Chios Sheep Research Articles

Effect of seasonally changing aerial environment on testosterone in Karagouniko and Chios sheep

A well-established activity in Greece and other Mediterranean countries is sheep farming. Karagouniko and Chios sheep are promising breeds and targets for the reproductive physiologist’s attention. Under this context, part of the reproductive physiology of Karagouniko and Chios was investigated, taking into account the environment. Specifically, four time periods were considered; April-June (Long days, increasing photoperiod length), July-September (Long days, decreasing photoperiod length), October-December (Short days, decreasing photoperiod length), and January-March (Short days, increasing photoperiod length). The effect of the period on the concentration of the testosterone (main male hormone) in rams of the breeds above was studied, by using repeated measures analysis of variance, also taking into account the environmental variables air temperature, relative humidity, sunshine, rainfall, and photoperiod, in the Artificial Insemination Center of Karditsa (39°21’18’’N, 21°54’19’’E), Greece. The lowering of photoperiod from April-June to July-September (long days) and afterward, even more to October-December (short days) coincided with a progressive increase of testosterone in both breeds. Photoperiod seems to have a major role in the concentration of Karagouniko and Chios breeds' testosterone compared to the other environmental variables. When considering the whole experimental period, Chios sheep had significantly higher (P < 0.05) testosterone (1.95 ng/ml) than the Karagouniko one (1.55 ng/ml). Our findings could contribute towards the more rational exploitation of the examined sheep breeds.

Scrotal circumference in Karagouniko and Chios sheep in relation to the aerial environment

Scrotal circumference in Karagouniko and Chios sheep in relation to the aerial environment

A comprehensive genome-wide scan detects genomic regions related to local adaptation and climate resilience in Mediterranean domestic sheep

BackgroundThe management of farm animal genetic resources and the adaptation of animals to climate change will probably have major effects on the long-term sustainability of the livestock sector. Genomic data harbour useful relevant information that needs to be harnessed for effectively managing genetic resources. In this paper, we report the genome characterization of the highly productive Mediterranean Chios dairy sheep and focus on genetic diversity measures related with local adaptation and selection and the genetic architecture of animal resilience to weather fluctuations as a novel adaptative trait linked to climate change.ResultsWe detected runs of homozygosity (ROH) and heterozygosity (ROHet) that revealed multiple highly homozygous and heterozygous hotspots across the Chios sheep genome. A particularly highly homozygous region was identified on chromosome 13 as a candidate of directional genetic selection associated with milk traits, which includes annotated genes that were previously shown to be linked to local adaptation to harsh environmental conditions. Favourable heterozygosity related with a potentially protective role against livestock diseases and enhanced overall fitness was revealed in heterozygous-rich regions on sheep chromosomes 3, 10, 13 and 19. Furthermore, genomic analyses were conducted on sheep resilience phenotypes that display changes in milk production in response to weather variation. Sheep resilience to heat stress was a significantly heritable trait (h2 = 0.26) and genetically antagonistic to milk production. Genome-wide association and regional heritability mapping analyses revealed novel genomic markers and regions on chromosome 5 that were significantly associated with sheep resilience to climate change. Subsequently, an annotation analysis detected a set of genes on chromosome 5 that were associated with olfactory receptor complexes that could participate in heat stress mitigation through changes in respiration rate and respiratory evaporation. Other genes were grouped in previously reported biological processes relevant to livestock heat dissipation, including stress and immune response.ConclusionsOur results may contribute to the optimal management of sheep genetic resources and inform modern selective breeding programmes that aim at mitigating future environmental challenges towards sustainable farming, while better balancing animal adaptation and productivity. Our results are directly relevant to the studied breed and the respective environmental conditions; however, the methodology may be extended to other livestock species of interest.

Feeding olive cake silage up to 20% of DM intake in sheep improves lipid quality and health-related indices of milk and ovine halloumi cheese.

This study aimed to evaluate the use of a by-product, olive cake silage (OCS), as a forage replacement in sheep diets for the improvement of fatty acid (FA) content of milk and thus, the lipids of the ovine halloumi cheese produced. Sixty second-parity purebred Chios ewes in mid-lactation were assigned to three diet treatments (2 lots of 10 animals per treatment) receiving 0%, 10%, and 20% of OCS on dry matter basis for 3 weeks (treatments S0, S10, and S20, respectively). Halloumi cheese was manufactured from fresh raw milk of ewes fed the three different diets. Inclusion of OCS in the diets increased linearly the concentration in milk of unsaturated FA up to 20%, monounsaturated FA up to 23%, polyunsaturated FA up to 11%, rumenic acid (CLA cis-9, trans-11) up to 61%, and consequently reduced the atherogenicity and thrombogenicity milk indices by 31% and 27%, for the S10 and S20 treatments, respectively, compared with the control treatment. Moreover, these differences were carried over to the lipid profile of ovine halloumi cheese showing, on average, more than 25% increase of unsaturated, polyunsaturated, and monounsaturated FA, with particularly enhanced oleic and rumenic acid content. These changes resulted in reduced atherogenicity by 29% and 45% and thrombogenicity by 23% and 24% of ovine halloumi cheese made from milk of S10 and S20 diets, respectively. Milk yield, milk fat, or protein content was not affected by S10 or S20 feeding treatments compared to control. Overall, the applied ensiling method of olive cake produces a by-product that can be included as a forage replacement up to 20% of DM intake in Chios sheep without adversely affecting the lactating performance. Furthermore, the present study showed that such substitution improves the lipid quality of milk and related halloumi cheese enriching these ovine dairy products with beneficial to human health fatty acids.

A Comparative Study of Simple Regression Models to Estimate Fibre Length Growth in Chios Sheep from Common Meteorological Variables

Chios sheep is a promising sheep breed, with wool, one of its products, to be of special interest to genetic improvement programs. Recently, it has been reported significant linear correlation between the fibre length growth (FLG) of Chios sheep, an important component of its wool quality, and each of the meteorological variables air temperature (T) and sunshine (SUNS), but nothing is known about the prediction of FLG from T and SUNS. Thus, this work aims to investigate the effectiveness of five simple regression models (linear, quadratic, cubic, logarithmic and inverse), concerning the aforementioned prediction, using visual examination and two widely accepted statistical measures, the adjusted coefficient of determination (R2adj) and the root mean square error (RMSE). Results showed that the applied nonlinear regression models were characterized by higher R2adj and lower RMSE in comparison to the linear one, irrespective of input variable. The inverse model presented the greatest effectiveness to predict FLG from T and SUNS, separately (maximum R2adj and minimum RMSE), followed by the logarithmic and the linear ones, under visual examination and applied statistical measures. Air temperature was superior to SUNS in all cases (higher R2adj and lower RMSE), when comparing the regression models of the same type to check their effectiveness for predicting FLG. The findings of our study could be a decisive step towards a better exploitation of the examined meteorological variables for the sustainable production of Chios sheep.

The relationships between the myocardial bridge andramusinterventricularisparaconalischaracteristics in lamb and sheep.

The myocardial bridge (MB) is an anomaly that the myocardial fibres cover on a segment of the subepicardial coronary arteries or their branches in domestic animals and humans. The aim of the present study was to determine the relationships between the characteristics of the MB and ramus interventricularis paraconalis at three levels in lambs and adult sheep. Thirty-three hearts (16 lambs and 17 sheep) were used to determine the MB (length, angle and thickness) and vessel (vessel diameter and thicknesses of tunica intima et media of ramus interventricularis paraconalis) characteristics. Independent-samples t test was applied to compare variables between lambs and sheep. Spearman's correlation analysis was conducted to evaluate the relationships between bridge and vessel characteristics at three bridge levels. Length, angle and thickness of myocardial bridges were not significantly different between the lambs and sheep (p>.05). The mean length, angle and thickness were 24.9±16.1mm, 113.7±11.2° and 1,098±555µm in 33 hearts, respectively. In lambs, the mean vessel diameters were 1,930±742µm (1,534-2,325µm), 1,247±665µm (893-1,601µm) and 865±172µm (774-957µm) at the pre-bridge, bridge and post-bridge levels, respectively. In sheep, the mean vessel diameters in the same order were 1,861±1,068µm, 1,337±308µm and 1,287±549µm. The bridge prevalence was 100% in the samples examined. In conclusion, coronary arterial diseases related to myocardial bridge should not be expected in sheep for veterinary cardiology practice. It may also be concluded that the cross-breeds of the Awassi and Chios sheep may be useful in experimental studies related to myocardial bridge surgery.

ACAA2 and FASN polymorphisms affect the fatty acid profile of Chios sheep milk.

The objective of the research reported in this research communication was the identification and association of single nucleotide polymorphisms (SNP) in the ovine DGAT1, FASN, SCD1 and ACAA2 genes with milk fat percentage and fatty acid (FA) content. Three consecutive monthly milk samplings were obtained from a total of 429 purebred Chios ewes during mid-lactation. Genotypic data were jointly analyzed with 1184 fat content and 37 718 FA percentage records using mixed models. The 3' untranslated region (UTR) of the DGAT1 gene and the 5' and 3'UTRs of the SCD1 gene appeared to be monomorphic. The FASN g.14777C>T SNP on exon 31 was associated with C13:0 and the ACAA2 g.2982T>C SNP on the 3'UTR was associated with C9:0, C11:0, C12:1 cis-9, C13:0 and the ω6/ω3 index, while fat percentage was not affected by the identified SNPs. The results could be useful for breeding programs aiming to improve the quality and nutritional value of ovine milk.

Genetic and genomic analyses underpin the feasibility of concomitant genetic improvement of milk yield and mastitis resistance in dairy sheep.

Milk yield is the most important dairy sheep trait and constitutes the key genetic improvement goal via selective breeding. Mastitis is one of the most prevalent diseases, significantly impacting on animal welfare, milk yield and quality, while incurring substantial costs. Our objectives were to determine the feasibility of a concomitant genetic improvement programme for enhanced milk production and resistance to mastitis. Individual records for milk yield, and four mastitis-related traits (milk somatic cell count, California Mastitis Test score, total viable bacterial count in milk and clinical mastitis presence) were collected monthly throughout lactation for 609 ewes of the Chios breed. All ewes were genotyped with a mastitis specific custom-made 960 single nucleotide polymorphism (SNP) array. We performed targeted genomic association studies, (co)variance component estimation and pathway enrichment analysis, and characterised gene expression levels and the extent of allelic expression imbalance. Presence of heritable variation for milk yield was confirmed. There was no significant genetic correlation between milk yield and mastitis traits. Environmental factors appeared to favour both milk production and udder health. There were no overlapping of SNPs associated with mastitis resistance and milk yield in Chios sheep. Furthermore, four distinct Quantitative Trait Loci (QTLs) affecting milk yield were detected on chromosomes 2, 12, 16 and 19, in locations other than those previously identified to affect mastitis resistance. Five genes (DNAJA1, GHR, LYPLA1, NUP35 and OXCT1) located within the QTL regions were highly expressed in both the mammary gland and milk transcriptome, suggesting involvement in milk synthesis and production. Furthermore, the expression of two of these genes (NUP35 and OXCT1) was enriched in immune tissues implying a potentially pleiotropic effect or likely role in milk production during udder infection, which needs to be further elucidated in future studies. In conclusion, the absence of genetic antagonism between milk yield and mastitis resistance suggests that simultaneous genetic improvement of both traits be achievable.

Seasonal variation of wool fibre length in Karagouniko and Chios sheep in relation to meteorological factors

Karagouniko and Chios sheep breeds present a lot of advantages on the implementation of sheep farming in Greece, a country with diverse relief resulting in a microclimatic variety, but nothing is known about the impact of season, as the outcome of important meteorological variables, on the fibre length growth (FLG) of the aforementioned breeds. Thus, the effect of season (Winter, Spring, Summer, Autumn) on the FLG of these breeds (by using analysis of variance) was studied in the Artificial Insemination Center of Karditsa (39021΄18΄΄N, 21054΄19΄΄E), Periphery of Thessaly, Greece, combined with a correlation analysis between FLG of each examined sheep breed and each of the studied meteorological variables, air temperature (AIRT), relative humidity (RH), sunshine (SUNS) and rainfall (R) for a two-year period. It was found that the FLG of Karagouniko sheep was significantly higher than the respective growth of Chios sheep, for each examined season, while the descending order of seasonal FLG for both breeds was Winter&gt;Spring&gt;Autumn&gt;Summer. Fibre length growth of Karagouniko and Chios breeds correlated negatively with AIRT and SUNS and positively with RH, implying a better FLG in cooler, more overcast and wetter time periods. Our study adds new knowledge concerning the effect of season, and particularly, the effect of the aforementioned meteorological variables on the wool growth of two considerable sheep breeds in Greece, Karagouniko and Chios, opening up new horizons for their exploitation.

Nuclear magnetic resonance screening of changes in fatty acid and cholesterol content of ovine milk induced by ensiled olive cake inclusion in Chios sheep diets

Lipid supplementation of dairy ewe diets has been shown to introduce changes in the fatty acid (FA) profile and cholesterol content of milk. In the present study sheep were fed diets including ensiled olive cake (OC), a conserved by-product of olive oil production, and the lipid content of their milk was assessed in lyophilized samples with nuclear magnetic resonance (NMR) technique. Thirty lactating Chios ewes were allocated into three groups of ten animals fed isonitrogenous and isoenergetic diets which differed in the quantity of ensiled OC inclusion: G0, G500 and G1000 groups with 0, 500, 1000 g (on fresh weight basis) of ensiled OC inclusion per ewe, per day, respectively. Fat percentage, FA profile and cholesterol content were determined in milk samples collected after a 4-week feeding period. Results indicated that saturated FA were reduced by 7.2% and 11.3% in milk samples from the G500 and G1000 groups, respectively. Ensiled OC increased unsaturated FA content by 26.3% and 41.4% and monounsaturated FA content of milk by 30.3% and 45.6% in the G500 and G1000 groups, respectively. Furthermore, the inclusion of 1000 g ensiled OC significantly increased the content of beneficial for human health FA such as conjugated linoleic acids (CLA isomers: 9-cis, 11-trans CLA; 9-trans, 11-cis CLA and 10-trans, 12-cis CLA) by 47.2% and linoleic acid by 14.4% compared to control group. However, any rate of ensiled OC inclusion in the diets of ewes had no effect on milk cholesterol content or milk fat percentage. Overall, the present work provides novel experimental data with NMR fingerprinting of the lyophilized milk lipid fraction, and suggests the use of ensiled OC in sheep rations since it induces desirable changes in ovine milk lipids.

Evaluation of reference lactation length in Chios dairy sheep

Definition and establishment of a fixed reference lactation length could provide useful tools for on-farm comparison of ewes and flock management as well as genetic evaluations for the breeding programme. The objectives of this study were to (i) evaluate different reference lactation lengths for the Chios dairy sheep and (ii) define the most suitable reference length for the breed. A total of 260 042 test-day milk records from 24 474 ewes in 130 flocks collected between 2003 and 2014 were used; 15 different lactation lengths were evaluated ranging from 120 to 260 days, defined at 10-day intervals as reference for the Chios sheep. The evaluation criteria included: (a) heritability and repeatability of milk yield in each reference lactation, (b) genetic correlation of reference lactation milk yield with actual lactation milk yield and yield at first test-day record and (c) correlated response in reference lactation milk yield from selection based on first test-day milk yield. The latter emulates genetic gains achieved for milk yield based on early lactation selection. Heritability and repeatability estimates of reference lactation milk yield and genetic correlation with actual lactation yield favoured long reference lactations (180 to 230 days). On the contrary, correlation with first test-day record milk yield was higher for short lactations (120 to 170 days). Moreover, selection on first test-day record milk yield would lead to a correlated response in reference yield in 220 days equal to 85% of the highest estimate achieved in the maximum reference length of 260 days (190 days when only considering first lactation milk yield). Based on the results of the present study, an overall reference lactation length for the Chios breed of 220 days post-lambing and a first lactation reference length of 190 days post-lambing are recommended.

Effects of some medical and aromatic plant seeds on growth performance, milk yield and its composition of Rahmani and Chios sheep

The study was carried out to evaluate the effect of dried mixture of four herbal plant seeds as feed additives and some environmental factors on growth performance, milk yield and its composition of Rahmani and Chios sheep. Fifty four pregnant Rahmani and Chios ewes, during the last periods of pregnancy were divided into 3 groups (8 Rahmani and 10 Chios ewes each) using complete random block design. Group2 (G2) and group3 (G3) were supplemented with polyherbal combination at the rate of 3 and 6 g/100kg-1 LBW, respectively. Ewes without polyherbal combination served as a control (CTR). Body weight and ADG of G2 lambs was significantly (P<0.05) higher than G1 and control. Variations among genetic groups regarding body weights, TG and ADG were highly significant (P<0.01). Male lambs were significantly heavier (P<0.05 or P<0.01) than female except at birth, male lambs have attained TG heavier (P<0.01) than female lambs. There was a significant (P<0.01) effect of medical and aromatic plant seeds on colostrum yield at birth, 12, 24 and 36 hours, TMY and ADMY was affected significantly. There were significant difference between the two breeds in the production of milk per week, TMY and ADMY. Sex of lambs had a significant (p<0.05) effect on milk produced at the 2nd, 6th, 7th, 8th and 9th weeks of lactation. TMY and ADMY was affected significantly by sex of lambs. TMY and ADMY was (P<0.01) greater in ewes rearing twin lambs compared with ewes rearing singles. Colostrum fat and energy was affected (P<0.05) by treatments. As well as, milk components except lactose are (P<0.01) affected. Colostrum ingredient, except TS were not significantly affected by breed of ewes. TS level significantly increased in colostrum of Chios than Rahmani ewes. The ewe breed had a significant (P<0.01) effect on fat, TS, ash, SNF and milk energy. All colostrum components were not significantly affected by age of ewes. But, TS, ash and energy of milk were affected (P<0.01) by age of ewes. Milk constituents were affected significantly (P<0.01) by different lactation stages. The results of this study indicated that the inclusion of some medical and aromatic plant seeds as feed additives in Rahmani and Chios diet improves growth performance, feed intake and milk yield.

Genotype frequency of FecXB (Belclare) mutation of BMP15 gene in Chios (Sakiz) sheep

Ovulation rate and litter size, varies between breeds or individulas who belong to the same breed, are evaluated as fertility traits. Fertility traits are important for economic values in animal breeding. However these traits exhibit only in females and they are determined in the later stages of lifes. Hence the genetic perspective is more effective way to confirm the fertility capacities early period of life time. Fecundity genes such as BMP15 regulate the fertility traits by increasing the ovulation rate due to the occuring mutations. Despite some prolific breed were investigated for FecXB mutation; the researches carried out to determine thatmutation in Chios sheep breed are limited. The objective of the current study was to estimate the the genotype frequencies of FecXB mutation of BMP15 gene in prolific Chios sheep. We investigated the FecXB mutation by PCR-RFLP method in Chios sheep (n=77). According to result, the investigated Chios breed was found monomorphic for FecXB mutation. All individuals were digested by DdeI restriction enzyme and showed wild-type genotype and did not carry FecXB mutation nin present study. In conclusion it’s thought that the high prolificacy in Chios sheep may be based on another region of BMP15 gene or different major gene. Thus the effect of other major genes or regions/QTL’s should be investigated in future studies with a large number of animals.

Farm conditions and production methods in Chios sheep flocks

The objective was to describe farm conditions and production methods in intensively reared flocks of Chios sheep in Greece. The total of 66 farms of the Chios sheep Breeders Cooperative "Macedonia" were included in the study that was carried out using a purpose-built questionnaire and farm visits for onsite assessment by an experienced veterinarian. A detailed databasewas constructed using the information obtained from individual farms. Thereafter, four parameters concerning structural and management components were selected (flock size, sheep breeding experience, pasture use and application of three milkings daily) and their effect on milk production was estimated using one-way ANOVA. The results showed that the average flock comprisedof 314 sheep (16 rams, 210 ewes and 88 lamb ewes), whereas flock size was positively correlated to milk production (P&lt;0.05). Inaddition, large flocks had more personnel and practiced three milkings per day (P&lt;0.05). The majority of farms (83.3%) had milking parlours and the average milk yield per ewe was 276.6±55.6. The majority of farmers were relatively young (41.2±8.9years old) with limited experience in sheep production. However, they had a good level of education and showed increased interest in intensification and specialization of production methods. The acreage of private land was generally small (7.6 hectares) and was used mainly for production of feedstuffs; grazing was a secondary objective. In most farms, the feeding management wasinappropriate; overfeeding of concentrates and unbalanced rations was the dominant practice. Preventive measures included vaccinations (100% of farms vaccinated for clostridial diseases) and anthelminthic treatments (at least once a year in all flocks). In conclusion, farm conditions and production methods in studied flocks were considered satisfactory and revealed the potential for further improvements that are discussed here.

Production of transgenic sheep: Microinjection of the bovine P77 gene construct in Chios sheep breed zygotes

The feasibility of integration of the bovine P77 construct into zygotes and two cell embryos of Chios sheep breed was examined. The P77 gene construct comprised bovine as l casein promoter regulatory sequence fused to the fragment between exons 2 and 9 of the bovine chymosin gene. One of the two pronuclei of the zygote or a nucleus of a blastomere of a two cell embryo was microinjected with 1 pi of DNA solution containing approximately 1000 copies of the gene construct. In total 193 zygotes and 87 two cell embryos collected from 49 donor ewes were used. After 1 - 5 h culture microinjected zygotes (n=175) and two cell embryos (n=76) were transferred by a laparoscopic technique to the oviducts of 68 recipients. 22 recipients (32.4%) gave birth to 29 lambs which correspond to 11.6% of the total number of zygotes - embryos transferred. PCR analysis performed in skin samples of these lambs revealed that in one ewe lamb the P77 construct has been integrated in its genome. The growth and puberty of this lamb was physiological and is currently pregnant. This is the first transgenic farm animal born in Greece.

Haematology values and effect of age and reproductive stage on haematological parameters of Chios sheep

The main aim of the present study was to determine the values of the haematological parameters of dairy sheep reared under intensive and semi-intensive conditions, as well as to test for the effects of age and reproductive stage of the animals on the values of these parameters. In total, 200 clinically healthy Chios sheep from 10 farms of Central Macedonia were used in the study. For the determination of the effect of age 150 sheep were assigned in three groups. Group A consisted of 50 lambs aged 3-6 months (meantSD: 4.45±1.22 months), group Β of 50 non-pregnant ewes into lactation aged 1-3 years (meantSD: 2.18±0.74 years) and group C of 50 non-pregnant ewes into lactation aged more than 3 years (meantSD: 5.88±1.87 years). For evaluating the effect of reproductive status 50 pregnant ewes in dry period were used, 15-30 days before the expected day of lambing (group D), along with the 100 non-pregnant ewes into lactation of groups Β and C (group E). Blood sampling was performed once, in dry ewes from December to January, and in lambs and lactating ewes from March to May. The mean values of the determined haematological parameters were within the range provided by the literature, except for red blood cells count of ewes. The results also showed that haematocrit, haemoglobin concentration and red blood cells, white blood cells, neutrophils, lymphocytes, eosinophils and platelets count were significantly affected by the age; only monocytes and eosinophils count by the reproductive stage of the animals.

The feeding of rams on farms of the "Macedonia" Cooperative of Chios sheep breeders

The aim of this study was to verify the adequacy of ram rations in intensively reared flocks of the Chios breed. Data were collected from the 66 farms of the "Macedonia" Cooperative of Chios Sheep Breeders and were evaluated using requirements published by INRA and NRC. Statistical analysis was performed using analysis of variance. Ram requirements for net energy lactation, digestible protein, absorbable calcium and absorbable phosphorus were greatly exceeded. Farm classification in three groups (A, Β and C, 26,15 and 25 farms, respectively), based on net energy offered during maintenance (100%, 122% and 154% of requirements, respectively), showed that there was considerable area for improvement; the use of large quantities of concentrates is unjustified. Location, considerable on-farm feed production and zero grazing were associated with farm classification in group C. Rations used during the pre-breeding and the breeding periods offered 40-50% more net energy than required. Protein requirements were greatly exceeded (200-250%); alfalfa hay was the basic roughage and soybean and other oilseed meals (10% and 5%, respectively) were included in the concentrates. Calcium requirements were greatly exceeded as well. However, 1 out of 4 farms was providing inadequate amounts of phosphorus during maintenance. Moreover, adequate amounts of vitamins and trace minerals were offered by 37.9% of farms only, during maintenance. This situation was improved during the pre-breeding and the reeding periods (54.5% and 74.2%, respectively), but it was still far from desirable. It was estimated that balanced rations would decrease annual ram feeding expenses by at least 20€. At the same time, incidences of elevated body condition scores and their detrimental effects on ram fertility and some diseases, like urolithiasis, would be greatly reduced.

The genomic architecture of mastitis resistance in dairy sheep

BackgroundMastitis is the most prevalent disease in dairy sheep with major economic, hygienic and welfare implications. The disease persists in all dairy sheep production systems despite the implementation of improved management practises. Selective breeding for enhanced mastitis resistance may provide the means to further control the disease. In the present study, we investigated the genetic architecture of four mastitis traits in dairy sheep. Individual animal records for clinical mastitis occurrence and three mastitis indicator traits (milk somatic cell count, total viable bacterial count in milk and the California mastitis test) were collected monthly throughout lactation for 609 ewes of the Greek Chios breed. All animals were genotyped with a custom-made 960-single nucleotide polymorphism (SNP) DNA array based on markers located in quantitative trait loci (QTL) regions for mastitis resistance previously detected in three other distinct dairy sheep populations.ResultsHeritable variation and strong positive genetic correlations were estimated for clinical mastitis occurrence and the three mastitis indicator traits. SNP markers significantly associated with these mastitis traits were confirmed on chromosomes 2, 3, 5, 16 and 19. We identified pathways, molecular interaction networks and functional gene clusters for mastitis resistance. Candidate genes within the detected regions were identified based upon analysis of an ovine transcriptional atlas and transcriptome data derived from milk somatic cells. Relevant candidate genes implicated in innate immunity included SOCS2, CTLA4, C6, C7, C9, PTGER4, DAB2, CARD6, OSMR, PLXNC1, IDH1, ICOS, FYB, and LYFR.ConclusionsThe results confirmed the presence of animal genetic variability in mastitis resistance and identified genomic regions associated with specific mastitis traits in the Chios sheep. The conserved genetic architecture of mastitis resistance between distinct dairy sheep breeds suggests that across-breed selection programmes would be feasible.

Effect of β-lactoglobulin gene polymorphism, lactation stage and breed on milk traits in Chios and Karagouniko sheep breeds

Abstract The animal selection with favourable phenotypes of the past has been, currently, replaced by the genotype selection on quantitative traits, assisted by the expanding molecular techniques in the context of livestock improvement. In this study, the c.112T&gt;C polymorphism in exon II of β-lactoglobulin (β-LG) gene was investigated in Karagouniko and Chios sheep breeds by using polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP), and possible associations with milk traits were examined. In total, 125 blood DNA samples were isolated for PCR-RFLP analysis and the respective 217 milk samples′ composition profile was obtained. The goodness of fit test to Hardy-Weinberg equilibrium (HWE) for β-LG genotypes was estimated and associations found between β-LG genotypes and raw milk composition. Two alleles and three genotypes were observed (AA, AB and BB) in both breeds, and Chios breed significantly deviated (P≤0.05) from Hardy-Weinberg equilibrium (HWE). Conclusively, linear mixed model analysis on samples, from both breeds collectively, showed significant effects of β-LG genotype on lactose percentage and somatic cell count (SCC), lactation stage on daily milk yield and protein, while the breed effect was significant only on daily milk yield.

Short communication: Identification of variation in the ovine prolactin gene of Chios sheep with a cost-effective sequence-based typing assay

The present study identified single nucleotide polymorphisms (SNP) in the coding and untranslated regions of the ovine prolactin gene of Chios sheep. By developing a cost-effective direct sequence-based typing assay, around 600 bp of reliable sequencing data and clear identification of heterozygous positions was achieved. Five SNP were found, located in exons 2 (KC764410:g.567G>A, g.625C>T, g.683C>A) and 3 (KC764410:g.2015C>A, g.2101G>A), whereas the remaining exons were monomorphic. The identified SNP were synonymous, with the exception of the g.567G>A SNP, which results in an Arg to His amino acid change. As the sequencing cost of the sequence-based typing assay was 20 orders of magnitude lower compared with a standard Sanger method, the assay was also used as a genotyping tool. The identified polymorphism was genotyped for 247 ewes and was subsequently used in mixed model association analyses of milk yield, milk fat content, and litter size at birth. The association analysis revealed a significant dominance effect of 0.17 ± 0.07 of the g.2015C>A SNP on milk fat percentage, whereas a dominance effect of -21.33 ± 10.51 of the same SNP on total lactation milk yield was also estimated. The g.2015C>A SNP explained 2.47 and 3.68% of the total phenotypic variance of milk yield and milk fat percentage, respectively, whereas the corresponding values for the animal variance were 7.14 and 11.75%. A suggestive association of the nonsynonymous g.567G>A SNP with litter size at birth was also detected.