A comparison of Scottish Blackface and Cheviot ewes and five sire breeds in terms of lamb output at weaning in hill sheep systems

A study was carried out on six hill farms in Northern Ireland over 2 years (1996-1998) to investigate the effect of ewe and ram breed on ewe prolifica cy, lamb viability and weaned lamb output. On each farm, groups of 40 Scott ish Blackface ewes (mature weight of 53.8 kg) were mated to Scottish Blackf ace, Blue-Faced Leicester and Texel rams. Similarly, groups of 40 Wicklow C heviot ewes (mature weight 63.7 kg) were mated to Cheviot, Suffolk and Texe l rams. All ewe x ram breed combinations were present on each farm. Overall , ewe prolificacy was similar in Blackface and Cheviot ewes (1.52 and 1.55 (S.E,. 0.026) lambs born/ewe lambed). However, there was a farm x ewe breed interaction (P < 0.001) indicating that, whilst prolificacy was similar in Blackface and Cheviot ewes on the majority of farms (4 out of 6), on one f arm prolificacy was higher in Blackface and on another lower, compared with Cheviot ewes. There were no farm x breed interactions for any of the other main production traits. The proportion of ewes lambing without assistance was higher in Cheviot compared with Blackface ewes when crossed with Texel sires (P < 0.001). Cheviot ewes produced heavier Texel-sired lambs compared with Blackface ewes (4.76 versus 4.51 (S.E. 0.076) kg; P < 0.05). Mortalit y levels were similar in lambs produced from Blackface and Cheviot ewes. Th e weight of lamb weaned per ewe was higher in Cheviot compared with Blackfa ce ewes (41.5 versus 38.8 (S.E. 1.01) kg/ewe lambed; P < 0.05). However, th e weight of lamb weaned per kg of ewe metabolic weight did not differ signi ficantly between the breeds. With Blackface ewes, the proportion of ewes lambing without assistance was lower for Blue-Faced Leicester compared with Blackface sires (P < 0.001). I n addition, the proportion of ewes lambing without assistance was lower (P < 0.001) for Texel compared with both Blackface and Blue-Faced Leicester-si red lambs. Lamb birth weights were higher in Blue-Faced Leicester (P < 0.05 ) and Texel (P < 0.001) compared with Blackface-sired lambs (4.38, 4.51 and 4.09 (S.E. 0.076) kg, respectively). Similarly, the weight of lamb weaned per ewe lambed was higher (P < 0.001) with Blue-Faced Leicester and Texel c ompared with Blackface sires (39.8, 38.8 and 33.8 (S.E. 1.01) kg, respectiv ely). The carcass weight of the male lambs 3 weeks post-weaning was signifi cantly higher (P < 0.001) in Blue-Faced Leicester and Texel compared with B lackface-sired lambs (12.5, 12.0 and 10.2 (S.E. 0.20) kg, respectively). Ca rcass conformation classification was higher in Texel compared with Blue-Fa ced Leicester and Blackface-sired lambs (P < 0.001). Fat classification was higher in Texel (P < 0.01) and Blue-Faced Leicester (P < 0.05) compared wi th Blackface-sired lambs. With Cheviot ewes, a greater number of ewes lambe d unaided (P < 0.05) with Cheviot and Texel compared with Suffolk-sired lam bs. The number of lambs born dead was higher (P < 0.01) with Suffolk compar ed with Cheviot and Texel-sired lambs (0.14, 0.08 and 0.07 (S.E. 0.016) lam bs born dead/ewe lambed, respectively). Growth rates were higher in Suffolk compared with Cheviot-sired lambs (P < 0.05). Overall, Suffolk (P = 0.06) and Texel (P < 0.001) sires produced a greater weight of lamb at weaning co mpared with Cheviot sires (40.0, 41.5 and 36.9 (S.E. 1.01) kg, respectively ). Carcass weight of lambs 3 weeks postweaning was higher for Suffolk (P < 0.05) and Texel (P < 0.01) compared with Cheviot-sired male lambs. Carcass conformation classification was higher in Texel and Suffolk compared with C heviot-sired (P < 0.001) lambs. Fat classification was also higher in Texel compared with Cheviot-sired lambs (P < 0.05). Carcass chemical composition was not significantly affected by lamb genotype.