Establishment of an immortalized sheep mammary epithelial cell line for studying milk fat and protein synthesis.

The mammary gland, crucial for milk production in mammals, presents challenges for in vitro study due to its complex structure and limited cell lifespan. We addressed this by introducing the SV40 large T antigen into primary mammary epithelial cells (MECs) from sheep, creating an immortalized T-tag MEC line. This line, stable for over 50 passages, maintained typical epithelial cell morphology during long-term culture. Through transcriptome sequencing and validation, we discovered 3833 differentially expressed genes between MECs and T-tag MEC line, encompassing key biological processes and signaling pathways like cell cycle, p53, and cancer. The cell line, expressing MEC markers (KRT8, KRT18, proliferating cell nuclear antigen, SV40, CSN2, and acetyl-CoA carboxylase alpha), proved capable of synthesizing milk fat and protein. Despite its infinite proliferation potential, the T-tag MEC line showed no tumor formation in mice or cell migration in vitro, indicating stability. This development offers a valuable resource for studying MECs in dairy sheep, facilitating the advancement of long-term culture systems and in vitro lactation bioreactors.

Genetic parameters of milk mid-infrared spectra and their genetic relationships with milk production and feed efficiency traits in French Lacaune dairy sheep.

In French dairy sheep, Fourier transform infrared (FTIR) milk spectral data routinely predict the major milk components used in national genetic evaluations. The direct influence of genetic and environmental factors on milk FTIR spectra has been widely studied in dairy cattle, and relatively little in dairy ewes. In this study, 36,873 milk test-day records were available for 4,712 French Lacaune ewes farmed on 8 commercial farms. Our main goals were to provide the first description of spectral data and estimate the genetic parameters of French Lacaune dairy sheep during lactation. Principal component analysis (PCA) results demonstrated the impact of the lactation period on specific wavenumbers, allowing the identification of FTIR spectra collected at early (mo 2-4) and late (mo 5-7) lactation stages. The average estimated heritability (±mean SE) of the FTIR milk spectra from 2,971 to 926 cm-1 (446 wavenumbers) was 0.29 ± 0.02, ranging from 0.13 ± 0.01 to 0.42 ± 0.02. Furthermore, the heritabilities of spectra collected at the beginning or end of lactation changed at each point of the spectrum. However, at each wavenumber, the genomic correlation of transmittance values between these 2 lactation periods was high (>0.77), indicating the absence of a genotype-environment interaction. The genomic correlations between spectral regions and milk production traits (i.e., daily milk yield, fat and protein content, somatic cell score) varied from moderate to high. The results suggested that the most heritable areas of the spectrum were also genetically associated with dairy traits. Finally, the genomic correlations observed between the ewes' feed efficiency traits and the FTIR spectrum were moderate to high, while the genomic correlations between the change in body condition score and spectral data were rather low to moderate. This study confirmed that spectral data from Lacaune ewe milk were heritable, evolved phenotypically and genetically during lactation and were genetically correlated with traits included in breeding goals or traits of interest to the dairy industry.

Impact of truncating historical data on prediction ability of dairy sheep selection candidates.

Along the last decades, the genetic evaluation methodology has evolved, improving breeding value estimates. Many breeding programmes have historical phenotypic records and large number of generations, but to make use of them could result in more inconveniences than benefits. In this study, the prediction ability of genotyped young animals was assessed by simultaneously evaluating the removal of historical data, two pedigree deepness and two methodologies (traditional BLUP and single-step genomic BLUP or ssGBLUP), using milk yield records of 40 years of three Latxa dairy sheep populations. The linear regression method was used to compare predictions of young rams before and after progeny testing, with six cut-off points, by intervals of 4 years (from 1992 to 2012), and statistics of ratio of accuracies, bias, and dispersion were calculated. The prediction accuracy of selection candidates, when genomic information was included, was the highest in all Latxa populations (between 0.54 and 0.69 with full data set). Nevertheless, the deletion of historical phenotypic data resulted on moderate accuracy gain in the bigger data size populations (mean gain 2.5%), and the smaller population took advantage of a moderate data deletion (2.7% gain by removing data until 2004), reducing accuracy when more records were removed. The bias of validation individuals was lower when the breeding value was predicted based on genomic information (between 2.1 and 13.9), being lower when the biggest amount of data was deleted in the bigger data size populations (5.2% reduction), and the smaller population was benefited from data deletion between 1996 and 2008 (3.8% bias reduction). Meanwhile, the slope of estimated genetic trend was lower when less data were included, and an overestimation of the unknown parent group estimates was observed. The results indicated that ssGBLUP evaluations were outstanding, compared with traditional BLUP evaluations, while the depth of pedigree had a very small influence, and deletion of historical phenotypic data was beneficial. Thus, Latxa routine genetic evaluations would benefit from truncating phenotypic records between 2000 and 2004, the use of two pedigree generations and the implementation of ssGBLUP methodology.

Milk transcriptome biomarker identification to enhance feed efficiency and reduce nutritional costs in dairy ewes.

In recent years, rising prices for high-quality protein-based feeds have significantly increased nutrition costs. Consequently, investigating strategies to reduce these expenses and improve feed efficiency (FE) have become increasingly important for the dairy sheep industry. This research investigates the impact of nutritional protein restriction (NPR) during prepuberty and FE on the milk transcriptome of dairy Assaf ewes (sampled during the first lactation). To this end, we first compared transcriptomic differences between NPR and control ewes. Subsequently, we evaluated gene expression differences between ewes with divergent FE, using feed conversion ratio (FCR), residual feed intake (RFI), and consensus classifications of high- and low-FE animals for both indices. Lastly, we assess milk gene expression as a predictor of FE phenotype using random forest. No effect was found for the prepubertal NPR on milk performance or FE. Moreover, at the milk transcriptome level, only one gene, HBB, was differentially expressed between the NPR (n = 14) and the control group (n = 14). Further, the transcriptomic analysis between divergent FE sheep revealed 114 differentially expressed genes (DEGs) for RFI index (high-FERFI = 10 vs low-FERFI = 10), 244 for FCR (high-FEFCR = 10 vs low-FEFCR = 10), and 1 016 DEGs between divergent consensus ewes for both indices (high-FEconsensus = 8 vs low-FEconsensus = 8). These results underscore the critical role of selected FE indices for RNA-Seq analyses, revealing that consensus divergent animals for both indices maximise differences in transcriptomic responses. Genes overexpressed in high-FEconsensus ewes were associated with milk production and mammary gland development, while low-FEconsensus genes were linked to higher metabolic expenditure for tissue organisation and repair. The best prediction accuracy for FE phenotype using random forest was obtained for a set of 44 genes consistently differentially expressed across lactations, with Spearman correlations of 0.37 and 0.22 for FCR and RFI, respectively. These findings provide insights into potential sustainability strategies for dairy sheep, highlighting the utility of transcriptomic markers as FE proxies.

Subacute Rumen Acidosis in Greek Dairy Sheep: Prevalence, Impact and Colorimetry Management.

Subacute rumen acidosis (SARA) is a current issue in intensive livestock farming, and it is particularly associated with feeding high-concentrate diets. This study investigated the prevalence and impact of SARA in forty-two Greek dairy sheep flocks by recording rumen pH, milk composition, and milk yield over a period of nine months. Moreover, it explored the use of computerized rumen colorimetry as a management and diagnostic tool for SARA in dairy sheep. In culled ewes, computerized rumen mucosal colorimetry was applied, and rumen wall samples taken for histological examination. SARA cases were identified in 19 farms (45%, n = 42). Farms with SARA cases had lower milk fat levels, while milk yield and milk protein levels did not differ based on the SARA status of the farms. In culled ewes, rumen color was significantly associated with the flock's SARA status, and affected ewes showed increased thickness in non-keratinized and total epithelial layers. It was concluded that computerized rumen mucosal colorimetry in aged, culled ewes shows promise as an indicator, post mortem, of SARA present in dairy sheep flocks whose impact can be minimized by making significant changes in dietary management.

Risk Categorization in On-Farm Welfare in Different-Sized Dairy Sheep Flocks.

The objective of the present work was to categorize the risks in the on-farm welfare of dairy sheep in semi-extensive systems in order to highlight if risks in welfare vary according to the farm size. To the best of our knowledge, this study constitutes one of the few categorizations of the risks in the welfare of dairy sheep reared semi-extensively. The survey was conducted on 12 semi-extensive dairy sheep farms in Tuscany (Central Italy), which were classified according to flock size: <500, from 500 to 1000, and >1000. The results showed an adequate rating for all the farms included in the study. The most critical issues concerned the ratio between the number of stockpersons and the number of animals within the farms, the small decubitus areas, the lack of udder cleaning procedures during milking operations, and, in terms of biosecurity, the lack of prevention, control, and eradication plans for the most important infectious ovine diseases. The results show that different items in the five areas evaluated, including the assessments of management of the flock, the number of daily inspections, and the hygiene of the water supplies are associated with the farm size. In large farms, the assessment of management of the flock was better, but the number of daily inspections and the hygiene of the water supplies were worse.

Biotransformation of Cynomorium flavan-3-ols in dairy sheep and their effects on inflammation and liver growth retardation.

The stems of Cynomorium songaricum are used in traditional Chinese medicine as a tonic and also used locally as a food material and livestock feed. It is known that some of the falvan-3-ol monomers and dimers that entered the milk of dairy sheep fed with C. songaricum stems are biotransformation products of the original flavan-3-ol polymers in C. songaricum stems. This study was performed to investigate the biotransformation process of the flavan-3-ols in dairy sheep and to evaluate the bioactivities. The results showed that procyanidin A2 and epicatechin could be released from the polymeric flavan-3-ols of C. songaricum through rumen microbial metabolism. On traumatic and lipopolysaccharide (LPS)-induced inflammation models of Tg (mpx: EGFP) zebrafish larvae and LPS-induced liver injury models of Tg (fabp10a: DsRed) zebrafish larvae, the milk from sheep fed with C. songaricum stems showed stronger anti-inflammatory and hepatoprotective activities compared to blank milk. The absorbed chemical constituents of C. songaricum stems and the metabolites also exhibited anti-inflammatory and hepatoprotective activities, with the dimeric flavan-3-ols being more effective than the monomers. The milk, the absorbed chemical constituents of C. songaricum stems, and the metabolites alleviated the increased level of reactive oxygen species induced by LPS in zebrafish larvae. PRACTICAL APPLICATION: This study found that C. songaricum stems as livestock feed could produce milk that has a beneficial impact on consumer and livestock health in terms of anti-inflammation and hepatoprotection.

Assessment of milk metabolites as biomarkers for predicting feed efficiency in dairy sheep.

Estimating feed efficiency (FE) in dairy sheep is challenging due to the high cost of systems that measure individual feed intake. Identifying proxies that can serve as effective predictors of FE could make it possible to introduce FE into breeding programs. Here, 39 Assaf ewes in first lactation were evaluated regarding their FE by 2 metrics, residual feed intake (RFI) and feed conversion ratio (FCR). The ewes were classified into high, medium and low groups for each metric. Milk samples of the 39 ewes were subjected to untargeted metabolomics analysis. The complete milk metabolomic signature was used to discriminate the FE groups using partial least squares discriminant analysis. A total of 41 and 26 features were selected as the most relevant features for the discrimination of RFI and FCR groups, respectively. The predictive ability when utilizing the complete milk metabolomic signature and the reduced data sets were investigated using 4 machine learning (ML) algorithms and a multivariate regression method. The orthogonal partial least squares algorithm outperformed other ML algorithms for FCR prediction in the scenarios using the complete milk metabolite signature (R2 = 0.62 ± 0.06) and the 26 selected features (R2 = 0.62 ± 0.15). Regarding RFI predictions, the scenarios using the 41 selected features outperformed the scenario with the complete milk metabolite signature, where the multilayer feedforward artificial neural network (R2 = 0.18 ± 0.14) and extreme gradient boosting (R2 = 0.17 ± 0.15) outperformed other algorithms. The functionality of the selected metabolites implied that the metabolism of glucose, galactose, fructose, sphingolipids, amino acids, insulin, and thyroid hormones was at play. Compared with the use of traditional methods, practical applications of these biomarkers might simplify and reduce costs in selecting feed-efficient ewes.

A genome-wide association study reveals novel SNP markers associated with resilience traits in two Mediterranean dairy sheep breeds.

Genetic selection for higher productivity increased dairy sheep susceptibility to diseases and environmental stressors, challenging their health and welfare status and production efficiency. Improving resilience to such stressors can enhance their ability to face these challenges without compromising productivity. Our objective was to estimate genomic heritability and perform genome-wide association studies (GWAS) to detect SNPs and candidate genes associated with three proxy traits for resilience (milk somatic cell count-SCC, lactation persistency-LP, body condition score-BCS) of Chios and Frizarta dairy ewes. We used genome-wide genotypes of 317 Chios and 346 Frizarta ewes. Individual records of milk yield and BCS, and milk samples were collected monthly for two consecutive milking periods; samples were analyzed to determine SCC. The LP was calculated as the regression coefficient of daily milk yield on days from lambing. Within breed, variance components analyses and GWAS were performed using genomic relatedness matrices in single-trait animal linear mixed models. Genomic-based heritability estimates were relatively high (BCS: h2 = 0.54 and 0.55, SCC: h2 = 0.25 and 0.38, LP: h2 = 0.43 and 0.45, for Chios and Frizarta ewes, respectively), compared to previous pedigree-based studies. The GWAS revealed 7 novel SNPs associated with the studied traits; one genome-wide and two suggestive significant SNPs for SCC (Frizarta: rs403061409, rs424064526 and rs428540973, on chromosomes 9, 1 and 12, respectively), one suggestive significant SNP for BCS (Chios: rs424834097 on chromosome 4) and three suggestive significant SNPs for LP (Frizarta: rs193632931 and rs412648955 on chromosomes 1 and 6, Chios: rs428128299 on chromosome 3). Nineteen candidate genes were detected: two for BCS (Chios: POT1, TMEM229A), thirteen for SCC (Frizarta: NTAQ1, ZHX1, ZHX2, LOC101109545, HAS2, DERL1, FAM83A, ATAD2, RBP7, FSTL1, CD80, HCLS1, GSK3B) and four for LP (Frizarta: GRID2, FAIM, CEP70-Chios: GRIP1). Present results show that resilience in the studied dairy sheep breeds is heritable and advance existing knowledge on the genomic background of SCC, LP, and BCS. Future research will quantify effects of different alleles of significant SNPs on the studied traits and search for possible correlations among traits to facilitate their effective incorporation in breeding programs aiming to improve resilience.

Gastrointestinal Parasite Infections and Environmental Sustainability of the Ovine Sector: Eimeria spp. Infections and Nitrogen and Phosphorus Excretions in Dairy Sheep in Italy.

In sheep farming, gastrointestinal parasites can be responsible for significant reductions in animal health and production. Nitrogen (N) and phosphorus (P) fecal excretions are the main determining factors for N2O emissions from manure management and may pose other environmental problems, such as the acidification and eutrophication of natural habitats. By using the Mini-FLOTAC technique on fecal samples from sheep of different ages and physiological status from 19 dairy sheep farms in Tuscany (central Italy), gastrointestinal parasite infections were evaluated. The animal N and P fecal contents were also assessed, with the aim of evaluating possible relationships between the identified parasites and the environmental sustainability of the examined farms. The obtained results showed that Eimeria spp. (86.36%) and gastrointestinal strongyle (54.55%) infections are prevalent in the examined farms. Moreover, significantly higher (p ≤ 0.05) P and Eimeria oocyst/gram-of-feces (OPG) values were found in fecal samples from animals < 1 year of age, and a significant (p ≤ 0.05) positive correlation resulted between N content and Eimeria OPG in fecal samples from animals in the first month of lactation. The findings from this study suggest for the first time that Eimeria spp. infections may have an impact on the environmental sustainability of sheep farming.

Evaluation of the effect of melatonin implantation in rams and eCG dose in ewes synchronized by a CIDR-eCG protocol on reproductive performance of Lacaune sheep breed during non-breeding season.

Sustainable production of milk is favorable in dairy sheep industry, which necessitates year-round reproduction of rams and ewes even during non-breeding season. Hence, protocols facilitating reproduction of rams and ewes during non-breeding season are of importance for this purpose. Therefore, the present study was conducted to investigate the effect of melatonin implantation in rams and administration of 400 IU eCG (E400) versus 300 IU eCG (E300) in ewes on reproductive performance of Lacaune sheep breed during non-breeding season. Rams were allocated to two groups including untreated (control, CON; n = 36) and melatonin-treated (MEL; n = 37). A subset of rams from CON (n = 7) and MEL (n = 7) groups were used for assessment of scrotal circumference, kinematic and functional characteristics of sperm, total antioxidant capacity (TAC) of semen and circulating testosterone on Days 0 (the beginning of study) and 60 (60 days after melatonin implantation). Further, the study had a 2 × 2 factorial design with four experimental groups including 1) ewes treated with E300 and introduced to CON rams (E300CON; n = 17 rams and 172 ewes), 2) ewes treated with E300 and introduced to MEL rams (E300MEL; n = 18 rams and 177 ewes), 3) ewes treated with E400 and introduced to CON rams (E400CON; n = 19 rams and 192 ewes), and ewes treated with E400 and introduced to MEL rams (E400MEL; n = 19 rams and 190 ewes). Melatonin implantation improved scrotal circumference, concentration, progressive motility, velocity, mitochondrial membrane potential and viability of sperm, TAC of semen, concentration of testosterone and fertility of rams (P < 0.05). Besides, E400 compared with E300 enhanced synchronization of estrus and fertility in ewes (P < 0.05). In conclusion, melatonin implantation promoted reproductive performance in Lacaune rams, and increase in dose of eCG improved reproductive performance in Lacaune ewes.

Evaluation of Streptococcus species isolated from subclinical sheep mastitis by molecular methods and determination of virulence factors and antimicrobial resistance genes.

Streptococcus (S.) species are important pathogens that cause mastitis in sheep. The study aimed to examine Streptococcus species in sheep milk with subclinical mastitis, assessing their prevalence, antimicrobial resistance, and virulence genes. A total of 200 milk samples were collected from sheep farms in Izmir's five districts. Out of 32 (28.6%) Streptococcus isolates identified by phenotypic methods, 25 were genotypically identified as S. uberis, 5 as S. agalactiae, and 2 as S. dysgalactiae. Disk diffusion was used to determine the antimicrobial resistance of the isolates. PCR was employed to identify antimicrobial resistance and virulence genes in the isolates. The highest resistance was found for cloxacillin (100%), and the highest sensitivity was found for florfenicol (84%). The most common resistance gene combination was tetM+tetS (3/32) for S. uberis in 9.4%. A total of five virulence genes were detected. GapC+sua (56.2%) constituted the most common gene pattern. The highest virulence gene gapC was detected in 78.1% (25/32) of the isolates. The cylE gene was not detected (0%) in the isolates. Streptococcus species may play a role in mastitis in sheep, emphasising the need for meticulous hygienic milking practices.

Microbiability of milk composition and genetic control of microbiota effects in sheep.

Recently, high-dimensional omics data are becoming available in larger quantities, and models have been developed that integrate them with genomics to understand in finer detail the relationship between genotype and phenotype, and thus improve the performance of genetic evaluations. Our objectives are to quantify the effect of the inclusion of microbiome data in the genetic evaluation for dairy traits in sheep, through the estimation of the heritability, microbiability, and how the microbiome effect on dairy traits decomposes into genetic and nongenetic parts. In this study we analyzed milk and rumen samples of 795 Lacaune dairy ewes. We included, as phenotype, dairy traits and milk fatty acids and proteins composition; as omics measurements, 16S rRNA rumen bacterial abundances; and as genotyping, 54K SNP chip for all ewes. Two nested genomic models were used: a first model to predict the individual contributions of the genetic and microbial abundances to phenotypes, and a second model to predict the additive genetic effect of the microbial community. In addition, microbiome-wide association studies for all dairy traits were applied using the 2,059 rumen bacterial abundances, and the genetic correlations between microbiome principal components and dairy traits were estimated. Results showed that in general the inclusion of both genetic and microbiome effect did not improve the fit of the model compared with the model with the genetic effect only. In addition, for all dairy traits the total heritability was equal to the direct heritability after fitting microbiota effects, due to a microbiability being almost zero for most dairy traits and heritability of the microbial community was very close to zero. Microbiome-wide association studies did not show operational taxonomic units with major effect for any of the dairy traits evaluated, and the genetic correlations between the first 5 principal components and dairy traits were low to moderate. So far, we can conclude that, using a substantial data set of 795 Lacaune dairy ewes, rumen bacterial abundances do not provide improved genetic evaluation for dairy traits in sheep.

Genome-Wide Signal Selection Analysis Revealing Genes Potentially Related to Sheep-Milk-Production Traits.

Natural selection and domestication have shaped modern sheep populations into a vast range of phenotypically diverse breeds. Among these breeds, dairy sheep have a smaller population than meat sheep and wool sheep, and less research is performed on them, but the lactation mechanism in dairy sheep is critically important for improving animal-production methods. In this study, whole-genome sequences were generated from 10 sheep breeds, including 57 high-milk-yield sheep and 44 low-milk-yield sheep, to investigate the genetic signatures of milk production in dairy sheep, and 59,864,820 valid SNPs (Single Nucleotide Polymorphisms) were kept after quality control to perform population-genetic-structure analyses, gene-detection analyses, and gene-function-validation analyses. For the population-genetic-structure analyses, we carried out PCA (Principal Component Analysis), as well as neighbor-joining tree and structure analyses to classify different sheep populations. The sheep used in our study were well distributed in ten groups, with the high-milk-yield-group populations close to each other and the low-milk-yield-group populations showing similar classifications. To perform an exact signal-selection analysis, we used three different methods to find SNPs to perform gene-annotation analyses within the 995 common regions derived from the fixation index (FST), nucleotide diversity (Ɵπ), and heterozygosity rate (ZHp) results. In total, we found 553 genes that were located in these regions. These genes mainly participate in the protein-binding pathway and the nucleoplasm-interaction pathway, as revealed by the GO- and KEGG-function-enrichment analyses. After the gene selection and function analyses, we found that FCGR3A, CTSK, CTSS, ARNT, GHR, SLC29A4, ROR1, and TNRC18 were potentially related to sheep-milk-production traits. We chose the strongly selected genes, FCGR3A, CTSK, CTSS, and ARNT during the signal-selection analysis to perform a RT-qPCR (Reale time Quantitative Polymerase Chain Reaction) experiment to validate their expression-level relationship with milk production, and the results showed that FCGR3A has a significant negative relationship with sheep-milk production, while other three genes did not show any positive or negative relations. In this study, it was discovered and proven that the candidate gene FCGR3A potentially contributes to the milk production of dairy sheep and a basis was laid for the further study of the genetic mechanism underlying the strong milk-production traits of sheep.

Influence of a temporary restriction of dietary protein in prepubertal ewe lambs on first lactation milk traits and response to a mammary gland inflammatory challenge.

This study evaluated the influence of a temporary nutritional protein restriction (NPR) performed, under commercial conditions, in prepubertal female lambs on first lactation milk production traits and the inflammatory response triggered by an inflammatory challenge of the. From 40 Assaf female lambs, we defined a control group (Cn = 20), which received a standard diet for replacement lambs and the NPR group (n = 20), which received the same diet but without soybean meal between 3 and 5 months of age. About 150 days after lambing, 24 of these ewes (13 NPR, 11C) were subjected to an intramammary infusion of E. coli lipopolysaccharide (LPS). Our dynamic study identified indicator traits of local (SCC) and systemic (rectal Ta, IL-6, CXCL8, IL-10, IL-36RA, VEGF-A) response to the LPS challenge. The NPR did not show significant effects on milk production traits and did not affect the SCC and rectal Ta after the LPS challenge. However, the NPR had a significant influence on 8 of the 14 plasma biomarkers analysed, in all the cases with higher relative values in the C group. The effects observed on VEGF-A (involved in vasculogenesis during mammary gland development and vascular permeability) and IL-10 (a regulatory cytokine classically known by its anti-inflammatory action) are the most remarkable to explain the differences found between groups. Whereas further studies should be undertaken to confirm these results, our findings are of interest considering the current concern about the future world's demand for protein and the need for animal production systems to evolve toward sustainability.

Feed efficiency in dairy sheep: An insight from the milk transcriptome.

Introduction: As higher feed efficiency in dairy ruminants means a higher capability to transform feed nutrients into milk and milk components, differences in feed efficiency are expected to be partly linked to changes in the physiology of the mammary glands. Therefore, this study aimed to determine the biological functions and key regulatory genes associated with feed efficiency in dairy sheep using the milk somatic cell transcriptome. Material and methods: RNA-Seq data from high (H-FE, n = 8) and low (L-FE, n = 8) feed efficiency ewes were compared through differential expression analysis (DEA) and sparse Partial Least Square-Discriminant analysis (sPLS-DA). Results: In the DEA, 79 genes were identified as differentially expressed between both conditions, while the sPLS-DA identified 261 predictive genes [variable importance in projection (VIP) > 2] that discriminated H-FE and L-FE sheep. Discussion: The DEA between sheep with divergent feed efficiency allowed the identification of genes associated with the immune system and stress in L-FE animals. In addition, the sPLS-DA approach revealed the importance of genes involved in cell division (e.g., KIF4A and PRC1) and cellular lipid metabolic process (e.g., LPL, SCD, GPAM, and ACOX3) for the H-FE sheep in the lactating mammary gland transcriptome. A set of discriminant genes, commonly identified by the two statistical approaches, was also detected, including some involved in cell proliferation (e.g., SESN2, KIF20A, or TOP2A) or encoding heat-shock proteins (HSPB1). These results provide novel insights into the biological basis of feed efficiency in dairy sheep, highlighting the informative potential of the mammary gland transcriptome as a target tissue and revealing the usefulness of combining univariate and multivariate analysis approaches to elucidate the molecular mechanisms controlling complex traits.

Alternative hormone-free reproduction management of a dairy sheep flock disrupts the farm's annual feeding system calendar and its associated strategies.

Hormone-free (HF) reproduction in dairy sheep is a way to meet current societal demands, but it requires being prepared for collateral impacts on related system components. The efficiency of HF practices (e.g., using the male effect for estrus induction and synchronization) is uncertain compared with hormonal treatment (HT). For example, these practices can lead to higher variability in the flock physiological stage patterns throughout the year, which has direct consequences for feeding regimens. The objective of this work was to simulate the impacts of HF reproduction management, including artificial insemination (AI), on the temporal distribution of productive performance and nutritional requirements of a conventional dairy sheep flock. Using the REPROsheep2.0 model, 6 scenarios were compared over one typical production season for the same flock (n = 597 Lacaune ewes) intensively reared in the Roquefort region of France. These scenarios depicted reproduction with HT and AI in mid-May (Early); HT and AI in July (Summer Late); HT and AI in November (Autumn Late); and their HF versions (HF-Early; HF-Summer Late, and HF-Autumn Late, respectively). In all HF scenarios, a reduction in the number of ewes lambing and consequently in the annual milk production of the farm was observed (-1 to -7%). This affected annual performance with a subsequent decrease of total annual nutritional requirements (-2 to -6%). The HF scenarios resulted in a staggering of lambing events with a 7- to 14-d shift in the appearance of milk production peaks and related nutritional requirements compared with the HT scenarios. Transitioning from conventional to HF reproduction management, while preserving AI, would increase farm workload, lengthen milking period operations, and necessitate a readjustment of feeding management strategies with regard to available feed resources. Depending on the production season, the observed delay in the distribution of nutritional requirements could be either an attractive or an unfavorable outcome for farmers. The delay may be concordant, for example, with the recently observed impacts of climate change on seasonal forage availability in Mediterranean regions (less spring herbage production and warmer temperatures) that are affecting farmers' decision-making about the most efficient use of forage and feed resources.

Grape, Pomegranate, Olive, and Tomato By-Products Fed to Dairy Ruminants Improve Milk Fatty Acid Profile without Depressing Milk Production.

The continuous increase in the cost of feeds and the need to improve the sustainability of animal production require the identification of alternative feeds, such as those derived from the agro-industrial sector, that can be effectively used for animal nutrition. Since these by-products (BP) are sources of bioactive substances, especially polyphenols, they may play an important role as a new resource for improving the nutritional value of animal-derived products, being effective in the modulation of the biohydrogenation process in the rumen, and, hence, in the composition of milk fatty acids (FA). The main objective of this work was to evaluate if the inclusion of BP in the diets of dairy ruminants, as a partial replacement of concentrates, could improve the nutritional quality of dairy products without having negative effects on animal production traits. To meet this goal, we summarized the effects of widespread agro-industrial by-products such as grape pomace or grape marc, pomegranate, olive cake, and tomato pomace on milk production, milk composition, and FA profile in dairy cows, sheep, and goats. The results evidenced that substitution of part of the ratio ingredients, mainly concentrates, in general, does not affect milk production and its main components, but at the highest tested doses, it can depress the yield within the range of 10-12%. However, the general positive effect on milk FA profile was evident by using almost all BP at different tested doses. The inclusion of these BP in the ration, from 5% up to 40% of dry matter (DM), did not depress milk yield, fat, or protein production, demonstrating positive features in terms of both economic and environmental sustainability and the reduction of human-animal competition for food. The general improvement of the nutritional quality of milk fat related to the inclusion of these BP in dairy ruminant diets is an important advantage for the commercial promotion of dairy products resulting from the recycling of agro-industrial by-products.

When to shear dairy ewes: before breeding, during pregnancy or let them unshorn?

Shearing dairy ewes may improve their fitness and heat tolerance during late pregnancy, with positive effects on lambs and lactation performances. To test this hypothesis, two Mediterranean breeds (MN, Manchega, n = 43; LC, Lacaune, n = 28), differing in lactation performances and fleece traits, were submitted to three shearing strategies: (i) shorn before breeding (SBB), (ii) shorn at day 100 of pregnancy (S100) and (iii) unshorn (CO). Ewes were bred in spring and gestated during summer. Fleece traits and respiratory rate were measured on pregnant (107-121 days) resting ewes at different barn temperatures. Blood and colostrum were sampled at lambing. Ewes suckled their lambs (28 days) and were machine-milked until 180 days of lactation. Lamb and ewe weights, and condition score of the ewes, were recorded throughout the experiment. Milk yield was assessed during suckling (fortnightly) and milking (daily), and milk was sampled for composition (fortnightly). Fleece extension and wool weight at S100 were 13 and 45% greater in MN than in LC ewes, respectively, but the ewe's respiration rate at late pregnancy, between 20 and 25 °C, did not vary among shearing treatments nor breeds. Nevertheless, S100 ewes had a 37% lower respiration rate than SBB and CO ewes at 28 °C. At lambing, SBB and S100 ewes had 86% higher glycaemia than CO in MN, but LC ewes did not vary. Shearing treatment had no effect in plasma insulin, ß-hydroxybutyrate or non-esterified fatty acids (NEFAs) at lambing in both breeds. Lamb's birthweight and growth during suckling did not differ by shearing treatment in both breeds. Colostrum composition and milk yield during suckling were not modified by shearing treatment in either breed, although S100 suckling milk composition increased in MN (protein and casein, 6%) and LC ewes (total solids, 8%; fat, 18%), compared to CO and SBB. No effects were detected in milk yield or composition during milking, but S100 tended to yield 28% more milk than CO in the LC ewes. The S100 treatment improved the body reserves in late pregnancy, when compared to CO and SBB in both breeds. In conclusion, shearing dairy ewes in late pregnancy was a recommendable management practice under summer conditions, because alleviated heat stress and improved the weight of the ewes, without detrimental effects on lambing and lactational performances, the last tending to increase milk yield in high-yielding dairy ewes.

Modelling Lactation Curves for Dairy Sheep in a New Zealand Flock.

Lactation curves were modelled for dairy sheep in a New Zealand flock, providing information on the lactation yields of milk, fat, protein, and lactose, corrected for 130 days of milking. From 169 ewes, a total of 622 test-day records were obtained during the milk production season of 2021-2022 (from October to January). The flock produced an average of 86.1 kg of milk, 5.1 kg of fat, 4.5 kg of protein, and 4.1 kg of lactose, and moderate to large coefficients of variation were observed (27-31%) for these traits. The lactation persistency of milk, fat, protein, and lactose yields ranged from 52.3 to 72.7%. Analyses of variance for total yield and persistency were performed with an animal model that included the fixed effects of age (parity number), litter size, coat colour, and milking frequency (days in twice-a-day milking) and random residuals. Age and milking frequency were the only factors that significantly affected the yields of milk, fat, protein, and lactose. Age significantly affected the lactation persistency of milk and lactose yields, whereas litter size affected the persistency of protein, and milking frequency affected the persistency of fat. This study on this single flock provides valuable experience for a larger-scale animal breeding programme in New Zealand.