Post-weaning performance of East Friesian cross ewe lambs grazing ryegrass or plantain-based pastures after rearing on two contrasting diets

Abstract

Abstract Artificial rearing is used routinely on dairy sheep farms. Different strategies are used to optimise the growth and development of the young lamb with an economic ration of milk and other feed components. Early weaning, and early introduction to pasture can both reduce these costs, but may also reduce the liveweight gains of the growing lamb. Can differences in pre-weaning feeding strategies be mitigated using specialist pastures such as plantain/red/white clover? Lambs from an experiment investigating the impacts of rearing with and without meal access (n=30/group) and weaned at 12 weeks of age were grazed on either perennial ryegrass-based or plantain/red clover-based pastures in 3 replicates. Liveweight gain, animal health, feed supply and feed quality parameters were recorded over the following 5 weeks. Liveweights of the lambs reared on the different feeding regimens were similar at 12 weeks of age when the grazing study began (25.9 kg). Using plantain/red clover-based pastures provided no advantage to the liveweight gain of lambs reared under different milk and concentrate feeding regimens. Both feed types provided adequate nutrition to ensure growth rates of approximately 180 g/day over the 5 week measurement period in late spring. However, lambs reared under a high concentrate system has consistently lower liveweight gains (160 g/day) over the 5 weeks than those lambs reared with access to pasture (200 g/day; P<0.05). Feed quality was high on both pasture types. Symptoms of photosensitivity were recorded on both pasture types, but predominantly in lambs reared with ad libitum access to meal until week 10 of life, posing a question over functional liver development. This may have also affected liveweight gain. Keywords: artificial rearing, lamb liveweight gain, ryegrass, plantain, post-weaning