Hill Sheep Systems Research Articles

Genetic improvement of hill sheep – Impacts on profitability and greenhouse gas emissions

Scottish Blackface hill sheep from two research flocks, based in environments of differing climatic severity, were selected for 8 years based on a selection index incorporating ewe and lamb traits, designed to improve flock sustainability and profitability. Compared to a control line of sheep kept at average performance, after 8 years of selection, sheep selected on this index have shown increased overall profitability, largely due to an increase in the weight of lambs at weaning (2–2.5kg, depending on farm). A model was used to estimate greenhouse gas (GHG) emission changes in hill sheep systems when performance traits were altered, to investigate the potential to use genetic selection as a tool to reduce GHG. Results from this model suggested that the actual genetic changes observed in the hill flocks are likely to have increased GHG emissions, both at the level of the breeding ewe and per kg of lamb produced, mainly as a result of an increase in ewe mature size (2.8–3kg difference vs. the control line after 8 years of selection). Any future selection index designed to minimise GHG emissions, would need to incur heavier penalties for increasing ewe mature weight, compared to the current economic index, which would be likely to reduce selection response in lamb growth. These changes are only likely to occur if payment or subsidy systems were to change in a way that would reward producers for reducing GHG emissions.

Effects of sire breed on ewe dystocia, lamb survival and weaned lamb output in hill sheep systems

A study was carried out on six hill farms, located in the main hill regions of Northern Ireland, over three breeding seasons to investigate the effect of sire breed on ewe dystocia, lamb survival and weaned lamb output. On each farm, groups of 26 to 40 purebred Scottish Blackface ewes (n = 3174) were crossed with Blackface, Swaledale, North Country Cheviot, Lleyn and Texel sires by natural service (year 1) and artificial insemination (years 2 and 3). Each of the mating groups was initially balanced for ewe age, live weight and condition score, and a total of 15 sires of each breed were used over the 3 years. In total, 2272 ewes were recorded at lambing, producing 3451 lambs, over the 3 years. Sire breed had a significant effect (P < 0.001) on lamb birth weight with Blackface and Swaledale the lowest and Texel the highest. The proportion of ewes with dystocia was higher with Texel sires compared with Lleyn, Swaledale and Blackface sires (P < 0.05). Ewes mated to Cheviot sires had more dystocia than those mated to Blackface and Swaledale sires (P < 0.05), while ewes mated to Lleyn sire breed had more dystocia (P < 0.05) than those mated to Blackface sire breed. Most of the incidence of dystocia was attributable to increased lamb birth weight (P < 0.001), and some to litter size (P < 0.05). Swaledale, Cheviot, Lleyn and Texel sire breeds increased the incidence of malpresentations (P < 0.05). Lamb live weight at weaning was higher with Texel- and Cheviot- and Lleyn-sired lambs compared with Blackface- and Swaledale-sired lambs (P < 0.01). The level of lamb mortality at birth was not affected by sire breed. However, lamb mortality at weaning was lower for Lleyn-sired lambs compared with the other lamb genotypes (P < 0.05). These results indicate that the use of sires from larger breeds, such as Lleyn and Texel, within the Blackface ewe flocks can increase lamb output, with no apparent detrimental effects on lamb mortality or ewe survival, but increased assistance at lambing will be required.

The effect of genotype and diet on lamb meat quality from hill sheep systems

Crossbreeding can be used in the hill sector to improve the efficiency of production. Carsonet al. (2001) showed that ram breed substitution increased lamb output per ewe by 24% with concomitant improvements in carcass quality. However, information is required for a range of crossing sire breeds for the hill sector to enable the most effective crossbreeding programmes to be developed. Therefore, the primary aim of this study was to evaluate the effects of a range of lamb genotypes on lamb meat quality. Furthermore, a range of production systems (long-keep grass-based systems to short-keep concentrate-based systems) are used to finish hill lambs. Diet type (i.e. roughage-versus concentrate-based) can also affect lamb growth rates and carcass characteristics (Carsonet al., 2001). Consequently, a secondary aim of this study was to evaluate the effects of diet and its interaction with lamb genotype on lamb meat quality.

Effects of genotype and plane of nutrition on growth and carcass characteristics of lambs from hill sheep systems

The objective of this study was to determine the effect of lamb genotype and plane of nutrition on post-weaning lamb growth, and carcass characteristics in hill sheep systems. The lamb genotypes compared were as follows: purebred Scottish Blackface, Swaledale × Scottish Blackface, Cheviot × Scottish Blackface, Lleyn × Scottish Blackface and Texel × Scottish Blackface lambs. During the finishing period, lambs were allocated to a (i) low plane of nutrition (LP), based on a fixed allowance of dried grass pellets representing a grass-based system; (ii) high plane of nutrition (HP-cereal), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate offered ad libitum; (iii) high plane of nutrition (HP-cereal/oil), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate containing oilseed rape offered ad libitum. There were significant genotype × diet interactions for dry matter (DM) intake (P < 0.001), live weight gain (P < 0.05) and carcass gain (P < 0.05). On the LP diet, carcass gains were higher for Texel cross compared to Blackface and Swaledale cross lambs (P < 0.05). On both HP diets, carcass gains were lower in Blackface and Swaledale crosses compared with the Cheviot, Lleyn and Texel cross lambs (P < 0.01). Feed conversion efficiency, expressed in terms of carcass gain per unit of DM, was highest for Texel cross and Cheviot cross, lowest in Swaledale cross and Blackface and intermediate for Lleyn cross lambs (P < 0.001). Conformation classification was lowest for Swaledale cross (P < 0.05) and highest for Texel cross lambs (P < 0.001), whilst those of Blackface, Cheviot and Lleyn cross lambs were similar. Carcasses from Blackface and Lleyn cross lambs had higher fat classifications than Texel and Cheviot cross lambs (P < 0.01). Feed conversion efficiency was lowest with the LP diet compared with the HP diets, resulting in a 5-week longer finishing period and lower carcass weights, fat scores, dressing proportions and subcutaneous fat depth measurements. These results indicate that crossbreeding can have a major effect on lamb performance in the hill sheep sector. Feeding a HP increased lamb growth rates, particularly for high growth-potential genotypes, improved feed efficiency, shortened the finishing period but increased carcass fatness. Including oilseed rape in concentrate-based diets did not affect performance.

Effect of selenium supplementation on the performance of ewes from hill sheep systems

Selenium (Se) is an essential trace mineral that when deficient, has been associated with increased disease evidence in sheep. Selenium deficient areas are widespread in UK and Ireland affecting, soils, forages and consequently livestock. Se supplementation of ewes throughout pregnancy has been reported to reduce peri-natal lamb mortality and improve lamb growth rates (Muñoz et al., 2005). The aim of this trial was to evaluate the effect of long term Se supplementation of adult ewes within a range of hill sheep systems.

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.

Effects of crossbred ewe genotype and ram genotype on lamb meat quality from the lowland sheep flock

Ewe and ram genotype have been shown to have a significant effect on carcass quality. For example, Dawson and Carson (2001) demonstrated that lambs from Bluefaced Leicester X Blackface ewes were of poorer conformation than lambs from the Texel X Blackface, Suffolk X Cheviot or Texel Cheviot ewes while high lean growth index sired lambs had an improved conformation compared with lambs sired by non-recorded rams. Recent work has shown that genotype can have significant effects on the meat quality of lambs from hill sheep systems (Carson et al. 2001). Therefore the aim of the current study was to investigate the effect of ewe and ram genotype from the lowland sector on meat quality.

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 prolificacy, lamb viability and weaned lamb output. On each farm, groups of 40 Scottish Blackface ewes (mature weight of 53·8 kg) were mated to Scottish Blackface, Blue-Faced Leicester and Texel rams. Similarly, groups of 40 Wicklow Cheviot ewes (mature weight 63·7 kg) were mated to Cheviot, Suffolk and Texel rams. All ewe×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×ewe breed interaction (P &lt; 0·001) indicating that, whilst prolificacy was similar in Blackface and Cheviot ewes on the majority of farms (4 out of 6), on one farm prolificacy was higher in Blackface and on another lower, compared with Cheviot ewes. There were no farm×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 &lt; 0·001). Cheviot ewes produced heavier Texel-sired lambs compared with Blackface ewes (4·76 versus 4·51 (S.E. 0·076) kg; P &lt; 0·05). Mortality levels were similar in lambs produced from Blackface and Cheviot ewes. The weight of lamb weaned per ewe was higher in Cheviot compared with Blackface ewes (41·5 versus 38·8 (S.E. 1·01) kg/ewe lambed; P &lt; 0·05). However, the weight of lamb weaned per kg of ewe metabolic weight did not differ significantly between the breeds.With Blackface ewes, the proportion of ewes lambing without assistance was lower for Blue-Faced Leicester compared with Blackface sires (P &lt; 0·001). In addition, the proportion of ewes lambing without assistance was lower (P &lt; 0·001) for Texel compared with both Blackface and Blue-Faced Leicester-sired lambs. Lamb birth weights were higher in Blue-Faced Leicester (P &lt; 0·05) and Texel (P &lt; 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 &lt; 0·001) with Blue-Faced Leicester and Texel compared with Blackface sires (39·8, 38·8 and 33·8 (S.E. 1·01) kg, respectively). The carcass weight of the male lambs 3 weeks post-weaning was significantly higher (P &lt; 0·001) in Blue-Faced Leicester and Texel compared with Blackface-sired lambs (12·5, 12·0 and 10·2 (S.E. 0·20) kg, respectively). Carcass conformation classification was higher in Texel compared with Blue-Faced Leicester and Blackface-sired lambs (P &lt; 0·001). Fat classification was higher in Texel (P &lt; 0·01) and Blue-Faced Leicester (P &lt; 0·05) compared with Blackface-sired lambs. With Cheviot ewes, a greater number of ewes lambed unaided (P &lt; 0·05) with Cheviot and Texel compared with Suffolk-sired lambs. The number of lambs born dead was higher (P &lt; 0·01) with Suffolk compared with Cheviot and Texel-sired lambs (0·14, 0·08 and 0·07 (S.E. 0·016) lambs born dead/ewe lambed, respectively). Growth rates were higher in Suffolk compared with Cheviot-sired lambs (P &lt; 0·05). Overall, Suffolk (P = 0·06) and Texel (P &lt; 0·001) sires produced a greater weight of lamb at weaning compared with Cheviot sires (40·0, 41·5 and 36·9 (S.E. 1·01) kg, respectively). Carcass weight of lambs 3 weeks post-weaning was higher for Suffolk (P &lt; 0·05) and Texel (P &lt; 0·01) compared with Cheviot-sired male lambs. Carcass conformation classification was higher in Texel and Suffolk compared with Cheviot-sired (P &lt; 0·001) lambs. Fat classification was also higher in Texel compared with Cheviot-sired lambs (P &lt; 0·05). Carcass chemical composition was not significantly affected by lamb genotype.

Effects of genotype and dietary forage to concentrate ratio during the finishing period on carcass characteristics and meat quality of lambs from hill sheep systems

The study investigated the effects of lamb genotype produced from hill flocks on feed efficiency, carcass characteristics and meat quality in animals finished on either a high forage:concentrate ratio diet (HFC) or a low forage:concentrate ratio diet (LFC). Purebred Scottish Blackface (BXB) lambs were compared with Blue-Faced Leicester×Scottish Blackface (BLXB) and Texel×Scottish Blackface (TXB) lambs. Purebred Cheviot (CXC), Suffolk×Cheviot (SXC) and Texel×Cheviot (TXC) lambs were also investigated. Lambs on the LFC diet were offered grass silage and concentrates mixed in the proportion of 0·80 silage and 0·20 concentrates on a dry matter basis. The LFC diet consisted of 0·20 grass silage and 0·80 concentrates on a dry matter basis. Representative lambs were slaughtered at the start of the experiment and on reaching 38 and 46 kg live weight. Averaged over the two slaughter weights, within the Blackface cross lambs, BXB had a lower liveweight gain (P &lt; 0·01) than either BLXB or TXB (138, 207 and 203 (S.E. 11·1) g/day, respectively). Within the Cheviot cross lambs, CXC had a lower liveweight gain (P &lt; 0·05) than SXC (188 v. 220 (S.E. 11·1) g/day), while SXC and TXC (204 g/day) had similar liveweight gains. Lambs on the LFC diet had a higher dressing proportion (P &lt; 0·001) compared with lambs finished on the HFC diet (0·466 v. 0·434 (S.E. 0·0018) kg carcass per kg live weight). Averaged over the two slaughter weights BXB lambs had a lower (P &lt; 0·05) dressing proportion than the other genotypes. Carcass conformation classification (assessed on a five-point scale) was higher (P &lt; 0·001) in lambs finished on the LFC diet (3·0 v. 2·4 (S.E. 0·04)). Conformation classification was higher in lambs produced from Cheviot compared with Blackface ewes (P &lt; 0·05). Within the Blackface cross lambs, BXB and BLXB lambs had a lower conformation classification (P &lt; 0·001) than TXB lambs (2·4, 2·4 and 2·9 (S.E. 0·08) respectively). Within the Cheviot ewes, TXC lambs had a higher (P &lt; 0·001) classification than either CXC or SXC (3·1, 2·7 and 2·7 (S.E. 0·08) respectively). Lambs finished on the LFC diet had a higher fat classification score compared with lambs on the HFC diet (P &lt; 0·001) (3·4 v. 2·8 (S.E. 0·04)). Fat classification was similar across all genotypes. Lambs finished on the LFC diet had a lower ash content in the carcass than lambs finished on a HFC diet (P &lt; 0·01) (44 v. 47 (S.E. 0·8) g/kg). Lamb genotype and dietary forage:concentrate ratio had no significant effect on cooking loss, sarcomere length, Warner–Bratzler shear force and L* values. Ultimate pH (pHU) was not influenced by dietary forage:concentrate ratio, but was significantly (P &lt; 0·01) higher in BXB lambs compared with BLXB, TXB, CXC and TXC lambs. Lambs offered the LFC diet during the finishing period had significantly higher values for a* (P &lt; 0·05), b* (P &lt; 0·001), C* (P &lt; 0·001) and H0 (P &lt; 0·05) than lambs offered a HFC diet. Of these parameters only b* was significantly affected by lamb genotype, with BXB lambs having a lower value (P &lt; 0·05) than the other genotypes.

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

Improvements in the level and quality of lamb output are required to help sustain the financial viability of hill sheep farming. In the lowland sector breed substitution has been shown to be an effective means of increasing ewe productivity and lamb carcass lean content. However, there is a lack of adequate contemporary breed comparisons for the hill sector to base breeding decisions on. Consequently, the objectives of this study were to investigate the effects of ewe and ram breed on lamb output under a range of hill environments.

Animal welfare and sustainability of production under extensive conditions—A European perspective

Many factors associated with welfare of animals kept under extensive conditions differs from those in intensive systems. Across Europe both the welfare of the animals and the sustainability of production are under pressure. This paper concentrates on Scottish hill sheep systems because they provide particularly powerful examples of links between welfare, sustainability and forces to further extensify production. These systems are currently extensive with relatively little daily care of stock. Lamb mortality is taken as an indicator of welfare within the flock. Links are described between level of nutrition of the pregnant ewe, supervision and nutrition during the period of lambing and level of lamb mortality. The impact of reductions in flock income upon the capacity to support fixed costs, particularly those of labour are discussed. In a worked example, a 30% reduction in both flock size and income would need a 74% reduction in fixed costs to achieve the same flock gross margin. Converting this to labour saving would increase sheep to shepherd ratio from 817: 1 to 1485:1. The impact of this type of reduction on animal care is discussed. A model considering shepherding at lambing time at different densities of sheep clearly demonstrates how more extensive stocking rates during lambing dramatically reduce the effectiveness of the shepherd and the number of sheep he can provide close attention to during lambing. It is concluded that forces to extensify already extensive systems are likely to lead to possibilities of poorer welfare through reduced animal care. Conflict is predicted between policies which seek to reduce stocking rates for environmental reasons and those that in combination achieve social and animal welfare objectives by attempting to maintain labour.

The effect of increased inputs to twin-bearing ewes within an extensive hill sheep system

There is a general belief that reduced stock numbers on hill areas will be beneficial to the environment. A decrease in stock numbers may lead to farmers opting for lower input systems of hill sheep production in order to reduce costs, to meet the requirements of specific schemes or simply to maintain profitability. A large scale systems experiment has been set up at SAC Kirkton and Auchtertyre Farms to examine the effects of extensification on the ecology, animal production and welfare and the socio-economics of the local community. Within this extensive system, a 4-year trial was undertaken to examine the effects of a limited increase in inputs to twin-bearing ewes which are particularly at risk within such a system.

The effect of increased inputs to twin-bearing ewes within an extensive hill sheep system

There is a general belief that reduced stock numbers on hill areas will be beneficial to the environment. A decrease in stock numbers may lead to farmers opting for lower input systems of hill sheep production in order to reduce costs, to meet the requirements of specific schemes or simply to maintain profitability. A large scale systems experiment has been set up at SAC Kirkton and Auchtertyre Farms to examine the effects of extensification on the ecology, animal production and welfare and the socio-economics of the local community. Within this extensive system, a 4-year trial was undertaken to examine the effects of a limited increase in inputs to twin-bearing ewes which are particularly at risk within such a system.

The effects of shepherding and nutritional inputs in an extensive hill sheep system

There is increasing pressure on hill farmers to reduce stock numbers on the hills. With such a reduction in sheep numbers, farmers would have the option of either maintaining or reducing management and physical inputs. In general, current extensive hill sheep farming systems are characterised by low stocking densities, low inputs and high lamb mortality.The trial was conducted as part of a work programme studying extensive systems. Compared to a system with very low inputs this trial examined the effects of increasing inputs, in terms of supplementary feeding in late pregnancy and shepherding at lambing.Within an extensive hill fanning system (0.66 ewes/ha) two hundred ewes were allocated to one of two nutritional treatments in late pregnancy together with the provision or absence of shepherding at lambing in a 2x2 factorial design. All the ewes were of the Scottish Blackface breed and were mated on the open hill without access to improved grazing. Ewes remained on the hill until mid-pregnancy at which stage they were assigned to either Group H (supplementation with feedblocks, low forage availability) or Group L (minimal supplementation, high forage availability). Group L continued to graze on the open hill whilst Group H were confined to a hill park (approximately 45 ha).

Strategies to avoid parasitic gastro-enteritis in an intensive organic hill sheep system

In hill sheep systems, a major concern for health and welfare is for lambs grazing improved land at higher stocking rates and succumbing to parasitic gastro-enteritis. With only a small amount of improved land available, there is little or no scope for ‘clean grazing’ systems as access to this better land is crucial on an annual basis to achieve better performance from the flock. Access at lambing and at ewe mating is of particular value. There may however be some scope for reduced parasitic challenge to lambs during the summer grazing period because of the differential in stocking densities between the hill and the improved grazings.

The effects of increased prolificacy on lamb and ewe mortality in an intensive hill sheep system

Increased prolificacy is often believed to increase the incidence of both lamb and ewe mortality especially in harsher environments. Fecundin® (Coopers Pittman Moore) is a vaccine which leads to immunization against androstenedione and a resulting increase in prolificacy (Rhind, 1987). The use of this drug gives a method of manipulating prolificacy without confounding any effects with improved nutrition, the most usual means of modifying reproductive success.A programme was commenced in 1985 in which half the ewes in a flock of Scottish Blackface ewes was vaccinated with Fecundin (F), the remainder left unvaccinated (N). In subsequent years ewes were maintained on the same treatment. The data presented here are an analysis of a single age group of ewes completing a full lifetime on each treatment. Eighty-five ewes were allocated at random to each treatment. These were vaccinated in autumn 1985, given a booster vaccination 4 weeks pre-ram joining in 1986, 1987 and 1988 and sold as ‘cast for age’ after lamb weaning in 1989. With the exception of injection with Fecundin, at all times management was independent of treatment.

3.2 Modelling Sheep Systems

At the Hill Farming Research Organization (HFRO), we have been modelling various components of sheep systems and we have also attempted to model, where a need was seen, whole sheep systems at different levels of organization. The sheep systems involved are of course pastoral grazing systems on hill or upland farms. The purpose of this paper is to briefly describe these models, to identify reasons for their existence and to outline some of the problems encountered in their construction.Models have been constructed at HFRO to satisfy particular needs. They cover a spectrum of interests. There are those which are concerned with resource allocation and economic evaluation, those which are built in an attempt to develop more precise operational management procedures and those which describe biological mechanisms and processes which may be conceptual but which provide a better understanding of particular components of an animal production system.The first model (Maxwell, Eadie and Sibbald, 1973) was built to provide answers to the economic questions “Is a particular level of investment in a hill sheep system a viable proposition in both the short and the long term?” and “How does the economic performance of this strategy compare with those of alternatives?”, alternatives being, for example, different levels and rates of flock build-up, with variations in the timing of investments. The model makes year-by-year calculations of cash flow and balance based on Gross Margin, taking account of capital invested, changes in variable costs, tax and interest rates. The Gross Margin is determined from price and cost data and from biological performance. The model also calculates overall economic performance, for a pre-selected project length, as Net Present Value and Internal Rate of Return, taking account of increased stock valuation. These results are used to compare alternative schemes with different rates of investment.