Evaluation of reference lactation length in Chios dairy sheep

The Effect of Milking Frequency, Breed, and Stage of Lactation on the Milk Fat Globule Size and Fatty Acid Composition in Sheep's Milk

This study examined the effects of milking frequency, breed, and stage of lactation on the milk fat globules (MFG) size and fatty acids (FA) composition of sheep milk. Milk from Karagouniko (n = 13) and Chios (n = 13) ewes was sampled postpartum on the 93rd, 101st, 108th, 121st, 156th, and 188th days of lactation. On the 108th day, the ewes were divided randomly into two milking groups: Once daily at 06:00 a.m. or twice daily at 06:00 a.m. and 16:00 p.m. Morphometric characteristics of MFG and FA composition were determined for each sample. Once versus twice daily milking had no effect on MFG dimensions, which tended to vary according to breed (smaller MFG were secreted from Chios with p = 0.065), while the stage of lactation had a significant effect (p < 0.001). FA composition differed significantly according to the stage of lactation and breed. The FA profile of the Karagouniko breed showed higher concentrations of short-chain FA. The milk samples from late lactation were characterized by higher concentrations of mono-unsaturated FA (MUFA) compared to early and mid-lactation. Moreover, correlations were found between the average diameter of MFG and FA concentrations, where the size of MFG was positively correlated with saturated FA (SFA) and negatively correlated with MUFA.

Novel genomic markers and genes related to reproduction in prolific Chios dairy sheep: a genome-wide association study

Genetic architecture of sheep reproduction is increasingly gaining scientific interest due to the major impact on sheep production systems. In the present study, we conducted pedigree-based analyses and genome-wide association studies using the Illumina Ovine SNP50K BeadChip to explore the genetic mechanisms underlying the reproduction of the highly prolific Chios dairy sheep. First lambing age, total prolificacy and maternal lamb survival were selected as representative reproductive traits and estimated as significantly heritable (h² = 0.07-0.21) with no evident genetic antagonism among traits. We identified novel genome-wide and suggestive significant single-nucleotide polymorphisms (SNPs) on chromosomes 2 and 12 associated with age at first lambing. The new variants detected on chromosome 2 span a region of 357.79 kb with high pairwise linkage disequilibrium estimates (r² = 0.8-0.9). Functional annotation analysis revealed candidate genes, such as the collagen-type genes and the Myostatin gene, that participate in osteogenesis, myogenesis, skeletal and muscle mass development resembling the functionality of major genes affecting the ovulation rate and prolificacy. Additional functional enrichment analysis associated the collagen-type genes with multiple uterine-related disfunctions, such as cervical insufficiency, uterine prolapse and abnormalities of the uterine cervix. Several genes (e.g., KAZN, PRDM2, PDPN, LRRC28) localised close to the SNP marker on chromosome 12 were grouped in annotation enrichment clusters majorly involved in developmental and biosynthetic pathways, apoptosis, and nucleic acid-templated transcription. Our findings may further contribute to unravel the genomic regions that are important for sheep reproduction and could be incorporated into future selective breeding programmes.

The effect of different management systems on milk yield and milk quality in Awassi sheep

This study aimed to evaluate the effect of concentrate-based feeding (CF) and artificial pasture-based grazing (APG) management systems on milk yield, fatty acids, nutritional indices, and milk physicochemical characteristics of Awassi ewes. The research involved 300 heads of Awassi ewes, which were divided into two groups. Awassi sheep were managed in a CF and APG system to test the milk yield characteristics. The results showed a significant ( P < 0.01 ) difference in milk yield and lactation length between CF and APG management systems of ewes. The average daily milk yield showed a nonsignificant difference for both management systems, and no significant changes ( P > 0.05 ) in the chemical composition of CF and APG management systems were observed. Palmitic (C16:0), myristic (C14:0), stearic (C18:0) capric (C10:0), and lauric (C12:0) acids were the major saturated fatty acids found in milk from both management systems. The level of linoleic acid (C18:2 n-6) was significantly different in both treatments ( P < 0.05 ), but the linolenic (C18:3 n-3) acid level was nonsignificant in milk from the CF and APG management systems. The hypocholesterolemic / hypercholesterolemic (h / H) fatty acid and thrombogenicity (TI) ratios were significantly different ( P < 0.05 ); however, the atherogenicity (AI) had no significant difference between confined and grazing systems. In conclusion, it can be said that the lactation length and lactation milk yield were prolonged by the APG management system, though the milk composition and quality were not significantly affected.

Comparative Transcriptome Analysis of Milk Somatic Cells During Lactation Between Two Intensively Reared Dairy Sheep Breeds

In dairy sheep industry, milk production dictates the value of a ewe. Milk production is directly related to the morphology and physiology of the mammary gland; both being designated targets of breeding strategies. Although within a flock breeding parameters are mutual, large differences in milk production among individual ewes are usually observed. In this work, we tested two of the most productive dairy sheep breeds reared intensively in Greece, one local the Chios breed and one foreign the Lacaune breed. We used transcriptome sequencing to reveal molecular mechanisms that render the mammary gland highly productive or not. While highly expressed genes (caseins and major whey protein genes) were common among breeds, differences were observed in differentially expressed genes. ENSOARG00000008077, as a member of ribosomal protein 14 family, together with LPCAT2, CCR3, GPSM2, ZNF131, and ASIP were among the genes significantly differentiating mammary gland's productivity in high yielding ewes. Gene ontology terms were mainly linked to the inherent transcriptional activity of the mammary gland (GO:0005524, GO:0030552, GO:0016740, GO:0004842), lipid transfer activity (GO:0005319) and innate immunity (GO:0002376, GO:0075528, GO:0002520). In addition, clusters of genes affecting zinc and iron trafficking into mitochondria were highlighted for high yielding ewes (GO:0071294, GO:0010043). Our analyses provide insights into the molecular pathways involved in lactation between ewes of different performances. Results revealed management issues that should be addressed by breeders in order to move toward increased milk yields through selection of the desired phenotypes. Our results will also contribute toward the selection of the most resilient and productive ewes, thus, will strengthen the existing breeding systems against a spectrum of environmental threats.

Understanding the seasonality of performance resilience to climate volatility in Mediterranean dairy sheep

As future climate challenges become increasingly evident, enhancing performance resilience of farm animals may contribute to mitigation against adverse weather and seasonal variation, and underpin livestock farming sustainability. In the present study, we develop novel seasonal resilience phenotypes reflecting milk production changes to fluctuating weather. We evaluate the impact of calendar season (autumn, winter and spring) on animal performance resilience by analysing 420,534 milk records of 36,908 milking ewes of the Chios breed together with relevant meteorological data from eastern Mediterranean. We reveal substantial seasonal effects on resilience and significant heritable trait variation (h² = 0.03–0.17). Resilience to cold weather (10 °C) of animals that start producing milk in spring was under different genetic control compared to autumn and winter as exemplified by negative genetic correlations (− 0.09 to − 0.27). Animal resilience to hot weather (25 °C) was partially under the same genetic control with genetic correlations between seasons ranging from 0.43 to 0.86. We report both favourable and antagonistic associations between animal resilience and lifetime milk production, depending on calendar season and the desirable direction of genetic selection. Concluding, we emphasise on seasonal adaptation of animals to climate and the need to incorporate the novel seasonal traits in future selective breeding programmes.