CROSSBREEDING SCOTTISH Blackface ewe flocks has seen lamb output at weaning rise by up to 18% compared with pure breeding, according to studies in Northern Ireland reported at BSAS.

Alistair Carson of the Agricultural Research Institute said the trial was investigating potential for retaining crossbred female replacements to improve the genetic potential of hill flocks. It involves six farms in the main hill regions of Northern Ireland, each with 200 purebred Blackface ewes.

“These ewes were allocated to five mating groups according to liveweight, condition score and age,” said Dr Carson. Mating sires were Blackface, Swaledale, Cheviot, Lleyn and Texel rams.

In the first year of study, single sire mating groups were used separately on each farm, but in the second and third years a team of rams was used across all farms using artificial insemination, he added.

“Ewes were weighed and condition scored prior to mating and lambing, post-lambing and at weaning. Lambs from each of the crosses were weighed at birth, at six weeks of age and at weaning.

“When mated with Blackface ewes, Texel and Swaledale sires produced a greater number of lambs compared with Blackface sires.” Coupled with that, more Cheviot and Texel cross lambs required assistance at lambing compared with purebred Blackface and Swaledale cross lambs. But, as Dr Carson pointed out, this would be due to greater birth weights of Cheviot and Texel cross lambs.

“Output of weaned lamb, in terms of total weight of lambs weaned a ewe lambed, was greater for Texel and Lleyn cross lambs relative to purebred Blackface or Cheviot cross lambs,” he added. In 2003 crossbred ewes were put to Poll Dorset and Texel rams. Lleyn x Blackface ewes were the most prolific, had more lambs weaned and highest weight of lamb weaned a ewe. These ewes produced 23% more weight of weaned lamb a ewe.

From these results, Dr Carson believes retaining crossbred females could improve output from hill flocks. “In the first year of breeding, crossbred ewes produced a quarter more lamb output than Scottish Blackface ewes.” However, he warned that lifetime performance would need to be evaluated, before advising it on commercial farms.

jessica.buss@rbi.co.uk