Effects of crossbred ewe genotype and ram genotype on ewe prolificacy, lamb viability and lamb output in the lowland sector

A study was carried out on five lowland farms in Northern Ireland over 3 years to investigate the effect of crossbred ewe and ram genotype on ewe prolificacy, lamb viability and weaned lamb output. Four crossbred ewe genotypes were sourced from six hill farms involved in a previous study – Bluefaced Leicester×Blackface (BLXB), Texel×Blackface (TXB), Suffolk×Cheviot (SXCH) and Texel×Cheviot (TXCH). On each farm, groups of 20–30 of each crossbred ewe genotype were mated with Suffolk or Texel rams. Throughout the 3 years of the study, the ewe genotypes lambed at 1, 2 and 3 years of age. Within each of the ram breeds, high lean growth index rams sourced from UK sire reference schemes were compared with rams sourced from flocks not involved in objective genetic improvement programmes (control). BLXB ewes were the most prolific of the four ewe genotypes producing 1.73 lambs per ewe lambed compared with 1.47 for TXB, 1.46 for SXCH and 1.41 for TXCH (P