The high sulphur proteins of wool: Towards an understanding of sheep breed diversity

High sulphur proteins (HSPs) form part of the matrix surrounding the intermediate filaments in the cortical cells of the wool fibre. There are three known families of HSPs, comprising in excess of 40 components and their molecular weights range from 10-30 kDa. Here we report the use of the increased resolving power of isoelectric focusing in the first dimension of two-dimensional electrophoresis and modern gel comparison software to investigate the nature of within- and between-breed variations amongst the proteins of three breeds of sheep: Merino, Romney and Corriedale. In agreement with past studies we observed very little variation in the intermediate filament protein content in wool, both between and within these three sheep breeds. Instead, most of the observed variation occurred among the HSPs, along with some minor variation among the high glycine-tyrosine proteins. Breed-specific differences were observed in the HSP patterns in the wool proteome maps. Merino sheep were found to exhibit the simplest HSP expression patterns, with eight major spots linked to form four pairs. In contrast, the Romney and Corriedale HSP patterns exhibited more spots at lower isoelectric point values (around 4.8), while some of the lower molecular weight HSPs were less prevalent in Romney sheep and absent from the Corriedales.     

Effects of phenylalanine and analogues of methionine and phenylalanine on the composition of wool and mouse hair

Administration of the methionine analogue methoxinine (O-methyl-DL-homoserine) to sheep substantially changed the composition of wool; in addition wool fibres were weakened and the staple crimp frequency was reduced for a prolonged period. The proportions of high-tyrosine proteins were reduced by 40-45% whereas the high-sulfur proteins were usually slightly increased. The content of high-tyrosine proteins in wool was still depressed in most sheep 70 days after dosing with methoxinine. These experiments supported a previous finding that the cystine content of wool and its crimp frequency are not causally related. Ethionine, another methionine analogue, did not consistently change the composition of wool. In some sheep there was no change in the proportions of high-tyrosine proteins following administration of ethionine, even though weak wool was produced. This result, together with the lack of association between the content of high-tyrosine proteins and the strength of wool fibres in a sheep given methoxinine plus methionine, indicates that a reduction of the high-tyrosine proteins is not a prerequisite for the production of weak wool. Neither a threefold increase in the phenylalanine intake by mice nor the administration of three analogues of phenylalanine (4-fluoro-DL-phenylalanine, 4-chloro-DL-phenylalanine and beta-(2-thienyl)-DL-alanine) to sheep altered the composition of hair or wool. Fluorophenylalanine was incorporated into all the constituent proteins of wool to the extent of c. 2% of phenylalanine residues. The other analogues studied could not be detected in wool.     

Pigmentation in Black-boned sheep (<Emphasis Type="Italic">Ovis aries</Emphasis>): association with polymorphism of the <Emphasis Type="Italic">Tyrosinase</Emphasis> gene

Measurements were made in Black-boned (n = 40) and normal (n = 23) sheep (Ovis aries) from a flock in Nanping County of Yunnan Province, China, as well as a group (n = 21) of Romney Marsh sheep (O. aries) with the view to explaining the basis of the dark pigmentation occurring in the Black-boned animals. Plasma colour was significantly darker (P < 0.01) in Black-boned sheep than in their normal flock mates, which in turn had significantly darker plasma (P < 0.01) than the Romney Marsh sheep. Similar significant (P < 0.01) differences were measured for plasma tyrosinase activity and both groups of sheep from Nanping County had similar plasma concentrations of glutathione which were significantly smaller (P < 0.01) than for the Romney Marsh sheep.A partial fragment of 750 bp of exon 1 of the gene encoding tyrosinase was constructed and found to contain two silent mutation sites (G192C and C462T) but there was no effect on amino acid sequences of tyrosinase. Using restriction fragment length polymorphism analyses two allelic variants of site G192C were identified giving rise to the genotypes GG, GC and CC; the frequencies of allele G being 0.914, 0.824 and 0.286 in the Black-boned sheep, their flock mates and the Romney Marsh sheep respectively. Plasma tyrosinase activity was similar for genotypes GG and GC and for both genotypes significantly higher (P < 0.05) than for genotype CC. The sheep from Nanping County displayed only the GG and GC genotypes and had predominantly black or black and white coat colour whereas the Romney Marsh sheep were of either genotype GC or CC and exhibited only white coat colouration. It is not appears that the dark pigmentation of the Black-boned sheep arises because of polymorphisms in the exon 1 of tyrosinase gene. However, this result could explain the differences between Black-boned and Romney Marsh sheep but not for differences between Black-boned and Nanping Normal sheep. Moreover, this result has provided evidence of genetic markers in the form of polymorphisms of the tyrosinase gene which may help to find the black traits causing mutations. There would be merit in further studies using histochemical and molecular techniques to elucidate the causes of the dark pigmentation in these Black-boned sheep.     

Minimum Effective Dose of Cattle and Sheep BSE for Oral Sheep Infection

The minimum dose required to cause infection of Romney and Suffolk sheep of the ARQ/ARQ or ARQ/ARR prion protein gene genotypes following oral inoculation with Romney or Suffolk a sheep Bovine spongiform encephalopathy (BSE)-derived or cattle BSE-derived agent was investigated using doses ranging from 0.0005g to 5g. ARQ/ARQ sheep which were methionine (M) / threonine (T) heterozygous or T/T homozygous at codon 112 of the Prnp gene, dosed ARQ/ARR sheep and undosed controls did not show any evidence of infection. Within groups of susceptible sheep, the minimum effective oral dose of BSE was found to be 0.05g, with higher attack rates following inoculation with the 5g dose. Surprisingly, this study found no effect of dose on survival time suggesting a possible lack of homogeneity within the inoculum. All clinical BSE cases showed PrP^d accumulation in brain; however, following cattle BSE inoculation, LRS involvement within Romney recipients was found to be significantly lower than within the Suffolk sheep inoculated group which is in agreement with previous reports.     

绵羊肌肉H-FABP和PPARγ基因表达的发育性变化及其对肌内脂肪含量的影响

选取不同日龄的雄性哈萨克羊和新疆细毛羊,屠宰后取背最长肌,用索氏抽提法检测肌内脂肪（Intamuscular fat,IMF）含量,用荧光实时定量PCR法检测心脏脂肪酸结合蛋白（heart fatty acid-binding protein,H-FABP）和过氧化物酶体增殖物激活受体γ（peroxisome proliferator-activated receptorγ,PPARγ）基因表达的发育性变化极其对IMF含量的影响.结果表明：（1）随着日龄的增加,IMF含量在雄性哈萨克羊中持续上升,且在各生长期间的差异显著（P＜0.05）,而在新疆细毛羊的各生长期间无显著差异（P＞0.05）.雄性哈萨克羊的IMF含量在30～90日龄间极显著高于新疆细毛羊（P＜0.01）;（2）雄性哈萨克羊肌肉H-FABP基因的表达量在2日龄时最高,30日龄时降到最低,然后持续上升,各日龄间差异显著（P＜0.05）.新疆细毛羊中的表达量在2日龄时也最高,然后持续下降,到90日龄时降到了最低点,然后上升,各日龄间差异也显著（P＜0.05）;（3）雄性哈萨克羊肌肉PPARγ基因的表达量随着日龄的增加而呈下降趋势,各日龄间差异显著（P＜0.05）;新疆细毛羊中的表达量在2～60日龄期间持续上升且各日龄间差异显著（P＜0.05）,但在90日龄时降到最低点,然后上升;（4）在哈萨克羊中,H-FABP基因在30～90日龄间的表达量与IMF含量的相关系数为0.737（P＜0.01）,而PPARγ基因在2-90日龄间的表达量与之的相关系数为-0.835（P＜0.01）.     

Characterisation of white and black merino wools: a proteomics study

Wool is an important agricultural commodity with merino wool being rated alongside the finest quality fibres, which include the goat fibres Mohair and Cashmere. Although pigmented wool merinos have become extremely rare, the market for this wool is increasing. In Portugal, there are two merino breeds: white and black, descendants of animals originally bred on the Iberian Peninsula. These breeds have the potential to assist in our understanding of how protein expression relates to wool traits of importance to the textile industry. Herein, we study the characteristics and protein expression profiles of wool from ewes of the Portuguese black and white merino (n=15). Both breeds had very similar results for fibre diameter (25 µm) and curvature (105 to 111°/mm). Significant between-breed differences were found in the two types of keratin-associated proteins (KAPs): high-sulphur proteins (HSPs) and high-glycine–tyrosine proteins (HGTPs). The expression of HSPs, KAP2-3 and KAP2-4, decreased expression in the pigmented animals, whereas KAP13-1 was found in higher amounts. Likewise, the expression of the ultra-high-sulphur proteins, KAP4-3 and KAP4-7-like, was reduced in black sheep to half the levels of the white wools, whereas the HGTPs, KAP6, KAP6-1, KAP6-2 and KAP16-2, were more abundant in black sheep. These results suggest structural differences between the black and white merino wool, because of differences among some KAPs. These differences have important implications for the textile industry.     

The keratin BIIIB gene family: isolation of cDNA clones and structure of a gene and a related pseudogene

The nucleotide sequence of cDNA clones encoding the three major BIIIB high-sulfur wool keratin proteins (BIIIB2, 3, and 4) and the structure of a BIIIB4 gene and a BIIIB3 pseudogene are reported. Although Southern blot analysis indicates that the BIIIB genes comprise a multigene family in the sheep genome, they are poorly represented in genomic DNA libraries. The family sequence homology of the coding region extends into the 5' and 3' untranslated regions and the near 5' flanking region of the BIIIB3 and 4 genes. These homologies suggest that the BIIIB3 and 4 genes represent the latest gene duplication event in the evolution of the BIIIB multigene family. Like the genes coding for other wool keratin matrix protein components, the BIIIB genes have the conserved 18-bp sequence immediately 5' to the initiation codon and also appear to lack introns.     

Polymorphism in two genes for B2 high sulfur proteins of wool

Variation in the nucleotide sequence of the B2 high-sulfur protein genes has not been reported previously. This paper reports 15 nucleotide substitutions in each of the genes for the B2A and B2C proteins and a length of polymorphism in the B2A gene which translates to the insertion/deletion of one 30-nucleotide repeat sequence. Evidence is presented for gene conversion occurring within the B2 high-sulfur multigene family. These DNA polymorphisms may account for some of the microheterogeneity observed in the B2 high-sulfur proteins and may also be useful genetic markers of the B2 high-sulfur protein gene loci for future use in analysing wool fibre characteristics.     

Modification of the pathogenicity of Schistosoma mattheei for sheep by passage of the parasite in hamsters

Border Leicester X Suffolk sheep infected with a strain of S. mattheei maintained in hamsters do not develop the same pathological changes as Romney Marsh sheep infected with the same strain of parasite before hamster passage. To determine the cause of this reduced pathogenicity, five Romney Marsh sheep were each infected with 10 000 cercariae of the hamster-passaged parasite and five with 10 000 cercariae of a S. mattheei strain from Onderstepoort, South Africa, passaged exclusively through sheep. Striking pathological and parasitological differences were found between the two strains. Infection with the "sheep" strain was lethal, whereas infection with the "hamster" strain produced little evidence of clinical disease. By 13 weeks post-infection the mean body weight of the sheep infected with the sheep strain had declined by 15% compared with both the uninfected controls and the sheep infected with the hamster strain, and the mean PCV was lowered to 20% in the sheep strain infected animals. Egg production began at seven weeks with the sheep strain, faecal counts rising to more than 300 e.p.g., whereas only two of the sheep infected with the hamster strain passed eggs in the faeces (at nine weeks) and the maximum egg count was 50 e.p.g. Twice as many adult worms of the sheep strain were recovered, and, although the number of eggs found in the tissues "per worm pair" was not significantly different, overall egg production was higher for the sheep strain; also more of the sheep strain eggs were deposited in the intestines. Similar parasite differences were seen in a supplementary study in mice and it seemed that "attenuation" of the parasite had occurred, presumably due to its maintenance in hamsters. Histopathological observations and faecal egg counts both indicated an inability of hamster strain eggs to penetrate the intestinal lumen; this was probably important in reducing the pathogenicity of the hamster strain.     

Identification of microRNAs in Wool Follicles during Anagen,Catagen, and Telogen Phases in Tibetan Sheep

Background

Wool quality is one of the most important economic traits in sheep. The wool fiber is derived from specialized skin cells that are referred to as wool follicles. To understand the roles of microRNAs (miRNAs) in wool fiber growth, we detected the expression patterns of miRNAs in wool follicles at the anagen, catagen, and telogen stages from Tibetan sheep through Solexa sequencing.

Results

A total of 244 mature miRNAs were identified. Of these, only five miRNAs are listed in the database of sheep miRNAs (miRBase Database V19), and the other 239 miRNAs have not been previously described in this species. Further analyses indicated that 204 miRNAs are evolutionarily conserved among mammal species, whereas 35 of the identified miRNAs were first found specifically in sheep. The expression pattern analyses showed that the expression levels of 39, 34, and 20 of the miRNAs significantly change between anagen and catagen, between anagen and telogen, and between catagen and telogen, respectively. The results of the bioinformatics analysis show that these differentially expressed miRNAs might regulate wool follicle development by targeting genes in many different pathways, such as the MAPK and Wnt pathways, as well as the pathways that regulate the actin cytoskeleton, focal adhesion, and tight junctions. Furthermore, we identified six differentially expressed miRNAs (oar-miR-103-3P, oar-miR-148b-3P, oar-miR-320-3P, oar-miR-31-5P, oar-novel-1-5P, and oar-novel-2-3P) that might target the key genes of the Wnt pathway. It has been reported that the Wnt pathway is critical for wool follicle development. Therefore, these miRNAs may regulate wool development through the Wnt pathway.

Conclusions

Our results provide new information on the identification and expression pattern of miRNAs in wool follicles. Our data might therefore aid in the understanding of the mechanisms of wool follicle development in sheep.     

BMP-15基因外显子Ⅰ在三种绵羊中的多态性及与繁殖力相关性分析

为研究绵羊繁殖力与绵羊BMP-15 (bone morphogenetic protein 15)基因的多态位点关系,并寻找调控绵羊繁殖力的分子标记,以甘肃高山细毛羊、蒙古羊、小尾寒羊三种绵羊为研究对象,采用PCR-SSCP技术与DNA碱基测序相结合的方法,检测该基因第一外显子67、92两个位点在上述三个不同品种绵羊中是否存在FecX^H (Q23→Ter)和FecX^I (V31→D)突变,同时根据检测结果与其繁殖力做相关性分析。结果表明,在三种绵羊中既未检测出与Inverdale绵羊相同的FecX^I突变,也未检测出与Romney绵羊相同的FecX^H突变,因此推测BMP-15基因中影响Romney与Inverdale绵羊高繁殖力的突变位点对以上三种绵羊均无显著影响。     

Allocation of greenhouse gas production between wool and meat in the life cycle assessment of Australian sheep production

Purpose

Australia is the largest supplier of high-quality wool in the world. The environmental burden of sheep production must be shared between wool and meat. We examine different methods to handle these co-products and focus on proportional protein content as a basis for allocation, that is, protein mass allocation (PMA). This is the first comprehensive investigation applying PMA for calculating greenhouse gas (GHG) emissions for Australian sheep production, evaluating the variation in PMA across a large number of farms and locations over 20 years.

Materials and methods

Inventory data for two superfine wool Merino farms were obtained from farmer records, interviews and site visits in study 1. Livestock GHG emissions were modelled using Australian National GHG Inventory methods. A comparison was made of mass, protein mass and economic allocation and system expansion methods for handling co-production of wool and sheep meat. In study 2, typical crossbred ewe, Merino ewe and Merino wether flocks in each of the 28 locations in eight climate zones were modelled using the GrassGro/GRAZPLAN simulation model and historical climatic data to examine the variation in PMA values for different enterprise types.

Results and discussion

Different methods for handling co-products in study 1 changed allocated GHG emissions more than fourfold, highlighting the sensitivity to method choice. In study 2, enterprise, climate zone and year and their interactions had significant effects on PMA between wool and liveweight (LW) sold. The wool PMA (wool protein as proportion of total protein sold) least square means (LSM) were 0.61?±?0.003 for wethers, 0.43?±?0.003 for Merino ewes and 0.27?±?0.003 for crossbred ewe enterprises. The wool PMA LSM for the main effect of Köppen climate zone varied from 0.39 to 0.46. Two zones (no dry season/warm summer and distinctively dry and hot) had significantly lower wool PMA LSM, of 0.39 and 0.41, respectively, than the four other climate zones.

Conclusions

Effects of superfine wool production on GHG emissions differed between regions in response to differences in climate and productivity. Regarding methods for handling co-production, system expansion showed the greatest contrast between the two studied flocks and highlighted the importance of meat from wool production systems. However, we also propose PMA as a simple, easily applied allocation approach for use when attributional life cycle assessment (LCA) is undertaken.

     

Binding characteristics of 125I-labelled human FSH to granulosa cells from Booroola ewes which were homozygous, heterozygous or non-carriers of a major gene(s) influencing their ovulation rate

At 37 degrees C 125I-labelled human (h) FSH (NIAMDD-hFSH-I-3) bound rapidly to granulosa cells from Booroola and Romney ewes with 50% maximum binding achieved after 3 min and equilibrium being reached within 45 min, irrespective of whether the cells were obtained from the FF, F+ or ++ Booroola genotypes or from Romney ewes. Binding of 125I-labelled FSH followed second order kinetics and there was no effect of follicle diameter (1-2.5 mm vs greater than or equal to 3 mm). Irrespective of breed, genotype or follicle size, the mean (+/- s.e.m.) calculated association rate constant, (ka) was 7.3 (+/- 0.8) x 10(5) litres mol-1 sec-1 (n = 12). Dissociation of receptor bound 125I-labelled hFSH was less than 5% after 30 min and low but variable (i.e. between 0 and 30%) after 2-6 h irrespective of breed, genotype or follicle size. No gene-specific differences were noted in binding specificity between F+ and ++ genotypes: studies were not performed with cells from FF ewes because of insufficient cells. The binding of 125I-labelled hFSH could be displaced with sheep FSH (NIH-FSH-S16; 10% cross-reaction) and FSH-P (2.5% cross-reaction) but other sheep pituitary hormones and hCG showed little or no cross-reaction (less than or equal to 0.1%). The calculated binding capacities (Bmax) and equilibrium dissociation constants (Kd) for 125I-labelled hFSH binding to granulosa cells did not differ between the Booroola genotypes or between Booroola or Romney follicles of different diameter (i.e. 1-2.5 mm; or greater than or equal to 3 mm). The overall mean +/- s.e.m. (n = 24) Bmax and Kd values were 16.7 +/- 0.8 fm/mg protein (i.e. approximately 800 available receptor binding sites/cell) and 1.1 +/- 0.1 nM respectively. Collectively, these findings suggest that the earlier maturation of follicles in FF or F+ ewes compared to ++ ewes is unlikely to be due to gene-specific differences in the FSH binding characteristics of the granulosa cells.     

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.     

125I-labelled hCG binding characteristics in theca interna and other tissues from Romney ewes and from Booroola x Romney ewes with and without a major gene influencing their ovulation rate

Specific receptors for 125I-labelled hCG in ovarian follicle wall were located in the theca interna. No specific binding of 125I-labelled hCG was found in theca externa and/or stromal tissue. The kinetics of 125I-labelled hCG binding to theca interna followed second order kinetics with calculated association rate constants (ka +/- s.d.) of 1.57 +/- 0.16 X 10(6) and 0.57 +/- 0.02 X 10(6) litres mol-1 sec-1 at 37 degrees C and 22 degrees C respectively. Dissociation of specifically bound 125I-labelled hCG from theca interna was minimal at 37 degrees C and 22 degrees C. The binding of 125I-labelled hCG to theca interna could be displaced with PMSG, FSH-P and sheep LH but other sheep pituitary hormones and LH-releasing hormone showed little or no cross-reaction. The calculated binding capacities (Bmax) and equilibrium dissociation constants (Kd) for 125I-labelled hCG binding to theca interna did not differ between Romney ewes and Booroola x Romney ewes with and without the fecundity (F) gene on Day 10 of the oestrous cycle, during anoestrus or at 36 h after an injection of cloprostenol on Day 10 of the oestrous cycle. When the data for Day 10 and anoestrus were pooled, the median (range) Bmax and Kd values in non-atretic follicles (greater than or equal to 3 mm diameter) were 12.0 (5.1-23.5) fmol/mg protein and 0.10 (0.05-0.16) nM respectively. At 36 h after cloprostenol injection the respective median (range) Bmax and Kd values in non-atretic follicles (greater than or equal to 3 mm diam.) increased to 46.9 (28.4-70.3) fmol/mg protein and 0.23 (0.13-0.65) nM respectively. In corpora lutea the hCG binding characteristics were similar in all the above breeds/genotypes. On Day 10 of the cycle, the mean Bmax but not the mean Kd value was significantly higher (P less than 0.01) than the corresponding value at 36 h after cloprostenol injection. In granulosa cells, from follicles of greater than or equal to 5 mm diameter of Romney and Booroola x Romney (++) ewes and from follicles of greater than or equal to 3 mm diameter of Booroola x Romney (F+) ewes, the hCG binding characteristics were similar. In granulosa cells from smaller sized follicles from the above breeds/genotypes, no specific hCG binding was noted.     

The relationship between ovine lymphocyte antigens and parasitological and production parameters in Romney sheep

The occurrence of ovine lymphocyte antigen (OLA) types in two flocks of New Zealand Romney sheep was examined in relation to resistance to nematode parasites [as judged by faecal egg counts (FEC)], plasma pepsinogen levels, liveweight and weight gains. A panel of OLA-typing antisera (SY 1-16) which determine class 1 MHC antigens of the sheep was used. The OLA combination SY 1a + 1b was found exclusively in Romney sheep of both flocks having below average FEC, but was present in low frequency (5%). In one flock, sheep possessing this antigen combination had consistently lower FEC from weaning to 1 year of age than sheep without this combination. SY 6 occurred significantly more frequently in above average FEC sheep and was associated with significantly higher FEC during secondary challenge infection. Plasma pepsinogen levels were significantly lower in those sheep possessing SY 2 or SY 3 but these OLA types were not associated with lower than average FEC. No OLA type was associated with above average weight gain but in one flock sheep with SY 1b and SY 1a + 1b had significantly lower weight gains between weaning and 6 months of age than sheep without these OLA types. A similar association was not found in the other flock. Sheep in one flock with SY 16 were significantly heavier than those without this antigen. No other associations between OLA types and liveweight were found.     

The dietary-regulated biosynthesis of high-sulphur wool proteins

1. When the diet of sheep is supplemented by the abomasal infusion of sulphur-containing amino acids or casein, a special group of proteins, with a very high content of sulphur (about 8.3%), is incorporated into the high-sulphur proteins of wool. These special proteins cannot be detected in control wool from the same sheep. 2. This is a naturally occurring process, as these special proteins are found in wool from sheep on a high level of nutrition under ordinary conditions of feeding, and in wool of an inherently high sulphur content. 3. This represents a control mechanism in protein synthesis that has not previously been observed, and may be further evidence that the high-sulphur proteins of wool are produced by an unusual synthetic route.     

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.     

The Developmental Changes and Effect on IMF Content of H-FABP and PPARγ mRNA Expression in Sheep Muscle

Male Kazak sheep and Xinjiang fine wool sheep of different ages were selected to investigate the developmental changes and effect on intramuscular fat (IMF) content of heart fatty acid-binding protein (H-FABP) and peroxisome proliferator-activated receptor γ (PPARγ) mRNA expression in muscle. Longissimus dorsal muscle was sampled to measure IMF content; and total RNA was extracted to determine H-FABP and PPARγ mRNA expression levels by real-time PCR. The results showed that: (1) The IMF content increased continuously with growing and showed significant differences (P<0.05) between ages in male Kazak sheep, but no such differences (P>0.05) existed in Xinjiang fine wool sheep. Furthermore, the IMF content in Kazak sheep was very much higher (P<0.01) than that of the other breed from day 30 to 90; (2) H-FABP mRNA expression level was the highest on day 2 and showed significant differences (P<0.05) between ages in male Kazak sheep as well as in Xinjiang fine wool sheep. In the former breed, the expression reached the lowest point at day 30, and then rose continuously. But in the latter breed, it declined continuously from day 2 to 90, and then increased; (3) Significant differences (P<0.05) of PPARγ mRNA expression between ages occurred in both breeds. In male Kazak sheep, PPARγ mRNA expression declined from day 2 to 90, while in the other breed it increased continuously from day 2 to 60, but reached the lowest level at day 90, then increased; (4) In male Kazak sheep, the mRNA expression level of H-FABP was highly positively correlated (r=0.737, P<0.01) with IMF content from day 30 to 90, but that of PPARγ was highly negatively correlated (r=−0.835, P<0.01) with IMF content from day 2 to 90.