Pre-Exposure of Early-Weaned Lambs to a Herb-Clover Mix Does Not Improve Their Subsequent Growth.

Twin sets of lambs were randomly allocated to one of six treatments: (1) lambs born and managed on ryegrass-clover-based pasture until conventional weaning approximately at 99 days of age (Grass-GrassCW); (2) lambs born on ryegrass-clover-based pasture and early weaned onto a herb-clover mix at ~45 days of age (Grass-HerbEW); (3) lambs born on ryegrass-clover-based pasture, transferred with their dam onto a herb-clover mix at ~45 days of age until conventional weaning (Grass-HerbCW); (4) lambs born on ryegrass-clover-based pasture, transferred with their dam onto a herb-clover mix at ~15 days of age and early weaned onto a herb-clover mix at ~45 days of age (Grass-HerbD15EW); (5) lambs born and managed on herb-clover mix until conventional weaning (Herb-HerbCW); (6) lambs born on herb-clover mix and weaned early onto a herb-clover mix at ~45 days of age (Herb-HerbEW). In both years, Herb-HerbCW lambs had greater (p < 0.05) growth rates than lambs in other treatments. The liveweight gains and rumen papillae development of Herb-HerbEW, Grass-HerbD15EW and Grass-HerbEW lambs did not differ (p > 0.05). The weight of the empty digestive tract components at either early weaning or conventional weaning did not differ (p > 0.05) between treatments. Exposing early-weaned lambs to the herb mix for a prolonged period, prior to early weaning, does not improve their subsequent growth.

Lambs Weaned Early onto a Herb-Clover Mix Have the Potential to Grow at a Similar Rate to Unweaned Lambs on a Grass-Predominant Pasture.

Liveweight gain of lambs weaned early at a minimum live weight of 14 kg, at ~50 days of age, onto a herb-clover mix was compared with lambs that remained unweaned on a grass-predominant pasture or a herb-clover mix until conventional weaning (at ~99 days of age). Over two years, twin sets of lambs that had a minimum live weight of 14 kg were randomly allocated to one of three treatments: (1) Early weaning of lambs onto a herb-clover mix (HerbEW); (2) ewes and lambs grazing a herb-clover mix until conventional weaning (HerbCW); and (3) ewes and lambs grazing a grass-predominant pasture until conventional weaning (GrassCW). HerbEW lambs had slower (p < 0.05) growth rates than GrassCW lambs between early weaning and conventional weaning in 2016 and were 800 g lighter (p < 0.05) at conventional weaning. In 2017, however, both HerbEW and GrassCW had similar (p > 0.05) growth rates and did not differ (p > 0.05) in live weight at conventional weaning. HerbCW lambs had a greater (p < 0.05) growth rates than both HerbEW and GrassCW lambs in both years. Lambs weaned early onto a herb-clover mix have the potential to achieve live weights similar to lambs unweaned on grass-predominant pasture. Further research, however, is required to understand conditions under which early-weaned lambs can achieve similar live weights.