Do ewes that grow faster have greater embryo and lamb survival?

Context Embryo survival, lamb survival and lamb growth rate are key factors in achieving peak performance of a sheep flock. Aims We used monthly ewe lamb growth records from approximately 400 ewes born over three successive years to test the hypothesis that mature ewes with greater relative growth rate as a lamb have greater embryo survival, lamb survival and lamb growth rate. Methods The Brody growth model was used to describe the nonlinear ewe lamb growth in their first year, and the estimated Brody model parameters were used as covariates in models for embryo survival, lamb survival and lamb growth rate as an adult ewe. Key results Ewes with greater relative growth rates as a lamb had greater embryo survival (P = 0.0002), lamb survival (P = 0.02) and lamb growth rate (P = 0.001) as an adult ewe. For example, over the measured range of ewe lamb relative growth rate, the expected embryo survival for ewes with a single embryo when they were pregnant as an adult ranged from 0.80 to 0.94, the expected probability of the survival of single lambs when they lambed as an adult ewe ranged from 0.92 to 0.97 and the expected single lamb growth rate when they lambed as an adult ewe ranged from 0.31 to 0.33 kg day−1. Conclusions Ewes with greater relative growth rate as a lamb had greater embryo survival, and offspring survival and growth rate as an adult ewe. Implications This new positive association between ewe lamb growth and embryo survival, lamb survival, and lamb growth rate as an adult ewe can potentially be exploited to improve flock performance.