Compositional profile of ovine milk with a high somatic cell count: A metabolomics approach

Metabolomics-a powerful tool in livestock research

Advancements in the Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) along with recent developments in omics sciences have resulted in a better understanding of molecular mechanisms and pathways associated with the physio-pathological state of the animal. Metabolomics is a post-genomics tool that deals with small molecular metabolites in a given set of time which provides clear information about the status of an organism. Recently many researchers mainly focus their research on metabolomics studies due to its valuable information in the various fields of livestock management and precision dairying. The main aim of the present review is to provide an insight into the current research output from different sources and application of metabolomics in various areas of livestock including nutri-metabolomics, disease diagnosis advancements, reproductive disorders, pharmaco-metabolomics, genomics studies, and dairy production studies. The present review would be helpful in understanding the metabolomics methodologies and use of livestock metabolomics in various areas in a brief way.

Enhanced Goat Milk MUFA Quality via Date Pit Supplementation: A Time-Based Pattern Recognition Analysis Utilizing Agricultural Waste Byproduct

Date pits are agricultural waste byproducts and are available in tons yearly. Milk MUFAs are lipids beneficial for health and sorted out for food product development. This work is aimed at researching the effect of supplementing dairy goats with date pit powder (DPP) as a source of fatty acids (FA), an alternative to enhancing the unsaturated FA in milk and analysed via chemometrics in a 3-month supplementation-based study. Saanen-Boer crossed dairy goats were divided into six groups comprising of control, 10 g and 20 g both for Ajwa DPP (high-quality dates) and Mariami DPP (agricultural waste byproduct), and another 30 g for Mariami DPP only. The supplementation exercise was done daily on each dairy goat. The DPP and milk samples were analysed for its FA profile applying GC-FID and followed by chemometric techniques, namely, PCA and PLS. Results indicated that the n-6/n-3 ratio was the highest for the unsupplemented group compared to the DPP-treated goats with lower n-6/n-3 ratios. The M30 group showcased the most promising health-related class of FAs viewed by 3D PCA and PLS model clustering patterns, in particular monounsaturated FA (MUFA) (C18:1n9c or oleic acid). These results suggest that Mariami DPP supplementation at higher doses and time to lactating Saanen-Boer cross goats can be a means to milk FA quantity and quality enhancement and that chemometrics via pattern recognition can be useful statistical tools when dealing with overwhelming data.

Physiological Aspects of Milk Somatic Cell Count in Small Ruminants—A Review

The aim of this review was to focus on the physiological aspects of milk somatic cell count (SCC) in small ruminants (SM). The SCC is an important component naturally present in milk and is generally used as an indicator of milk quality and udder health in milk producing ruminants. SCC contains the following cells: polymorphonuclear neutrophils (PMN), macrophages, lymphocytes, and many milk epithelial (MEC) cells, cell fragments, and cytoplasmic particles/vesicles. PMN (40–80%) represent the major cell type in milk in healthy uninfected goats, whereas the macrophages (45–88%) are the major cell type in sheep’s milk. However, dairy goats and sheep have an apocrine secretory system that produces cytoplasmic cellular particles/vesicles and large numbers of cell fragments, resulting in the physiological SCC limit being exceeded. It is obvious that the SCC level in milk of SM can be affected by various influencing factors, such as milk fraction, breed, stage of lactation, parity, type of birth, milking system, and others. An increase in the SCC above the physiological level not only indicates an udder or general health problem but reduces milk production, changes the milk composition, and hence affects milk processing. Moreover, the milking machine plays an important role in maintaining udder health in SM and stable SCC at physiological levels in the milk obtained. So far, there are no healthy or pathological physiological SCC levels defined in SM milk. Furthermore, a differential cell count (DCC) or even a high resolution DCC (HRDCC), which were recently developed for cattle milk, could also help in SM to gain deeper insight into the immunology of the mammary gland and find biomarkers to assess udder health. In conclusion, SCC is an indication of udder health or exposure of the udder to infectious agents or mechanical stress and should therefore always be considered a warning sign.

Influence of Functional Feed Supplements on the Milk Production Efficiency, Feed Utilization, Blood Metabolites, and Health of Holstein Cows during Mid-Lactation

A 70-day feeding trial was performed to assess the effect of feeding a mixture of functional feed supplements (FFS; contains encapsulated cinnamaldehyde, condensed tannins, capsaicin, piperine, and curcumin) during mid-lactation on the milk production and composition, feed intake, and blood profile of multiparous dairy cows. Sixty Holstein dairy cows (116.1 ± 17.1 days in milk, 606 ± 9.3 kg BW, and 45.73 ± 6.7 kg/d milk production) were distributed into two trial groups: control (CON: n = 30), which received a basal diet; and FFS (n = 30) treatment, which received a basal diet fortified with the FFS at a rate of 35 g/day/head. The results revealed that daily milk production (p = 0.01) and solids-not-fat yield (p = 0.05) were significantly higher in dairy cows that had received FFS compared with the control group. In addition, the 3.5% fat-corrected milk, energy-corrected milk, lactose and protein yields, and milk energy output tended to be higher (p ≤ 0.10) in dairy cattle that consumed FFS during the experimental period. Significant treatment x period interactions were identified (p ≤ 0.02) with respect to feed efficiency and somatic cell count. Dry matter intake tended to be greater (p = 0.064) in dairy cattle that consumed FFS during weeks 0–2 and 2–4 of the trial period. Most serum biochemical parameters were not changed (p ≥ 0.114) between FFS and control cows. However, a greater concentration of serum albumin (p = 0.007) was observed in cows fed diets supplemented with FFS. In summary, supplementing FFS to lactating Holstein cows during mid-lactation was associated with enhanced lactation performance, feed efficiency, and a tendency to increase feed intake, with no obvious adverse effects.

Nuclear magnetic resonance spectroscopy to investigate the association between milk metabolites and udder quarter health status in dairy cows

Nuclear magnetic resonance spectroscopy was applied to investigate the association between milk metabolome and udder quarter health status in dairy cows. Mammary gland health status was defined by combining information provided by traditional somatic cell count (SCC) and differential SCC (DSCC), which expresses the percentage of neutrophils and lymphocytes over total SCC. Quarter milk samples were collected in triplicate (d 1 to 3) from 10 Simmental cows, 5 defined as cases and 5 defined as controls according to SCC levels at d 0. A total of 120 samples were collected and analyzed for bacteriology, milk composition, SCC, DSCC, and milk metabolome. Bacteriological analysis revealed the presence of mostly coagulase-negative staphylococci in quarter milk samples of cows defined as cases. Nuclear magnetic resonance spectra of all quarter samples were first analyzed using the unsupervised multivariate approach principal component analysis, which revealed a specific metabolomic fingerprint of each cow. Then, the supervised cross-validated orthogonal projections to latent structures discriminant analysis unquestionably showed that each cow could be very well identified according to its milk metabolomic fingerprint (accuracy = 95.8%). The comparison of 12 different models, built on bucketed 1-dimensional NOESY spectra (noesygppr1d, Bruker BioSpin) using different SCC and DSCC thresholds, corroborated the assumption of improved udder health status classification ability by joining information provided by both SCC and DSCC. Univariate analysis performed on the 34 quantitated metabolites revealed lower levels of riboflavin, galactose, galactose-1-phosphate, dimethylsulfone, carnitine, hippurate, orotate, lecithin, succinate, glucose, and lactose, and greater levels of lactate, phenylalanine, choline, acetate, O-acetylcarnitine, 2-oxoglutarate, and valine, in milk samples with high somatic cells. In the 5 cases, results of the udder quarter with the highest SCC compared with its symmetrical relative were in line with quarter-level findings. Our study suggests that increased SCC is associated with changes in milk metabolite fingerprint and highlights the potential use of different metabolites as novel indicators of udder health status and milk quality.

Mastitis pathogens and somatic cell count in ewes milk

The aim of this study was to determine the occurrence of pathogens in selected group of ewes and the relationship between somatic cell count (SCC) and the presence of pathogens. The experiment was carried out on a dairy farm, where predominantly breed was a Tsigai. Sampling was carried out in monthly intervals as part of the milk recording test day from February to July 2019. A total of 303 ewes were included in the survey, during the milk recording test day. The ewes with SCC ≥1000 × 103 cells.mL-1 were selected for further sampling at half udder level. Based on SCC the ewes were divided into five groups: <200 ×103; ≥200 <400 × 103; ≥400 <600 × 103; ≥600 <1000 × 103; ≥1000 × 103 cells.mL-1. The first group of SCC contained 33.9% of milk samples, the second 14.1% of samples, the third 5.7% of samples, the fourth 6.2% and the fifth 40.1% of samples. The most common pathogens were coagulase negative staphylococci (CNS). The most frequent CNS was Staphylococcus (S.) simulans (24.4%). S. aureus was identified in 5.3% of bacteriological positive samples. Almost 70% of ewes with bacteriological positive samples were repeated identified the presence of pathogens during tested period. SCC ≥500 × 103 cells.mL-1  were detected in 92.5% bacteriological positive milk samples. The presence of pathogens increased SCC in milk (p <0.001) as compared to samples free of pathogens. In conclusion, the SCC ≥500 × 103 cells.mL-1 could be important for detection of subclinical mastitis at half udder level in dairy ewes.

Milk yield and somatic cells in dairy ewes with respect to their mutual relations

The objective of this study was to analyze milk yield and somatic cell count (SCC) expressed as somatic cell sore (SCS) in Lacaune dairy breed. Data from milk performance testing recorded between 2016 and 2018 (farm in West Slovakia) were used. A total, 377 individual milk yield and SCC records of 61 ewes (first, second and third lacation, respectively) were analysed. Mixed model for milk yield included fixed factors: SCC class (lowest, low, middle, high and highest), year of measurement, lactation number, month in milk and interaction between month in milk and SCC class, and random factors of ewe and error. Mixed model for SCS included milk yield class (lowest, low, middle, high, highest), year of measurement, lactation number, month in milk and interaction between month in milk and milk yield class. Random factors of ewe and error were considered as well. Milk yield was significantly affected ( p <0.05 or p <0.01) by all investigated factors. Except for interaction between month in milk and milk yield class, the remaining factors significantly affected (p <0.05 or p <0.01) also SCS. The analyses confirmed that SCC may be used as a useful indicator of udder health. It may help in identifying infected ewes, and thus, avoiding mammary infections to be spread throughout the whole flock.

An Untargeted Metabolomic Comparison of Milk Composition from Sheep Kept Under Different Grazing Systems

This study aimed to evaluate the effects of different feedings on main traits and polar and semi-polar metabolite profiles of ovine milk. The milk metabolome of two groups of Sarda sheep kept under different grazing systems were analyzed by gas chromatography coupled with mass spectrometry (GC-MS) and multivariate statistical analysis (MVA). The results of discriminant analysis indicated that the two groups showed a different metabolite profile, i.e., milk samples of sheep kept under Grazing System 1 (GS1) were richer in nucleosides, inositols, hippuric acid, and organic acids, while milk of sheep under Grazing System 2 (GS2) showed higher levels of phosphate. Statistical analysis of milk main traits indicates that fat content was significantly higher in GS1 samples while milk from GS2 sheep had more urea, trans-vaccenic acid, and rumenic acid. MVA studies of the associations between milk main traits and metabolite profile indicated that the latter reflects primarily the long chain fatty acid content, the somatic cell count (SCC), and lactose levels. All together, these results demonstrated that an integrated holistic approach could be applied to deepen knowledge about the effects of feeding on sheep’s milk composition.

Somatic cell count during first and second lactation in ewes

The aim of this study was to describe the frequency of distribution of ewes in SCC groups on the basis SCS (somatic cells score) per lactation and estimate changes of SCC from 1st lactation on 2nd lactation. The experiment was carried at seven farms in 1st observed period (2016 and 2017) and at eight farms in 2nd observed one (2017 and 2018). Within each of periods the same animals were sampled on their 1st and following 2nd lactation in next year of study, only. Totally 1199 milk samples from 159 ewes and 1653 milk samples from 219 ewes were collected during 1st period and 2nd period, respectively. Milk sampling were taken monthly from April to August in both periods. For evaluation only ewes with minimum three sampling per year (minimum six samples per animal) were included in the study within both periods. The ewes were divided into the five SCC groups on basis of their SCS per lactation: G1 = SCC <200 × 103 cells.mL-1, G2 = SCC ≥200 <400 × 103 cells.mL-1, G3 = SCC ≥400 <600 × 103 cells.mL-1, G4 = SCC ≥600 <1000 × 103 cells.mL-1 and G5 = SCC ≥1000 × 103 cells.mL-1. In total statistically significant impact of parity on SCC in 2nd period was detected (p <0.0001) only. From the farm point of view in 1st period only in two farms and in 2nd one in five farms significant effect of parity was found out. Thus in some farms no increase of SCC from first to second lactation was observed. When comparing the changes in SCC from the first to the second lactation in both first and second periods, 6.92% and 10.96%, respectively ewes moved from SCC group G1 to G5. The significant effect of farm management and parity on SCC was demonstrated.

A metabolomics comparison between sheep's and goat's milk

Despite the worldwide consumption of bovine milk, dairy products from small ruminants, such as goat's and sheep's milk, are gaining a large interest especially in the Mediterranean area. The aim of this work was to study the metabolite profiles of 30 sheep's and 28 goat's milk using an untargeted metabolomics approach by a gas chromatography coupled with mass spectrometry (GC-MS) analysis. Results showed several differences in the metabolite profiles: arabitol, citric acid, α-ketoglutaric acid, glyceric acid, myo-inositol, and glycine were more abundant in sheep's milk, while goat's milk had higher levels of mannose-6-phosphate, isomaltulose, valine, pyroglutamic acid, leucine, and fucose. Associations between metabolite profile and milk compositional traits were also found. Predictive capabilities of statistical models indicated a good correlation between the metabolite profile and the protein content in sheep's milk, and with the fat content in goat's milk. This work leads to a better understanding of milk metabolites in small ruminants and their role in the evaluation of milk properties.

Udder types and associated traits affect milk composition and subclinical mastitis in Karayaka sheep

This study was carried out to determine the relationships between udder type and udder traits and milk composition and subclinical mastitis in Karayaka sheep. For this purpose, udder types were determined and udder and teat traits were measured in 32 Karayaka sheep. In addition, milk fat, protein, lactose, dry matter contents, freezing point, SCC and pH were measured. Our results showed that udder type had an effect on right (RTL) and left (LTL) teat length, right (RTDM) and left (LTDM) teat diameter and teat distance (TD). In addition, udder type was found to have an effect on lactose and pH. High or moderate phenotypic correlations were found between teat traits and lactose, freezing point and pH. In addition, of the phenotypic correlations between udder and teat traits, only the correlation between RTL and SCC was significant. SCC showed high phenotypic correlations with fat, lactose, dry matter, protein, freezing point and pH. Our results showed that udder type was effective on teat size, the sheep whose teats were vertical had low milk lactose and high pH, and the sheep with this type of udder were found to have a higher probability of mastitis.

Impact of somatic cell count and lameness on the production and composition of ewe's milk

High somatic cell count (SCC) in milk and lameness are two very serious problems on the farms. The aim of the study was to evaluate the impact of lameness, SCC, month and order of entry into the milking parlour on the milk production and its composition. The relationship between lameness and SCC and their impact on the order of entry was also evaluated. The experiment was carried out at the farm, located in northern Slovakia. The farm keeps sheep crossbred of Improved Valachian and Lacaune. Milking was performed two times a day in milking parlor 1x24. Samples of milk were taken once a month by evening milking: May, July. In May, individual milk samples were taken from 214 random sampling ewes with milk yield minimum 300 mL per milking. In July, only from selected ewes in May, the milk samples, milk yield and lameness were recorded. Order of ewes entry into the milking parlour in milking row (one milking row is 24 animals) was recorded in both months. In total 23 milking rows were recorded. Ewes was divided by lameness (non-lame, slightly lame, strong lame), by SCC (A1 = to 2x105 cells, A2 = from 2x105 to 4x105 cells, A3 = from 4x105 to 7x105 cells, A4 = from 7x105 to 10x105 cells, A5 = over 10x105 cells.mL-1) and by the order of entry of ewes into the milking parlour (in first group of ewes were milked in 1-5 rows, second 6-11, third 12-17, fourth 18-23 ones). No effect of lameness was found out on milk yield. Lameness in July affected the order of entry into milking parlour in July as compared with their order of entry recorded in May. The strong lame ewes entered 4.19  ±1.07 milking rows later in July than in May. Only 11.2% and 4.2% of milk samples were found out in a group with SCC >10x105 cells.mL-1 during May and July respectively. In both months, the production of lactose was lower in groups with higher SCC. Ewes entering into the milking parlour earlier had higher SCC as ewes entering into milking parlour later in July but no effect was seen in May. In conclusion the studies under practical conditions deserve continuous research attention to identify risk factors of management affecting lameness and udder health for further improvement of sheep breeding.