Poll Dorset Sheep Research Articles

A Critical Functional Missense Mutation (T117M) in Sheep MC4R Gene Significantly Leads to Gain-of-Function.

The melanocortin 4 receptor (MC4R) gene plays a central role in regulating energy homeostasis and food intake in livestock, thereby affecting their economic worth and growth. In a previous study, the p.T117M mutation in the sheep MC4R gene, which leads to the transition of threonine to methionine, was found to affect the body weight at six months and the average daily gain in Hu sheep. However, there are still limited studies on the frequency of the sheep p.T117M missense mutation globally, and the underlying cellular mechanism remains elusive. Therefore, this study first used WGS to investigate the distribution of the MC4R gene p.T117M mutation in 652 individuals across 22 breeds worldwide. The results showed that the mutation frequency was higher in European breeds compared with Chinese sheep breeds, particularly in Poll Dorset sheep (mutation frequency > 0.5). The p.T117M mutation occurs in the first extracellular loop of MC4R. Mechanistically, the basal activity of the mutated receptor is significantly increased. Specifically, upon treatment with α-MSH and ACTH ligands, the cAMP and MAPK/ERK signaling activation of M117 MC4R is enhanced. These results indicate that the T117M mutation may change the function of the gene by increasing the constitutive activity and signaling activation of cAMP and MAPK/ERK, and, thus, may regulate the growth traits of sheep. In conclusion, this study delved into the global distribution and underlying cellular mechanisms of the T117M mutation of the MC4R gene, establishing a scientific foundation for breeding sheep with superior growth, thereby contributing to the advancement of the sheep industry.

Population structure and selection signal analysis of indigenous sheep from the southern edge of the Taklamakan Desert

Analyzing the genetic diversity and selection characteristics of sheep (Ovis aries) holds significant value in understanding their environmental adaptability, enhancing breeding efficiency, and achieving effective conservation and rational utilization of genetic resources. In this study, we utilized Illumina Ovine SNP 50 K BeadChip data from four indigenous sheep breeds from the southern margin of the Taklamakan Desert (Duolang sheep: n = 36, Hetian sheep: n = 74, Kunlun sheep: n = 27, Qira black sheep: n = 178) and three foreign meat sheep breeds (Poll Dorset sheep: n = 105, Suffolk sheep: n = 153, Texel sheep: n = 150) to investigate the population structure, genetic diversity, and genomic signals of positive selection within the indigenous sheep. According to the Principal component analysis (PCA), the Neighbor-Joining tree (NJ tree), and Admixture, we revealed distinct clustering patterns of these seven sheep breeds based on their geographical distribution. Then used Cross Population Extended Haplotype Homozygosity (XP-EHH), Fixation Index (FST), and Integrated Haplotype Score (iHS), we identified a collective set of 32 overlapping genes under positive selection across four indigenous sheep breeds. These genes are associated with wool follicle development and wool traits, desert environmental adaptability, disease resistance, reproduction, and high-altitude adaptability. This study reveals the population structure and genomic selection characteristics in the extreme desert environments of native sheep breeds from the southern edge of the Taklimakan Desert, providing new insights into the conservation and sustainable use of indigenous sheep genetic resources in extreme environments. Additionally, these findings offer valuable genetic resources for sheep and other mammals to adapt to global climate change.

Investigation of methods for inclusion of systematic environmental effects in weaning and post-weaning weights for meat sheep in large-scale genetic evaluation

Context Genetic evaluation of Australian sheep is conducted for millions of animals for more than 100 traits. Currently, the Australian sheep genetic-analysis software (OVIS) applies a pre-adjustment of phenotype for fixed effects rather than fitting all fixed and random effects jointly in a linear mixed model to estimate breeding values. However, the current correction factors might be outdated and potential interactions among fixed effects not accounted for, which could lead to bias in estimated breeding values (EBVs). Aims This study aimed to assess whether correction factors used in OVIS for early bodyweights recorded in meat sheep breeds are appropriate, so as to explore whether the pre-adjustment method is still suitable and how this compares with a linear mixed model, and to estimate the significance of interactions between fixed effects. Methods Correlations between EBVs from different models and regression slopes from forward prediction were calculated, using weaning-weight data on 365 956 White Suffolk and 370 649 Poll Dorset sheep and post-weaning weight data on 292 538 White Suffolk and 303 864 Poll Dorset sheep. Key results The current OVIS procedure resulted in regression slopes of progeny performance on sire EBVs (averaged over breeds) of 0.37 and 0.35 for weaning and post-weaning weights respectively. Updated pre-adjustment factors improved the regression slopes to 0.40 and 0.38 respectively. Analysis with a linear mixed model produced significantly better regression slopes than did pre-adjustment (0.47 and 0.44 respectively). Further, regression slopes obtained from the linear mixed model with flock by sex by age interaction averaged over breeds were 0.48 for weaning and 0.46 for post-weaning weight respectively, which was a moderate improvement over the current OVIS model. Including a flock by sex by age interaction produced significantly better improvement in Poll Dorset sheep and modest improvement in White Suffolk sheep than did linear mixed model without interaction. Conclusions Using a linear mixed model with a flock by sex by age interaction significantly improves the utility of estimated breeding values for weaning and post-weaning weight in predicting the performance of future progeny. Implications To account for systematic environmental effects, a linear mixed model should be used in OVIS to jointly estimate the fixed effects and EBVs.

Genome-wide comparative analyses reveal selection signatures underlying adaptation and production in Tibetan and Poll Dorset sheep

The identification of genome-wide selection signatures can provide insights on the mechanisms of natural and/or artificial selection and uncover genes related to biological functions and/or phenotypes. Tibetan sheep are an important livestock in Tibet, providing meat and wool for Tibetans who are renown for breeding livestock that adapt well to high altitudes. Using whole-genome sequences with an effective sequencing depth of 5×, we investigated the genomic diversity and structure and, identified selection signatures of White Tibetan, Oula and Poll Dorset sheep. We obtained 30,163,679 Single Nucleotide Polymorphisms (SNPs) and 5,388,372 indels benchmarked against the ovine Oar_v4.0 genome assembly. Next, using FST, ZHp and XP-EHH approaches, we identified selection signatures spanning a set of candidate genes, including HIF1A, CAPN3, PRKAA1, RXFP2, TRHR and HOXA10 that are associated with pathways and GO categories putatively related to hypoxia responses, meat traits and disease resistance. Candidate genes and GO terms associated with coat color were also identified. Finally, quantification of blood physiological parameters, revealed higher levels of mean corpuscular hemoglobin measurement and mean corpuscular hemoglobin concentration in Tibetan sheep compared with Poll Dorset, suggesting a greater oxygen-carrying capacity in the Tibetan sheep and thus better adaptation to high-altitude hypoxia. In conclusion, this study provides a greater understanding of genome diversity and variations associated with adaptive and production traits in sheep.

BTV-14 Infection in Sheep Elicits Viraemia with Mild Clinical Symptoms.

In 2011, Bluetongue virus serotype 14 (BTV-14) was detected in Russia during routine surveillance, and was subsequently found in a number of European countries. The strain had high sequence similarity to a BTV-14 vaccine strain. We aimed to determine the risk of this BTV-14 strain causing disease in a UK sheep breed. Four Poll Dorset sheep were infected with a Polish isolate of BTV-14 and infection kinetics were monitored over 28 days. BTV RNA was detected in EDTA blood by 4 days post-infection (dpi) and remained detectable at 28 days post-infection (dpi). Peak viraemia occurred at 6 and 7 dpi with Ct values ranging between 24.6 and 27.3 in all infected animals. BTV antibodies were detected by 10 dpi using a commercial ELISA and neutralising antibodies were detected from 10 dpi. BTV was isolated between 6 and 12 dpi. All infected sheep developed mild clinical signs such as reddening of conjunctiva and mucosal membranes, with one sheep demonstrating more overt clinical signs. Two uninoculated control animals remained clinically healthy and did not have detectable BTV RNA or antibodies. The overall mild clinical symptoms caused by this BTV-14 in this highly susceptible sheep breed were in accordance with the asymptomatic infections observed in the affected countries.

Variation in susceptibility of different breeds of sheep to Mycobacterium avium subspecies paratuberculosis following experimental inoculation

Exposure to Mycobacterium avium subspecies paratuberculosis (MAP) does not always lead to Johne’s disease. Understanding differences in disease susceptibility of individual animals is a key aspect to controlling mycobacterial diseases. This study was designed to examine the susceptibility or resistance of various breeds of sheep to MAP infection. Merino, Suffolk first cross Merino, Border Leicester, and Poll Dorset sheep were orally inoculated with MAP and monitored for 14 months. Clinical disease occurred more frequently in the Merino (42%) and Suffolk first cross Merino (36%) compared to the Border Leicester (12%) and Poll Dorset (11%) breeds. Infection risk, as determined by culture of gut and associated lymphoid tissues, ranged from 75% for the Suffolk first cross Merino to 47% for the Poll Dorset sheep. Significant differences were identified in the site in the intestines of the most severe histopathological lesions and the immune responses to infection between the breeds. However, there was no difference in faecal MAP shedding by clinical cases between breeds. All breeds tested were susceptible to MAP infection, as determined by infection and clinical disease development, although there were differences in the proportions of diseased animals between the breeds. Poll Dorset and Border Leicester sheep were more resilient to MAP infection but there was evidence that more animals could have developed disease if given more time. These findings provide evidence of potential differential disease susceptibility between breeds, further our understanding of disease pathogenesis and risks of disease spread, and may have an influence on control programs for paratuberculosis.

Effect of sire breed on the productivity of Kazakh mutton-semifine-wool sheep

In recent years, the world demand for a low fat and high protein content lean meat had increased to meet the needs of the organism in proteins. This article presents the results of an expedient scientific-research analysis on establishing the influence of Poll Dorset and Texel breed on the particular growth variability, development of both meat and wool productivity of Kazakh mutton-semifine-wool breed of sheep. Results of the study were obtained under the same grazing conditions of 110 head of purebred and 110 crossbreed Texel and Poll-Dorset sheep of second generation. It was found that peers of the experimental group exceeded their peers in the control group on the dynamics of growth in body weight (P£0.05), i.e. crossing helped to improve the performance of daily gain (P£0.05). In terms of slaughter indicators, such as the slaughter and carcass weight, crossbreed male lambs also surpassed purebred male lambs (P£0.05). Herein, it was found that crossbreed lambs of Texel breed observe the superiority in terms of meat output (fat free) in relation to purebred male lambs (P£0.01). The study of longissimus muscle chemical composition showed that crossbreed male lambs of Texel breed in protein content in this very muscle are superior to purebred peers (P£0.05). A study of wool characteristics of experimental sheep showed that at the age of 12 months the high wool clip was observed in male lambs of Texel second generation (P£0.05). The high yield of washed wool was also observed in Texel male lambs (P£0.05) as compared to purebred peers.

Study of the correlation between GH gene polymorphism and growth traits in sheep.

The growth hormone gene plays an important role in the physiological function of an organism. The current study aimed to investigate the correlation between polymorphisms in the 5' regulatory region, exon 4, and 3' untranslated region (UTR) of the sheep GH gene and sheep growth traits. The DNA from 510 adult sheep was analyzed by DNA sequencing and polymerase chain reaction single-strand conformation polymorphism. Two alleles (A and B) and 3 genotypes (AA, AB, and BB), 2 alleles (A and B) and 3 genotypes (AA, AB, and BB), and 3 alleles (A, B, and C) and 4 genotypes (AA, AB, BB, and AC) were found within the 5' regulatory region, exon 4, and 3' UTR, respectively. In Tibetan sheep, the association analysis indicated that there were statistically significant differences in the scores of weight, length, and heart girth within the 5' regulatory region; weight, length, wither height, and heart girth within exon 4; and weight, length, wither height, and heart girth within the 3' UTR among the different genotypes. For exon 4, Poll Dorset sheep individuals with genotype AA showed a lower score than those of genotypes BB and AB (P<0.05). With regard to the 3' UTR, Poll Dorset sheep with genotype AC showed higher scores than those of genotypes AA and AB (P<0.05).

Site-directed mutagenesis of the myostatin gene in ovine fetal myoblast cells in vitro

Myostatin is an important negative regulator of muscle growth and development. Natural mutations of the myostatin gene cause a double muscling phenotype in beef cattle, pigs and sheep. Therefore, it is feasible to produce a high growth domestic breed by generating a transgenic animal with a mutation, deletion or knockout of the myostatin gene. Our objective was to introduce a subtle mutation of G to A 281-bp upstream of the 3′ untranslated region (3′UTR) end of the myostatin gene in Poll Dorset fetal myoblast cells in vitro. Fetal myoblast cells were isolated from fetuses at day 50 of gestation from Poll Dorset sheep and transfected with linear gene-targeting vector pMSTN-A using electroporation. We obtained seven gene-targeted cell colonies with homologous recombination, which were positive as confirmed by PCR, Southern blot. The Western blot analysis result demonstrated that the myostatin protein expression in positive colonies is lower than that of negative ones. These results strongly suggest that we successfully mutated the myostatin gene of Poll Dorset ovine fetal myoblast cells and the mutation can effectively downregulate the myostatin protein expression.

Multiple Factors Affecting Superovulation in Poll Dorset in China

To expand the breeding flock of Poll Dorset sheep in China, multiple ovulation and embryo transfer breeding program was applied to the limited number of imported Australian Poll Dorset sheep. This study investigated the effects of FSH from three different manufacturers, parity (nulliparous vs multiparous), repeated superovulation, oestrus induction, corpus luteum regression and oestrus delay on Poll Dorset superovulation. The results showed that gonadotropin FSH from Canada Folltropin-V (Ca-FSH) was successfully used for superovulatory treatment with 160 mg-200 mg dosage per ewe and recovered 12.91 ± 7.80 embryos. Multiparous ewes for superovulation treatment were significantly better nulliparous ewes (p<0.05). The successive superovalution treatment reduced significantly embryo collection but did not affect transferable embryo number. Ewes with natural oestrus resulted in significantly higher number of embryos (13.83 ± 4.64) and of transferable embryos (12.00 ± 5.76) than ewes with induced oestrus (7.00 ± 4.92; 4.22 ± 3.42) and unknown oestrus cycle (5.94 ± 3.38; 3.19 ± 2.56, p<0.05). The delayed oestrus ewes at 24 h after superovulatory treatment produced significantly fewer embryos and transferable embryos (0.92 ± 1.51 vs 0.42 ± 0.90) than those with normal oestrus (p<0.01). Furthermore, the more transferable embryos were recovered from ewes with normal corpus luteum than those with corpus luteum regression (5.88 ± 5.09 vs 3.59 ± 4.30 and 8.83 ± 5.75 vs. 6.66 ± 5.41, p<0.01). These results suggest that in our farm practice, a comprehensive treatment method by using the Canadian FSH (Folltropin-V), plus choosing multiparous and natural oestrus ewes with normal corpus luteum might obtain an optimum embryo collection and embryos transfer in sheep.

Virological and pathological findings in Bluetongue virus serotype 8 infected sheep

Twenty-seven sheep of the four most common Swiss breeds and the English breed Poll Dorset were experimentally infected with a northern European field strain of bluetongue virus serotype 8 (BTV-8). Animals of all breeds developed clinical signs, viremia and pathological lesions, demonstrating that BTV-8 is fully capable of replicating and inducing bluetongue disease (BT) in the investigated sheep. Necropsy performed between 10 and 16 days post-infectionem (d.p.i.) revealed BT-typical hemorrhages, effusions, edema, erosions and activation of lymphatic tissues. Hemorrhages on the base of the Arteria pulmonalis and the left Musculus papillaris subauricularis were frequently present. Histology confirmed the macroscopical findings. Using a score system, clinical manifestation and pathology were found to be significantly related. Furthermore, clinical signs and fever were shown to be indicative for the concurrent presence of high amounts of viral ribonucleic acid (RNA) in blood. Spleen, lung, lymph nodes and tonsils from all animals were analyzed regarding viral RNA loads and infectivity using real-time reverse transcriptase PCR (rRT-PCR) and virus isolation in cell culture, respectively. The highest amount of viral RNA was detected in spleen and lung and rRT-PCR revealed to be a more sensitive method for virus detection compared to virus isolation. A long-term follow-up was performed with three sheep showing that BTV-8 viral RNA in blood was present up to 133 d.p.i. and in certain tissues even on 151 d.p.i. No significant breed-related differences were observed concerning clinicopathological picture and viremia, and the Swiss sheep were as susceptible to BTV-8 infection as Poll Dorset sheep, demonstrating a remarkably high virulence of BTV-8 for indigenous sheep breeds.

The effects of a loin muscling quantitative trait locus (LoinMAX™) on carcass and VIA-based traits in crossbred lambs

LoinMAX (LM) is a quantitative trait locus (QTL), which was found to be segregated in Australian Poll Dorset sheep, and maps to the distal end of sheep chromosome 18. LM-QTL was reported to increase Musculus longissimus dorsi area and weight by 11% and 8%, respectively. The aim of this study was to comprehensively evaluate the direct effects of LM-QTL in a genetic background typical of the stratified structure of the UK sheep industry, before it can be recommended for use in the United Kingdom. Crossbred lambs, either non-carriers or carrying a single copy of LM-QTL, were produced out of Scottish Mule ewes (Bluefaced Leicester × Scottish Blackface) artificially inseminated with semen from two Poll Dorset rams that were heterozygous for LM-QTL. Unexpectedly, one of these rams was also heterozygous for a QTL that affects the overall carcass muscling (MyoMAX™). This was accounted for by nesting MyoMAX™ status (carrier or non-carrier) within sire in the statistical analysis. Lambs were weighed and scanned by using X-ray computed tomography (CT) at an average age of 113 days. Ultrasound scan measurements, along with lamb weights, were taken at an average age of 140 days and lambs were then slaughtered. Carcasses were weighed and classified for fat cover and conformation scores, based on the Meat and Livestock Commission (MLC) carcass classification scheme, and then scanned by using a video image analysis (VIA) system. M. longissimus lumborum (MLL) width, as measured by CT scanning, was greater (P < 0.05) in lambs heterozygous for LM-QTL compared with non-carriers. MLL in LM-QTL carrier lambs was also significantly deeper, as measured by both ultrasound muscle depth at the third lumbar vertebrae (+3.7%; P < 0.05) and CT scanning at the fifth lumbar vertebrae (+3.4%; P < 0.01). Consequently, MLL area, was measured by using CT scanning, was significantly higher (+4.5%; P < 0.01) in lambs carrying a single copy of LM-QTL compared with non-carriers. Additional traits measured by CT, such as leg muscle dimensions, average muscle density and tissue proportions, were not significantly affected by LM-QTL. LM-QTL did not significantly affect total carcass lean or fat weights or MLC conformation and fat score classifications. Using previously derived algorithms, VIA could detect a significant effect of the LM-QTL on the predicted weight of saleable meat yield in the loin primal cut (+2.2%; P < 0.05), but not in the other primal cuts, or the total carcass.

Study on single nucleotide polymorphisms of &lt;I&gt;H –FABP&lt;/I&gt; gene in sheep

PCR-SSCP and DNA sequencing approaches were applied to assess the single nucleotide polymorphisms (SNPs) and analyze the genetic polymorphisms at partial exon 2 and intron 2 of H-FABP(Heart fatty acid-binding protein)gene, and five sheep populations that comprised of Small-Tailed Han sheep (SH, 48), Ningxia Tan sheep (Tan, 121), Tan x SH F1 (23), Poll Dorset (48) and Suffolk (24) sheep were screened in this study. The result showed: (1)four SNPs at 981(G/A), 1014(A/C) 1019(T/C) and 1058 (-/G ) and nine genotypes (AA, BB, CC, AB, AC, BC, AD, CD and BD) were detected using primer 2, the AA was the predominant genotype. A chi-square analysis suggested that the allele frequencies and genotype frequencies of H-FABP were in Hardy-Weinberg equilibrium except the Tan and Suffolk populations. Statistical analysis revealed a low polymorphism information content (PIC) in the Suffolk and Tan x SH F1 populations (PIC amp; 0.25) but an intermediate PIC in the remaining three populations (0.25 amp; PIC amp;0.50). It meant that the fragment of H-FABP had polymorphisms, which could be used as a candidate gene associated gene with phenotypic traits like intramuscular fat content in different sheep populations. (2)Three genotypes (HH, Hh and hh) determined by a SNP at 2407(T-C) were detected using primer 4. The genotype frequencies were in the order of HHHhhh. A chi-square analysis suggested that the allele frequencies and genotype frequencies of H-FABP were in Hardy-Weinberg equilibrium in the Tan and Poll Dorset populations, and the PIC values were low (PIC amp; 0.25). However, there was no polymorphisms in SH, Tan x SH F1 and Suffolk populations.

The effects of three muscling Quantitative Trait Loci on growth patterns of crossbred lambs

Texel Muscling QTL (TM-QTL) and LoinMaxTM (LM-QTL) are located on chromosome 18 in Texel and Poll Dorset sheep, respectively, and have been shown to positively affect muscling of the loin in crossbred lambs carrying one copy of the QTL (Macfarlane et al., 2008, Masri et al., 2009). MyoMaxTM (MM-QTL), found on chromosome 2 of Texel sheep, increases muscling and decreases fatness in lambs of different genetic backgrounds (Campbell and McLaren, 2007). No differences in live weights, carcass weights or growth rates have been associated with these QTL to date. However, there is further need to investigate the effects of the three QTL on growth patterns in commercial crossbred populations, where fast-growing slaughter lambs of good carcass weights and quality are a prerequisite.

Comprehensive evaluation of the direct effects of LM-QTL on carcass traits in crossbred lambs

LoinMax (LM-QTL) increases M. longissimus dorsi (MLD) area and weight by 11% and 8% respectively (Nicoll et al., 1998). It was found to segregate in Australian Poll Dorset sheep (Banks, 1997) and has been mapped to chromosome 18 (Nicoll et al., 1998). The UK sheep industry may benefit from using LM-QTL to increase yield of the highly priced loin region. However, before being utilised, the effects of LM-QTL need to be verified in a genetic background typical to the stratified structure of the UK sheep industry.

Aromatase gene and its effects on growth, reproductive and maternal ability traits in a multibreed sheep population from Brazil

We determined the polymorphism C242T of the aromatase gene (Cyp19) and its allelic frequency, as well as the effect of the variants on productive and reproductive traits in 71 purebred Santa Inês sheep, 13 purebred Brazilian Somali sheep, nine purebred Poll Dorset sheep, and 18 crossbred 1/2 Dorper sheep. The animals were genotyped using the PCR-RFLP technique. The influence of the animal's genotype on its performance or on the performance of its lambs was analyzed by the least square method. Another factor assessed was the importance of the animal's genotype in analysis models for quantitative breeding value estimates, and whether there were differences among the averages of breeding values of animals with different genotypes for this gene. In the sample studied, no AA individuals were observed; the AB and BB frequencies were 0.64 and 0.36, respectively. All Brazilian Somali sheep were of genotype BB. All 1/2 Dorper BB animals presented a lower age at first lambing, and the Santa Inês BB ewes presented a lower lambing interval. In these same genetic groups, AB ewes presented higher litter weight at weaning. This is evidence that BB ewes have a better reproductive performance phenotype, whereas AB ewes present a better maternal ability phenotype. However, in general, animals with genotype AB presented better average breeding values than those with genotype BB.

Blauzungenkrankheit bei Schweizer Schafrassen: Klinische Symptome nach experimenteller Infektion mit dem BTV-Serotyp 8

Clinical disease of bluetongue (BT) in sheep may differ depending on breed, age and immunity of infected sheep and may also vary between serotype and strain of BT virus (BTV). Since there are no data available on the susceptibility of Swiss sheep breeds for BT, we performed experimental infection of the 4 most common Swiss sheep breeds and the highly susceptible Poll Dorset sheep with the BTV serotype 8 (BTV-8) circulating in Northern Europe since 2006. Clinical signs were assessed regarding severity, localisation, progression and time point of their appearance. The results clearly show that the Swiss sheep breeds investigated were susceptible to BTV-8 infection. They developed moderate, BT-characteristic symptoms, which were similar to those observed in Poll Dorset sheep. Regardless of breed, the majority of infected animals showed fever, swelling of the head as well as erosions of the mouth and subcutaneous haemorrhages.

An assessment of Culicoides surveillance techniques in northern Europe: have we underestimated a potential bluetongue virus vector?

Summary 1. Bluetongue virus (BTV), a pathogen of ruminants transmitted by Culicoides midges, has emerged dramatically across Europe since 1998. Surveillance of Culicoides is currently carried out in every European country affected by BTV, most commonly using standardized light-suction traps that sample the population of adult Culicoides present. To date, however, it is not clear whether these trap catches accurately reflect the biting population of Culicoides . 2. In our study, we carried out 192 drop-trap catches at dusk on Poll Dorset sheep, drawing comparisons with surveillance samples taken using standard trapping protocol at the same site. A multiplex polymerase chain reaction technique was optimized for high-throughput processing of cryptic species to allow Culicoides collected to be identified to species level, the first time this has been achieved in this region for an ecological study. A mathematical model was then constructed to describe rates of midge biting under the meteorological conditions recorded during trials. 3. Light-trapping surveillance was found to substantially underestimate the numbers of Culicoides chiopterus present on sheep. This finding is extremely significant given that, due to the low numbers of this species caught at light traps across northern Europe, C. chiopterus had not been seriously considered as a potential vector of BTV. 4. The models constructed of successful blood feeding predict that while biting rates on sheep are significantly reduced under conditions adverse to midge flight (wind speeds that exceeded 3 mps, wind turbulence of greater than 40 degrees change in direction during the trial and solar intensity exceeding 200 Wm ‐2 ), low levels of biting can also occur under sub-optimal meteorological conditions, that have the potential to span entire days in the later part of the adult season. 5. Synthesis and applications. It is clear from these results that light-trapping surveillance does not provide an accurate reflection of the biting population of Culicoides present. Given that the surveillance systems are already in wide employment across Europe, but provide misleading results as we have demonstrated, and considering the huge economic and animal welfare impact of BTV incursions, it is vital that alternative/additional methods of surveillance are explored. Additionally, the vector competence of C. chiopterus as a potential vector of arboviruses requires urgent assessment, along with a clearer understanding of diel periodicity of Culicoides attacks throughout the adult season.

Clinical signs and pathology shown by British sheep and cattle infected with bluetongue virus serotype 8 derived from the 2006 outbreak in northern Europen

Four poll Dorset sheep and four Holstein-Friesian cattle were infected with the northern European strain of bluetongue virus (btv), btv-8, to assess its pathogenicity in uk breeds. The time course...

Frequencies of PrP Genotypes in Meat Breeds of Japanese Sheep and Trail of Selective Breeding in Experimental Sheep Flock

The selection of sheep with scrapie-resistant PrP genotypes is one of the control measures for transmissible spongiform encephalopathies in ruminants. In this study, we investigated the frequencies of PrP genotypes in meat breeds in Japan. The nationwide surveillance revealed that nearly half of the Suffolk sheep, a major meat breed in Japan, carried scrapie-susceptible AQ/AQ and AQ/VQ genotypes. In addition, the VQ haplotype, which confers high susceptibility to scrapie within sheep, was also found in Poll Dorset sheep. A trial of selective breeding using sires with scrapie-resistant PrP genotypes AQ/AR and AR/AR could raise the ratio of scrapie-resistant sheep from less than 50% to 80% within 3 years. However, the use of sires with the AR/AR genotype and the selection of ewes would be required to achieve a higher ratio of scrapie-resistant sheep.