Scottish Halfbred Research Articles

Natural scrapie and PrP genotype: case-control studies in British sheep

Natural scrapie in sheep is associated with polymorphisms of the PrP gene, particularly at amino acid codons 136, 154 and 171. This paper reports the results of nine scrapie case-control...

Effects of continuous stocking with sheep or goats on sward composition and animal production from a grass and white clover pasture

Two groups of British Saanen does and two groups of Scottish Halfbred ewes, each rearing twin offspring, were continuously stocked on grass and white clover swards, maintained at a target surface height of 6 cm, over 2 years. In the second year there was either natural rearing or cross-fostering of offspring between animal species at parturition. In both years, for goats and sheep respectively, the total herbage mass was similar (3944 vs. 3634 kg DM ha −1) but the live clover mass was higher for goats (655 vs. 371 kg DM ha −1; P < 0.01), as were the clover growing point numbers (4480 vs. 3509 thousands m −2; P < 0.01) and stolon lengths (87.9 vs. 58.2 m m −2; P < 0.001) measured in the sward. Daily liveweight 0.75 carried was higher on goat paddocks than sheep paddocks (732 vs. 660 kg 0.75 ha −1; P < 0.05). Does lost more weight than ewes during lactation and their kids grew more slowly to 4 weeks than the lambs (e.g. in the first year, 183 vs. 280 g day −1; P < 0.05). Grazing a sward containing a mixture of grass and clover with goats increased the amount of clover in the sward when compared with grazing by sheep. This suggests grazing by goats could be used as a management to increase clover content in mixtures of grass and clover. Kids grew more slowly than lambs and, in general, growth rates of the kids and lambs were little affected by the dam species that reared them.

Temporal variation in grazing behaviour of sheep and the reliability of sampling periods

Grazing behaviour recordings of 24 h duration are frequently taken to represent behaviour patterns typical of a longer period. This experiment tested the repeatability of patterns of grazing behaviour of nine Scottish Halfbred (Border Leicester × Cheviot) yearling female sheep ( Ovis aries L.). Their behaviour was recorded continuously for 7 days between 25 February and 3 March 1992 using an automatic system which measured jaw movements. The mean times of sunrise and sunset during the experiment were 07:02 and 17:55 h. The animals were continuously stocked on a 0.65 ha perennial ryegrass paddock ( Lolium perenne L. cultivar ‘Parcour’) where the sward surface height was maintained between 5 and 6 cm. The hour of the day had a significant effect on time spent eating, idling and ruminating in that hour. There was a recurrent daily pattern of grazing behaviour, which was modified by rainfall. There was also a within-day grazing pattern, with peaks in eating activity every 8 h. Prehension biting rate was significantly affected by hour of the day with a maximum rate of 79 prehension bites min −1 between 03:00 and 04:00 h and a minimum in the late afternoon of 61 min −1. Total jaw movements whilst eating reached a maximum of 167 min −1 around the time of the late afternoon peak in eating activity. It was concluded that a 24 h recording could be taken as representative of grazing behaviour over a 7 day experimental period but care should be exercised to avoid bias due to atypical weather conditions.

The association of a codon 136 PrP gene variant with the occurrence of natural scrapie.

Incidence of both experimental and natural scrapie in sheep has been associated with polymorphisms of the PrP gene. In case/control studies the PrP allele which encodes valine at codon 136 (Val136) is found in 96-100% of naturally infected scrapie sheep of Shetland, Scottish Halfbred and Blue du Maine breeds. In contrast, in healthy animals from the same flocks, the most frequent allele encodes Ala136 (91-100% of sheep). However Val136 does not correlate with incidence of scrapie in two other flocks--Poll Dorsets and Suffolks--and there may therefore be breed differences in PrP genotypes affected by scrapie.

Responses of lactating ewes, offered fresh herbage indoors and when grazing, to supplements containing differing protein concentrations

ABSTRACTThe responses to supplements differing in protein concentration and degradability were measured in lactating ewes and their twin lambs when offered fresh ryegrass either cut or grazed. Housed Scottish Halfbred ewes, offered fresh-cut grass ad libitum received no supplement (N) or supplements with barley and maize starch (B); barley and soya-bean meal (S); barley, soya-bean meal and fish meal (SF) or barley and fish meal (F) in weeks 2 to 7 of lactation. By feeding supplements, herbage organic-matter (OM) intake was depressed (2·00 v. 1·74 kg/day). Mean daily milk yield was increased when protein supplements were given and, because milk protein concentration was higher for supplement F and similar for all other diets, mean daily milk protein output increased with increasing fish meal in the diet. Milk yields were N 2·55, B 2·59, S 3·17, SF 3·15 and F 3·17 kg/day. Total milk solids and fat concentrations were also higher for S, SF and F than N or B. Lambs from ewes supplemented with protein grew faster and the ewes generally lost less weight and body condition compared with unsupplemented ewes.At pasture, Masham ewes grazed at herbage allowances of either 4 (L) or 10 (H) kg OM per day and received no supplement (N) or supplements B or F, for the first 6 weeks of lactation and then, in weeks 7 to 12, grazed without supplements. For NL, BL, FL, NH, BH and FH respectively lamb growth rates from birth to 6 weeks were 235, 242, 274, 267, 286 and 302 g/day; from birth to 12 weeks were 210, 209, 249, 255, 275 and 287 g/day and losses in ewe body-condition score from birth to 12 weeks were 1·28, 1·22, 1·06, 0·97, 0·62 and 0·76.It is concluded that protein supplements increased milk yield and lamb growth rates and that the response tended to be greater with fish meal.

Effect of sward surface height of mixed swards of ryegrass/white clover on the intake and performance by ewes and their twin lambs

Mixed swards of perennial ryegrass (Lolium perenne cv. S23) and white clover (Trifolium repens cv. Huia) were maintained at sward surface heights (SSH) of 3 (GC3), 6 (GC6) and 9 cm (GC9) by continuous variable stocking to examine effects on sward and animal performance. In addition, a pure grass sward of S23 was kept at 6 cm (G6) and fertilized with 14 applications of 30 kg N per ha at fortnightly intervals, beginning on 25 March. The swards were sown in August 1983, cut twice in 1984, in May and June, and then grazed thereafter. Fertilizer was applied to the seedbed at 40 kg N per ha, 20 kg P205 per ha and 20 kg K20 per ha. In March 1984 and 1985, 20 kg per ha each of P205 and K2O were applied to all plots.Dry sheep grazed the paddocks (0.69 ha) to the required SSH's with grazing starting on 4 April, 9 April, 12 April and 24 April for treatments GC3, G6, GC6 and GC9, respectively. On 24 April, two days after lambing, core groups of 8 Scottish Halfbred ewes with twin lambs were put on the plots. Additional ewes, kept on swards similar to the treatment areas, were used to adjust the stocking rate to maintain the SSH's. These were measured three times each week with 200 readings per plot.

Growth and carcass characteristics of crossbred lambs by ten sire breeds, compared at the same estimated carcass subcutaneous fat proportion

ABSTRACTAn evaluation was carried out over a 5-year period in 10 commercial flocks of Scottish Blackface, Scottish Half-bred and Mule ewes to evaluate 10 sire breeds: Border Leicester, Dorset Down, Hampshire Down, He de France, North Country Cheviot, Oxford Down, Southdown, Suffolk, Texel and Wensleydale. An average of 43 sires was used per sire breed.The analysis involved a total of 3360 lambs of which one-third had the left side dissected. Sire breeds were compared when their progeny were slaughtered at the same estimated carcass subcutaneous fat proportion (approx. 120 g/kg).Carcass weights were related to the adult body size of the sire breeds with a range of 4 kg between Southdown and Wensleydale crosses. Crosses by the conventional meat sire breeds tended to have higher daily carcass-weight and lean-tissue gains than those by Border Leicester and Wensleydale sires. Texel and Suffolk crosses did not differ significantly in carcass weight, daily carcass-weight gain, daily lean gain or age at slaughter (P &gt; 0·05).Significant sire-breed × dam-breed interactions were recorded for daily carcass-weight gain and daily lean gain (P &lt; 0·05). Dorset Down and Southdown crosses tended to grow relatively faster when from Mule dams; Texel crosses grew relatively faster when from Blackface dams.There was relatively little difference between sire breeds in visually assessed carcass conformation; all the means were within two points on a 15-point scale. Texel crosses had a higher carcass lean proportion than other crosses: their advantage over Suffolk crosses was 22 g/kg.

Carcass composition of crossbred lambs by ten sire breeds compared at the same carcass subcutaneous fat proportion

ABSTRACTAn evaluation was carried out over a 5-year period in 10 commercial flocks of Scottish Blackface, Scottish Half-bred and Mule ewes to examine the carcass characteristics of 10 sire breeds: Border Leicester, Dorset Down, Hampshire Down, He de France, North Country Cheviot, Oxford Down, Southdown, Suffolk, Texel and Wensleydale. An average of 43 sires was used per sire breed.The analyses involved tissue separation data for a total of 1402 lambs. Analyses were carried out separately for early and late flocks determined by the time of the year in which lambs were slaughtered. Sire breeds were compared when their progeny were slaughtered at the same carcass subcutaneous fat proportion (125 g/kg, early flocks; 116 g/kg, late flocks).Texel crosses had the highest carcass lean proportion (P &lt; 005); their advantages over the Suffolk crosses were 19 g/kg (early flocks) and 17 g/kg (late flocks) reflecting both a higher lean:bone ratio and a higher lean:fat ratio. The Suffolk crosses had a similar carcass lean proportion to other breed crosses. Border Leicester, North Country Cheviot, Texel and Wensleydale crosses tended to have less of their total lean distributed in the higher-priced joints than the Down breed crosses. However, the differences were relatively small and not of major commercial significance: the range between sire breeds was 0-01 to 0-02 of average retail value.

Glucosephosphate isomerase polymorphism in sheep.

Two types of glucosephosphate isomerase (GPI) are described for the first time in sheep. Type T produced a 3-band pattern on polyacrylamide gel electrophoresis of serum samples, whereas type M produced a pattern of 5-7 bands. When 23 Scottish Halfbred ewes showing type T were mated to 3 Suffolk rams showing type M, their 32 offspring had frequencies of 0.72 and 0.28 for T and M respectively. There was no conclusive evidence that the types were controlled by codominant alleles or by simple Mendelian inheritance and neither was sex-linked. The frequency of the rarer type (M) was sufficiently high to provide conclusive evidence of true enzyme polymorphism.

Effects of cereal and protein supplements to swedes (Brassica napus) on intake and performance of pregnant and lactating ewes kept indoors

ABSTRACTIndividually penned Finnish Landrace × Dorset Horn and Suffolk × Scottish Halfbred ewes were used to study the effects of supplementing diets based on ad libitum swedes. Supplementing a pregnancy diet of ad libitum swedes plus 225 g of hay with 454 g of a barley/soya bean meal supplement per day had no effect on swede intake or ewe performance in terms of the birth weight and survival of lambs born. Level of swede intake during late pregnancy was constant.In early lactation, ewes offered ad libitum swedes plus 225 g hay per day were supplemented with 454 g of either barley or soya bean meal daily. Soya bean meal supplementation resulted in a 014 increase in swede intake to give a daily intake of 113g dry matter per kgM 0·7·5 and a total live-weight gain of 218kg in early lactation compared with a loss of 2·53 kg by barley-supplemented ewes. Lamb daily gain increased by 54g per day. The results are discussed in relation to trends towards the housing of ewes and current feeding practices for lactating ewes.

A survey of the carcass characteristics of the main types of British lamb

SUMMARYCommercial lamb carcasses were surveyed in 1971/72 as part of the development programme for a national classification scheme for Great Britain. Carcasses of 421 castrated male lambs were evaluated and their left sides dissected. The sample comprised seven groups representing the main breed types in the national population. Within these groups, lambs were selected from three regions on each of three occasions corresponding with the beginning, middle and end of the normal slaughtering season for each group.The overall means (±SD) for side weight and percentage subcutaneous fat in the side were 8·3 ± 1·8 kg and 12·6 ± 3·2 respectively. When adjusted to the overall mean subcutaneous fat percentage (constant % SF), the breed-type side weight means ranged from 6·4 kg (Welsh Mountain) to 10·8 kg (British Longwool). At constant% SF, lambs slaughtered earlier in the season were lighter than those of the same breed type slaughtered later.Significant differences (P&lt;0·05) were recorded between breed-type groups in fat distribution and lean/bone ratio. These were reflected as important differences in percentage lean at constant % SF, group means ranging from 54·5 (lambs by Suffolk rams out of Scottish Halfbred ewes) to 56·7 (lambs by British Longwool rams out of hill ewes).When lambs of the same breed type from different regions were compared at constant % SF and constant side weight, there were few important differences in carcass characteristics.The results are discussed in relation to the classification scheme which has since been introduced by the Meat and Livestock Commission.

The effect of density on the intake of dried forage pellets by young ruminants

SUMMARYDried grass pellets of high density (1·3 g/ml) were fed ad libitum to British Friesian male calves 5 to 7 mo old (Experiment 1) or 2 to 5 mo old (Experiment 2). All eight animals in Experiment 1 and eight out of 12 in Experiment 2 were fitted with rumen fistulae. In some subperiods of both experiments, pellets were broken down in water and administered as a slurry directly into the rumen at a level equivalent to approximately one-third that of voluntary intake. Intake per os was significantly reduced by this treatment but total intake (per os+per rumen) was not affected.In Experiment 3 pellets of high (1·24 g/ml) or medium (1·14 g/ml) density were fed ad libitum to 40 9-mo-old Suffolk × Scottish Halfbred wether sheep, either alone or with access limited to 3 hr a day, in which case chopped hay was always available. Pellet density did not affect total intake, but when offered as supplements to hay the consumption of medium-density pellets was higher than that of high-density pellets. In all three experiments animals required 2 or 3 weeks to reach maximum intake of pellets. Over the 42 days of Experiment 3 the proportion of pellets in the feed consumed by animals given pellets as supplements to hay increased from 60 to 80%.

The influence of the tasmanian Fine-Woolled Merino on carcass characteristics of lambs

Growth and carcass characteristics have been studied in lambs bred so as to illustrate the influence of Fine-Woolled Merino ancestry in contributing from 0% to 100% of the genotype. Five groups of lambs were bred as follows: 1. 0% Merino: Suffolk ♂ × Scottish Halfbred ♀ 2. 25% Merino: Suffolk ♂ × (Merino ♂ × Scottish Halfbred ♀) ♀ 3. 50% Merino: Merino ♂ × Scottish Halfbred ♀ 4. 75% Merino: Merino ♂ × (Merino ♂ × Scottish Halfbred ♀) ♀ 5. 100% Merino: Merino ♂ × Merino ♀ All the lambs were reared artificially on cold milk substitute after suckling their dams for one day only. They were weaned at six weeks of age and subsequently fattened on a barley plus fish meal concentrate diet to an empty body weight of approximately 35 kg, when they were slaughtered. Complete growth, slaughter and carcass records were taken. The main effects of increasing the proportion of Merino were to decrease the daily liveweight gain; to decrease the percentage of bone and increase the muscle:bone ratio in the trimmed carcass; in respect of carcass conformation to increase the percentage of thorax, rib, flank and foreloin, and decrease the percentage of upper leg and shoulder; to alter carcass shape, particularly leg shape by increasing its length and decreasing its thickness; and with regard to fat deposition, to increase the internal fat and decrease the external fat in the empty body. The growth, carcass composition and joint proportion differences can be related to the small mature size of the pure Merino, and thus its greater maturity at slaughter; shape and fat distribution differences typify the more primitive and less improved meat character of the Merino.

ラム肉生産に関する試験

1. The body weight gain and carcass characteristics of Suffolk male lambs grazed for 110 days on the grass pastures receiving two levels (480 and 1920kg/ha) of a compound fertilizer (12 : 9 : 12) were studied. And also, Suffolk X Scottish Half-bred were compared with Suffolk on the more fertilized pastures.2. The average stocking rate was 15.6 lambs/ha on the less fertilized pasture and 26.4 lambs/ha on the more fertilized pasture.3. The body weight gain of Suffolk lambs was 79g/day on the less fertilized pasture and 111g/day on the more fertilized pasture. Suffolk Lambs on the more fertilized pasture reached to 20.5kg of the carcass weight, but they were unsuitable for “lamb” in terms of fat thickness and rib eye area.4. The body weight gain of Suffolk X Scottish Half-bred lambs on the more fertilized pasture was 110g/day. They did not reach to 20kg of the carcass weight, but they were superior to Suffolk lambs in terms of fat thickness and rib eye area.5. Carcass output per hectare was 54.3kg on the less fertilized pasture and 135.3kg on the more fertilized pasture.

A comparison of the sown swards of perennial ryegrass S. 24 and Italian ryegrass RvP in a two-year lamb production system, with different breeds of sheep

SummaryA comparison was made between an intensive system of lamb production based on Italian ryegrass RvP and one based on perennial ryegrass S. 24, over 2 years, each at three stocking rates (14, 17, 20 ewes/ha). More grass was grown in the first year than in the second when the yield of RvP was particularly reduced. The ewes and lambs ate more RvP than S. 24 but there was no difference in lamb growth rate. The lambs grew faster at the low stocking rate from 0 to 18 weeks and from 0 to slaughter than at the medium and high stocking rates, in both years. Ewe intake and lamb growth rate were higher in the second year than the first. The Masham ewes with two lambs ate significantly more grass per unit of body weight than the Finnish Landrace × Scottish Halfbred and Finnish Landrace × Scottish Blackface ewes, and their lambs grew significantly faster. It was concluded that for an intensive system of lamb production from grass, S. 24 was more suitable than RvP.

A model of the effect of nutrition on litter size and weight in the pregnant ewe

A model has been developed to predict litter size, lamb birthweight, perinatal lamb mortality and ewe weight change during the second part of pregnancy from different nutritional regimes. The model, which can contain 200 ewes, has been tested against field data from experimental flocks of Masham, Finn × Scottish Halfbred and Welsh Mountain ewes. The prediction of litter size from weight at mating is reasonable as is the prediction of mean lamb birthweight for a range of litter sizes. The model currently overestimates the weight of Finn × S. Halfbred singles, and underestimates ewe weight increase in late pregnancy and the mortality of lambs from some litter sizes. The problem of predictive accuracy is discussed and weighed against the task of collecting a great deal of data. The problem with a predictive reproductive model is that reproductive performance is a breed characteristic whereas nutritional demand can be predicted from size and physiological state.

Some consequences of high flock prolificacy in an intensive grassland sheep production system

SummaryAn intensive sheep production system using flocks of 100 Scottish Halfbred (SHB), 100 Welsh Speckleface (WSF) and 100 Finn Blackface (FBF) ewes maintained by 8, 4 and 6 ha grassland respectively for a 5-year period, was investigated to establish the consequences of high flock prolificacy and the measures taken to achieve it, including PMS administration. Mating occurred in late October/November at ewe: ram ratios of 25 or 33: 1. Ewes were housed in winter and fed silage, with supplementary cereals in late pregnancy. Lambs in excess of 2 (SHB) and 1 (WSF and FBF) per ewe were artificially reared and fattened indoors; ewes and lambs at grass were rotationally grazed (with forward creep grazing by the lambs). Prolificacy in the SHB breed was 225 lambs born per 100 ewes mated for untreated ewes and 237 for hormone-treated ewes; 119 and 155 respectively for WSF ewes; and 255 for FBF ewes (all untreated). Lambs sold per 100 ewes mated were: for SHB, 200 and 177; WSF, 102 and 107; FBF, 201.Good ewe condition and heavy live weights at mating were associated with appetite problems on silage in late pregnancy; PMS injection with a failure to secure conception rates above 80% at the critical oestrus and a markedly lower prolificacy for ewes conceiving at later oestruses; mating in the middle of the breeding season and March/April lambing with slow lamb growth rates on grass in July and August. Hormone-induced high prolificacy was associated with a greater proportion of large multiple litters than natural high prolificacy, and consequent smaller lamb birth weights and more perinatal mortality. There was a significant negative regression relating fleece weight with litter size. The results suggest the existence of an optimal level of prolificacy for the system employed.

A NOTE ON THE INTAKE OF LACTATING EWES AT PASTURE

ABSTRACTThe grass intake of three breeds of ewe was measured in the 5th–7th week (Period 1) and the 9th–11th week (Period 2) of lactation. The breeds of ewe were Finnish Landrace × Scottish Halfbred (FH), Finnish Landrace × Scottish Blackface (FB) and Thornber Colburn Colbred × Scottish Blackface (TC2). The immature FH ewes had a lower intake of digestible OM (26±1g/kg LW per day) than the mature FB (32±2g/kg LW per day) and TC2 ewes (33±5g/kg LW per day) in Period 1, but there were no difference between the breeds in Period 2. The intakes in Period 2 were significantly lower than those in Period 1.

The Effect of Pregnant Mare Serum Gonadotrophin on Ovulation Rate in Scottish Half-Bred and Scottish Blackface Ewes

SUMMARY The effects on ovulation rate of intramuscular or subcutaneous injection of pregnant mare serum gonadotrophin (PMSG), and the timing of this injection in relation to the oestrous cycle, were examined in two experiments with Scottish Half-bred and Scottish Blackface ewes. Oestrus was synchronized with progestagen sponges in all experimental treatment groups with the exception of the group injected on day 13 of the oestrous cycle. PMSG was injected at sponge withdrawal, at the onset of oestrus and 8 hours after the onset of oestrus and on day 13 of the oestrous cycle. Neither the route of administration nor the timing of the injection influenced ovulation rate. Ovulation rate was highest with 1500 i.u. PMSG and 1000 i.u. PMSG in the Scottish Half-bred and Scottish Blackface respectively. There was a suggestion that conception rate at the first post-treatment oestrus was reduced by progestagen treatment.

Silage as a feed for pregnant ewes

1. Four experiments are described in which silages or kale were given to groups of ewes in the later stages of pregnancy and their voluntary intake recorded. A concentrate supplement was given in the last few weeks of pregnancy in each experiment. In experiments 1, 3 and 4 the ewes were housed in a semi-covered yard.2. In the first experiment, three groups of 10 Scottish Halfbred ewes were offered one of three silages. A fourth group was offered all three in equal amounts. The silage with a low DM content, low crude-protein content, low pH and high crude-fibre content was eaten in smaller quantities than the other two silages. The ewes fed on this poor silage gained less weight during the latter half of pregnancy.3. In a second experiment four groups of 15 ewes were offered either silage or kale and housed in a Dutch barn or left in a small paddock. There was no difference between the results from the two silage-fed groups in any respect. The ewes offered kale outside ate less than those offered it inside; they gained less weight and produced lighter lambs.4. There were two groups of 13 ewes in experiment 3a, one group lambing 5 weeks before the other. Both were fed on the sanie silage; intake was higher in the late lambing group but there was no difference in lamb birth weights.5. Experiment 3 was repeated with 15 ewes per group; the silage was of much poorer quality, intake being low and the ewes gaining very little weight. Lamb birth weights and growth rates were low.6. Groups of 15 Scottish Halfbred (90 kg. live-weight) and 15 Speckle-faced Welsh (45 kg.) ewes were fed on yet another silage. The Specklefaced ewes ate more silage DM per unit weight than did the Halfbred ewes and gained in weight, whereas the Halfbreds did not gain.7. In all experiments there was a decline in silage intake in the last few weeks of pregnancy. This decline did not always coincide with the start of concentrate feeding.8. The results are discussed and comparisons made between experiments. Suggestions are made for the feeding and management of ewes fed on silage, including the recommendation that a silage for pregnant ewes should have at least 20% DM and 14% crude protein in the DM, but not more than 32% crude fibre in the DM.