Does Dam Age, Ewe Birth Rank and Sex of a Co-twin Affect a Ewe’s Lifetime Performance?

A large sheep dataset including ewe and progeny records from 1982 through to 2006 was used in the present study. The data included the variables: sex of lamb, birth rank, weaning weight, year born and dam and sire. The aim was to firstly, determine if the age of the ewe’s dam, or the birth rank of the ewe affected her lifetime performance and secondly, to determine in twin-born lambs if the sex of the co-twin affected survival to weaning and the lifetime performance of ewe. Age of the ewe’s dam had no effect on her productive performance. The total number lambs born, weaned and total weight of lamb weaned per ewe increased with ewe birth rank. In twin-born sets of lambs, the sex of the co-twin had a small effect on survival to weaning. Sex of the co-twin did not affect the lifetime reproductive performance of ewes.