Effects of breed and age on the performance of crossbred hill ewes sourced from Scottish Blackface dams

Abstract

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...

Comparison of the longevity and lifetime performance of Scottish Blackface ewes and their crosses within hill sheep flocks

“…Selection of crossing sire breed to produce prolific females for hill flocks may be important. SW 3 BF ewes tended to remain in the flock longer than LL 3 BF even though both breeds had similar levels of prolificacy (Annett et al, 2010). Therefore, ewes sired by prolific hill breed types such as SW may be more appropriate for hill flocks than those sired by prolific lowland breeds.…”

“…In agreement with McGloughlin and Curran (1969), the primary reason for culling was due to infertility (0.408) and was followed by udder abnormalities (0.227), poor teeth condition (0.188), vaginal prolapse (0.069) and poor body condition (0.040). The relative rate of culling due to infertility was lower in LL 3 BF and T 3 BF compared with CH 3 BF and mirrors their higher prolificacy (Annett et al, 2010). Waterhouse et al (1992) reported increased survival in BF ewes treated with Fecundin R (Glaxo Animal Health, UK) to boost prolificacy.…”

“…Details of the animals used are outlined in a concurrent study (Annett et al, 2010). In brief, on each of the six farms, 200 purebred Lanark-type Scottish BF ewes were mated with BF, SW, North Country Cheviot (CH), LL and T rams over a 3-year period (October 2001(October to 2003.…”

“…First, within each age group, lamb output of ewes was determined as the product of the proportion of ewes alive and productive, and the mean productivity per ewe lambed within that age group. The latter was determined in a concurrent study (Annett et al, 2010) using linear mixed models with fixed effects for farm 1 year of birth 1 days to weaning 1 lamb sire breed 1 age 1 ewe breed 1 farm 3 ewe breed 1 age 3 ewe breed, and random effects for ewe id 3 age 1 ewe breed 3 sire of ewe. Second, lamb output was then cumulated across all preceding age groups.…”

“…Use of crossbred ewes in hill flocks is uncommon; however reports comparing purebred and crossbred ewes under hill conditions have consistently demonstrated higher lamb output from crossbred ewes (Donald et al, 1963;Al-Nakib et al, 1997). In a concurrent study, replicated across six commercial hill flocks, Annett et al (2010) demonstrated that retaining crossbred replacements from Scottish BF dams sired by Swaledale (SW), Lleyn (LL) or Texel (T) sires increased weaned lamb output/ewe mated by more than 21% compared with purebred Scottish BF due to their greater prolificacy and heavier lamb weights at weaning.…”