Consistent high body condition in meat ewes is associated with long survival rates and high lifetime productivity: a seven-year prospective longitudinal study of 6000 ewes from eleven flocks in England.

Improving the lifetime productivity of ewes is important to improve efficiency and reduce greenhouse gas emissions from sheep farming. In 2017, eleven English sheep flocks with 6000 nulliparous ewes were enrolled into a seven-year prospective longitudinal study to investigate lifetime performance of ewes joining the flock as ewe lambs or shearlings over six parities. Multivariable statistical models were used to investigate productivity and survival of ewes per year and over 6-years of production, adjusting for confounding variables. The key results were: lifetime performance of ewes was dependent on their survival for all six parities; ewes mated as ewe lambs (6-7 months old) produced approximately one lamb more over their lifetime than ewes mated as shearlings (18-20 months old); and ewe survival, litter size, lamb weight gain to eight-weeks and to weaning, increased, as ewe body condition at mating that season increased. Productivity plateaued in ewes with body condition score 4.0 on a 1-5 point scale, higher than reported previously. Weight gain from mating to mid-pregnancy also increased productivity, especially in ewe lambs. This is the longest prospective study of ewe performance in England, and it highlights that maximum productivity occurs in sheep with a consistent body condition score of 4.0. The results can be used by the sheep industry together with input factors, such as farm location, sheep breed, feeding and other costs, to optimise lifetime performance of ewes in different systems.