Genetic factors controlling wool shedding in a composite Easycare sheep flock

Historically, sheep have been selectively bred for desirable traits including wool characteristics. However, recent moves towards extensive farming and reduced farm labour have seen a renewed interest in Easycare breeds. The aim of this study was to quantify the underlying genetic architecture of wool shedding in an Easycare flock. Wool shedding scores were collected from 565 pedigreed commercial Easycare sheep from 2002 to 2010. The wool scoring system was based on a 10‐point (0–9) scale, with score 0 for animals retaining full fleece and 9 for those completely shedding. DNA was sampled from 200 animals of which 48 with extreme phenotypes were genotyped using a 50‐k SNP chip. Three genetic analyses were performed: heritability analysis, complex segregation analysis to test for a major gene hypothesis and a genome‐wide association study to map regions in the genome affecting the trait. Phenotypes were treated as a continuous or binary variable and categories. High estimates of heritability (0.80 when treated as a continuous, 0.65–0.75 as binary and 0.75 as categories) for shedding were obtained from linear mixed model analyses. Complex segregation analysis gave similar estimates (0.80 ± 0.06) to those above with additional evidence for a major gene with dominance effects. Mixed model association analyses identified four significant (P < 0.05) SNPs. Further analyses of these four SNPs in all 200 animals revealed that one of the SNPs displayed dominance effects similar to those obtained from the complex segregation analyses. In summary, we found strong genetic control for wool shedding, demonstrated the possibility of a single putative dominant gene controlling this trait and identified four SNPs that may be in partial linkage disequilibrium with gene(s) controlling shedding.     

Genome-Wide Association Study for Wool Production Traits in a Chinese Merino Sheep Population

Genome-wide association studies (GWAS) provide a powerful approach for identifying quantitative trait loci without prior knowledge of location or function. To identify loci associated with wool production traits, we performed a genome-wide association study on a total of 765 Chinese Merino sheep (JunKen type) genotyped with 50 K single nucleotide polymorphisms (SNPs). In the present study, five wool production traits were examined: fiber diameter, fiber diameter coefficient of variation, fineness dispersion, staple length and crimp. We detected 28 genome-wide significant SNPs for fiber diameter, fiber diameter coefficient of variation, fineness dispersion, and crimp trait in the Chinese Merino sheep. About 43% of the significant SNP markers were located within known or predicted genes, including YWHAZ, KRTCAP3, TSPEAR, PIK3R4, KIF16B, PTPN3, GPRC5A, DDX47, TCF9, TPTE2, EPHA5 and NBEA genes. Our results not only confirm the results of previous reports, but also provide a suite of novel SNP markers and candidate genes associated with wool traits. Our findings will be useful for exploring the genetic control of wool traits in sheep.     

Rapid morphological change in an insular population of feral sheep

Artificially selected qualities can reduce fitness in a wild setting, thus feral domesticates should experience strong selective forces. Domestic sheep Ovis aries have frequently become feral on islands, which differ substantially from mainland environments. We examined changes in body mass and wool traits in feral sheep inhabiting Santa Cruz Island (SCI), California for ≥90 years. To elucidate the influence of nutrition, we compared the mass of feral island sheep with that of island sheep raised in farm conditions. We found that feral sheep on SCI were smaller than purported founder breeds, and that most documented populations of insular feral sheep worldwide have converged to similar body sizes (within 6 kg). SCI rams attained greater mass in farm conditions but ewes did not, suggesting phenotypic plasticity in ram body mass. Ewes exhibited self-shedding of wool at a greater frequency than rams, and sex differences and shedding patterns were consistent with thermoregulation and the risk of fly strike disease as benefits of wool loss. Pigmentation rates did not increase, further supporting the influence of heat stress on wool traits. These changes occurred in <25 generations and may have had a genetic basis, representing a potential example of rapid evolution in insular feral sheep.     

How to predict attachment potential of seeds to sheep and cattle coat from simple morphological seed traits

Dispersal is a process that determines many aspects in the life-history of plants. Up to now, however, it is difficult to quantify. Many studies rather assess it as a categorical trait, i.e. assuming a species is dispersed by a certain vector or not. Gradual differences in the dispersal potential between species are rarely considered.
In this paper we focus on the key process of epizoochory: the attachment potential of species to animal coats. We present two simple models (GLMs) how to quantify and to predict attachment potentials to sheep wool and to cattle hair from easily measurable seed traits. To calibrate the models, we investigated the attachment potential of seeds of 130 plant species on mechanically shaken coats of sheep and cattle and measured traits describing the seeds. We found that seed mass and seed morphology were correlated with attachment potentials. For sheep wool, the combination of the logarithm of seed mass and a constant for the different seed morphology types explained 85% of the variation of attachment potentials. For cattle hair, 71% were explained. To validate the models, they were applied to 36 additional species. Predicted and experimentally measured attachment potentials were correlated with r=0.84 for sheep wool and r=0.61 for cattle wool. Thus, the attachment potential of seeds to sheep or cattle coat can be assessed for a large set of species using the described models if seed mass and seed morphology are known.     

Utilization of gene mapping information in livestock animals

A number of recent advances in genomic research will change and improve livestock production in the near future. Genetic linkage maps have been developed for a number of livestock species including cattle, sheep, and pigs. These maps allow scientists to identify chromosomal regions that influence traits of economic importance. This information will lead to improved genetic selection practices by identifying animals with superior copies of the chromosomal regions that affect the selected trait. This mapping information will also be used to identify the genes controlling the trait. A number of genomic regions or loci have already been reported that affect production, carcass or disease traits, and in a few cases, a specific gene has been identified. Production of transgenic animals with sequence changes in these genes may be beneficial for evaluating the effect of the gene upon the selected trait and more specifically the effect of certain polymorphisms (mutations) within the gene.     

Merino sheep: a further look at quantitative trait loci for wool production

A quantitative trait loci (QTL) analysis of wool traits from experimental half-sib data of Merino sheep is presented. A total of 617 animals distributed in 10 families were genotyped for 36 microsatellite markers on four ovine chromosomes OAR1, OAR3, OAR4 and OAR11. The markers covering OAR3 and OAR11 were densely spaced, at an average distance of 2.8 and 1.2 cM, respectively. Body weight and wool traits were measured at first and second shearing. Analyses were conducted under three hypotheses: (i) a single QTL controlling a single trait (for multimarker regression models); (ii) two linked QTLs controlling a single trait (using maximum likelihood techniques) and (iii) a single QTL controlling more than one trait (also using maximum likelihood techniques). One QTL was identified for several wool traits on OAR1 (average curvature of fibre at first and second shearing, and clean wool yield measured at second shearing) and on OAR11 (weight and staple strength at first shearing, and coefficient of variation of fibre diameter at second shearing). In addition, one QTL was detected on OAR4 affecting weight measured at second shearing. The results of the single trait method and the two-QTL hypotheses showed an additional QTL segregating on OAR11 (for greasy fleece weight at first shearing and clean wool yield trait at second shearing). Pleiotropic QTLs (controlling more than one trait) were found on OAR1 (clean wool yield, average curvature of fibre, clean and greasy fleece weightand staple length, all measured at second shearing).     

Estimates of economic values for traits of Arabic sheep in village system

A deterministic bio-economic model was used to estimate the economic values of different traits in Arabic sheep native to the Khuzestan province of Iran. In the studied system, variable costs accounted for about 98.5% of the total costs and among variable costs, feed costs had the highest proportion with 70.7%. Revenue sources included meat, wool, and manure, where meat was the most important one and formed 95.5% of total revenues. Economic value for a trait was estimated as the amount of change in the profit of system as its mean increased by one unit, while the means of other traits were constant. The most important trait in this system was litter size, followed by ewe survival, dressing percentage, and wool weight, respectively. Birth weight had a negative economic value but weight at older ages especially weaning weight and 12-month weight had positive economic values. The sensitivity of economic values of traits was investigated by changing feed and non-feed costs, meat and wool prices by ±10%. Results showed that economic values for dressing percentage and wool weight are not sensitive to change in costs. In addition, changes in marketing and management costs had no effect on the economic value for traits related to body weight in different ages. In general, the economic value for traits which showed sensitivity to the changes of costs, except ewe survival, decreased due to an increase in costs. The economic value for all traits, except birth and wool weight, changed because of a change in meat price. Increasing meat price meant a higher economic importance. Among different factors, meat price fluctuations had the most effect on the economic value of traits.     

Estimates of economic values for traits of Arabic sheep in village system

A deterministic bio-economic model was used to estimate the economic values of different traits in Arabic sheep native to the Khuzestan province of Iran. In the studied system, variable costs accounted for about 98.5% of the total costs and among variable costs, feed costs had the highest proportion with 70.7%. Revenue sources included meat, wool, and manure, where meat was the most important one and formed 95.5% of total revenues. Economic value for a trait was estimated as the amount of change in the profit of system as its mean increased by one unit, while the means of other traits were constant. The most important trait in this system was litter size, followed by ewe survival, dressing percentage, and wool weight, respectively. Birth weight had a negative economic value but weight at older ages especially weaning weight and 12-month weight had positive economic values. The sensitivity of economic values of traits was investigated by changing feed and non-feed costs, meat and wool prices by ±10%. Results showed that economic values for dressing percentage and wool weight are not sensitive to change in costs. In addition, changes in marketing and management costs had no effect on the economic value for traits related to body weight in different ages. In general, the economic value for traits which showed sensitivity to the changes of costs, except ewe survival, decreased due to an increase in costs. The economic value for all traits, except birth and wool weight, changed because of a change in meat price. Increasing meat price meant a higher economic importance. Among different factors, meat price fluctuations had the most effect on the economic value of traits.     

Identification of the ovine KAP11-1 gene (<Emphasis Type="Italic">KRTAP11</Emphasis>-<Emphasis Type="Italic">1</Emphasis>) and genetic variation in its coding sequence

Keratin-associated proteins (KAPs) are a structural component of the wool fibre and form the matrix between the keratin intermediate filaments (KIFs). The gene encoding high sulphur-protein KAP11-1 has been identified in human, cattle and mouse, but not yet in sheep, despite the economic importance of wool. In this study, PCR using primers based on the cattle KAP11-1 gene sequence produced an amplicon of the expected size with sheep DNA. Upon using PCR–Single Stranded Conformational Polymorphism (PCR–SSCP) analysis in 260 sheep, six different PCR–SSCP patterns were detected. Either one or a combination of two banding patterns was observed for each sheep, suggesting they were either homozygous or heterozygous for this gene. Sequencing of the amplicons confirmed the occurrence of six DNA sequences. All of these were unique, and the greatest homology was with KRTAP11-1 sequences from cattle, human and mouse, suggesting that they were derived from the ovine KAP11-1 gene and were allelic variants. The ovine KAP11-1 gene had an open reading frame of 477 nucleotides encoding 159 amino acids. The putative protein was rich in serine, cysteine, and threonine which account for 18.2–18.9, 12.6 and 12.0 mol%, respectively. Of these, approximately 20 of the serine and threonine residues might be phosphorylated. Five nucleotide substitutions were identified, and one was non-synonymous and would result in an amino acid change at a potential phosphorylation site. The genetic variation found in KRTAP11-1 may influence its expression, protein structure, and/or post-translational modifications, and consequently affect wool fibre structure and wool traits.     

THE OLFACTORY BEHAVIOUR OF LUCILIA SPECIES (DIPTERA) UNDER NATURAL CONDITIONS

Using an apparatus of the 'two-choice' type under field conditions, it has been demonstrated that a wool-factor forms an important part of the mechanism whereby female Lucilia sericata may be attracted to sheep. The 'wool-factor' could not wholly be replaced by ammonium- or sulphydryl-type attractants.
L. sericata was strongly attracted by the combination of ammonium carbonate/indole with sheep wool but less strongly attracted when ethyl mercaptan/hydrogen sulphide was used with sheep wool. L. caesar and L. illustris , on the other hand, were not markedly responsive to the ammonium-type attractants but were strongly attracted by the sulphydryl mixture used either alone or in combination with sheep wool.
Temperature is an important element in the oviposition stimulus. The amount of oviposition by L. sericata was increased when substances known to induce oviposition were exposed at 30–40† C.
Sheep wool kept moist and incubated at approx. 38† C. under field conditions for 3 weeks did not attract L. sericata and oviposition did not occur on such wool. This suggests that bacteria normally present on the wool fibre as distinct from the skin, do not play an important part in rendering sheep susceptible to blowfly attack.     

Influence of hydrothermal factors on wool development of Tan sheep in China

Hydrothermal factors in Ningxia, an arid and semi-arid area in Northwestern China, were examined to determine their influence on the geographical differentiation of the wool quality of Tan sheep lambskin. Prospective areas for extension of the Tan sheep industry were also investigated. Two sheep groups were sampled; one consisted of artificial insemination flocks (1241 lambs sampled from 25 flocks) and the other of natural mating flocks (1009 lambs from 38 flocks). Six phenotypical traits were measured for each lamb and six hydrothermal factors were collected from the meteorological stations located in the sampling areas. A significant correlation was found between wool characteristics of the lambskin and hydrothermal conditions. Data further indicated that among all the hydrothermal factors measured, those causing the geographical differentiation of soil and vegetation were the major factors responsible for the corresponding differentiation of the lambskin and wool quality of Tan sheep. Thermal factors were mostly positively correlated with wool quality, while the influence of moisture was negative. Three eco-geographical regions were defined based on a combination of the hydrothermal conditions and corresponding wool characters: (i) typical region or super-suitable region, (ii) sub-typical region or suitable region and (iii) transitional region. The delimitation could be used as a basis for the extension of the Tan sheep industry. It is also suggested that the wool quality of lambskin of Tan sheep in these three regions could be improved by means of controlled breeding and selection.     

Effects of mimosine, a potential chemical defleecing agent, on wool growth and the skin of sheep.

Twenty-two Merino sheep were dosed with various amounts of L-mimosine, given either as an intravenous or an intraperitoneal injection, or as a continuous intravenous infusion for periods of 1-4 days. Single injections of mimosine (1-16 g) had no effect on the strength of wool, and wool growth rates were not appreciably altered by injections of small amounts (4 g or less). Injections of larger amounts slightly reduced both length growth rate and diameter of tibres during the 4 days after dosing. The effects of intravenous infusions of mimosine depended on the rate and the duration of administration. Small amounts (0.5 or 1 g/day given for 4 days) has no effects on the strength of wool or on wool growth rates. Infusions of a total of 8 g, either at the rate of 2 or 8 g/day, weakened the wool but not sufficiently to allow the sheep to be defleeced. Both these treatments caused a temporary reduction in length growth rate and in diameter of fibres, and transient degenerative changes were observed in wool follicles. A region of the fibres representing 1-2 days' growth was constricted to about half the pre-infusion diameter when 8 g was given for 1 day. Infusions of at least 8 g mimosine over a period of 1 1/2-2 days were effective for defleecing all sheep dosed. This corresponded to a daily rate of infusion of about 80 mg/kg. No toxic effects were observed with infusions given for periods of 2 days. Defleecing was judged to be possible by 6-7 days after the start of infusion, and was readily carried out by about 14 days. Defleecing was associated with follicle retrogression and an abrupt cessation of wool growth within 2 days of the start of the infusions. It was estimated that fibre growth stopped for about 10 dyas; regrowth was first observed 17-18 days from the beginning of dosing. Low rates of infusion of mimosine (up to 2 g/day) resulted in plasma levels below 0.1 mmol/l. Infusion at the rate of 4 g/day or above, which produced defleecing, quickly resulted in levels of mimosine in plasma above 0.1 mmol/l; after 2 days the concentration was steady at aboug 0.2 mmol/l. Injections of 8 or 16 g mimosine resulted in very large, but transient, rises of the level in plasma.     

Identification of the e allele at the Extension locus (MC1R) in Brazilian Creole sheep and its role in wool color variation

The melanocortin 1 receptor (MC1R) gene has been described as responsible for the black color in some breeds of sheep, but little is known about its function in many colored breeds, particularly those with a wide range of pigmentation phenotypes. The Brazilian Creole is a local breed of sheep from southern Brazil that has a wide variety of wool colors. We examined the MC1R gene (Extension locus) to search for the e allele and determine its role in controlling wool color variation in this breed. One hundred and twenty-five animals, covering the most common Creole sheep phenotypes (black, brown, dark gray, light gray, and white), were sequenced to detect the mutations p.M73K and p.D121N. Besides these two mutations, three other synonymous sites (429, 600, and 725) were found. The dominant allele (E(D): p.73K, and p.121N) was found only in colored animals, whereas the recessive allele (E(+): p.73M, and p.121D) was homozygous only in white individuals. We concluded that MC1R is involved in the control of wool color in Brazilian Creole sheep, particularly the dark phenotypes, although a second gene may be involved in the expression of the white phenotype in this breed.     

新疆肉羊18号染色体上与后臀肌发育相关基因的多态性分析

通过对新疆肉羊18号染色体与后臀肌发育相关基因的多态性分析,试图找到与新疆肉羊后臀肌性状发达相关基因,为肉羊分子标记辅助选择提供理论线索。运用PCR-SSCP、PCR-RFLP方法,对陶赛特和萨福克两个肉羊品种群体及其与本地细毛羊杂交1代和2代群体Callipyge（CLPG）基因的多态性进行分析,结果表明：位于18号染色体内的DLK1和GTL2间的103849 bp处没有发现PCR-RFLP多态性,表明新疆肉羊后臀肌过度发育与CLPG基因无关。随后,实验进一步对18号染色体Meg3.9位点158520处进行PCR-SSCP分析,发现扩增片段存在着多态性;Meg3.9扩增片段多态性位点在肉羊群体中的基因型有AA、AB和AC,以AA型为主。其中AA、AB基因型与新疆肉羊后臀肌肉发达的表型无关（P>0.05）,AC基因型与新疆肉羊后臀肌肉发达的表型相关（P<0.05）。在陶赛特与本地细毛羊杂交1代群体中,AC基因型的屠体重和屠宰率与AA、AB基因型差异显著（P<0.05）,但三种基因型的各月龄体重没有差异(P>0.05)。通过以上分析可以推断,引起新疆肉用绵羊后臀肌过度发育的性状不是CLPG基因内9571-268.3位点突变导致,可能还存在其他基因或与其连锁的多个QTL的共同作用。     

Breeding objectives for sheep should be customised depending on variation in pasture growth across years

Breeding programmes for livestock require economic weights for traits that reflect the most profitable animal in a given production system, which affect the response in each trait after selection. The profitability of sheep production systems is affected by changes in pasture growth as well as grain, meat and wool prices between seasons and across years. Annual pasture growth varies between regions within Australia’s Mediterranean climate zone from low growth with long periods of drought to high growth with shorter periods of drought. Therefore, the objective of this study was to assess whether breeding objectives need to be adapted for regions, depending on how reliable the pasture growth is across years. We modelled farms with Merino sheep bred for wool and meat in 10 regions in Western Australia. Across these 10 regions, mean annual pasture growth decreased, and the CV of annual pasture growth increased as pasture growth for regions became less reliable. We calculated economic values for nine traits, optimising management across 11 years, including variation for pasture growth and wool, meat and grain prices between and within years from 2002 to 2012. These economic values were used to calculate responses to selection for each trait for the 10 regions. We identified two potential breeding objectives, one for regions with low or high reliability and the other for regions with medium reliability of pasture growth. Breeding objectives for high or low pasture growth reliability had more emphasis on live weight traits and number of lambs weaned. Breeding objectives for medium reliability of pasture growth had more emphasis on decreasing fibre diameter. Relative economic weights for fleece weight did not change across the regions. Regions with low or high pasture reliability had similar breeding objectives and response to selection, because the relationship between the economic values and CV of pasture growth were not linear for live weight traits and the number of lambs weaned. This non-linearity was caused by differences in distribution of pasture growth between regions, particularly during summer and autumn, when ewes were pregnant, with increases in energy requirements affecting the value of lambs weaned. In addition, increasing live weight increased the intake capacity of sheep, which meant that more poor quality pasture could be consumed during summer and autumn, which had more value in regions with low and high pasture reliability. We concluded that breeding values for sheep production systems should be customised depending on the reliability of pasture growth between years.     

绵羊产羔性状主效基因检测研究

以绵羊BMP15基因和BMPR-IB基因为候选基因,以湖羊、中国美利奴单胎品系、中国美利奴肉用和毛用多胎品系为研究对象,采用PCR-RFLP方法对候选基因进行单核苷酸多态性（SNP）位点检测和基因型分析,同时研究基因对绵羊产羔数的影响。对BMP15基因进行SNP检测,结果未发现多态性位点;对BMPR-IB基因进行多态性检测,结果发现了一个A746 G SNP位点。依据A746 G SNP位点进行基因型分析,结果在各品种（系）羊中发现了3种基因型,即BB、B+和++。等位基因型频率在各品种（系）间差异极显著（P<0.001）,在湖羊中以BB基因型为主,在中国美利奴单胎品系中以++基因型为主, 而在中国美利奴肉用和毛用多胎品系中以B+基因型为主。BMPR-IB A746G位点的变异明显影响绵羊的产羔数,与++基因型母羊相比, BB和B+基因型母羊产羔数明显较多。研究结果同时表明,利用BMPR-IB基因型可以很好的预测母羊的产羔数。研究获得的这些结果强烈表明BMPR-IB为影响绵羊的产羔数的主效基因,可以用于对绵羊产羔数的选择。Abstract: The current study was designed to detect SNPs within BMP15 and BMPR-IB gene and investigate the effect of the genes on sheep litter size. Four sheep lines, HU-Yang, Chinese M erino monotocous, Chinese Merino multiparous for wool production and Chinese Merino multiparous for mutton production, were used in this study. Litter sizes were recorded for each ewe in the four lines. Primers for BMP15 and BMPR-IB gene were designed from database sheep sequence and polymorphisms were detected by PCR-RFLP method. The results showed that there was no polymorphism with BMP15 gene among the four lines, and there was an A / G SNP with BMPR-IB gene at base 746 among the four lines. Three types of genotype (BB, B+ and ++), based on A / G locus, were found within each line. The frequencies of genotypes were significantly different among the lines (P<0.001), with BB genotype primarily existing in HU-Yang, ++ genotype in Chinese Merino monotocous line, and B+ genotype in Chinnese Merino multiparous lines. The A / G mutation influence significantly the sheep litter sizes, and the BB and B+ ewes had significant higher litter sizes than ++ ewes. The results of present study showed simultaneously that the genotype of BMPR-IB was a perfect predictor of the sheep litter sizes. These results intensively indicated that BMPR-IB is a major gene to affect litter size in sheep, and could be used as the molecular genetic marker to select litter size in sheep.