Hill Sheep Flocks Research Articles

Genetic associations of ewe body condition score and lamb rearing performance in extensively managed meat sheep

Many small ruminant production systems are relatively low input and rely heavily on animals grazing pastures often in extensive and harsh environmental conditions, unsuitable for any other type of agriculture. New breeding goal traits for lifetime resilience for maternal sheep breeding programmes have been investigated, focusing on body tissue mobilisation phenotypes and their genetic relationships with maternal production traits. Performance records of 8,355 Scottish Blackface ewes, from 2 extensively reared hill sheep flocks, collected over a 20-year period, were used to quantify relationships between body condition score (BCS) and the ewe's ability to successfully rear lambs. Between 14,000 and 25,000 data records per trait were available, measured across the annual sheep reproductive cycle. The pedigree file used for the analyses included sire and dam information for 50,207 animals. Most heritability estimates for the BCS traits - measured at key time points within the annual production cycle, or considering BCS changes between time points - were low, but significantly different from zero, ranging between 0.07 and 0.17. The heritability estimate for the number of lambs at pregnancy scanning was 0.09. Heritabilities for foetal loss from pregnancy scanning to lambing, lamb loss from lambing to weaning and number of lambs weaned were 0.02, 0.02 and 0.06, respectively. These estimates indicate that genetic control over the reproductive and lamb survival traits (expressed as a trait of the dam), is lower than that for BCS (and BCS changes) over the reproductive cycle. The genetic relationships amongst the BCS of ewes at pre-mating, pregnancy scan and at pre-lambing, with litter size at pregnancy scan and number of lambs weaned, were consistent. They indicate that ewes of higher body condition score (potentially over-fat, within the range recorded in these flocks) conceive, and rear, fewer lambs, with genetic correlations ranging between -0.18 and -0.58. However, post-weaning, animals with genetic propensity for greater gain in BCS from weaning to pre-mating produce larger litters and rear more lambs. In addition, the selection of ewes that lose less condition during pregnancy will reduce foetal losses. The results from this study paint a complex picture that should be interpreted in the context of specific management practices for extensively managed hill sheep, at critical times in their reproductive cycle. The traits relating to body tissue mobilisation, as assessed using BCS, are mostly heritable and their inclusion in future breeding programmes, to aid future selection for resilience, should be considered.

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

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 × BF (SW × BF), North Country Cheviot × BF (CH × BF), Lleyn × BF (LL × BF) and Texel × BF (T × 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 × BF and CH × 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 = 0.06), respectively. The relative proportion of LL × BF and T × BF culled due to infertility was lower (P < 0.05) than SW × BF and CH × BF, while a higher (P < 0.05) proportion of LL × BF and T × BF ewes were culled for prolapses compared with the other breed crosses. SW × BF ewes had consistently higher bite scores (P < 0.001) compared with BF, LL × BF and T × BF, indicating a greater prevalence and degree of overshoot. In ewes aged 5.5 years old, SW × BF also had a higher incidence of tooth loss (P < 0.01) compared with the other breeds. However, the proportion of SW × 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.

Effects of dam breed and dietary source of n-3 polyunsaturated fatty acids on the growth and carcass characteristics of lambs sourced from hill sheep flocks

The objectives of this study were to investigate the effect of dietary lipid source on the growth and carcass characteristics of lambs sourced from a range of crossbred hill ewes. Over a 2-year period, 466 lambs representing the progeny of Scottish Blackface (BF × BF), Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes were sourced from six commercial hill flocks and finished on one of four diets: grass pellets (GP), cereal-based concentrate (CC), CC enriched with oilseed rape (CR) and CC enriched with fish oil (CF). Dry matter intake (DMI) was highest (P < 0.001) in lambs offered GP; however, carcass weight gain (CWG) and feed conversion efficiency were higher (P < 0.001) in lambs fed concentrate-based diets. For lambs offered concentrate-based diets, DMI and live weight gain were lower (P < 0.001) for CF than CC or CR. Lambs with T × BF dams achieved a higher (P < 0.05) daily CWG and CWG/kg DMI than BF × BF, SW × BF or LL × BF dams. When lambs were slaughtered at fat score 3, CH × BF, LL × BF and T × BF dams increased carcass weight by 0.8 to 1.4 kg (P < 0.001) and conformation score (CS) by 0.2 to 0.4 units (P < 0.001) compared with BF × BF or SW × BF dams. However, breed effects on carcass conformation were reduced by 50% when lambs were slaughtered at a constant carcass weight. Diets CC and CR increased carcass weight by 0.8 to 1.6 kg (P < 0.001) and CS by 0.1 to 0.3 units (P < 0.001) compared with GP and CF. Both, dam breed and dietary effects on carcass conformation were associated with an increase (P < 0.001) in shoulder width of the lambs. Lambs fed CF and slaughtered at a constant carcass weight had more subcutaneous fat over the Longissumusdorsi (P < 0.05), Iliocostalisthoracis (P < 0.001) and Obliquus internusabdominis (P < 0.001) compared with those fed CC. However, these effects were removed when lambs were slaughtered at a constant fat score. At both endpoints, lambs from T × BF dams contained less (P < 0.05) perinephric and retroperitoneal fat than SW × BF or LL × BF dams fed GP or CC, respectively. The results from this study show that using crossbred ewes sired by CH, LL or T sires will increase carcass weight and improve carcass conformation of lambs sourced from hill flocks. Inclusion of oilseed rape in lamb finishing diets had only minor effects on performance compared with a standard CC but feeding fish oil or GP impacted negatively on lamb growth and carcass quality.

Sustainability of hill sheep flocks in England

Sheep production has been taking place on the hills and uplands of England for many centuries and has made a major contribution to environmental and social development and sustainability in these areas. Traditionally, hill farms have provided the crossbred breeding stock for the upland areas, older “cast” ewes for further breeding on improved grazing and naturally reared lamb meat. Under current economic conditions, there is a severe lack of profitability in these units with consequent reduction in sheep and shepherd numbers on the hills. Factors involved in the loss of profitability include persistently poor lamb prices and increased disease risk. Furthermore, 2012 will see the end of many of the current subsidy schemes and from 2010 there will also be the requirement for electronic tagging which requires extra expenses and administrative efforts. The only “growth industry” on this type of land seems to be grouse-shooting, which has low personnel requirement and few long-term social benefits. This paper reviews factors involved in this de-population of the hills, using examples from the Cheviot Hills of Northern England in particular, over the last 20 years and comments on the economic and management requirements necessary for continued sheep farming in these areas, as well as the animal welfare and social effects the trend for lower stock numbers will result in.

The comparative efficacy of four anthelmintics against a natural acquired Fasciola hepatica infection in hill sheep flock in the west of Ireland

The aim of this study was to evaluate the efficacy of four different anthelmintics against F. hepatica in a naturally infected hill sheep flock in the west of Ireland. In a randomised trial, 138 ewes were divided into four groups. On day 0 each group was dosed with one of four anthelmintics: triclabendazole, closantel, oxyclozanide or nitroxynil. Faecal samples were obtained from each animal per rectum on the day of treatment and again at 7, 14, 21 and 56 days post-treatment. The number of F. hepatica eggs per gram of faeces was determined using the sedimentation technique and the efficacy of each anthelmintic was calculated in terms of the percentage reduction in egg count at each time point. The results for closantel, oxyclozanide and nitroxynil indicate that these drugs are effective with faecal egg count being reduced by 100% by day 14 post-treatment. However, the results for triclabendazole group yielded lower efficacy levels, with faecal egg count reductions of between 49% and 66% based on arithmetic means, over the period 7–56 days post-treatment. These results are highly indicative of triclabendazole resistant F. hepatica in sheep on this farm.

Evidence of Fasciola hepatica infection in Radix peregra and a mollusc of the family Succineidae in Ireland

Worldwide molluscs of the genera Lymnaea, Pseudosuccinea, Galba and Stagnicola act as intermediate hosts of the common liver fluke, Fasciola hepatica. Galba truncatula is the only recorded intermediate host of F. hepatica within Ireland and is the principle intermediate host within Europe. To investigate the transmission of liver fluke on the Teagasc hill sheep farm, Co. Mayo, Ireland, snail species other than G. truncatula, were collected from the lowland pasture (snail sp. ‘A’) in May (n=23) and from the hill area (snail sp. ‘B’) in March, April and May 2008 (n=78, 53 and 36 respectively). Morphological characteristics identified snail sp. ‘A’ as a Succinea sp. and snail sp. ‘B’ as Radix peregra. PCR and subsequent sequencing of the 18S gene and internal transcribed spacer 2 (ITS-2) region of the snail rDNA were used for molecular identification. The 18S ribosomal DNA (rDNA) sequences revealed a 99% similarity with Omalonyx matheroni (Succineidae) for snail sp. ‘A’, and for snail sp. ‘B’ a 99% and 98% similarity with Radix auricularia and R. peregra, respectively. The ITS-2 sequences of snail sp. ‘B’ revealed a 100% similarity with R. peregra. Using PCR F. hepatica DNA was identified in 73.9% (n=17) of snail sp. ‘A’ collected during May and 10.3% (n=8), 60.4% (n=32) and 61.1% (n=22) of snail sp. ‘B’ collected during March, April and May, respectively. A priori knowledge of habitat preference and environmental tolerances of G. truncatula has failed to explain the prevalence of infection recorded in the hill sheep flock on Teagasc hill sheep farm. These findings may explain the presence of infection in sheep populations grazing hill habitats considered too acidic to maintain G. truncatula populations.

Lifetime performance of crossbred ewes in the hill sheep sector

Hill sheep flocks in the UK are dominated by purebred ewe genotypes, with the Scottish Blackface being the most common. However a long term decline in economic returns, combined with recent changes to the Common Agricultural Policy, has lead many hill sheep producers to consider keeping crossbred ewes to exploit the benefits of hybrid vigour for lamb survival and to introduce beneficial traits for prolificacy, ease of lambing and carcass quality. In 2001, a major on-farm research programme was initiated to evaluate the performance of a range of crossbred ewe genotypes for the Northern Ireland hill sheep sector. Provisional data has already identified that retaining Lleyn X Blackface and Texel X Blackface ewes can improve lamb output at weaning by up to 10% relative to purebred Blackface ewes (Speijerset al., 2007). However, ewe longevity is a major issue for hill flocks, where the annual replacement rate often exceeds 20%. Therefore it is inappropriate to evaluate crossbred ewe genotypes based on average annual performance alone, and the aims of this study were to investigate the lifetime performance of a range of crossbred genotypes under hill conditions.

Performance of crossbred ewes in the hill sheep sector

Flock genetics has a very major effect on the level and quality of output from the hill sheep sector. For example, ram breed substitution can increase output per ewe by up to 24% with concomitant improvements in carcass quality (Carson et al., 2001). Major opportunities now lie in improving the output potential of hill ewes through breeding. Currently, hill sheep flocks in the UK and Ireland consist mainly of purebred Scottish Blackface, Welsh Mountain, Swaledale and, to a lesser extent, Cheviot ewes. Using purebreds, rather than crossbred ewes, means that the potential benefits of heterosis are not exploited in harsh hill conditions where they are likely to be of greatest benefit. Crossbreeding can also be used to take advantage of breed differences in genetic merit for different traits e.g. hardiness, ease of lambing, prolificacy and carcass traits. In view of this background, a research programme was initiated to investigate the relative merits of a range of crossbred ewe types within hill sheep systems in Northern Ireland. This paper presents the results from the second phase of the study in which the performance of mature ewes (1-3 lambings) was investigated.

Farmers' opinions on welfare, health and production practices in extensive hill sheep flocks in Great Britain

Abstract Despite large numbers of hill sheep reared in the UK, little is known about how hill farmers react to health challenges in their flocks. This paper addresses this lack of knowledge of sheep health management practices and presents farmers' opinions and concerns, particularly regarding ectoparasite control. Focus groups and interviews with UK hill sheep farmers were carried out to collect information on management practices, health concerns, in addition to incidence and impacts of six major ectoparasites (ticks, lice, sheep scab mite, blowfly, keds and headfly), to determine how they viewed the effects of ectoparasites and their control on production practices. We conclude that despite variations between hill sheep farm conditions and levels of input, similar health concerns and ectoparasite issues were found across different hill sheep farming areas of the UK. Farm labour was also an important issue and most farmers would prefer more labour to be available to effectively manage ectoparasites in their flocks. Finally, there was variation in farmers' opinions of the impact of ectoparasite species on welfare and productivity. This variation in opinion can be related to a trend in their past experience of ectoparasites, but no relationships were found with the animal health treatments farmers use, the number of animals in their flock or variation in the type of grazing land available.

Genetic analysis of live weight and ultrasonic fat and muscle traits in a hill sheep flock undergoing breed improvement utilizing an embryo transfer programme

AbstractGenetic parameters for pre-weaning live weights and ultrasonic scanning measurements were estimated from a flock of Scottish Blackface sheep undergoing an embryo transfer programme. Maternal environmental effects could be evaluated without confounding with maternal genetic effects because embryos were transferred to unrelated recipient ewes. The data for the study were collected over a 7-year period (1993-1999) and related to a conventional hill farming system. The data were from 1465 lambs, the progeny of 60 sires, 263 donors and 784 recipient ewes. The only exception to the conventional farming system was at mating time when embryos were collected from selected donor ewes, following superovulation, and transferred to unrelated recipient ewes. Maternal environmental effects were important for birth weight (BW), 4-week weight (W4) and weaning weight (WW) but of less importance for ultrasonic fat depth (UFD), muscle depth (UMD) and muscle width (UMW). The heritabilities of the pre-weaning weights were moderate (0·17 to 0·23). The heritabilities of UFD and UMD were 0·44 and 0·27 respectively and were higher than found in previous similar studies. The heritability of UMW was low, 0·06. The genetic and phenotypic correlations among the pre-weaning weight traits were positive and moderate. There was a positive genetic ( + 0·25) and phenotypic ( + 0·24) correlation between UFD and UMD. The phenotypic and genetic correlations between BW and W4 and the scanning traits (UFD, UMD and UMW) were close to zero, and the correlations of WW with UFD, UMD and UMW were positive. The results of this study clearly demonstrate the importance of maternal environmental effects for lamb weights up to weaning and also suggest that genetic improvement for carcass composition in some populations of extensively reared hill sheep could be achieved more rapidly than previously thought possible.

Variance components due to direct and maternal effects and estimation of breeding values for 12-week weight of Welsh Mountain lambs

AbstractThe purpose of this study was to examine the importance of the genetic and maternal environmental factors influencing the 12-week weight (12WW) of Welsh Mountain lambs and to estimate genetic parameters for this trait. Records of 8880 Welsh Mountain lambs born between 1979 and 1995 were analysed. The records were from the nucleus flock of the CAMDA cooperative breeding group. In this flock selection of replacements had been based on a multi-trait index incorporating lamb growth and maternal ability as important objectives and 12WW as one of the selection criteria. Twelve models were examined, all including direct additive genetic variance and various combinations of genetic and environmental maternal effects. The most appropriate model was chosen based on log-likelihood ratio tests. It included appropriate fixed effects, and direct additive, maternal additive, maternal permanent environment and maternal common environment (litter) random effects that defined proportionally 0⋅21 (h2), 0⋅09 (m2), 0⋅06 (pe2) and 0⋅18 (ce2) of the phenotypic variance. Ignoring the additive maternal effect resulted in inflated estimates of direct heritability and ignoring the environmental effects associated with dam inflated the direct and maternal heritabilities. There was no correlation (P &lt; 0⋅05) between the additive direct and additive maternal effects. Additive direct and maternal breeding values increased by 0⋅12 (s.e. 0⋅006) kg/year and 0Ό3 (s.e. 0⋅003) kg/year respectively. The results demonstrate the effective incorporation of selection index methodology in the context of a hill sheep flock and also the importance of several categories of maternal effects.

The effects of improved management based on ultrasound scanning of scottish blackface ewes from a high hill flock

The objective of the study was to assess the potential benefits of using real-time ultrasound scanning in a hill sheep flock where the incidence of twinning is low. A high hill hirsel of some 320 Scottish Blackface ewes, typically lambing in the range 0.6-0.9 lambs per ewes mated, was divided across age into two groups. One group was scanned, colour marked and subsequently managed according to foetal number (the SCANNED flock). The other group was also scanned but not colour marked, and therefore managed irrespective of foetal number (the UNSCANNED flock).

Correlated responses in lamb mortality due to long term selection for cannon bone length and fleece medullation in sheep

ABSTRACTLamb mortality in a Scottish Blackface hill sheep flock subjected to long term selection for cannon bone length and fleece medullation score was investigated, using maximum likelihood analyses. The selection for cannon bone length and for medullation score had no significant effect on lamb mortality.