sheep fed RSM and FRSM was intermediate in both experiments. When ewes were mated on high-quality feed after grazing stubbles, conception was delayed for about 14 days in a high proportion (about 40%) of those ewes that had lost considerable weight during stubble grazing. This effect was overcome by feeding daily 300 g DM sheep-1 of SFM for 7 days prior to and during mating. Delayed conception extended the lambing period. although final numbers of lambs born were not different among groups.