Border Leicester Research Articles

Short duration heatwaves increase body temperature and alter blood gas balance but may not cause oxidative stress and intestinal structure variations in lambs

This study investigated the impact of short duration heatwaves (HW) on the body temperature, blood gas, intestinal histology, and oxidative stress parameters of second cross lambs. Seventy-two second cross lambs [Poll Dorset × (Border Leicester × Merino)] were selected and exposed to either one, three or five days HW (28–38°C and 40–60 % relative humidity (RH)) or thermoneutral (TN; 18–21°C, 40–55 % RH) conditions in climate-controlled chambers. Lambs exposed to one to five days HW exhibited higher face, eye and ear temperature compared to animals exposed to equal duration under TN conditions. HW also had a significant impact on blood gas parameters which include higher blood pH, and lower CO2, Ca2+, Na+, CHCO3- and Cl-. However, HW lambs’ histology structure of the ileum and the GSSG: GSH of the ileum and Longissimus thoracis (LT) muscle were not influenced (P > 0.05) by HW. LT muscle showed higher total antioxidant capacity (TAC) in HW conditions, but the TAC of intestine and blood had no difference between HW and TN groups. These results suggest that short-duration HW (one to five days) had a significant impact on lambs’ body temperature and blood parameters, but neither caused oxidative stress nor any changes in their intestinal structure.

Average daily gain in lambs grazing mixed annual forage species compared with single species and relationship to feed on offer

Context Annual forage crops provide high-quality fodder for livestock during typical autumn and winter feed-gaps in the south-east of Australia and benefits through rotations in cropping systems. While benefits from intercropping with cereals and pasture or mixing canola and peas have been studied in Australia, the potential animal-production benefits of grazing mixed annual species forage crops have not been examined. Aims To determine average daily gain (ADG) and rumen fluid parameters when sheep graze mixtures of annual fodder crops compared with a single species. Methods Ninety six Dorset × Border Leicester × Merino lambs (mean = 44.3 ± 0.55 kg) were allocated to one of the following four treatment groups (n = 24/treatment) on the basis of sex and liveweight; a single species brassica control (canola) (Br) or annual forage species mixes containing brassica (canola, turnip, radish) and cereal (wheat, cereal rye) (B + C), brassica and legume (vetch, arrowleaf clove) (B + L) or brassica, cereal and legume (B + C + L). Liveweight and rumen fluid parameters were assessed prior to grazing and again 21 and 35 days after the commencement of grazing. Key results Mean ADG from Day 0 to Day 21 was lower for female, but not male, lambs grazing the Br control (231 ± 23 g head−1 day−1) than for those grazing any forage mix (B + C = 292 ± 23 g head−1 day−1, B + L = 296 ± 23 g head−1 day−1, B + C + L = 310 ± 22 g head−1 day−1). Liveweight change over 35 days of grazing was not different between any forage mixtures. Rumen fluid pH was higher (P < 0.001) for sheep grazing forages containing cereals (B + C = 6.97 ± 0.06, B + C + L = 6.86 ± 0.06) than for those grazing brassica or legume (Br = 6.59 ± 0.06, B + L = 6.68 ± 0.06). Total volatile fatty acid concentration was lower and rumen pH was higher when sheep grazed B + C than when they grazed any other forage mix. Conclusions The higher ADG in females grazing mixtures than in those grazing the Br was related to higher dry matter on offer. Further research should determine whether the lower pH observed when sheep grazed brassica and legume than when grazing mixes containing cereals is associated with subacute rumen acidosis and reduced fibre degradation and forage energy utilisation. Implications Mixed forage species can provide higher DM on offer and ADG. Improved rumen efficiency could be related to improved growth.

Effects of Sugarcane-Derived Polyphenol Supplementation on Methane Production and Rumen Microbial Diversity of Second-Cross Lambs.

The objective of this study was to evaluate the effects of feeding sugarcane-derived polyphenolic supplement (Polygain, The Product Makers Australia, Keysborough, VIC, Australia) on enteric methane (CH4) emission, rumen microbiota, and performance of second-cross lambs. For this purpose, 24 Poll Dorset × (Border Leicester × Merino) lambs were allocated to 3 different treatments: Control (C), 0.25% Polygain (0.25 PG), and 1% Polygain (1 PG) diets with a uniform basal feed (25% cracked wheat grain, 25% cracked barley grain, 25% oaten chaff, 25% lucerne chaff). Both doses of Polygain reduced the total CH4 production (g/day; p = 0.006), CH4 yield (CH4, g/kg of dry matter intake; p = 0.003) and CH4 intensity (CH4, g/kg of BW; p = 0.003). Dry matter intake tended to be greater (p = 0.08) in sheep fed 1 PG compared to the C group, with the 0.25 PG group being intermediate. The average daily gain of the lambs was improved (p = 0.03) with 1% Polygain supplementation. The relative abundance of genera Methanobrevibacter_unidentified, Methanomethylophilaceae_uncultured, Methanogenic archaeon mixed culture ISO4-G1, Methanosphaera uncultured rumen methanogen, Methanogenic archaeon ISO4-H5, and Methanobrevibacter boviskoreani JH1 were reduced with Polygain supplementation. In conclusion, feeding Polygain reduced lambs' enteric CH4 emissions, altered the rumen microbiome, and improved the growth performance of lambs.

Whole-Genome Resequencing Reveals Genetic Diversity and Wool Trait-Related Genes in Liangshan Semi-Fine-Wool Sheep

Understanding the genetic makeup of local sheep breeds is essential for their scientific conservation and sustainable utilization. The Liangshan semi-fine-wool sheep (LSS), a Chinese semi-fine-wool breed renowned for its soft wool, was analyzed using whole-genome sequencing data including 35 LSS, 84 sheep from other domestic breeds, and 20 Asiatic mouflons. We investigated the genetic composition of LSS by conducting analyses of the population structure, runs of homozygosity, genomic inbreeding coefficients, and selection signature. Our findings indicated that LSS shares greater genetic similarity with Border Leicester and Romney sheep than with Tibetan (TIB), Yunnan (YNS), and Chinese Merino sheep. Genomic analysis indicated low to moderate inbreeding coefficients, ranging from 0.014 to 0.154. In identifying selection signals across the LSS genome, we pinpointed 195 candidate regions housing 74 annotated genes (e.g., IRF2BP2, BVES, and ALOX5). We also found the overlaps between the candidate regions and several known quantitative trait loci related to wool traits, such as the wool staple length and wool fiber diameter. A selective sweep region, marked by the highest value of cross-population extended haplotype homozygosity, encompassed IRF2BP2—an influential candidate gene affecting fleece fiber traits. Furthermore, notable differences in genotype frequency at a mutation site (c.1051 + 46T > C, Chr25: 6,784,190 bp) within IRF2BP2 were observed between LSS and TIB and YNS sheep (Fisher’s exact test, p < 2.2 × 10−16). Taken together, these findings offer insights crucial for the conservation and breeding enhancement of LSS.

Utilising male stimulus to improve the reproductive efficiency of 8-month-old nulliparous ewes and adult parous ewes

We tested whether utilising the male effect to stimulate ewes before the mating period can reduce the time to conception following the introduction of entire rams, and increase fertility, prolificacy, and reproductive rate (number of fetuses per 100 ewes exposed to fertile rams). A retrospective analysis was used to analyse records from 59,716 ewes collected over 34 years (1986–2020) from seven genotypes: Border Leicester, Composite (crossbred), Dorset, Merino, Dorset x Polypay, Rambouillet, White Suffolk. The dataset also included nulliparous young ewes (mated at age 8 months) and adult parous ewes. Vasectomized rams were used to stimulate 20,632 ewes before a mating period that lasted 2 or 3 estrous cycles, and the outcomes were compared with those from 39,084 ewes that had not been stimulated. Independently of genotype, utilising the male stimulus advanced the average conception date by 8 days for young ewes (P < 0.0001) and by 1 day for adult ewes (P < 0.0001). The male stimulus also increased the proportion of ewes that conceived in their first cycle by 33 % for young ewes and by 6 % for adult ewes (P < 0.0001). For the cycle of conception, there were significant (P < 0.0001) effects of two interactions: male stimulus x age at mating and male stimulus x live weight at mating. The male stimulus improved fertility in both adult ewes (99.8 % vs 89 %; P < 0.001) and young ewes (77.7 % vs 81.3 %; P < 0.001). The male stimulus increased the number of young ewes (41.9 % vs 11.1 %; P < 0.001) and adult ewes (16.6 % vs 2.7 %; P < 0.001) that conceived multiple fetuses in the first 17 days of the mating period. The reproductive rate was improved by the male stimulus in young ewes (129 % vs 135 %; P < 0.001) but not in adult ewes (120 % vs 122 %; P = 0.12). When all animals for all breeds were included in the analyses, there were improvements in fertility, prolificacy, and reproductive rate as age and live weight increased at mating (P < 0.0001). We conclude that, independently of genotype, utilising the male stimulus before the mating period reduces the time to conception and improves reproductive performance in both young and adult ewes.

Melatonin dose: testicular and testosterone response in Border Leicester rams during spring

The negative effects of seasonality on ram fertility during the spring months (non-breeding season) can be addressed by administration of melatonin. Slow-release implants containing 18 mg of melatonin are available to improve reproductive responses in ewes but as far as we are aware nobody has examined the effects of dose on increasing testicular size and plasma testosterone levels. Mature Border Leicester rams were randomly allocated to four doses (0, 18, 36 and 54 mg) with treatment beginning in mid-September (spring). Measurements (scrotal size, testosterone and melatonin concentrations, live weight and body condition score) began before hormone administration and continued at monthly intervals until January (mid-summer). Scrotal circumference increased with increasing dose with 36 and 54 mg treatments producing larger responses than 0 and 18 mg treatments (p < 0.05). Plasma testosterone concentration was positively related (p ≤ 0.05) with plasma melatonin levels on days 60 and 90 after melatonin administration. There was a negative relationship (p < 0.01) between plasma melatonin concentration and liveweight on day 30. It is concluded that a higher dose of melatonin is required to maintain plasma melatonin levels in larger animals, and that at least 36 mg is required to elicit a threshold response in testicular size.

Impact of Heatwaves on the Physiology and Retail Meat Quality of Lambs.

The experiment investigated the impact of heatwaves (HWs) on the physiology, postmortem muscle metabolism and meat quality of lambs. Seventy-two second-cross lambs (Poll Dorset × (Border Leicester × Merino)) were selected and exposed to either 1, 3 or 5 days of HWs or thermoneutal (TN) (28–38 °C and 40–60% relative humidity, RH; 18–21 °C, 40–55% RH) conditions in climate-controlled chambers. Lambs exposed to 1–5 days of a HW exhibited higher respiration rates (RRs), rectal temperatures (RTs), skin temperatures (STs) and heart rates (HRs) compared to lambs exposed to an equal duration of TN conditions. However, HWs had no significant effects on muscle metabolism (rate and extent of pH decline, muscle glycogen and lactate content) and meat quality (cooking loss and shear force). Similarly, there were limited impacts of 1–5 days of HW on the colour (L*, a*, b* and R630/580) and drip loss of the longissimus thoracis et lumborum (LTL) and semimembranosus (SM) muscles for 4 days’ overwrap retail display. Results suggest that short-duration HWs (1–5 days) had significant negative effects on animal physiology but had no effect on the muscle metabolism and meat quality.

Mating weight and condition score are both good predictors of lambing potential for young Merino and Border Leicester Merino ewes across different environments and years in Australia

Context Increasing mating weight or condition score increases the lambing potential of ewes (fetuses scanned per 100 ewes joined). Aim We hypothesised that in some years, condition score would contribute an additional effect to mating weight on lambing potential. Methods Border Leicester Merino and Merino ewes were mated naturally to Merino or Terminal rams between 2008 and 2013 at eight linked sites across Australia. Border Leicester Merino ewes were mated in their first year while Merino ewes were not mated until their second year. All ewes were mated for a second time as 2 year olds (Border Leicester Merinos) or 3 year olds (Merino). A total of 4270 Border Leicester Merino and 5788 Merino ewes were weighed and condition scored at mating and scanned for pregnancy. Key results Lambing potential increased by 3.1% per 1 kg increase in mating weight, compared to 1.3% for 1 and 2 year old Border Leicester Merinos respectively, and by 2.1% compared to 1.4% for 2 and 3 year old Merinos respectively (P &lt; 0.05). Lambing potential increased by 27% compared to 13% per increase in condition score for 1 and 2 year old Border Leicester Merinos respectively, and by 29% compared to 25% for for 2 and 3 year old Merinos respectively (P &lt; 0.05). All relationships were linear. When both mating weight and condition score were fitted together, mating condition score explained additional variation to weight in one instance of all the 160 possible breed (n = 2) × age (n = 2) × site (n = 8) × mating year (n = 5) combinations. Conclusions Mating weight and condition score increased the lambing potential of ewes linearly with differences due to ewe age, year and possibly ewe breed. Mating condition score rarely explained additional variation in lambing potential to weight in young Merino or Border Leicester Merino ewes. Implications If ewes are weighed at mating then condition scoring is of minimal extra benefit to predict lambing potential. Achieving the heaviest possible mating weights or highest condition score maximises the lambing potential of ewes in their first two mating years.

Non-invasive measure of heat stress in sheep using machine learning techniques and infrared thermography

Heat stress (HS) leads to altered sheep behavior, physiological, and biochemical processes which negatively affects their welfare and performance. While suitable strategies are needed to ameliorate the impacts of HS in sheep, it is equally important to accurately and non-invasively measure HS. Traditionally, rectal temperature (RT) is considered an indicator of thermal balance and is used to assess the impacts of hot conditions on sheep. However, measuring RT itself can be a stressor as it often requires restraining of the animals. The main objective of this study was to establish whether a combination of infrared thermography (IRT) and machine learning techniques can be applied to predict sheep RT when subjected to HS. Thermal images and RT were taken twice weekly from Dorper, and 2nd Cross (Poll Dorset X (Border Leicester X Merino)) lambs (n = 24/breed, 4−5 months old), for two weeks. Sheep were randomly allocated to either (i) thermoneutral (TN; 18–21 °C, 30–50 % relative humidity (RH), n = 12/group) or (ii) cyclic HS treatments (28–40 °C, 40–60 % RH, the cycle comprised of high temperatures 38−40 °C between 0800 and 1700 h daily and 28 °C, 30–40 % RH maintained overnight). The head was selected as the region of interest because of less wool cover; specifically, the IRT of forehead, eye, ear, nostril, and face locations were measured. Artificial neural network (ANN) models were developed using three different backpropagation algorithms with temperature-humidity index (THI), and IRT temperatures as inputs and RT measured manually as targets. Results showed that the forehead and eye IRT temperatures had the highest correlation (P < 0.01) with THI and RT. Further, Bayesian Regularization, with one hidden layer containing 10 neurons with a tangent sigmoid transfer function, showed the best correlation (R = 0.92) and highest performance (MSE = 0.02). The model developed may be a rapid and cost-effective technique to monitor real-time body temperatures in sheep and also to detect HS with minimal restraint.

Sexual behaviour, semen quality and fertility of young Border Leicester rams administered melatonin during spring

This study was conducted to test the hypothesis that between year variability in reproductive response to melatonin treatment of young Border Leicester (BL) rams in spring was related to sexual maturity at the time of treatment. Two variables of sexual maturity (mating behaviour and semen quality) were examined. In Experiment 1, mating activity of melatonin-treated and untreated rams was examined at two sites before a flock mating at one site. In Experiment 2, testosterone concentrations, semen quality and variables of in vitro fertilising capacity were examined. In Experiment 1, melatonin treatment did not alter sexual behaviour (latency to nose, total nosings, courtings including Flehmen expression, attempted mounts, mounts, ejaculations) with the exception of a lesser (P < 0.05) Flehmen expression at Site 1 whereas values for most variables were greater (P < 0.05) at Site 2. Treatment resulted in a greater pregnancy rate (89 % and 82 %, respectively; P < 0.05) and advanced distribution of pregnancies (P < 0.001) at Site 1. Testicular size and testosterone concentrations were also greater (P < 0.05) as a result of melatonin treatment in spring whilst the reverse occurred in autumn. In Experiment 2, sperm motility and in vitro fertilising capacity were greater (P < 0.05) and acrosome damage less (P < 0.05) as a result of melatonin treatment. In conclusion, variability in age at sexual maturity of young BL rams at spring mating can be reduced with melatonin treatment and is associated with differences in sexual behaviour, testicular growth, testosterone concentrations, and sperm quality.

Impact of heat stress on the growth performance and retail meat quality of 2nd cross (Poll Dorset × (Border Leicester × Merino)) and Dorper lambs

The present study investigated the impact of heat stress and genetics on lamb growth performance and meat quality. Forty-eight Dorper and 2nd cross [Poll Dorset×(Border Leicester×Merino)] lambs (38--42kg; 4-5months old) were allocated to either thermoneutral [TN; 18-21°C, 45-55% relative humidity (RH)], or heat stress (HS; 28°C-38°C, 40-60% RH) conditions in a 2×2 factorial design for 2weeks. Compared with 2nd cross, Dorper lambs had a lower respiration rate (RR) and rectal temperature (RT), and exhibited less decline in body weight under HS. 2nd cross lambs showed a higher body weight gain than Dorpers under TN conditions. HS increased a* and chroma of the Longissimus thoracis et lumborum (LTL) from 2nd cross lambs over 10days of display, but had no impact on Dorper LTL. In conclusion, Dorpers showed higher heat tolerance compared with 2nd cross lambs during the 2weeks HS.

Comparative Assessment of Thermotolerance in Dorper and Second-Cross (Poll Dorset/Merino × Border Leicester) Lambs.

Simple SummarySelection of animal breeds that are adapted to extreme climatic conditions may help to sustain livestock production in the face of climate change. We measured the thermotolerance of 4–5-month-old Dorper and second-cross lambs (Poll Dorset × (Border Leicester × Merino)) by assessing feed intake, physiological, blood biochemical and prolactin responses. Heat stress reduced feed intake only in second-cross lambs but not in Dorpers. As expected, heat stress also increased water intake, respiration rate, rectal temperature, and skin temperature in both genotypes, but to a lesser extent in Dorpers. The comparatively lower influence of heat stress on thermotolerance indices in Dorper indicates adaptability of this breed to heat challenge.The objective of this study was to compare the thermotolerance of second-cross (SC; Poll Dorset × Merino × Border Leicester) and Dorper lambs. Dorper and SC lambs (4–5 months of age) were subjected to cyclic heat stress (HS) (28–40 °C). The temperature was increased to 38–40 °C between 800 and 1700 h daily and maintained at 28 °C for the remainder of the day (30–60% relative humidity (RH)) in climatic chambers for 2 weeks (n = 12/group), with controls maintained in a thermoneutral (TN) (18–21 °C, 40–50% RH) environment (n = 12/group). Basal respiration rate (RR), rectal temperature (RT) and skin temperature (ST) were higher (p < 0.01) in SC lambs than in Dorpers. HS increased RR, RT and ST (p < 0.01) in both genotypes, but the levels reached during HS were lower (p < 0.01) in Dorpers. HS increased (p < 0.01) water intake to a greater extent in SC lambs, while feed intake was reduced (p < 0.05) by HS in SC lambs but not in Dorpers. HS increased (p < 0.01) blood urea nitrogen and creatinine in SC lambs only. Plasma non-esterified fatty acid concentrations were reduced (p < 0.05) by HS in SC lambs but increased (p < 0.05) in Dorpers. There was no effect of HS on pO2, cHCO3− and cSO2, but higher (p < 0.01) blood pH and lower (p < 0.01) pCO2 were recorded under HS in both genotypes. Blood electrolytes and base excess were reduced (p < 0.01) under HS, while a genotype difference (p < 0.05) was only observed in blood K+ and hemoglobin concentrations. Basal plasma prolactin concentrations were lower (p < 0.01) in Dorpers but were elevated at a similar level during HS (p < 0.01) in both genotypes. Dorper lambs are more resilient to HS than SC lambs. Future research should focus on confirming whether the better heat tolerance of Dorpers is translated to better returns in terms of growth performance and carcass traits over the summer months.

The performance of the Border Leicester in Australia

Aims We examine the average performance of Border Leicester (BL) flocks that are part of LAMBPLAN, Australia’s sheep performance recording and genetic evaluation system. We also summarise outcomes from the New South Wales Department of Primary Industry’s research on BL improvement, and discuss the performance required for the BL to continue to be a pivotal part of the Australian prime lamb industry. Key results Modest gains have been recorded in the BL in growth since 2000 and faecal egg counts have reduced, suggesting improved worm resistance. The net reproductive rate has slightly improved, while inbreeding continues to increase. In work conducted by the New South Wales Department of Primary Industries, an improved BL flock, encompassing selection for multiple births and a broadening of the breed’s genetic base, had advantages over purebred BLs in many aspects of performance, including a 19.3% advantage in the net reproductive rate. Advantages in fertility were ~5%, litter size ~7% and lamb rearing ability ~5%. BL improved × Merino and (BL improved × BL) × Merino crossbred ewes also had advantages over traditional BL × Merino ewes in their joining performance when joined to Dorset rams. Conclusions Selection in the BL needs to emphasise traits in a manner consistent with their importance to commercial lamb production. Implications Embracing this selection and broadening the BL’s genetic base will assist the BL to maintain its place in the Australian lamb industry.

The Impact of Antioxidant Supplementation and Heat Stress on Carcass Characteristics, Muscle Nutritional Profile and Functionality of Lamb Meat.

The impact of antioxidant supplementation and short-term heat stress on lamb body weight gain, meat nutritional profile and functionality (storage stability of lipids and colour) of lamb meat was investigated. A total of 48 crossbred ((Merino × Border Leicester) × Dorset) lambs (42 ± 2 kg body weight, 7 mo age) were randomly allocated to three dietary treatments (n = 16) by liveweight (LW) that differed in dosage of vitamin E and selenium (Se) in the diet. Vitamin E and Se levels in the control (CON), moderate (MOD) and supranutritional (SUP) dietary treatments were 28, 130 and 228 mg/kg DM as α-tocopherol acetate and 0.16, 0.66 and 1.16 mg Se as SelPlex™/kg DM, respectively. After four weeks of feeding in individual pens, including one week of adaptation, lambs were exposed to two heat treatments. Animals were moved to metabolism cages for one week and subjected to heat treatments: thermoneutral (TN; 18-21 °C and 40-50% relative humidity) and heat stress (HS; 28-40 °C and 30-40% relative humidity) conditions, respectively. Final LW and hot carcass weight were influenced by dietary treatments with higher final live weight (FLW) (p = 0.05; 46.8 vs. 44.4 and 43.8 kg, respectively) and hot carcass weight (HCW) (p = 0.01; 22.5 vs. 21.3 and 21.0 kg, respectively) recorded in lambs fed the SUP as opposed to the CON and MOD diets. Vitamin E concentration in the longissimus lumborum (LL) muscle tended to be higher in lambs fed MOD or SUP diets than the CON group. Lipid oxidation of aged meat at 72 h of simulated retail display was reduced by antioxidant supplementation. Short-term (one week) heat stress treatment significantly increased muscle linoleic acid and total omega-6 concentrations compared with the CON group. The results demonstrate that four-week antioxidant supplementation at the SUP level improved animal productivity by increasing LW and carcass weight and the functionality of meat exhibited by reduced lipid oxidation. An increase in muscle omega-6 fatty acid concentration from short-term heat stress may induce oxidative stress via proinflammatory action.

Population structure and breed composition prediction in a multi-breed sheep population using genome-wide single nucleotide polymorphism genotypes

Knowledge of population structure and breed composition of a population can be advantageous for a number of reasons; these include designing optimal (cross)breeding strategies in order to maximise non-additive genetic effects, maintaining flockbook integrity by authenticating animals being registered and as a quality control measure in the genotyping process. The objectives of the present study were to 1) describe the population structure of 24 sheep breeds, 2) quantify the breed composition of both flockbook-recorded and crossbred animals using single nucleotide polymorphism BLUP (SNP-BLUP), and 3) quantify the accuracy of breed composition prediction from low-density genotype panels containing between 2000 and 6000 SNPs. In total, 9334 autosomal SNPs on 11 144 flockbook-recorded animals and 1172 crossbred animals were used. The population structure of all breeds was characterised by principal component analysis (PCA) as well as the pairwise breed fixation index (Fst). The total number of animals, all of which were purebred, included in the calibration population for SNP-BLUP was 2579 with the number of animals per breed ranging from 9 to 500. The remaining 9559 flockbook-recorded animals, composite breeds and crossbred animals represented the test population; three breeds were excluded from breed composition prediction. The breed composition predicted using SNP-BLUP with 9334 SNPs was considered the gold standard prediction. The pairwise breed Fst ranged from 0.040 (between the Irish Blackface and Scottish Blackface) to 0.282 (between the Border Leicester and Suffolk). Principal component analysis revealed that the Suffolk from Ireland and the Suffolk from New Zealand formed distinct, non-overlapping clusters. In contrast, the Texel from Ireland and that from New Zealand formed integrated, overlapping clusters. Composite animals such as the Belclare clustered close to its founder breeds (i.e., Finn, Galway, Lleyn and Texel). When all 9334 SNPs were used to predict breed composition, an animal that had a majority breed proportion predicted to be ≥0.90 was defined as purebred for the present study. As the panel density decreased, the predicted breed proportion threshold, used to identify animals as purebred, also decreased (≥0.85 with 6000 SNPs to ≥0.60 with 2000 SNPs). In all, results from the study suggest that breed composition for purebred and crossbred animals can be determined with SNP-BLUP using ≥5000 SNPs.

Genomic prediction based on selected variants from imputed whole-genome sequence data in Australian sheep populations

BackgroundWhole-genome sequence (WGS) data could contain information on genetic variants at or in high linkage disequilibrium with causative mutations that underlie the genetic variation of polygenic traits. Thus far, genomic prediction accuracy has shown limited increase when using such information in dairy cattle studies, in which one or few breeds with limited diversity predominate. The objective of our study was to evaluate the accuracy of genomic prediction in a multi-breed Australian sheep population of relatively less related target individuals, when using information on imputed WGS genotypes.MethodsBetween 9626 and 26,657 animals with phenotypes were available for nine economically important sheep production traits and all had WGS imputed genotypes. About 30% of the data were used to discover predictive single nucleotide polymorphism (SNPs) based on a genome-wide association study (GWAS) and the remaining data were used for training and validation of genomic prediction. Prediction accuracy using selected variants from imputed sequence data was compared to that using a standard array of 50k SNP genotypes, thereby comparing genomic best linear prediction (GBLUP) and Bayesian methods (BayesR/BayesRC). Accuracy of genomic prediction was evaluated in two independent populations that were each lowly related to the training set, one being purebred Merino and the other crossbred Border Leicester x Merino sheep.ResultsA substantial improvement in prediction accuracy was observed when selected sequence variants were fitted alongside 50k genotypes as a separate variance component in GBLUP (2GBLUP) or in Bayesian analysis as a separate category of SNPs (BayesRC). From an average accuracy of 0.27 in both validation sets for the 50k array, the average absolute increase in accuracy across traits with 2GBLUP was 0.083 and 0.073 for purebred and crossbred animals, respectively, whereas with BayesRC it was 0.102 and 0.087. The average gain in accuracy was smaller when selected sequence variants were treated in the same category as 50k SNPs. Very little improvement over 50k prediction was observed when using all WGS variants.ConclusionsAccuracy of genomic prediction in diverse sheep populations increased substantially by using variants selected from whole-genome sequence data based on an independent multi-breed GWAS, when compared to genomic prediction using standard 50K genotypes.

High mobility group box protein 1 neutralization therapy in ovine bacteremia: Lessons learned from an ovine septic shock model incorporating intensive care support.

Sepsis is a highly complex and often fatal syndrome which varies widely in its clinical manifestations, and therapies that target the underlying uncontrolled immune status in sepsis are needed. The failure of preclinical approaches to provide significant sepsis survival benefit in the clinic is often attributed to inappropriate animal disease models. It has been demonstrated that high mobility group box protein 1 (HMGB1) blockade can reduce inflammation, mortality and morbidity in experimental sepsis without promoting immunosuppression. Within this study, we explored the use of ovine anti-HMGB1 antibodies in a model of ovine septic shock incorporating intensive care supports (OSSICS). Results: Septic sheep exhibited elevated levels of HMGB1 within 12 h after the induction of sepsis. In this study, sepsis was induced in six anaesthetized adult Border Leicester × Merino ewes via intravenous instillation of E. coli and sheep monitored according to intensive care unit standard protocols for 26 h, with the requirement for noradrenaline as the primary endpoint. Septic sheep exhibited a hyperdynamic circulation, renal dysfunction, deranged coagulation profile and severe metabolic acidosis. Sheep were assigned a severity of illness score, which increased over time. While a therapeutic effect of intravenous anti-HMGB1 antibody could not be observed in this model due to limited animal numbers, a reduced bacterial dose induced a septic syndrome of much lower severity. With modifications including a reduced bacterial dose, a longer timeframe and broad spectrum antibiotics, the OSSICS model may become a robust tool for preclinical assessment of sepsis therapeutics.

Population structure and genetic characterization of two native Danish sheep breeds

ABSTRACTGenetic diversity in livestock animals has become recognized as important genetic resource for future sustainable livestock production. Especially native breeds, adapted to their local environment, are of considerable interest. Here, we report a genome-wide characterization of two native Danish sheep breeds, the Danish Landrace sheep and the Danish White-Headed Marsh sheep. We investigated the genetic diversity both at national and European breed level using a European-derived reference panel. The native Danish breeds are genetically distinct from other Nordic breeds. Their closest relatives are Border Leicester, Galway, and Texel. Apart from gene flow between native Danish breeds, Texel admixture was most dominant. For Danish Landrace sheep, a population split into two genetically distinct sub-populations was detected. Compared to other livestock species, genomic inbreeding was moderate. However, among European-derived sheep the native Danish breeds were among the 10 most inbred investigated, illustrating the need for sustainable management strategies to preserve genetic diversity.

Effects of High Ambient Temperature and Bypass Protein Supplementation on Performance of Crossbred Lambs

The objective of this experiment was to study the effect of dietary supplementation with a source ofbypass protein (cottonseed meal, CSM) on the performance of growing crossbred wethers fed lowdigestibility roughage at high ambient temperature. Sixteen unshorn Border Leicester x Merino lambsaged 6 months and weighing 24.90.37 kg were allocated into a 2x2 factorial design (2 diets and 2ambient temperatures). Each group was fed either wheaten chaff + 2% urea ad libitum or wheaten chaff +1% urea ad libitum + 100g/d cottonseed meal. The results show that respiration rate and rectal temperaturewere significantly affected by ambient temperature (P&lt;0.01), but not by diet. Total dry matter intake wassignificantly higher (P&lt;0.01) at lower temperature than at high temperature, and significantly higher(P=0.04) on the supplemented diet than on the control diet. Water intake tended (P=0.06) to be higher onthe CSM+ diet than on the control diet, and was significantly at greater (P&lt;0.01) high ambient temperaturethan at low temperature. The concentration of NH3-N in the rumen fluid (ranged from 310±17 to 413±20mg N/L) did not differ significantly either between diets or ambient temperatures. Blood plasma ureanitrogen concentration was significantly higher in sheep on the control diet than in those on thesupplemented diet, and at low than high temperature. The organic matter digestibility was not significantlyaffected by temperature and diet. The rate of live weight gain was significantly (P&lt;0.01) reduced by highambient temperature and the interaction between diet and temperature was significant (P&lt;0.01). At lowtemperature, lambs on the supplemented diet grew significantly faster than those on the control diet, butnot at high temperature. In conclusion, high ambient temperature increases respiration rate, rectaltemperature and water intake but reduces dry matter intake and live weight gain. Supplementation with100 g/d of cottonseed meal could not outweigh the depressing effects of constant high ambienttemperature and humidity imposed in this experiment.

Accuracy of imputation to whole-genome sequence in sheep

BackgroundThe use of whole-genome sequence (WGS) data for genomic prediction and association studies is highly desirable because the causal mutations should be present in the data. The sequencing of 935 sheep from a range of breeds provides the opportunity to impute sheep genotyped with single nucleotide polymorphism (SNP) arrays to WGS. This study evaluated the accuracy of imputation from SNP genotypes to WGS using this reference population of 935 sequenced sheep.ResultsThe accuracy of imputation from the Ovine Infinium® HD BeadChip SNP (~ 500 k) to WGS was assessed for three target breeds: Merino, Poll Dorset and F1 Border Leicester × Merino. Imputation accuracy was highest for the Poll Dorset breed, although there were more Merino individuals in the sequenced reference population than Poll Dorset individuals. In addition, empirical imputation accuracies were higher (by up to 1.7%) when using larger multi-breed reference populations compared to using a smaller single-breed reference population. The mean accuracy of imputation across target breeds using the Minimac3 or the FImpute software was 0.94. The empirical imputation accuracy varied considerably across the genome; six chromosomes carried regions of one or more Mb with a mean imputation accuracy of < 0.7. Imputation accuracy in five variant annotation classes ranged from 0.87 (missense) up to 0.94 (intronic variants), where lower accuracy corresponded to higher proportions of rare alleles. The imputation quality statistic reported from Minimac3 (R2) had a clear positive relationship with the empirical imputation accuracy. Therefore, by first discarding imputed variants with an R2 below 0.4, the mean empirical accuracy across target breeds increased to 0.97. Although accuracy of genomic prediction was less affected by filtering on R2 in a multi-breed population of sheep with imputed WGS, the genomic heritability clearly tended to be lower when using variants with an R2 ≤ 0.4.ConclusionsThe mean imputation accuracy was high for all target breeds and was increased by combining smaller breed sets into a multi-breed reference. We found that the Minimac3 software imputation quality statistic (R2) was a useful indicator of empirical imputation accuracy, enabling removal of very poorly imputed variants before downstream analyses.