There will be 2 replicates of 2 treatments:
1. Control: 25% tail end weaners in the same pen as 75% bigger weaners (this will be representative of the mob if not drafted into weights) (60 lambs per pen)
2. Separated: 100% tail end weaners in a pen (60 lambs per pen)
There will total 240 lambs used for the experiment. The study involves pen-feeding for 3 months after weaning, after which lambs are combined into a single mob and are managed under normal farm management for a further 3 months, to enable both short and longer-term impacts of feeding treatments to be measured.
At weaning or soon after (awaiting animal ethics approval) weaners will be drafted into heavy and light groups, and appropriate numbers of each randomly allocated to 4 groups. The lambs will be fed daily in containment group-feeding pens, and after introduction to the ration, fed to grow at 100 g/day for 3 months. The ration will be a mix of 70% barley, 30% lupins, with lucerne hay fed at 30% of the total ration. All lambs will also have access to molyfos mineral supplement. All lambs will be individually identified and once monthly for 3 months will be weighed, condition scored and for a sample in each pen FEC recorded. A behavioural analysis will also be completed on each pen of lambs, three times in the first two weeks and then once more a month later, to record the number of lambs in each pen coming to the trough at feeding and being bullied by bigger lambs. Blood tests may be taken from a sample of lambs on some occasions to monitor metabolites. After 3 months the lambs will be combined into a single mob and graze pastures (or be pen fed for longer if pasture conditions require) under farm management for a further 3 months. FEC will be recorded 3 months after pen-feeding to assess any long-term impact of treatments on worm burdens. A final weight and condition score will also be recorded to assess weight gains.
A dyeband will be applied to the midside wool of a sample of lambs at the start of the study, then again at 3 months and after the 3 month grazing period to measure wool length. growth in each period. A midside wool sample will be taken at 3 months and again 3 months after pen-feeding to monitor the treatment effect on wool quality (fibre diameter, staple strength, yield).