Sarda Dairy Sheep Research Articles

Investigation of phenotypic, genetic and genomic background of Milk spectra in Sarda dairy sheep.

Aim of this study was to analyse the genetic background of milk Fourier transform infrared (FTIR) spectra in dairy sheep. Individual milk FTIR spectra, with 1060 wavenumbers each, were available for 793 adult Sarda breed ewes genotyped at 45,813 SNP. The absorbance values of each wavenumber was analysed using a linear mixed model that included dim class, parity and lambing month as fixed effects and flock-test date and animal as random effects. The model was applied to estimate variance components and heritability and to perform a genome-wide association study for each wavenumber. Average h2 of wavenumbers absorbance was 0.13 ± 0.08, with the largest values observed in the regions associated with the characteristic bonds of carbonylic and methylenic groups of milk fat (h2 = 0.57 at 1724-1728 cm-1; and h2 = 0.34 at 2811-2834 cm-1, respectively). The absorbance values of wavenumbers were moderately correlated with the estimated heritabilities. After the Bonferroni correction, a total of nine markers were found to be significantly associated with 32 different wavenumbers. Of particular interest was the SNP s63269.1, mapped on chromosome 2, that was found to be associated with 27 wavenumbers. Genes previously found to be related to traits of interest (e.g. disease resistance, milk yield and quality, cheese firmness) are located close to the significant SNP. As expected, the heritability estimated for the absorbance of each wavenumbers seems to be associated with the related milk components.

Phenotypic and genetic characterisation of methane emission predicted from milk fatty acid profile of Sarda dairy ewes

Individual methane emissions are a potential breeding goal for selection plans aimed at improving the sustainability of ruminant farming systems. However, a large-scale recording of individual methane emissions is hampered by the high costs of the equipment and the logistics of the experiments. Equations have been developed to predict methane emissions in dairy cattle based on variables such as dry matter intake (DMI), gross energy intake, body weight and milk fatty acids (FAs) profile. No equations are currently available for dairy sheep. The aims of this study were: (i) to estimate the enteric methane yield (eMY, expressed as g/kg of DMI) and enteric methane intensity (eMI, expressed as g/kg of FPCM) of dairy sheep using equations developed for dairy cattle that consider as predictors milk FA; (ii) to evaluate the effect of stage of lactation, parity and month of lambing on eMY and eMI; (iii) to estimate the heritability of eMY and eMI. For this purpose, 964 individual milk samples from Sarda dairy ewes were analysed for milk composition and FA profile. Nine different equations were used to predict eMY and eMI. Values of eMY ranged from 19.4 g/kg to 20.4 g/kg of DMI, whereas values of eMI ranged from 15.1 g/kg to 21.0 g/kg of DMI, respectively. Stage of lactation was an important factor in the variability of eMY (p < .01). Indeed, this trait increased towards the end of lactation. Both eMY and eMI were negatively correlated with milk yield, lactose concentration and urea and positively correlated with fat concentration and NaCl, respectively. Heritability of eMI and eMY estimated using a single trait model was 0.13 ± 0.05 and 0.05 ± 0.04, respectively. The values of heritability estimated for eMY using a bivariate models ranged from 0.10 to 0.16 and they were higher than the value estimated for eMI. Results of the present study, even if based on prediction equations developed for cows, increased the knowledge about the phenotypic and genetic background of methane emissions in Sarda dairy sheep.

The heavy suckling lamb of Sarda dairy sheep and its crossbreed with Dorper rams: Performance, meat quality and consumer perceptions

The increase of meat production in dairy sheep farms, has been evaluated by the extension of the suckling period from the traditional 28 days to 75 days to obtain a new product, the heavy suckling lamb. Nineteen single-born Sarda (S) lambs (10 male, 9 female) and 20 single-born Dorper x Sarda (DS) lambs (9 male, 11 female), randomly selected from autumn lambing season, were fed exclusively with maternal milk until slaughtering at 20 ± 0.28 kg of body weight (BW, mean ± standard deviation, SD) and approximately 11 weeks of age. Body weight were recorded at birth and every 15 days until slaughter to estimate average daily gain (ADG). At slaughter, carcass measurements, pH and colour traits were recorded from the left side of the carcass. Proximate composition, fatty acid (FA) profile, cooking and drip losses were evaluated using the Longissimus thoracis et lumborum (LTL) muscle. In addition, Visual Panel Test (VPT) and Taste Panel Test (TPT) were performed. Experimental results evidenced that ADG did not differ between pure and crossbreed lambs and between sexes. The S lamb carcasses showed a higher fat content and rib fat thickness compared to that of crossbreed. No significant differences were found between genetic types and sex for colour and pH determinations, cooking and drip losses, whereas LTL fat of DS displayed a higher nutritional FA profile with higher content of 22:5n-3, 22:6n-3, branched-chain FA, and odd- and branched chain FA. No differences emerged during VPT and TPT, demonstrating that both DS and S lamb meats present no distinguishable visual and eating quality characteristics. The production of heavy suckling lambs from Sarda and Dorper crossbreed by the extension of suckling period appeared a promising strategy for producing meat of high quality, well appreciated by the consumers.

Understanding the phenotypic and genetic background of the lactose content in Sarda dairy sheep

Lactose, the principal carbohydrate found in milk, plays an important role in the physiological processes of milk production because it is related to milk volume, and it is responsible for the osmotic equilibrium between blood and milk in the mammary gland. In this study, factors affecting lactose content (LC) in sheep milk are investigated. For this purpose, 2,358 test-day records were sampled from 509 ewes (3-7 records per animal). The LC and other main milk traits were analyzed using a mixed linear model that included days in milk (DIM) class, parity, lambing month, and type of lambing as fixed effects and animal, permanent environment, and flock test day as random effects. The pedigree-based approach was used to estimate the heritability and repeatability of LC. Moreover, the genomic background of LC was investigated through a GWAS. The LC was affected by all tested factors (i.e., DIM class, parity, lambing month, and type of lambing). Low heritability (0.10 ± 0.05) and moderate repeatability (0.42 ± 0.02) were estimated for LC. High negative genetic correlations were estimated between LC and NaCl (-0.99 ± 0.01) and between LC and somatic cell count (-0.94 ± 0.05). Only 2 markers passed the chromosome-wide Bonferroni threshold. Results of the present study, although obtained on a relatively small sample, suggest the possibility to include LC in the breeding programs, particularly because of its strong relationship with NaCl and somatic cell count.

Dry Matter Intake Prediction from Milk Spectra in Sarda Dairy Sheep

Individual dry matter intake (DMI) is a relevant factor for evaluating feed efficiency in livestock. However, the measurement of this trait on a large scale is difficult and expensive. DMI, as well as other phenotypes, can be predicted from milk spectra. The aim of this work was to predict DMI from the milk spectra of 24 lactating Sarda dairy sheep ewes. Three models (Principal Component Regression, Partial Least Squares Regression, and Stepwise Regression) were iteratively applied to three validation schemes: records, ewes, and days. DMI was moderately correlated with the wavenumbers of the milk spectra: the largest correlations (around ±0.30) were observed at ~1100-1330 cm-1 and ~2800-3000 cm-1. The average correlations between real and predicted DMI were 0.33 (validation on records), 0.32 (validation on ewes), and 0.23 (validation on days). The results of this preliminary study, even if based on a small number of animals, demonstrate that DMI can be routinely estimated from the milk spectra.

Essential and Toxic Mineral Content and Fatty Acid Profile of Colostrum in Dairy Sheep.

Simple SummaryColostrum is of interest to the scientific community because of its nutritional and therapeutic capabilities. The aims of this study were to characterize the macro and micro composition of colostrum from Sarda dairy sheep and to compare it with the composition of the mature milk of the same breed. The results of this survey showed a large variation in the immunoglobulin concentration in colostrum, which could affect the acquisition of passive immunity by lambs. The strong correlation between immunoglobulin G and the total protein content suggests that this can be used to estimate the immunoglobulin content in sheep colostrum. The concentration of essential minerals is higher in colostrum than in milk as a result of mineral salt block supplementation at the end of gestation. Colostrum has a significantly different fatty acid profile than milk, and this is due to the specific needs of newborn lambs.Colostrum is a major source of immunity in ruminants. It allows the transfer of antibodies from the mother to the fetus, and it is the exclusive source of nutrients for the newborn. The objectives of this study were (i) to characterize the macro and the micro composition of colostrum; (ii) to analyze the antioxidant capacity, fatty acid profile, and essential and toxic mineral content of colostrum; and (iii) to compare FA profiles and the amount of trace elements between colostrum and mature milk. For these purposes, samples of colostrum and milk were collected from a representative sample of animals from eight sheep dairy farms in the north of Sardinia (Italy). Fat, proteins, and seven essential and toxic minerals were measured in all samples of colostrum and milk. Furthermore, the FA profile was also measured in both matrices, while total antioxidant capacity was measured only in colostrum samples. The average amounts of fat and protein (TP) concentration in colostrum were 7.8% and 16%, respectively. Additionally, an average amount of 40 ± 20 g dm−3 was found for immunoglobulin G (IgG). As regards the antioxidant capacity of colostrum, a large variation was observed between samples from different farms for test 2, 2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), which was 30 ± 10% (mean ± standard deviation). High levels of selenium (Se), zinc (Zn), and copper (Cu) were found in colostrum (200 µg kg−1, 25,000 µg kg−1, and 1200 µg kg−1, respectively). A strong positive correlation between TP and IgG was observed (r = 91%). In colostrum, the amount of IgG is positively correlated with Se and Zn, as they are essential minerals to the immune system. The FA profile demonstrated higher levels of medium and long chain fatty acids in colostrum than in mature milk, and this is mainly true for arachidonic acid (ARA), ecosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). This study provided new information on the quality of colostrum in Sarda dairy sheep and showed the different composition of fatty acids between colostrum and mature milk.

Association analysis and functional annotation of imputed sequence data within genomic regions influencing resistance to gastro-intestinal parasites detected by an LDLA approach in a nucleus flock of Sarda dairy sheep

BackgroundGastroinestinal nematodes (GIN) are one of the major health problem in grazing sheep. Although genetic variability of the resistance to GIN has been documented, traditional selection is hampered by the difficulty of recording phenotypes, usually fecal egg count (FEC). To identify causative mutations or markers in linkage disequilibrium (LD) to be used for selection, the detection of quantitative trait loci (QTL) for FEC based on linkage disequilibrium-linkage analysis (LDLA) was performed on 4097 ewes (from 181 sires) all genotyped with the OvineSNP50 Beadchip. Identified QTL regions (QTLR) were imputed from whole-genome sequences of 56 target animals of the population. An association analysis and a functional annotation of imputed polymorphisms in the identified QTLR were performed to pinpoint functional variants with potential impact on candidate genes identified from ontological classification or differentially expressed in previous studies.ResultsAfter clustering close significant locations, ten QTLR were defined on nine Ovis aries chromosomes (OAR) by LDLA. The ratio between the ANOVA estimators of the QTL variance and the total phenotypic variance ranged from 0.0087 to 0.0176. QTL on OAR4, 12, 19, and 20 were the most significant. The combination of association analysis and functional annotation of sequence data did not highlight any putative causative mutations. None of the most significant SNPs showed a functional effect on genes’ transcript. However, in the most significant QTLR, we identified genes that contained polymorphisms with a high or moderate impact, were differentially expressed in previous studies, contributed to enrich the most represented GO process (regulation of immune system process, defense response). Among these, the most likely candidate genes were: TNFRSF1B and SELE on OAR12, IL5RA on OAR19, IL17A, IL17F, TRIM26, TRIM38, TNFRSF21, LOC101118999, VEGFA, and TNF on OAR20.ConclusionsThis study performed on a large experimental population provides a list of candidate genes and polymorphisms which could be used in further validation studies. The expected advancements in the quality of the annotation of the ovine genome and the use of experimental designs based on sequence data and phenotypes from multiple breeds that show different LD extents and gametic phases may help to identify causative mutations.

Effects of melatonin treatment on milk traits, reproductive performance and immune response in Sarda dairy sheep

In ruminants, the role of melatonin in the control of reproductive seasonality is well reported, but it is still little known about its action on milk traits and on the immune system. The aim of this study was to assess the effect of melatonin on milk yield and composition, somatic cell count (SCC), some cytokine blood concentration and reproductive resumption in sheep. One hundred lactating sheep were allocated to two groups (of 50 sheep each), M (treated with melatonin) and C (controls), and exposed to the rams for 50 d. Time period in days from ram introduction to lambing (TRIL) and litter size were recorded. Every 15 d, from 1 March to 30 April, the individual daily milk yield was registered and milk composition and SCC, were analysed. The levels of Interleukin 2 and 6 (IL-2 and 6) and tumour necrosis factor-alpha (Tnf-α) were evaluated every 15 d. The highest fertility rate (p < .01) and the shortest TRIL (p < .05) was recorded in M group. Milk yield and composition were similar between groups. The somatic cells decreased continuously in the treated ewes (p < .01) and increased continuously in untreated ewes (p < .05). IL-2 and IL-6 increased in M group, although no statistical differences were found between groups. Melatonin administration improved reproductive efficiency, did not affect milk yield and composition and decreased somatic cells. This last effect could help to maintain healthy mammary gland and encourage farmers to reduce the use of drugs against mastitis. Highlights Melatonin is involved in different physiological processes, such as the control of reproductive seasonality, milk production and the immune response. Melatonin administration in Sarda sheep did not modify milk yield and composition, decreased SCC and advanced reproductive resumption in spring. Melatonin could be used to strengthen the sheep immune response in order to reduce the use of drugs for both therapeutic and preventive purposes against mastitis.

Association Analysis between SPP1, POFUT1 and PRLR Gene Variation and Milk Yield, Composition and Coagulation Traits in Sarda Sheep.

Simple SummaryThe purpose of our research was to analyze the association between the three candidate genes secreted phosphoprotein 1 (SPP1), protein O-fucosyltransferase 1 (POFUT1) and prolactin receptor (PRLR) with milk production, quality and coagulation properties in 380 Sarda dairy sheep. Results revealed an association between SPP1 and somatic cells count, in line with the function of this gene and with its genomic position. We revealed an association of POFUT1 variation with milk coagulation properties, and PRLR with quality. This information can be useful for future breeding schemes in sheep.Many studies focus on the identification of genomic regions that undergo selective processes, where evidence of selection is revealed and positional candidate genes are identified. The aim of the research was to evaluate the association between positional candidate genes, namely secreted phosphoprotein 1 (SPP1, sheep chromosome Ovis aries OAR6, 36.651–36.658 Mb), protein O-fucosyltransferase 1 (POFUT1, OAR13, 61.006–61.027 Mb) and prolactin receptor (PRLR, OAR16, 38.969–39.028 Mb) with milk yield, composition and coagulation traits. Eight single nucleotide polymorphisms (SNPs) mapping to the three genes were genotyped in 380 Sarda dairy sheep. Statistical analysis revealed an association between SNP rs161844011 at SPP1 (chromosome position Oar_v3 OAR6:36651870, gene region exon 7) and somatic cell score, while POFUT1 SNP rs424501869 (OAR13:61007495, intron 1) was associated with curd firmness both 45 and 60 min after rennet addition (p = 0.015 and p = 0.007, respectively). SNP rs400874750 at PRLR gene (OAR16:39004070, intron 2) had a significant association with lactose content (p = 0.020), somatic cell score (p = 0.038), rennet coagulation time (p = 0.018) and curd firming time (p = 0.047). The outcome of this research confirmed predictions based on genomic studies, producing new information regarding the SPP1, POFUT1 and PRLR genes, which may be useful for future breeding schemes.

Polymorphism of insulin-like growth factor 1 gene and its relationship with reproductive performances and milk yield in Sarda dairy sheep

The aim of this research was to detect polymorphisms within the IGF-I gene in dairy sheep and to verify their influence on milk yield and reproductive performances. Four hundred Sarda ewes in their second lactation were selected from 2 farms. Their reproductive traits (fertility rate, interval in days from ram introduction to lambing and litter size) and milk yield were recorded, from the second to the fourth lactation. DNA was extracted from individual blood samples and subjected to amplification and sequencing of the IGF-I gene 5′ UTR and Exon 3 regions. Three polymorphic sites were recorded at positions g184028491C>G and g184028489C>T of the 5′UTR, and g184023223G>A of the Exon 3. The C allele at position g184028491 showed a significant association with higher fertility rate (P < 0.05) and a shorter interval in days from ram introduction to lambing (P < 0.01). In addition, a significant effect of the CC genotype was found with higher milk yield for P < 0.05 in the second and third lactation, and P < 0.01 in the fourth lactation compared to the other genotypes. Even, AA genotype at position g184023223 of the exon 3 showed a positive significant effect on milk yield for P < 0.05, in the second and third lactation, and for P < 0.01 in fourth lactation compared to the other genotypes. In conclusion the found SNPs showed a significant influence on reproductive performances and milk yield in Sarda sheep breed suggesting a possible application in sheep selection plans.

Small amounts of agro-industrial byproducts in dairy ewes diets affects milk production traits and hematological parameters

The aim of this study was to evaluate the effect of diets containing different dried byproducts on milk yield and composition, and blood hematological parameters of lactating ewes. Thirty-six Sarda dairy sheep at about 120 ± 10 days in milk and with an average pre-trial milk yield of 1720 ± 430 g/day were assigned to 4 experimental groups and fed four different diets: no byproduct (CON), dry tomato pomace (TP), dry grape marc (GM), and exhausted myrtle berries (EMB) supplementation. Feed intake, milk yield, milk composition and hematological parameters were affected by byproduct supplementation of the diet. In particular, ewes fed byproducts combined diets consumed less dry matter compared with the CON (1.88 vs. 1.79 in GM and 1.71 kg in EMB and TP groups) diet daily. The GM group exhibited a larger milk production (+200 g/day), as well as protein (+8.4 g/day) and fat (+5.5 g/day) milk contents compared to the CON group. The EMB group produced less milk compared to CON group (1050 vs. 1220 g/day). The addition of TP did not affect production performance in comparison to CON group. Any significant interaction among dietary treatment and sampling time was observed on daily feed intake, animal performances and milk coagulation properties. The analysis of the hematological profile showed values within the physiological range of the species for all groups, and were used to assess apparent good health conditions of ewes throughout the experiment. In conclusion, 100 g/day of GM in addition to the basal sheep diet allowed to improve milk yield and to maintain the health status of lactating animals.

Genomic selection of milk fatty acid composition in Sarda dairy sheep: Effect of different phenotypes and relationship matrices on heritability and breeding value accuracy

Fatty acid (FA) composition is one of the most important aspects of milk nutritional quality. However, the inclusion of this trait as a breeding goal for dairy species is hampered by the logistics and high costs of phenotype recording. Fourier-transform infrared spectroscopy (FTIR) is a valid and cheap alternative to laboratory gas chromatography (GC) for predicting milk FA composition. Moreover, as for other novel phenotypes, the efficiency of selection for these traits can be enhanced by using genomic data. The objective of this research was to compare traditional versus genomic selection approaches for estimating genetic parameters and breeding values of milk fatty acid composition in dairy sheep using either GC-measured or FTIR-predicted FA as phenotypes. Milk FA profiles were available for a total of 923 Sarda breed ewes. The youngest 100 had their own phenotype masked to mimic selection candidates. Pedigree relationship information and genotypes were available for 923 and 769 ewes, respectively. Three statistical approaches were used: the classical-pedigree-based BLUP, the genomic BLUP that considers the genomic relationship matrix G, and the single-step genomic BLUP (ssGBLUP) where pedigree and genomic relationship matrices are blended into a single H matrix. Heritability estimates using pedigree were lower than ssGBLUP, and very similar between GC and FTIR regarding the statistical approach used. For some FA, mostly associated with animal diet (i.e., C18:2n-6, C18:3n-3), random effect of combination of flock and test date explained a relevant quota of total variance, reducing the heritability estimates accordingly. Genomic approaches (genomic BLUP and ssGBLUP) outperformed the traditional pedigree method both for GC and FTIR FA. Prediction accuracies in the older cohort were larger than the young cohort. Genomic prediction accuracies (obtained using either G or H relationship matrix) in the young cohort of animals, where their own phenotypes were masked, were similar for GC and FTIR. Multiple-trait analysis slightly affected genomic breeding value accuracies. These results suggest that FTIR-predicted milk FA composition could represent a valid option for inclusion in breeding programs.

The effect of different time epoch settings on the classification of sheep behaviour using tri-axial accelerometry

Monitoring behaviour of grazing animals is important for the management of grazing systems. A study was run to discriminate between the main behaviours (grazing, ruminating and other activities) of sheep at pasture wearing a halter equipped with an accelerometer (BEHARUM device), and to identify the epoch setting (5, 10, 30, 60, 120, 180 and 300 s) with the best performance. The BEHARUM device includes a three-axial accelerometer sensor and a force sensor positioned under the lower jaw of the animal. The halter was fitted to eight Sarda dairy sheep that rotationally grazed either a spatial association (mixture) or a time association of berseem clover (Trifolium alexandrinum L.) and Italian ryegrass (Lolium multiflorum Lam.) for 6 h day−1. The behaviour of the animals was also video-recorded. The raw acceleration and force data were processed for each epoch setting to create 15 variables: the mean, variance and inverse coefficient of variation (ICV; mean/standard deviation) per minute for the X-, Y-, Z-axis and force, and the resultant. Multivariate statistical techniques were used to discriminate between the three behavioural activities: canonical discriminant analysis (CDA), and discriminant analysis (DA). To validate the derived discriminant functions, a bootstrap procedure was run. To evaluate the performance of DA in discriminating between the three activities, the sensitivity, specificity, precision, accuracy and Coehn’s k coefficient were calculated, based on the error distribution in assignment. Results show that a discriminant analysis can accurately classify important behaviours such as grazing, ruminating and other activities in sheep at pasture. The prediction model has demonstrated a better performance in classifying grazing behaviour than ruminating and other activities for all epochs. The 30 s epoch length yielded the most accurate classification in terms of accuracy and Coehn’s k coefficient. Nevertheless, 60 and 120 s may increase the potential recording time without causing serious lack of accuracy.

Effect of winter and spring meteorological conditions on milk production of grazing dairy sheep in the Mediterranean environment

This three-year study evaluated the effects of winter and spring meteorological conditions on milk production of grazing dairy sheep in Mediterranean conditions, in order to define optimal and critical thresholds, quantify milk yield reductions due to environmental stress, and evaluate the immediate or delayed effects of meteorological factors (MF). Milk production was recorded twice a day (7:00 and 15:00) throughout the lactation period (January–June) in three flocks (FL) kept in the same experimental farm but grazed different pasture areas. The first flock (FLNA) was composed of Nera di Arbus dairy ewes managed conventionally; the second flock (FLSD) was composed of Sarda dairy ewes managed conventionally; and the third flock (FLORG) was a mixed flock of Nera di Arbus and Sarda dairy sheep raised under organic management. Daily MF and some biometeorological indices, i.e. Wind Chill Index (WCI), Temperature Humidity Index (THI) and derived indices, were evaluated by using hourly data recorded 24h before the last milking of each day and also 1, 2 and 3days before milking in winter and spring. Data on main MF associated with the morning and afternoon milkings were analyzed using the hourly data from 15:00 of the previous day to 6:00 of the day of milking and from 7:00 to 14:00 of the day of milking, respectively. The interaction between FL and MF was not significant in winter and spring. Milk yield was influenced by most of the MF studied, especially minimum, average and maximum air temperature in both seasons and, to a lesser extent, permanence at temperatures below 0°C and 3°C in winter and above 25°C in spring. The highest milk yield was related to the following optimal ranges: 6–12°C (Tmin), 6–15°C (Tavg) and 12–21°C (Tmax) in winter and 9–12°C (Tmin), 12–18°C (Tavg) and 15–24°C (Tmax) in spring. In winter, daily milk yield was negatively affected by WCI and the persistency of WCI at values lower or equal to −1. In spring, milk yield decreased at average and maximum THI higher than 65 and 68, respectively, and as hours of permanence at Mild-Discomfort level and Discomfort level increased. Wind speed equal to or higher than 2.5m/s in winter and 4m/s in spring and maximum wind speed equal to or above 8m/s in both seasons were detrimental to milk yield. Average wind values between 1.5 and 4m/s had a beneficial effect in spring. Radiation above 24MJ/m2 was detrimental to milk yield in spring, whereas rain had a negative effect only in winter. Milk yield reductions were as high as 19% for Tmax, 17% for Tavg and 15% for minimum WCI (WCImin) in winter, and 19% for Tmax, and 17% for both Tmin and maximum THI (THImax) in spring. The ewes responded immediately (0d and 1d) to almost all unfavourable conditions in winter, whereas the timing of responses was more variable during spring. A lag-effect of rainfall was detected. The 0–2d period before milking was the most influencing for most relevant MF in both seasons. When comparing the morning and afternoon milkings, the dairy ewes were more sensitive to low temperatures before the afternoon milking in winter, and to higher temperatures before the morning milking in spring. In conclusion, thermal stress caused reductions in milk yield in winter and spring, emphasizing the importance of adopting proper management practices to relieve the negative effects of stressful weather conditions on milk yield of grazing dairy sheep in the Mediterranean region.

Genetic analysis of coagulation properties, curd firming modeling, milk yield, composition, and acidity in Sarda dairy sheep

Sheep milk is an important source of food, especially in Mediterranean countries, and is used in large part for cheese production. Milk technological traits are important for the sheep dairy industry, but research is lacking into the genetic variation of such traits. Therefore the aim of this study was to estimate the heritability of traditional milk coagulation properties and curd firmness modeled on time t (CFt) parameters, and their genetic relationships with test-day milk yield, composition (fat, protein, and casein content), and acidity in Sarda dairy sheep. Milk samples from 1,121 Sarda ewes from 23 flocks were analyzed for 5 traditional coagulation properties by lactodynamographic tests conducted for up to 60min: rennet coagulation time (min), curd-firming time (k20, min), and 3measures of curd firmness (a30, a45, and a60, mm). The 240 curd firmness observations (1 every 15 s) from each milk sample were recorded, and 4 parameters for each individual sample equation were estimated: rennet coagulation time estimated from the equation (RCTeq), the asymptotic potential curd firmness (CFP), the curd firming instant rate constant (kCF), and the syneresis instant rate constant (kSR). Two other derived traits were also calculated (CFmax, the maximum curd firmness value; and tmax, the attainment time). Multivariate analyses using Bayesian methodology were performed to estimate the genetic relationships of milk coagulation properties and CFt with the other traits; statistical inference was based on the marginal posterior distributions of the parameters of concern. The marginal posterior distribution of heritability estimates of milk yield (0.16±0.07) and composition (0.21±0.11 to 0.28±0.10) of Sarda ewes was similar to those often obtained for bovine species. The heritability of rennet coagulation time as a single point trait was also similar to that frequently obtained for cow milk (0.19±0.09), whereas the same trait calculated as an individual equation parameter exhibited larger genetic variation and a higher heritability estimate (0.32±0.11). The other curd firming and syneresis traits, whether as traditional single point observations or as individual equation parameters and derived traits, were characterized by heritability estimates lower than for coagulation time and for the corresponding bovine milk traits (0.06 to 0.14). Phenotypic and additive genetic correlations among the 11 technological traits contribute to describing the interdependencies and meanings of different traits. The additive genetic relationships of these technological traits with the single test-day milk yield and composition were variable and showed milk yield to have unfavorable effects on all measures of curd firmness (a30, a45, a60, CFP, and CFmax) and tmax, but favorable effects on both instant rate constants (kCF and kSR). Milk fat content had a positive effect on curd firmness traits, especially on those obtained from CFt equations, whereas the negative effects on both coagulation time traits were attributed to the milk protein and casein contents. Finally, in view of the estimated heritabilities and additive genetic correlations, enhancement of technological traits of sheep milk through selective breeding could be feasible in this population.

Grape seed and linseed, alone and in combination, enhance unsaturated fatty acids in the milk of Sarda dairy sheep

This study evaluated the effect of dietary inclusion of grape seed and linseed, alone or in combination, on sheep milk fatty acids (FA) profile using 24 Sarda dairy ewes allocated to 4 isoproductive groups. Groups were randomly assigned to 4 dietary treatments consisting of a control diet (CON), a diet including 300g/d per animal of grape seed (GS), a diet including 220g/d per animal of extruded linseed (LIN), and a diet including a mix of 300g/d per animal of grape seed and 220g/d per animal of extruded linseed (MIX). The study lasted 10 wk, with a 2-wk adaptation period and an 8-wk experimental period. Milk FA composition was analyzed in milk samples collected in the last 4 wk of the trial. The milk concentration of saturated fatty acids (SFA) decreased and that of unsaturated, monounsaturated, and polyunsaturated fatty acids (UFA, MUFA, and PUFA, respectively) increased in GS, LIN, and MIX groups compared with CON. The MIX group showed the lowest values of SFA and the highest of UFA, MUFA, and PUFA. Milk from ewes fed linseed (LIN and MIX) showed an enrichment of vaccenic acid (VA), oleic acid (OA), α-linolenic acid (LNA), and cis-9,trans-11 conjugated linoleic acid (CLA) compared with milk from the CON group. The GS group showed a greater content of milk oleic acid (OA) and linoleic acid (LA) and tended to show a greater content of VA and cis-9,trans-11 CLA than the CON group. The inclusion of grape seed and linseed, alone and in combination, decreased the milk concentration of de novo synthesized FA C10:0, C12:0, and C14:0, with the MIX group showing the lowest values. In conclusion, grape seed and linseed could be useful to increase the concentration of FA with potential health benefits, especially when these ingredients are included in combination in the diet.

A partial suckling regime increases milk production in Sarda dairy sheep without affecting meat quality of lambs

The collection of milk from dairy sheep has to be balanced with the need for the sheep to feed their lambs at the start of their lives. In Sardinia the sheep nurse their lambs for the first 30 days of their lives when the lambs are slaughtered to produce the traditional PGI (Protected Geographical Indication) Sardinian lamb. In this study the traditional Total Suckling (TS) system was compared with a Partial Suckling (PS) method in which the sheep were separated from the lambs during the day, milked in the evening, and then were allowed to nurse the lambs overnight. Since the removal of milk enhances milk production, a larger milk yield in the TS group was expected compared to the PS group. The production and composition of the milk were measured during the suckling period and for four weeks after lamb weaning. The growth rates of the lambs and the characteristics of their carcasses were measured after slaughter and an economic evaluation of the milk production to compare the two systems was conducted. Sheep in the Partial Suckling group produced 562g of milk/day more than the sheep in the TS group during the suckling period and 168g/day more milk than the sheep in the PS group after the lambs were slaughtered. This resulted in extra returns of about 10€/ewe compared to the traditional TS technique. Although the milk fat concentration was lower in the milk of the PS sheep during the nursing period (4.6% vs. 6.3%; P<0.01) this rose to 5.4% as soon as the lambs were slaughtered and was not different from that of the TS group (5.6%; P>0.05). There were no significant differences in the characteristics of the carcasses of the two groups of lambs, with the exception of the cold dressing percentage, which was significantly lower in carcasses from the PS group (60% vs. 65.5%; P<0.05). It can be therefore concluded that PS allows harvesting more milk than the TS traditionally adopted by Sardinian shepherds thus resulting in greater returns from the sale of milk. In addition, this rearing system did not affect the production and quality of meat from the lambs.

Effects of grape seed supplementation, alone or associated with linseed, on ruminal metabolism in Sarda dairy sheep

Grape seed is a by-product of the winery and distillery industry which could be used in animal nutrition. To test the hypothesis that dietary supplementation with this by-product can decrease the biohydrogenation (BH) of healthy fatty acids (FA), the present study evaluated the effects of grape seed supplementation, alone or combined with linseed, on ruminal BH processes in dairy sheep. In this 60-d trial, 24 lactating Sarda dairy ewes were assigned to four homogeneous groups and fed as follows: (1) control diet (CON), (2) a diet supplemented with 300g/d per head of grape seed (GS), (3) a diet supplemented with 220g/d per head of extruded linseed (LIN), (4) and a diet supplemented with a mix of both grape seed and linseed (300 and 220g/d per head, respectively) (MIX). Ammonia, pH, volatile fatty acids (VFA) and FA composition were determined in rumen liquor at three sampling dates (20, 40 and 60 d). Rumen pH was not influenced by diet (P>0.05). The ammonia content was increased (P<0.05) in GS and MIX compared with LIN and CON. The molar proportions of acetate and propionate and their ratio were not affected by the diet (P>0.05), whereas the molar proportion of butyrate was the lowest in MIX. Rumenic acid (RA; CLA cis-9,trans-11) concentration increased in GS compared with CON (0.78 vs. 0.45mg/100mg FA; P<0.05), whereas the percentage of vaccenic acid (VA; C18:1 trans-11) tended to increase (P<0.10) in GS compared with CON. The concentration of VA was higher in MIX than in CON (8.18 vs. 3.77mg/100mg FA; P<0.05), whereas RA did not differ between the same groups. The concentration of linoleic acid (LA; C18:2 n–6) decreased and stearic acid (SA; C18:0) increased in all supplemented groups, whereas linolenic acid (LNA; C18:3 n–3) decreased in the two groups receiving grape seed compared with CON and LIN. The concentration of total odd- and branched-chain fatty acids (OBCFA) decreased in all supplemented groups compared with CON (P<0.05), evidencing that grape seed and linseed supplementation influenced the ruminal BH processes. Grape seed was able to increase the accumulation of RA when supplemented alone, and of VA when combined with linseed; however, the rumen accumulation of SA in both groups supplemented with grape seed evidenced that this by-product was not effective in decreasing the BH of dietary polyunsaturated fatty acids (PUFA).

Effects of cooked molasses licking block supplementation pre- and post-partum on feed intake, suckling lamb performance, milk yield and milk quality in dairy sheep. Part 1

This study tested the nutritional benefit of a supplement offered freely to dairy sheep over a period from 60 days before lambing to 60 days after lambing, at stall and grazing. Thirty Sarda dairy sheep on Day 90 of gestation, homogeneous for age, parity number, bodyweight (BW) and body condition score (BCS), were allocated to one of two groups: control (Ctr) or treated (Cry). Over 120 days, both groups received ryegrass hay and concentrate indoors. After weaning, the ewes also had access to pasture for 6 h/day. Throughout the experimental period, the Cry group had ad libitum access to a cooked molasses licking block. No significant differences were observed between the groups in forage, concentrate and total DM intake. During the experiment, the reduction in BCS in early lactation tended to be slower in the Cry than in Ctr group (Ptrend &lt; 0.09), whereas no significant effects were seen on BW. Lamb performance tended to be improved by Cry in terms of liveweight of litter size per sheep (9.65 vs 8.22 kg for Cry and Ctr, respectively; P &lt; 0.07), whereas no significant effects were observed on milk yield and composition, except for a trend for increased fat content in the Cry versus Ctr group (6.15% vs 5.95%, respectively; P &lt; 0.08). Cry ewes had higher blood cholesterol concentrations than did Ctr ewes (1.96 vs 1.63 mmol/L; P &lt; 0.01). Because there were no differences between feed intake at stall and the estimated total DM intake at stall and during grazing between the two groups, the better performance of the Cry group could be explained by an increase of feed use efficiency at the digestive and/or metabolic level.

Effects of short-term feed restriction on milk yield and composition, and hormone and metabolite profiles in mid-lactation Sarda dairy sheep with different body condition score

Ten Sarda dairy ewes (5 with high Body Condition Score: H-BCS, BCS>2.5; BW 48.8±5.4 kg; 5 with low BCS: L-BCS, BCS<2.5; BW 36.2±4.7 kg) were subjected, after 7-day preliminary (Prel) period, to short-term feed restriction (FR, 50% of nutrient requirements) for three days followed by refeeding (Re-Fed, 100% requirements) for three days. Milk yield and composition (protein, fat, lactose, MUN, SCC, fatty acids), and blood parameters (glucose, NEFA, BUN, insulin, GH, IGF-I, leptin) were monitored. Milk yield decreased during FR in both BCS groups: at day 3 it was 38% and 35% of Prel values in H- BCS and L-BCS ewes, respectively, reaching Prel levels at Re-Fed in both groups. Milk fat concentration was influenced by BCS×sampling, increasing in H-BCS ewes during FR, but not varying in L-BCS ewes throughout the trial. During FR, milk protein increased as milk yield decreased. There was no change in milk urea nitrogen concentration during FR, but this decreased in both BCS groups during Re-Fed. FR modified the FA profile of milk fat in both BCS groups, increasing LCFA at the expense of SCFA and MCFA. Some blood parameters (NEFA, GH and IGF-I) were influenced by BCS, whereas almost all parameters were influenced by sampling. There was a rapid return to initial levels in all parameters except milk urea, blood urea and insulin at Re-Fed.