Suffolk Cross Lambs Research Articles

The impact of gastrointestinal parasitism on the behaviour and welfare of weaned housed lambs

Gastrointestinal (GI) parasitism is a health and production concern in sheep, yet its impact on animal welfare remains unclear. The impact of subclinical infections is especially ambiguous as GI parasitism often remains undiagnosed until clinical signs such as diarrhoea are evident. This study applied quantitative and qualitative methods to examine the effects of subclinical Teladorsagia circumcincta infection on the behaviour and welfare of 96 Suffolk-cross lambs (24 pens of 4 lambs) weaned at 10 weeks old. The hypothesis that parasitism causes negative affective states was tested. Lambs were divided into three groups at the pen level: ad-lib fed control (AC), restricted-fed control (RC), and ad-lib fed parasitised (AP). Parasitised lambs (AP) were dosed three times weekly with 7000 third stage T. circumcincta larvae (L3) from 16 weeks of age. Lambs in the RC group were pair fed to match AP feed intake to separate the effects of infection-induced anorexia from the potential direct impacts of infection. From 7 days pre-infection to 23 days post-infection, scan and behaviour samples were taken from video recordings to quantitatively monitor behaviour, and animal-based measures such as faecal soiling score (FSS) were recorded as welfare indicators. Lying, standing, eating, play and social behaviour were monitored. Qualitative behaviour assessment (QBA) was conducted weekly using the AWIN (2015) protocol to gain insight into the lambs’ affective states over the onset of infection. Parasitised lambs were more likely to stand inactive than AC lambs as the infection progressed (P=0.006). They were also less likely to display eating behaviour in the third daily scan sample than RC lambs (P<0.001). Principal Component Analysis of the QBA data revealed that the first dimension (PC1) described arousal levels, the second (PC2) described the valence of the animals’ affective states, and the third (PC3) described fearfulness and aggression levels. Parasitised lambs (est=10.64,SE=0.33) scored higher than RC lambs (est=9.42, SE=0.33) on PC3, the fearfulness dimension (P=0.030). There were no differences between fearfulness scores of AC and AP lambs or RC lambs and treatment group had no significant impact on the distribution of scores on PC1 or PC2. These findings demonstrate that subclinical GI parasitism negatively impacts lamb welfare not only in the health domain but in the behaviour and mental domains as well. This has implications for welfare assessments and early disease detection in lambs. Future research could explore remote monitoring of the indicators of parasitism identified in this study.

224 Awardee Talk: Investigating Muscle Fiber Hypertrophy During pre- and Post-Natal Growth

Abstract Research has established that muscle fiber hyperplasia is complete during mid gestation; therefore, skeletal muscle fiber hypertrophy is responsible for the increase in muscle mass observed during late gestation and postnatal growth periods. Our research is investigating key times points during muscle fiber hypertrophy and the role of miRNA and mRNA transcriptome in this process. Two studies were conducted to examine changes in muscle mass, muscle fiber hypertrophy, and gene expression from gestational d (gd) 85 to market weight in Suffolk or Texel cross lambs. Longissimus muscle (LM) samples were taken for muscle fiber histology at the following time points: gd85, gd110, gd133, and market (d243) in study one and at postnatal d2, d14 and d203 in study two. microRNA (miRNA) and mRNA sequencing of the LM were conducted in study one and included biopsies at d 42 and 65. Type I and Type II muscle fiber area increased (P &amp;lt; 0.05) at each stage of growth evaluated. Type I muscle fiber area increased by 26.7-fold and Type II muscle fiber area increased by 37.4-fold from gd85 to market (d243). mRNA sequencing identified a total of 9360 unique genes differentially expressed (DEGs; P &amp;lt; 0.05) in LM during hypertrophic growth but the majority of DEGs were observed in the prenatal (51%) and early postnatal (54%) periods. There were 142 unique miRNAs differentially expressed (P &amp;lt; 0.05) during hypertrophic growth of LM but the majority (62%) were observed in the transition period from prenatal to postnatal growth. Overall, muscle fiber hypertrophy is dynamic from late gestation through postnatal growth, but transcriptomic changes indicate key time periods during development in which mechanisms underlying hypertrophic growth may be altered.

Effects of sire genotype on lamb performance at weaning in extensive sheep systems

A low finishing weight and poor carcass characteristics are major causes of lower incomes in extensive sheep flocks; however, the use of terminal sire crossbreeding would improve lamb performance and carcass traits under these conditions. The aim of this study was to evaluate sire breed effects on the performance of lambs born to Corriedale ewes in extensive sheep systems in Western Patagonia. A total of 10 Corriedale, 10 Dorset, nine Suffolk and seven Texel sires, 16 of which were under a genetic recorded scheme and 20 selected from flocks not participating in genetic improvement programmes, were used across six commercial farms for 2 successive years. Data were collected from 685 lambs of the four resulting genotypes. Overall, Corriedale lambs were 0.47 kg lighter at birth than crossbred lambs (P<0.001). Suffolk and Texel sired lambs required more assistance (P<0.01) at birth than Corriedale or Dorset sired lambs, with Suffolk sired lambs requiring the most assistance (8%). Ewes sired with Suffolk rams had larger (P<0.05) litters than ewes sired with Texel or Corriedale rams. Lamb live weight gain from birth to weaning was higher (P<0.001) in crossbred lambs compared with Corriedale lambs, therefore, crossbred lambs averaged 2.9 kg heavier BW (P<0.001) than Corriedale lambs. A significant sire breed x sire source interaction was detected for lamb live weight gain (P<0.05) and lamb live weight at weaning (P<0.01), showing that the heaviest lambs were from recorded sires, except for Suffolk crossbred lambs. Mortality rate to weaning was increased (P<0.05) in Suffolk cross lambs (31%), with Corriedale lambs showing the lowest (17%) mortality. Terminal sire breeds increased (P<0.001) cold carcass weight, with 13.8, 16.0, 15.2 and 14.9 kg for the Corriedale, Dorset, Suffolk and Texel sired lambs, respectively. Carcass length, kidney knob and channel fat, fat grade, grade rule and fat depth measurements were not affected by sire breed (P>0.05). Carcass conformation was higher in Texel sired lambs compared with Corriedale lambs (P<0.05), with Dorset and Suffolk sired lambs being intermediate. Crossbred lambs showed a greater (P<0.001) eye muscle than Corriedale. Commercial cuts were affected by sire breed, as a result of the Corriedale lambs being smaller and having lighter carcass than crossbred lambs. Significant improvement in lamb weights at weaning and carcass traits could be expected when using a terminal sire on Corriedale ewes in Western Patagonia. However, no advantages were detected with the use of recorded sires under these production systems.

Resultados econômicos da produção de cordeiros em confinamento utilizando na dieta casca de soja associada a quatro fontes de nitrogênio não-proteico

O objetivo neste estudo foi avaliar o custo de produção e a resposta econômica da utilização de casca de soja (CS) associada a duas fontes de nitrogênio não-proteico (NNP) na terminação de cordeiros em confinamento. Foram utilizados 80 cordeiros mestiços Suffolk, com idade inicial de 69 ± 6 dias e peso vivo inicial de 23,11 ± 1,78 kg. Os animais foram distribuídos em quatro grupos, cada um com uma dieta formulada com uma fonte de NNP: grupo ureia convencional, na proporção de 1%; grupo ureia protegida, na proporção de 1%; grupo ureia protegida convencional, na proporção de 1% + 0,5% de ureia convencional, da dieta total, respectivamente; e grupo controle, sem fonte adicional de NNP. O custo total de produção do cordeiro até a desmama foi de R$ 85,27/animal. Entre os componentes desse custo, a categoria de ovelhas foi a principal contribuinte, com 68,55%, seguida pelos custos referentes ao próprio cordeiro (0-67 dias), que representaram 25,57%, e a dos carneiros, com participação de apenas 5,88%. O custo total médio da terminação em confinamento foi de R$ 57,73/cordeiro. O custo operacional efetivo (COEf) representou R$ 57,35, ou 99,33% do custo total à terminação. As variáveis de maior representatividade do COEf foram alimentação (61,56%) e impostos (31,06%). As dietas que permitiram obter margem bruta/cordeiro positiva foram aquelas com ureia convencional e sem fonte adicional de NNP (R$ 1,77 e R$ 4,35), respectivamente. No entanto, todas as dietas apresentaram margem líquida e resultado econômico negativos. Em sistemas de terminação de cordeiros em confinamento, o uso de dietas sem fonte adicional de nitrogênio não-proteico é a opção que permite obter melhor resultado zootécnico e econômico.

The effect of sward surface height on the response to mixed grazing by cattle and sheep

AbstractAn experiment was conducted to examine the effects of mixed grazing of sheep plus cattle under continuous stocking of permanent pasture at different sward heights. The experiment had a 2×3 factorial design, with two sward surface heights (4–5 and 8–10 cm) and three combinations of animal species viz., sheep only, cattle only and sheep plus cattle. There were two replicate plots of each treatment combination and the experiment was conducted over 2 years consecutively. The sheep were Beulah Speckled Face ewes and their single Suffolk-cross lambs while the cattle were yearling Charolais-cross steers. Six ‘core’ steers and six ‘core’ ewes and their lambs grazed plots, as appropriately, while additional, non-experimental steers and ewes and their lambs were used to maintain sward heights. Each year the steers and the ewes grazed the pastures from May to October, while lambs were weaned and removed each year from the experiment in July. There was no significant effect of mixed grazing on live-weight gain of steers, but ewes had significantly higher live-weight gains on the sheep plus cattle treatment than on the sheep-only treatment (82 v. 61 g/day;P&lt;0·001). The live-weight gain of the lambs was higher on the mixed grazing treatment than on the sheep only treatment on the 8–10 cm sward height treatment (243 v. 212 g/day;P&lt;0·05) but there was no significant difference on the 4–5 cm sward height treatment (260 v. 250 g/day;P&gt;0·05). The total output of live-weight gain per ha from steers, ewes and lambs was not significantly affected by animal species combination. It is concluded that while output per ha is not enhanced by mixed grazing by sheep and cattle when sward height is controlled, the live-weight gain of ewes is increased and the live-weight gain of lambs can be increased on taller swards.

Induction of zinc deficiency in sheep and its correction with a soluble glass bolus containing zinc.

Balance studies were carried out on four Suffolk-cross lambs which were fed a diet containing only 1.2 mg zinc/kg dry matter; zinc deficiency was induced within three weeks. After a period during which the deficiency was relieved by a pica, the zinc deficient state was re-established. Each sheep was then treated with a soluble glass bolus containing zinc, cobalt and selenium. The plasma zinc concentration of the sheep rapidly increased and was maintained for between six and 10 weeks. The bolus was able to supply the daily requirement of the sheep for zinc, with no detrimental effect on their copper status.

Evaluation of the anthelmintic efficacy of an ivermectin controlled-release capsule in lambs under field conditions in Europe

Three field trials were conducted in Germany, Slovakia and UK to evaluate the anthelmintic efficacy and productivity responses attributable to treatment of lambs with an intra-ruminal controlled-release capsule which is designed to deliver ivermectin at 0.8 mg/day for 100 days to lambs weighing 20–40 kg at treatment. Sixty Merino Landrace, 60 Valaška or 52 Suffolk cross lambs weighing between 24.0 and 40.0 kg at the time of treatment were used. Lambs were either untreated (or subjected to salvage treatment) or they received an ivermectin controlled-release capsule. Faecal egg and larval counts of various nematodes, body weights and scores of the faecal soiling of the breech area (formation of dags) were determined before treatment and at 28, 56, 84, 98 and 112 days after treatment. Before treatment, faecal strongyle, Nematodirus and Trichuris egg counts and Dictyocaulus filaria larval counts were not significantly different ( P > 0.05 or P > 0.1) between groups, but at each point of time thereafter, egg and larval counts of the ivermectin controlled-capsule treated lambs were significantly reduced compared to the untreated controls. Lambs treated with the ivermectin controlled-release capsule gained significantly more weight (10.9, 11.1 or 11.1 kg, respectively) over the 112 days of the trials compared to untreated lambs (8.2, 9.7 or 5.5 kg, respectively). The mean scores of faecal soiling were not different at the start of the trials ( P > 0.05 or P > 0.1), but at the end of the trials, the ivermectin controlled-release capsule treated lambs had significantly lower scores of faecal soiling than the controls.

Genetic variation and relationship of ultrasonic measures and carcass composition in Suffolk cross lambs

Excess fat in lamb is regarded as an important reason for less lamb meat being purchased by consumers. This has encouraged the development and use (particularly in Terminal Sire breeds) of selection indices that can identify animals that will sire leaner progeny. These indices usually include live weight and in vivo predictors of body composition, such as an ultrasonic measurement of muscle and fat depth, as selection criteria (Simm and Dingwall, 1989). But the usefulness of such in vivo measurements as predictors of carcass composition depends on the correlation between, and the variation in, live and carcass measures. The objectives of this study were to determine the strength of the relationship between ultrasound and dissection measures of carcass composition, and the degree of genetic variation in these measures, in crossbred progeny of Suffolk rams.

Genetic variation and relationship of ultrasonic measures and carcass composition in Suffolk cross lambs

Excess fat in lamb is regarded as an important reason for less lamb meat being purchased by consumers. This has encouraged the development and use (particularly in Terminal Sire breeds) of selection indices that can identify animals that will sire leaner progeny. These indices usually include live weight and in vivo predictors of body composition, such as an ultrasonic measurement of muscle and fat depth, as selection criteria (Simm and Dingwall, 1989). But the usefulness of such in vivo measurements as predictors of carcass composition depends on the correlation between, and the variation in, live and carcass measures. The objectives of this study were to determine the strength of the relationship between ultrasound and dissection measures of carcass composition, and the degree of genetic variation in these measures, in crossbred progeny of Suffolk rams.

A putative role for larval nematode infection in diarrhoeas of lambs which did not respond to anthelmintic drenches.

Attempts to control a summer diarrhoea in grazing Finnish landrace lambs which had been unresponsive to anthelmintics and coccidiostats were made by supplementing them with cupric oxide particles and withdrawing a magnesium-rich mineral, while maintaining parasite control measures. The diarrhoea persisted from July to September and plasma pepsinogen activities were raised, suggesting that the anthelmintic did not prevent abomasal damage; the jejunum of an affected lamb showed lesions of parasitic gastroenteritis. Small responses to cupric oxide particles and larger responses to the withdrawal of magnesium were deceptive, possibly being confounded by differences in parasite challenge. In another experiment Finnish landrace lambs were more susceptible to diarrhoea than Suffolk cross lambs in autumn. The susceptibility was then linked to a strong inhibition of worm egg output and may have been caused by a hypersensitive mucosal response to the larval challenge. Plasma pepsinogen concentrations were again raised in the Finnish landrace lambs and did not decline after treatment with anthelmintic, whereas the concentrations increased later in the Suffolk cross lambs, and were apparently responsive to anthelmintic. The cases of diarrhoea were similar to 'July disease' and may have been caused by continuous nematode infections which were only briefly controlled by drenches. Anthelmintic-unresponsive diarrhoea is the term proposed for the disorder, which may be controllable by devices releasing anthelmintic continuously or by a move to less infected pasture. Faecal egg counts remained low in the condition and were diagnostically misleading.

A comparison of concentrate and silage-based finishing diets on the performance, carcass composition and meat quality of suffolk cross and scottish blackface lambs

There is great variation in lamb carcass quality due to there being many breeds and crosses involved in lamb production. Breed of lamb appears to influence the pattern of development of the important carcass components, and thus the carcass quality, when comparison is made at equal weights. Plane of nutrition may also affect the growth rate, carcass composition and eating quality of lambs of the same genotype. It was planned to study the effect of both breed and diet on growth performance, carcass and meat quality characteristics by feeding two different diets to the lambs of two different breeds similarly managed from birth to slaughter.

A comparison of concentrate and silage-based finishing diets on the performance, carcass composition and meat quality of suffolk cross and scottish blackface lambs

There is great variation in lamb carcass quality due to there being many breeds and crosses involved in lamb production. Breed of lamb appears to influence the pattern of development of the important carcass components, and thus the carcass quality, when comparison is made at equal weights. Plane of nutrition may also affect the growth rate, carcass composition and eating quality of lambs of the same genotype. It was planned to study the effect of both breed and diet on growth performance, carcass and meat quality characteristics by feeding two different diets to the lambs of two different breeds similarly managed from birth to slaughter.

Growth and meat quality assessment of entire and castrated suffolk-cross male lambs finished on a traditional grass system

The aim of this trial was to quantify the variation in growth and lamb meat quality between entire male and castrated male lambs reared under traditional grass systems, and to identify the possible problems in rearing mixed sex groups together. Much work has been carried out on the effects of castration on meat quality and growth (Butler-Hogg et al. 1984; O' Riordan and Hanrahan, 1992), and on pelt removal (Andersen et al.; 1991a, 1991b); this experiment set out to ascertain whether entire male lambs would finish quicker than wether lambs off average condition grass swards in a semi-commercial situation and therefore to determine the necessity of castrating lambs that will be finished by September.

Carcass fatness in lambs grazing various forages at different rates of liveweight gain

Abstract In three experiments, Dorset, Suffolk cross, or Coopworth lambs weighing c. 30 kg in January were offered a range of forages including high-endophyte Nui ryegrass-dominant pasture, white clover-dominant pasture, Moata or Concord ryegrasses, lucerne, rape, or chicory. Herbage allowances were adjusted to achieve target liveweight gains of 300, 200, or 120 g/day and lambs slaughtered at c. 43 kg liveweight from March to May. In Experiment 1, medium and low rates of liveweight gain were compared on both ryegrass-dominant and clover-dominant swards. In Experiment 3, the comparison was extended to include a high rate of liveweight gain (300 g/day) on clover-dominant swards. Allowances of Nui ryegrass required to achieve liveweight gains of 200 g/day were over 2 times greater than that of clover and up to 5 times greater than for chicory and lucerne. There was no effect of liveweight gain on carcass GR measurements of lambs grazing ryegrass-dominant pastures when compared at the same carcass weights but...

Assessment of contrasting perennial ryegrasses, with and without clover, under continuous sheep stocking in the uplands. 4. Animal performance in years 4–6

AbstractRelative sheep production from Aurora (very early flowering), Mellra (late‐flowering tetraploid) and Aberystwyth S23 (late flowering) perennial ryegrass (Lolium perenne L.) varieties was compared during harvest years 4‐6 (1988‐90) as grass only (200 kg N ha−1) and grass/clover (75 kg N ha −1 in 1988, 0 kg N ha−1 in 1989 and 1990) at Bronydd Mawr Research Centre (310‐363 m) in mid‐Wales. The pastures were continuously stocked with Beulah Speckled Face ewes and their Suffolk cross lambs from spring to mid‐July. From late July to early November only the weaned lambs grazed the swards.Mean (1988‐90) total annual lamb production per hectare from Aurora and Meltra was 70% and 16% more than that from S23. However, the difference between both varieties and S23 was much greater as grass/clover (Aberystwyth S184 small‐leaved type) than as grass‐only swards. Differences between the grasses in individual lamb growth rates were most pronounced during the post‐weaning period, when that on Meltra was 38% and 23% more than on Aurora and S23 respectively.Mean annual lamb output from grass/clover swards was only 70% of that from grass‐only swards during the 2 years when the former swards received no fertilizer N. Averaged over the 3 years (1988‐90) individual lamb liveweight gain post weaning was 38% higher on grass/clover than on grass‐only swards.The results are discussed in relation to those for the first 3 harvest years (1985‐87). It is concluded that, although Aurora was less persistent than both late‐flowering varieties, its superiority in providing an average of 29% more lamb output than S23 during the critical spring period (up to early June) would be of considerable practical significance in upland sheep systems, as would be the overall superiority of the tetraploid Meltra over S23.

Comparative aspects of resistance to body cooling in newborn lambs and kids

ABSTRACTThe aim of this study was to compare responses to cold stress in newborn lambs and kids. Two experiments were conducted in a climatic chamber with controlled air temperatures and artificial wind and rain. The first experiment involved 25 Poll Dorset × (Border Leicester × Romney) lambs and 16 Angora × feral kids while the second involved 30 Suffolk × (Border Leicester × Romney) lambs and 26 Angora × feral kids. Rectal temperatures were measured and the rate of decline in rectal temperature estimated in both experiments. In the second experiment, metabolic rate was also measured and coat characteristics (birth coat depth and wool weight per unit area of skin) were examined. The effects of birth rank and sex on resistance to cold exposure and their interaction with species were examined in both experiments.In experiment 1, kids had lower rectal temperatures than lambs at the start of the test but there was no species effect on the rate of decline in rectal temperature. In experiment 2, kids exhibited a significantly greater rate of decline in rectal temperature than did lambs. This difference in species effect between the experiments reflected primarily a greater rate of body cooling in the Poll Dorset-cross lambs (experiment 1) than in the Suffolk-cross lambs (experiment 2) rather than a difference between the kids in the two experiments. Additionally, in experiment 2, metabolic rate per unit live weight was significantly lower in the kids than in the lambs. No differences were apparent between the species in coat characters. Multiple-born lambs and kids were found to exhibit a significantly greater rate of decline in rectal temperature than singles, but only marginal differences in heat production were observed between the birth ranks. No significant effects of sex on resistance to cold stress were found in this study. Effects of birth rank and sex were additive with those of species. It is concluded that a combination of low heat production capacity and small body size is responsible for the generally poor responses of newborn kids to cold stress but there is probably little difference between lambs and kids in the insulative value of their birth coats.

Carcass and eating quality of ram, castrated ram and ewe lambs

ABSTRACTCarcass and meat composition and eating quality of m. longissimus lumborum (LI) and leg joints were compared in entire male (ram), castrated male (wether) and female (ewe) Dorset Down-cross and Suffolk-cross lambs at about 20 weeks old. Rams grew faster than wethers and ewes particularly in the earlier maturing Suffolk crosses. Carcass weights ranged from 13 to 24 kg and at the mean carcass weight of 17·7 kg ram carcasses yielded larger shoulder joints. Ram carcasses were assessed visually leaner than those from the other sexes with similar conformation scores. Dorset Down carcasses tended to be fatter than Suffolk carcasses and the leanest carcasses were from Suffolk rams. Intramuscular fatness in LI was similar in all sexes. Intramuscular collagen contents were higher in ram LI than in other sexes. There were no differences in protein content, pH or colour of raw or roast LI. In assessments of eating quality of LI by triangle tests, male and female assessors differentiated twin rams and wethers equally. Category scaling showed LI from ewes to be slightly tougher than those from rams and wethers. Consumer evaluation of leg joints did not detect any differences in odour due to sex and ram meat was assessed better than that from wethers or ewes.

Effects of cimaterol on energy utilization for maintenance and for protein and fat deposition by wether and ewe lambs given chopped lucerne hay or lucerne-barley pellets

ABSTRACTThe effects of sex (wethersv.ewes), diet (chopped lucerne hayv.lucerne-barley pellets) and cimaterol on energy utilization by Suffolk cross lambs were determined by comparative slaughter. Quadratic regression of energy retention (RE) on metabolizable energy intake (MEI) enabled estimation of maintenance energy requirements (Em), efficiencies of gain (ktotal) and maximum rates of gain (REMAX). Regressions using RE in fat and proteinv.MEI yielded analogous parameters for fat and protein deposition (Em fat, kfat, REMAX fatand Emprotcin, kprolein, REMAXprotcinrespectively). Emwas lower in wethers than ewes (455v.510 kJ/kg M0·75per day respectively), but was unaffected by diet or cimaterol. Sex and cimaterol did not affect ktotai. which was higher in lambs given pellets compared with lambs given hay (0·417v.0·224 respectively). Similarly, REMAXwas higher in lambs given pellets than in lambs given hay (326v.114 kJ/kg 0·75 per day respectively). None of the groups differed significantly in the parameters of fat deposition, which averaged 480 kJ/kg 0·75 per day for Emfal, 0·224 for ktat, and 250 kJ/kg M0·75per day for REMAX, fat-Em.proteinwas lower in wethers than in ewes (466v.569 kJ/kg 0·075 per day, respectively), and was further reduced by cimaterol (418 and 507 kJ/kg 0·75 per day for wethers and ewes respectively). Estimates of kprotcin were higher in wethers than in ewes (0·091v.0·064 respectively), and were increased by cimaterol (0·115 and 0·089 for wethers and ewes respectively). Similarly REMAX protein was higher in wethers than in ewes (47v.37 kJ/kg 0·75 per day respectively), and was increased by cimaterol (58 and 48 kJ/kg 0·75 per day for wethers and ewes respectively). The repartitioning action of cimaterol was additive with effects of diet, intake and sex.

Assessment of contrasting perennial ryegrasses, with and without white clover, under continuous sheep stocking in the uplands

AbstractPotential lamb production from grass‐clover (75–80 kg N ha−1) swards was compared with that from grass‐only (160–200 kg N ha−1) swards from 1985 to 1987 at the Bronydd Mawr Research Centre in mid‐Wales. Separate pastures of three perennial ryegrass (Lolium perenne L.) varieties; Aurora (very early‐flowering diploid), Meltra (late‐flowering tetraploid) and Aberystwyth S23 (late‐flowering diploid), with and without Aberystwyth S184 small‐leaved white clover (Trifolium repens L.), were continuously stocked with Beulah Speckled Face ewes and their Suffolk cross lambs from spring (late April) until weaning in mid‐July. From late July the pastures were grazed with weaned lambs until early November.Individual lamb liveweight gain was 8% more (P &lt; 0·001) pre‐weaning on grass‐clover than on grass‐only swards and 30% more (p &lt; 0·001) post‐weaning. Averaged over three years, mean stocking rate was 17% higher (p &lt; 0·001) pre‐weaning and 29% higher (p &lt; 0·001) post‐weaning on the grass‐only pastures. Even so, total lamb output (kg ha−1) was similar from the two sward types, although during the pre‐weaning period lamb production was 9% higher (P &lt; 0·05) from grass‐only swards.The results show the potential of grass‐clover (low N) swards to improve the efficiency of lamb production from grassland since better individual lamb growth rate compensated for the lower stock‐carrying capacity. That is, similar output was achieved with lower cost of fertilizer N input and with the lower costs associated with carrying fewer animals.

Assessment of contrasting perennial ryegrasses, with and without white clover, under continuous sheep stocking in the uplands

AbstractComparative sheep production from Aurora (very early‐flowering), Meltra (late‐flowering tetraploid) and Aberystwyth S23 (late‐flowering) perennial ryegrass (Lolium perenne L.) varieties was assessed as both grass‐only (200 kg N ha−1) and grass‐white clover (Trifolium repens L.) (75 kg N ha−1) swards under continuous stocking management. Beulah Speckled Face ewes and their Suffolk cross lambs were used from late April to mid‐July. From late July to early November only lambs grazed the pastures.Mean (1985–87) total annual lamb production per hectare from Aurora and Meltra was 16% and 13% more than that from S23. The magnitude of the differences between these varieties and S23 declined from the first to the third year. Aurora gave 29% more lamb output per hectare than S23 in 1985 but only 10% more in 1987, while the advantage of Meltra over S23 fell from 19% in 1985 to 6% in 1987. Seasonal lamb production per hectare varied between the grasses, especially during spring when lamb output from Aurora was 43% and 22% more than that from S23 and Meltra respectively, with that from the tetraploid being 17% higher than that from S23.It is concluded that the superior spring output from Aurora offers the farmer the opportunity to reduce his dependence on bought‐in feedstuffs, hence improving the efficiency and profitability of lamb production from grassland.