The aim of this study was to evaluate the effects of age and breed on the reproductive performance and lamb output of crossbred hill ewes relative to purebred Scottish Blackface (BF). BF ewes were compared alongside Swaledale (SW) 3 BF, North Country Cheviot (CH) 3 BF, Lleyn (LL) 3 BF and Texel (T) 3 BF ewes on six commercial hill farms across Northern Ireland, on which all the ewes were born and reared. Ewes were mated to a range of sire breeds, balanced across breeds, for up to five successive breeding seasons. Mature live weight of adult BF, SW 3 BF, CH 3 BF, LL 3 BF and T 3 BF ewes was 52.8, 54.9, 60.3, 55.6 and 58.6 kg ( P , 0.001), respectively. Compared with the pure BF, the number of lambs born per ewe lambed was higher with LL 3 BF and SW 3 BF ( P , 0.05), whereas the number of lambs weaned per ewe lambed was greater for LL 3 BF and T 3 BF ( P , 0.01). Total litter weight at birth of all the crossbred ewes was heavier ( P , 0.01) than the pure BF, except in primiparous 2-year-old ewes. Lambs born to CH 3 BF and T 3 BF dams were 0.24 to 0.35 kg heavier at birth ( P , 0.01) than the other ewe breeds, whereas lambs born to CH 3 BF, LL 3 BF and T 3 BF dams were, on average, 1.7, 1.3 and 1.5 kg, respectively, heavier ( P , 0.01) at weaning than those from BF dams due to their higher ( P , 0.05) average daily gain. Compared with the pure BF, total weaned lamb output per ewe lambed was 3.7, 4.8, 6.7 and 5.4 kg heavier ( P , 0.05) for SW 3 BF, CH 3 BF, LL 3 BF and T 3 BF, respectively. However, as a result of the heavier live weight of the crossbred ewes, production efficiency (lamb output per kilogram live weight (W) and lamb output per kilogram metabolic live weight (W 0.75 )) was higher ( P , 0.001) for LL 3 BF ewes only. For all ewe breeds, litter size at birth per ewe lambed, total lamb birth weight per ewe lambed and litter size at weaning increased ( P , 0.001) with age up to 5 years, but decreased in 6-year-old ewes. Average lamb weaning weight and total weaned lamb output per ewe lambed increased ( P , 0.001) with age up to 4 years . Production efficiency of the 6-year-old ewes was lower ( P , 0.01) than the younger ewes. This study shows that adopting a flock replacement policy based on crossing BF ewes with LL, SW, T and CH sires can lead to significant improvements in the productivity of hill flocks.Keywords: crossbreeding, hill flocks, prolificacy, lamb output ImplicationsThe results of this study showed that adopting a flock replacement policy based on crossbreeding Blackface (BF) ewes with Lleyn, Swaledale, Texel (T) or Cheviot (CH) sires can increase productivity of hill flocks compared with pure BF replacements. This is achieved mainly through the increased litter size of the crossbred ewes. While improvements in lamb performance were noted for CH and T-sired ewes, their heavier body weight limits the potential to increase biological efficiency and lamb output per hectare. Assessment of the longevity and lifetime output of these more prolific breed types under hill conditions is, however, essen...

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A study was undertaken to compare the longevity and lifetime lamb output of purebred Scottish Blackface (BF) ewes with a range of crossbred genotypes from Scottish BF dams. For up to five successive breeding seasons, 1143 Scottish BF, Swaledale 3 BF (SW 3 BF), North Country Cheviot 3 BF (CH 3 BF), Lleyn 3 BF (LL 3 BF) and Texel 3 BF (T 3 BF) ewes were mated to a range of sire breeds on six hill farms across Northern Ireland. Dentition and lamb output were recorded annually until completion of the study or until the ewe was removed due to death or culling. Timing of mortality and the main reason for culling were also recorded. When survival analysis was undertaken, SW 3 BF and CH 3 BF ewes had better longevity ( P , 0.05) than BF ewes due to their lower culling rate ( P , 0.01) and lower mortality rate ( P 5 0.06), respectively. The relative proportion of LL 3 BF and T 3 BF culled due to infertility was lower ( P , 0.05) than SW 3 BF and CH 3 BF, while a higher ( P , 0.05) proportion of LL 3 BF and T 3 BF ewes were culled for prolapses compared with the other breed crosses. SW 3 BF ewes had consistently higher bite scores ( P , 0.001) compared with BF, LL 3 BF and T 3 BF, indicating a greater prevalence and degree of overshoot. In ewes aged 5.5 years old, SW 3 BF also had a higher incidence of tooth loss ( P , 0.01) compared with the other breeds. However, the proportion of SW 3 BF culled due to poor teeth condition was lower ( P , 0.05) than BF. Across all breeds, the chances of surviving to their next mating were influenced by ewe breed ( P , 0.05), age at mating ( P , 0.001), body condition score at weaning ( P , 0.001), number of missing teeth ( P , 0.001) and average daily live weight gain per litter ( P , 0.05). The cumulative number and weight of lambs weaned per ewe over five successive matings was higher ( P , 0.05) for crossbred compared with pure BF ewes; however there were no differences in lifetime output between the different crossbred ewes studied. This study demonstrates that the higher lamb output of crossbred hill ewes does not compromise their longevity compared with pure Blackface, resulting in greater total lifetime production. When the crossbred ewes are sired by a second hill breed, longevity may be improved.

Forty-eight lowland lambs were used in a completely randomized design (23-d period) with a factorial arrangement of treatments: 2 breeds (Highlander vs. Texel) × 3 sexes (female vs. intact male vs. wether) × 2 diets (fresh grass vs. fresh grass plus 0.5 kg/d pelleted concentrate). Animals ( = 48) were approximately 5 mo old and 36 ± 5.0 kg BW at the commencement of the study with 4 lambs for each breed-sex-diet combination. Fresh grass was harvested daily from the first regrowth of perennial ryegrass sward and offered ad libitum with a similar growth stage throughout the experiment. The animals were individually housed in pens and fed experimental diets for 19 d before being transferred to individual calorimeter chambers for a further 4 d with feed intake, fecal and urine outputs, and methane (CH) emissions measured. Lambs offered 0.5 kg/d concentrate had greater DM and energy (i.e., GE, DE and ME) intake, BW, and CH production (g/d) and greater N intake, fecal and manure N outputs, and fecal N per N intake than those given only fresh grass ( < 0.05). However, diets had no effect on CH emission rates (i.e., CH/DMI [ = 0.408] and CH energy/GE intake [ = 0.821]). Texels produced more CH/DMI (g/kg) than Highlanders ( = 0.044), and sex had no effect on CH/DMI (g/kg; = 0.101). Neither breed nor sex had an effect on N utilization efficiency ( > 0.05). The results reflected that high-quality forages may play a role similar to concentrate in mitigation of enteric CH emissions. The effects of sex and breed on rumen function require further investigation to understand relationships with CH emissions and N excretion in sheep.

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