Prion protein gene polymorphisms in sheep in the state of Paraná, Brazil

To determine the polymorphisms of the prion protein gene in sheep from the state of Paraná, Brazil, 323 animals of meat breeds (Suffolk, Hampshire Down, Texel, Ile de France, Dorper, Dorset, Santa Inês and crossbreds) were genotyped by restriction fragment length polymorphism (RFLP) analysis. The most frequent allele was ARQ, with a frequency of 0.61, followed by ARR (0.30). VRQ and AHQ alleles were present at very low frequencies (0.13 and 0.05 respectively), and the ARH allele was not found. Seven genotypes were identified (ARR/ARR, ARR/ARQ, ARQ/ARQ, ARR/VRQ, ARR/AHQ, ARQ/VRQ and ARQ/AHQ), of which ARQ/ARQ was the most frequent (0.41). The Santa Inês breed and crossbred animals showed the highest genotypic variability.     

Caseous lymphadenitis in sheep flocks of the state of Minas Gerais,Brazil: Prevalence and management surveys

Corynebacterium pseudotuberculosis is the etiologic agent of caseous lymphadenitis, which is a serious, economically important problem for sheep production. We examined the seroprevalence of infection by C. pseudotuberculosis and possible risk factors associated with caseous lymphadenitis in sheep herds of the state of Minas Gerais, Brazil. Samples were collected from 642 sheep from 97 farms. Sera of all of the sheep were tested with ELISA for antibodies against C. pseudotuberculosis. A questionnaire was applied to gather data on the farm, the sheep herd, the farmer, and individual animal data (breed, sex and age). This is the first sero-epidemiological survey for caseous lymphadenitis in sheep herds in Minas Gerais. We found a high real prevalence, much higher than that suggested from information obtained with the questionnaire, which points to the scarcity of vaccination against caseous lymphadenitis in the sample evaluated. Only a small proportion of the farmers declared that cases of this disease were present in their flocks. The frequency of seropositive sheep varied significantly with breed (χ² test, P = 0.021). Age group also significantly affected the percentage of seropositivity (χ² test, P = 0.049), the highest frequency being found in adult animals (more than 12 months old), when compared to the 5–12 months old group (χ² test, P = 0.021). The prevalence of infection with C. pseudotuberculosis in sheep in the state of Minas Gerais was estimated to be 70.9% (95% confidence interval (CI): 64.7–77.0%) and the prevalence of infected flocks being 95.9% (95% CI: 89.8–98.9%). We concluded that C. pseudotuberculosis infection is widely disseminated in sheep flocks in Minas Gerais and that caseous lymphadenitis control and eradication programs are necessary in this state.     

Allelic frequencies of an ovine scrapie susceptibility gene

Abstract

The allelic frequencies of an ovine gene associated with susceptibility to scrapie was analyzed in a sample of 30 scrapie affected sheep and 545 clinically normal sheep from 12 flocks. The allele encoding glutamine at codon 171 occurred at a frequency of 0.76 in the overall population. All 30 scrapie affected sheep were homozygous for glutamine at codon 171. This genotype was observed in 56.5% of the clinically normal sheep. None of the 30 scrapie affected sheep carried the allele encoding Valine at codon 136 although this allele was observed in 2/12 flocks sampled.     

Assessment of DNA fingerprinting for determining genetic diversity in sheep populations

Genomic DNA, prepared from 12 animals from four sheep flocks, was digested with either HaeIII or Hin fI and probed with three DNA fingerprinting probes. Mean DNA fingerprint band sharing and band frequency calculated for each flock were used to estimate genetic diversity. Each of the DNA fingerprinting systems showed the same trend in diversity within the sampled flocks, and greater diversity between the flocks than within the flocks. DNA fingerprinting therefore provides a useful measure of genetic diversity in sheep.     

A new polymorphism in the Growth and Differentiation Factor 9 (GDF9) gene is associated with increased ovulation rate and prolificacy in homozygous sheep

Brazilian Santa Inês (SI) sheep are very well‐adapted to the tropical conditions of Brazil and are an important source of animal protein. A high rate of twin births was reported in some SI flocks. Growth and Differentiation Factor 9 (GDF9) and Bone Morphogenetic Protein 15 (BMP15) are the first two genes expressed by the oocyte to be associated with an increased ovulation rate in sheep. All GDF9 and BMP15 variants characterized, until now, present the same phenotype: the heterozygote ewes have an increased ovulation rate and the mutated homozygotes are sterile. In this study, we have found a new allele of GDF9, named FecG^E (Embrapa), which leads to a substitution of a phenylalanine with a cysteine in a conservative position of the mature peptide. Homozygote ewes presenting the FecG^E allele have shown an increase in their ovulation rate (82%) and prolificacy (58%). This new phenotype can be very useful in better understanding the genetic control of follicular development; the mechanisms involved in the control of ovulation rate in mammals; and for the improvement of sheep production.     

Rapid Analysis of Allelic Variants of the Sheep PrP Gene by Oligonucleotide Probes

A rapid method to determine the allelic variants of the sheep PrP gene was developed. DNA samples from 128 Suffolk sheep (39 rams and 89 ewes) were screened by using polymerase chain reactions and dot-blot hybridization with ³²P-labeled nine allele-specific oligonucleotide probes corresponding to the polymorphic PrP codons 112, 136, 154 and 171. Three allelic variants of the PrP gene, PrP^MARQ, PrP^TARQ and PrP^MARR, were found in the flocks. Among those variants, nearly half of the ewes had alleles of the 171-Arg variant that is closely associated with resistance to natural scrapie. Assessments of allelic mutations of the PrP gene may help to select the scrapie-resistant progenitors in the flocks.     

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.     

绵羊X染色体59571364与59912586位点在脂尾、瘦尾绵羊群体中的多态性检测及分析

为了探讨绵羊X染色体上两处SNP(59571364和59912586)与绵羊尾脂沉积性状的关系, 继而为利用分子标记辅助选择育种技术培育低脂绵羊品种提供依据, 文章以尾型极端差异的阿勒泰羊、湖羊、中国美利奴细毛羊以及萨福克羊为研究对象, 利用PCR-RFLP检测两位点在群体中的多态性, 并分析了两个SNP位点在阿勒泰羊群体中的单倍型。结果表明：59571364位点的TT基因型和59912586位点的GG基因型在瘦尾中国美利奴与萨福克羊群体中属于优势基因型, 而两种基因型在脂尾(臀)阿勒泰羊与湖羊群体中比率均不足2%; 两位点在阿勒泰羊群体中的单倍型分析结果显示, CA单倍型为主单倍型, 比率高达55%, CA与TA两单倍型约占88.33%。以上结果提示, 绵羊X染色体59571364与59912586位点在脂尾(臀)与瘦尾绵羊群体中分布存在较大差异, 可作为理想的分子标记应用于高、低脂绵羊品种选育。     

Norwegian sheep are an important reservoir for human-pathogenic Escherichia coli O26:H11

A previous national survey of Escherichia coli in Norwegian sheep detected eae-positive (eae(+)) E. coli O26:H11 isolates in 16.3% (80/491) of the flocks. The purpose of the present study was to evaluate the human-pathogenic potential of these ovine isolates by comparing them with E. coli O26 isolates from humans infected in Norway. All human E. coli O26 isolates studied carried the eae gene and shared flagellar type H11. Two-thirds of the sheep flocks and 95.1% of the patients harbored isolates containing arcA allele type 2 and espK and were classified as enterohemorrhagic E. coli (EHEC) (stx positive) or EHEC-like (stx negative). These isolates were further divided into group A (EspK2 positive), associated with stx(2-EDL933) and stcE(O103), and group B (EspK1 positive), associated with stx(1a). Although the stx genes were more frequently present in isolates from patients (46.3%) than in those from sheep flocks (5%), more than half of the ovine isolates in the EHEC/EHEC-like group had multiple-locus variable number of tandem repeat analysis (MLVA) profiles that were identical to those seen in stx-positive human O26:H11 isolates. This indicates that EHEC-like ovine isolates may be able to acquire stx-carrying bacteriophages and thereby have the possibility to cause serious illness in humans. The remaining one-third of the sheep flocks and two of the patients had isolates fulfilling the criteria for atypical enteropathogenic E. coli (aEPEC): arcA allele type 1 and espK negative (group C). The majority of these ovine isolates showed MLVA profiles not previously seen in E. coli O26:H11 isolates from humans. However, according to their virulence gene profile, the aEPEC ovine isolates should be considered potentially pathogenic for humans. In conclusion, sheep are an important reservoir of human-pathogenic E. coli O26:H11 isolates in Norway.     

Intraspecies prion transmission results in selection of sheep scrapie strains

Background

Sheep scrapie is caused by multiple prion strains, which have been classified on the basis of their biological characteristics in inbred mice. The heterogeneity of natural scrapie prions in individual sheep and in sheep flocks has not been clearly defined.

Methodology/Principal Findings

In this study, we intravenously injected 2 sheep (Suffolk and Corriedale) with material from a natural case of sheep scrapie (Suffolk breed). These 3 sheep had identical prion protein (PrP) genotypes. The protease-resistant core of PrP (PrPres) in the experimental Suffolk sheep was similar to that in the original Suffolk sheep. In contrast, PrPres in the Corriedale sheep differed from the original PrPres but resembled the unusual scrapie isolate, CH1641. This unusual PrPres was not detected in the original sheep. The PrPres distributions in the brain and peripheral tissues differed between the 2 breeds of challenged sheep. A transmission study in wild-type and TgBoPrP mice, which overexpressing bovine PrP, led to the selection of different prion strains. The pathological features of prion diseases are thought to depend on the dominantly propagated strain.

Conclusions/Significance

Our results indicate that prion strain selection occurs after both inter- and intraspecies transmission. The unusual scrapie prion was a hidden or an unexpressed component in typical sheep scrapie.     

Genetic structure and admixture in sheep from terminal breeds in the United States

Selection for performance in diverse production settings has resulted in variation across sheep breeds worldwide. Although sheep are an important species to the United States, the current genetic relationship among many terminal sire breeds is not well characterized. Suffolk, Hampshire, Shropshire and Oxford (terminal) and Rambouillet (dual purpose) sheep (n = 248) sampled from different flocks were genotyped using the Applied Biosystems Axiom Ovine Genotyping Array (50K), and additional Shropshire sheep (n = 26) using the Illumina Ovine SNP50 BeadChip. Relationships were investigated by calculating observed heterozygosity, inbreeding coefficients, eigenvalues, pairwise Wright’s F_ST estimates and an identity by state matrix. The mean observed heterozygosity for each breed ranged from 0.30 to 0.35 and was consistent with data reported in other US and Australian sheep. Suffolk from two different regions of the United States (Midwest and West) clustered separately in eigenvalue plots and the rectangular cladogram. Further, divergence was detected between Suffolk from different regions with Wright’s F_ST estimate. Shropshire animals showed the greatest divergence from other terminal breeds in this study. Admixture between breeds was examined using admixture , and based on cross-validation estimates, the best fit number of populations (clusters) was K = 6. The greatest admixture was observed within Hampshire, Suffolk, and Shropshire breeds. When plotting eigenvalues, US terminal breeds clustered separately in comparison with sheep from other locations of the world. Understanding the genetic relationships between terminal sire breeds in sheep will inform us about the potential applicability of markers derived in one breed to other breeds based on relatedness.     

Stable levels of <Emphasis Type="Italic">Coxiella burnetii</Emphasis> prevalence in dairy sheep flocks but changes in genotype distribution after a 10-year period in northern Spain

Bulk tank milk (BTM) samples were collected from 81 sheep flocks in the Basque Country, Spain, in 2015 and were analysed for antibodies against Coxiella burnetii by ELISA and for C. burnetii DNA by real-time PCR. Thirty-two percent of the flocks had BTM antibodies against C. burnetii. Presence of C. burnetii DNA in BTM was detected in 23% of the flocks, suggesting recent C. burnetii infections. Retrospective data of BTM samples obtained from 154 sheep flocks investigated in 2005 in the same geographic area were compiled to assess temporal changes in C. burnetii infection. The overall percentage of infected sheep flocks did not significantly change after the 10-year period. Among the 46 flocks sampled in both periods, 11 flocks that were negative in 2005 were positive in 2015, 18 maintained their initial status (positive or negative), and 17 positive flocks were negative in 2015. These findings indicate that C. burnetii infection is a dynamic process in dairy sheep in northern Spain. Single nucleotide polymorphism (SNP) genotyping of positive samples identified three genotypes, SNP1 being the most prevalent in 2015 and SNP8 in 2005; SNP4 was only detected once in 2005. These results suggest possible changes in the pattern of genotype infection over time.     

Apolipoprotein C Polymorphism in Sheep: Allele Frequencies and Association with Plasma Lipid and Lipoprotein Levels

The genetic polymorphism of apolipoprotein C in normal plasma of four European sheep breeds (Suffolk, Corriedale, Cheviot, and Finn) was first detected using one-dimensional polyacrylamide gel isoelectric focusing (pH 2.5–5.0) followed by immunoblotting with antihuman apolipoprotein CII antibody. Six phenotypes (1-1, 2-1, 2-2, 3-1, 3-2, and 3-3) were identified in the 4.3–4.8 pH range, consisting of the combination of three isoform groups. On the basis of family and population data, these phenotypes were controlled autosomally by three codominant alleles, designated APOC*1, APOC*2, and APOC*3, the first being the most common allele. The frequency distributions of these alleles were similar between the Suffolk and Corriedale sheep, and between the Cheviot and Finn sheep. The former breeds had a significantly lower APOC*2 frequency than the latter breeds (P< 0.001). The mean plasma total-, HDL- and LDL-cholesterol levels of type 3-1 animals were significantly higher compared to type 1-1 animals in the Suffolk sheep (P 0.04). However, these differences were not seen in the Corriedale sheep     

Seroprevalence of ovine paratuberculosis infection in the Northeast of Portugal

A survey to estimate the prevalence of ovine paratuberculosis in sheep flocks was conducted in the Northeast of Portugal. In total, 3900 samples of sheep older than 2 years belonging to 150 sheep flocks from 12 different territorial Livestock Farmers Organizations (OPP) were investigated for the presence of antibodies against Mycobacterium avium subspecies paratuberculosis using a commercial enzyme-linked immunosorbent assay (ELISA) test. Seventy (46.7%) flocks had one or more serologically positive animals. The individual paratuberculosis prevalence was 3.7% (144/3900), with values ranging from 0.0 to 10.3% per flock. Statistically significant differences between OPP, herd size and the presence of clinical signs was observed. According to the test sensitivity and specificity claimed by the manufacturer, the true prevalence in the Northeast of Portugal was calculated as 6.4%. In summary, a small percentage of animals and a high percentage of flocks in the Northeast of Portugal were serologically positive.     

Lambs with scrapie susceptible genotypes have higher postnatal survival

Background

Prion protein (PrP) alleles associated with scrapie susceptibility persist in many sheep populations even with high frequencies despite centuries of selection against them. This suggests that scrapie susceptibility alleles have a pleiotropic effect or are associated with fitness or other traits that have been subject to selection.

Methodology/Principal Findings

We genotyped all lambs in two scrapie-free Scottish Blackface sheep flocks for polymorphisms at codons 136, 154 and 171 of the PrP gene. We tested potential associations of the PrP genotype with lamb viability at birth and postnatal survival using a complementary log-log link function and a Weibull proportional hazard model, respectively. Here we show there is an association between PrP genotype, as defined by polymorphisms at codons 154 ad 171, and postnatal lamb survival in the absence of scrapie. Sheep carrying the wild-type ARQ allele have higher postnatal survival rates than sheep carrying the more scrapie-resistant alleles (ARR or AHQ).

Conclusion

The PrP genotypes associated with higher susceptibility to scrapie are associated with improved postnatal survival in the absence of the disease. This association helps to explain the existence, and in many instances the high frequency, of the ARQ allele in sheep populations.     

Genome-Wide Genetic Diversity and Differentially Selected Regions among Suffolk,Rambouillet, Columbia,Polypay, and Targhee Sheep

Sheep are among the major economically important livestock species worldwide because the animals produce milk, wool, skin, and meat. In the present study, the Illumina OvineSNP50 BeadChip was used to investigate genetic diversity and genome selection among Suffolk, Rambouillet, Columbia, Polypay, and Targhee sheep breeds from the United States. After quality-control filtering of SNPs (single nucleotide polymorphisms), we used 48,026 SNPs, including 46,850 SNPs on autosomes that were in Hardy-Weinberg equilibrium and 1,176 SNPs on chromosome × for analysis. Phylogenetic analysis based on all 46,850 SNPs clearly separated Suffolk from Rambouillet, Columbia, Polypay, and Targhee, which was not surprising as Rambouillet contributed to the synthesis of the later three breeds. Based on pair-wise estimates of F _ST, significant genetic differentiation appeared between Suffolk and Rambouillet (F _ST = 0.1621), while Rambouillet and Targhee had the closest relationship (F _ST = 0.0681). A scan of the genome revealed 45 and 41 differentially selected regions (DSRs) between Suffolk and Rambouillet and among Rambouillet-related breed populations, respectively. Our data indicated that regions 13 and 24 between Suffolk and Rambouillet might be good candidates for evaluating breed differences. Furthermore, ovine genome v3.1 assembly was used as reference to link functionally known homologous genes to economically important traits covered by these differentially selected regions. In brief, our present study provides a comprehensive genome-wide view on within- and between-breed genetic differentiation, biodiversity, and evolution among Suffolk, Rambouillet, Columbia, Polypay, and Targhee sheep breeds. These results may provide new guidance for the synthesis of new breeds with different breeding objectives.     

Genetic diversity and assessment of 23 microsatellite markers for parentage testing of Santa Inês hair sheep in Brazil

Santa Inês is the most common hair sheep breed in Brazil and probably has the highest genetic diversity among sheep breeds in this country. Successful breeding programs for Brazilian sheep breeds are not common for various reasons, including a lack of control of parentage in the flocks. We developed an allele frequency database for 23 STR loci for the Santa Inês breed based on 285 animals sampled from five populations distributed across the central-western and north-eastern regions of Brazil. The marker set included seven microsatellites used in the 2011 International Society for Animal Genetics sheep genotyping comparison tests and all eight microsatellites currently approved by the Brazilian Agricultural Ministry laboratory accreditation guidelines for sheep identification. The microsatellites had an average of 10 alleles and a mean expected heterozygosity of 0.745. Combined paternity exclusion probabilities when no parent or one parent was known were >99.99%. A small proportion (5.8%) of the existing genetic variation was found to be among the Santa Inês populations, possibly derived from genetic drift and selection. We found that the marker panel proposed by the Agricultural Ministry, although generally useful, should be enhanced by including more markers for improved exclusionary power in parentage testing. This database provides a useful tool for parentage testing of this major Brazilian breed, contributing to improved management and breeding of existing herds.     

Genetic polymorphism in sheep plasma detected using antibodies to human plasminogen

Protein variation was identified in sheep when Western blots of polyacrylamide gels (routinely used to resolve transferrin polymorphism) were stained using antibodies to human plasminogen. The affinity of the antibodies to ovine plasma was less than 7% that of a human standard but they bound specifically to a single polymorphic protein. In 146 lambs and their parents the inheritance of the ovine plasminogen antigen polymorphism was consistent with four autosomal alleles segregating codominantly. However, an additional two lambs had types which were incompatible with their putative parents. The pedigrees of these lambs were tested by DNA fingerprinting and shown to have been incorrectly recorded. The genetic polymorphism detected by human plasminogen antiserum provided a probability of sire exclusion (PE) ranging from 0.04 to 0.32 and a polymorphic information content (PIC) of 0.08 to 0.50 in flocks of five sheep breeds: Perendale, Romney, Merino, Texel and Coopworth (in order of increasing genetic variation in this locus). Significant differences in allele frequency were observed between breeds but sampling did not assess the variation among flocks within a breed.