Dr Tim Keady
Animal and Grassland Research and Innovation Centre,
Teagasc, Athenry, Co Galway.
Introduction
A key factor influencing profitability from prime lamb production is ewe productivity, which
is primarily a reflection of the number of lambs weaned per ewe joined. The factors
influencing ewe productivity are litter size, the proportion of ewes joined that actually
produce lambs, and lamb survival.
Ewe productivity has remained relatively static, at approximately 1.3 lambs weaned per ewe
joined, on Irish lowland farms for the last 30 to 40 years. This lack of improvement is most
probably attributable to the absence of significant increase in the use of more prolific ewe
genotypes. Currently, 73% of lowland ewes have been sired by one of the three main terminal sire breeds (Suffolk, Texel and Charollais), and two of these breeds have inherently low productivity. Suffolk and Suffolk-cross ewes account for 55% of lowland ewes. The Belclare breed accounts for the sire of 10% of ewes in lowland flocks.
Since the costs involved in sheep production are attributable primarily to the ewe, rather than
to her lambs, production cost per lamb can be reduced by increasing the number of lambs
produced per ewe lifetime. The number of lambs reared per ewe lifetime are influenced by
ewe prolificacy (ewe genotype).
Effect of ewe genotype
A number of studies have been undertaken by Teagasc at Athenry, and previously at Belclare, Blindwell and Knockbeg, to evaluate the effect of ewe genotype on ewe productivity. These studies were initiated in the 1980’s and completed in 2006. In these studies crossbred ewes were out of either Scottish Blackface or Cheviot dams and were sired by rams from a range of breeds. The resultant female progeny were retained for at least 3 production cycles, i.e., had an opportunity to produce 3 litters. The crossbred ewes were managed in lowland grass-based systems for prime lamb production. The results of these studies are summarised in Table 1. The number of lambs reared per ewe joined varied among genotypes by up to 0.44 lambs, equivalent in value to approximately €65. The ewe genotypes that reared the highest number of lambs per ewe joined were the Belclare-X and the Charollais-X. Relative to Belclare-X ewes Suffolk-X and Texel-X ewes reared 0.21 fewer lambs per ewe joined.
Athenry study
A recent study, just completed, was designed to evaluate the effects of ewe genotype (≥75%
Suffolk, Belclare×Suffolk and purebred Belclare) on the lifetime performance. The ≥75%
Suffolk was included in the study as over half of the national flock comprise Suffolk types
while the Belclare was chosen because of its proven high productivity. The Belclare and
Belclare×Suffolk ewes were born at Athenry while the ‘≥75%’ Suffolk ewes were purchased
off farms in Galway, Mayo and Roscommon. All ewes were March born and managed as one
group from 4 months of age, and were retained until they died or were culled for natural
reasons (mastitis, udder, teeth, condition, prolapse etc. but not for being barren). Ewes were
joined with Charollais sires to avoid maternal and terminal breed confounding and to
maximise hybrid vigour.
Ewe lambs were joined with rams to produce their first litter at 1 year of age. Ewes were
housed in mid-December, shorn and offered grass silage-based diets. The quantity of
concentrate offered during late pregnancy depended on expected litter size and grass silage
feed value. Ewes were put to pasture immediately post lambing. Ewes rearing singles or
twins, and their lambs, did not receive concentrate supplementation. Ewes rearing triplets
received 0.5 kg concentrate daily for 5 weeks post lambing and their lambs had access to 0.3
kg concentrate daily until weaning. Ewes lambing at one year of age, and their lambs, were
managed as described for triplet rearing ewes. Concentrate was removed at weaning.
The effect of ewe genotype on ewe and lamb performance when lambing at 1 year, 2 years
and as mature ewes is presented in Table 2.
Ewe lambs:
Belclare ewe lambs had a higher litter size than the Belclare×Suffolk and ≥75% Suffolk
genotypes and reared an extra 0.16 and 0.35 lambs per ewe joined relative to
Belclare×Suffolk and >75% Suffolk genotypes, respectively. Mean carcass weight of the
lambs at slaughter was 20.5 kg. Lambs from Belclare×Suffolk ewes were slaughtered at a
younger age probably associated with hybrid vigour.
2 years of age: When lambing at 2 years of age Belclare and Belclare×Suffolk ewes reared
0.25 and 0.23 more lambs per ewe joined, respectively, than ≥75% Suffolk ewes. Ewe
genotype had no effect on lamb performance from birth to slaughter. Mean carcass weight of
the lambs at slaughter and age at slaughter were 20.6 kg and 202 days, respectively.
Adult ewes: When lambing as adult ewes (3 years and older) Belclare and Belclare×Suffolk
ewes were more prolific, rearing an extra 0.28 and 0.41 lambs/ewe joined relative to the
≥75%Suffolk genotype. Mean lamb carcass weight and age at slaughter were 21.4 kg and 171 days respectively. Lambs from the ≥75% Suffolk ewes were 13 and 6 days older at slaughter than lambs from Belclare and Belclare×Suffolk ewes.
Lifetime performance: Ewe genotype had little impact on the number of lambings although
that for the Belclare×Suffolk was highest. However, ewe genotype had a major impact on the
number of lambs reared during their lifetime. Relative to the >75% Suffolk ewes, the
Belclare×Suffolk ewes reared an additional 1.4 lambs.
Conclusions
Belclare-cross ewes have a higher prolificacy than a wide selection of other crossbred types
Use of Belclare sires increased lifetime lamb output by 25% equivalent to
approximately €200
The results show clearly that using a Belclare ram on Suffolk-type ewes, found a
large proportion of lowland farms, will yield flock replacements with a vastly
increased productivity throughout their lifetime