[Show abstract][Hide abstract] ABSTRACT: Mid-infrared (MIR) spectrometry was used to estimate the fatty acid (FA) composition in cow, ewe, and goat milk. The objectives were to compare different statistical approaches with wavelength selection to predict the milk FA composition from MIR spectra, and to develop equations for FA in cow, goat, and ewe milk. In total, a set of 349 cow milk samples, 200 ewe milk samples, and 332 goat milk samples were both analyzed by MIR and by gas chromatography, the reference method. A broad FA variability was ensured by using milk from different breeds and feeding systems. The methods studied were partial least squares regression (PLS), first-derivative pretreatment + PLS, genetic algorithm + PLS, wavelets + PLS, least absolute shrinkage and selection operator method (LASSO), and elastic net. The best results were obtained with PLS, genetic algorithm + PLS and first derivative + PLS. The residual standard deviation and the coefficient of determination in external validation were used to characterize the equations and to retain the best for each FA in each species. In all cases, the predictions were of better quality for FA found at medium to high concentrations (i.e., for saturated FA and some monounsaturated FA with a coefficient of determination in external validation >0.90). The conversion of the FA expressed in grams per 100 mL of milk to grams per 100 g of FA was possible with a small loss of accuracy for some FA.
Full-text · Article · Nov 2013 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: Milk oligosaccharides (OS)—free complex carbohydrates—confer unique health benefits to the nursing neonate. Though human digestive enzymes cannot degrade these sugars, they provide nourishment to specific commensal microbes and act as decoys to prevent the adhesion of pathogenic micro-organisms to gastrointestinal cells. At present, the limited quantities of human milk oligosaccharides (HMO) impede research on these molecules and their potential applications in functional food formulations. Considerable progress has been made in the study of OS structures; however, the synthetic pathways leading to their synthesis in the mammary gland are poorly understood. Recent studies show that complex OS with fucose and N-acetyl neuraminic acid (key structural elements of HMO bioactivity) exist in goat milk. Polymorphisms in the CSN1S1 locus, which is responsible for synthesis of αs1-casein, affect lipid and casein micelle structure in goat milk. The present study sought to determine whether CSN1S1 polymorphisms also influence goat milk oligosaccharide (GMO) production and secretion. The GMO compositions of thirty-two goat milk samples, half of which were from genotype A/A (αs1-casein producers) and half from genotype O/O (αs1-casein non-producers), were determined with nanoflow liquid chromatography high-accuracy mass spectrometry. This study represents the most exhaustive characterization of GMO to date. A systematic and comprehensive GMO library was created, consolidating information available in the literature with the new findings. Nearly 30 GMO, 11 of which were novel, were confirmed via tandem mass spectrometric analyses. Six fucosylated OS were identified; 4 of these matched HMO compositions and three were identified for the first time in goat milk. Importantly, multivariate statistical analysis demonstrated that the OS profiles of the A/A and O/O genotype milks could be discriminated by the fucosylated OS. Quantitative analysis revealed that the goat milk samples contained 1.17 g/L of OS; however, their concentration in milks from A/A and O/O genotypes was not different. This study provides evidence of a genetic influence on specific OS biosynthesis but not total OS production. The presence of fucosylated GMO suggests that goat milk represents a potential source of bioactive milk OS suitable as a functional food ingredient.
No preview · Article · Apr 2013 · Small Ruminant Research
[Show abstract][Hide abstract] ABSTRACT: Background
S. aureus is one of the main pathogens responsible for the intra-mammary infection in dairy ruminants. Although much work has been carried out to understand the complex physiological and cellular events that occur in the mammary gland in response to S. aureus, the protective mechanisms are still poorly understood. The objectives of the present study were to investigate gene expression during the early response of the goat mammary gland to an experimental challenge with S. aureus, in order to better understand the local and systemic response and to compare them in two divergent lines of goat selected for high and low milk somatic cell scores.
No differences in gene expression were found between high and low SCS (Somatic Cells Score) selection lines. Analysing the two groups together, an expression of 300 genes were found to change from T0 before infection, and T4 at 24 hours and T5 at 30 hours following challenge. In blood derived white blood cells 8 genes showed increased expression between T0 and T5 and 1 gene has reduced expression. The genes showing the greatest increase in expression following challenge (5.65 to 3.16 fold change) play an important role in (i) immune and inflammatory response (NFKB1, TNFAIP6, BASP1, IRF1, PLEK, BATF3); (ii) the regulation of innate resistance to pathogens (PTX3); and (iii) the regulation of cell metabolism (CYTH4, SLC2A6, ARG2). The genes with reduced expression (−1.5 to −2.5 fold) included genes involved in (i) lipid metabolism (ABCG2, FASN), (ii) chemokine, cytokine and intracellular signalling (SPPI), and (iii) cell cytoskeleton and extracellular matrix (KRT19).
Analysis of genes with differential expression following infection showed an inverse relationship between immune response and lipid metabolism in the early response of the mammary gland to the S. aureus challenge. PTX3 showed a large change in expression in both milk and blood, and is therefore a candidate for further studies on immune response associated with mastitis.
[Show abstract][Hide abstract] ABSTRACT: Milk fat secretion is a complex process that initiates in the endoplasmic reticulum of the mammary epithelial cell by the budding of lipid droplets. Lipid droplets are finally released as fat globules in milk enveloped by the apical plasma membrane of the mammary epithelial cell. The milk fat globule membrane (MFGM) thus comprises membrane-specific proteins and polar lipids (glycerophospholipids and sphingolipids) surrounding a core of neutral lipids (mainly triacylglycerols and cholesterol esters). We have recently described major proteins of the MFGM in the goat and we have highlighted prominent differences between goats and bovine species, especially regarding lactadherin, a major MFGM protein. Here, we show that, in the goat species, the well-documented genetic polymorphism at the α(s1)-casein (CSN1S1) locus affects both structure and composition of milk fat globules. We first evidenced that both milk fat globule size and ζ-potential are related to the α(s1)-casein genotype. At midlactation, goats displaying strong genotypes for α(s1)-casein (A/A goats) produce larger fat globules than goats with a null genotype at the CSN1S1 locus (O/O goats). A linear relationship (R(2)=0.75) between fat content (g/kg) in the milk and diameter of fat globules (μm) was established. Moreover, we found significant differences with regard to MFGM composition (including both polar lipids and MFGM proteins) from goats with extreme genotype at the CSN1S1 locus. At midlactation, the amount of polar lipids is significantly higher in the MFGM from goats with null genotypes for α(s1)-casein (O/O goats; 5.97±0.11mg/g of fat; mean ± standard deviation) than in the MFGM from goats with strong genotypes for α(s1)-casein (A/A goats; 3.96±0.12mg/g of fat; mean ± standard deviation). Two MFGM-associated proteins, namely lactadherin and stomatin, are also significantly upregulated in the MFGM from goats with null genotype for α(s1)-casein at early lactation. Our findings are discussed with regard to techno-functional properties and nutritional value of goat milk. In addition, the genetic polymorphism in the goat species appears to be a tool to provide clues to the lipid secretion pathways in the mammary epithelial cell.
No preview · Article · Aug 2012 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: Fat is present in milk as droplets of triglycerides surrounded by a complex membrane deriving from the mammary epithelial cell and called the Milk Fat Globule Membrane (MFGM). In-depth proteomic studies have been published for bovine MFGM proteins. However, to date, only sparse studies exist on MFGM proteins from non-cow milks. The objective of this study was thus to investigate the protein composition of the goat Milk Fat Globule Membrane. MFGM proteins from goat milk were separated by 6% and 10% SDS-PAGE and Coomassie or Periodic Acid / Schiff (PAS) stained. Most of MFGM proteins (mucin-1, fatty acid synthase, xanthine oxidase, butyrophilin, lactadherin and adipophilin) already described in cow milk were identified in goat milk using peptide mass fingerprinting. A prominent difference between the cow and the goat species was demonstrated for lactadherin. Indeed, we have shown that lactadherin from goat milk appears as a single polypeptide chain in 6% SDS PAGE whereas 2 polypeptide chains are easily identified in cattle. In addition, goat MFGM proteins were subjected to 1D-LC-MS/MS (one dimensional gel coupled to tandem mass spectrometry) analysis. This approach led us to identify - with at least 2 unique peptides (Bos Taurus Database)- more than 160 proteins associated with the goat Milk Fat Globule Membrane. Interestingly, integrative analysis of MFGM-associated proteins using DAVID Bioinformatics Resources demonstrated that identified biological processes are not only connected with lipid metabolic processes or exocytosis-related biological processes, but also with G-protein receptor signaling pathway, translation, or regulation of apoptosis, as previously demonstrated for MFGM proteins from bovine milk. These findings may help in the understanding of lipid droplet formation in the goat species, where an apocrine mechanism for milk secretion is hypothesized.
[Show abstract][Hide abstract] ABSTRACT: To know and to control the fine milk composition is an important concern in the dairy industry. The mid-infrared (MIR) spectrometry method appears to be a good, fast and cheap method for assessing milk fatty acid profile with accuracy. Although partial least squares (PLS) regression is a very useful and powerful method to determine fine milk composition from spectra, the estimations are often less accurate on new samples coming from different spectrometers. Therefore a genetic algorithm (GA) combined with a PLS was used to produce models with a reduced number of wavelengths and a better accuracy. Number of wavelengths to consider is reduced substantially by 5 or 10 according the number of steps in the genetic algorithm. The accuracy is increased on average by 9% for fatty acids of interest.
[Show abstract][Hide abstract] ABSTRACT: cinétique d'émission du lait et l'anatomie de la mamelle sont associées à la résistance aux mammites : résultats d'une sélection divergente de brebis sur les comptages de cellules somatiques ALLAIN C. RESUME Les mammites représentent une pathologie majeure des ruminants laitiers de part leur fréquence et l'importance de leurs répercussions économiques. Des programmes d'amélioration génétique de la résistance aux mammites sont développés dans de nombreux pays, et sont basés sur le comptage de cellules somatiques (CCS) comme critère de sélection. Dans l'objectif d'évaluer les conséquences d'une telle sélection, nous avons étudié deux lignées de brebis divergentes (CCS+ et CCS-) produites à l'unité expérimentale INRA de La Fage. Nous avons évalué la résistance aux infections intra mammaires naturelles de ces brebis à l'aide de mesures régulières de CCS, d'examens cliniques des mamelles et de bactériologies du lait. La réponse corrélée de la sélection sur la cinétique d'émission du lait et l'anatomie de la mamelle et des trayons a été évaluée, respectivement, grâce à un automate de contrôle laitier développé par l'INRA et à l'analyse de photographies numériques. L'écart généré entre les deux lignées est équivalent à 3 écart-types génétiques du score de cellules somatiques, soit plus du double de la moyenne géométrique des CCS. La fréquence des prélèvements de lait infectés était significativement supérieure chez les brebis CCS+ par rapport aux brebis CCS-(OR=3,3 [2,5 ; 4,4] en moyenne), et ce, surtout à la mise bas (OR=7,0 [4,2 ; 11,7]). De plus, la plupart des cas de mammites cliniques sont survenus chez les brebis de la lignée CCS+ (25 cas sur 31). De même, la majorité des infections persistantes étaient observées chez les brebis CCS+ (24 cas sur 30) alors que les brebis CCS-n'étaient souvent infectées que brièvement. Les brebis CCS-sont donc plus résistantes aux mammites que les brebis CCS+. L'analyse des données de cinétique d'émission du lait montre que les brebis CCS-présentent un temps de latence significativement plus élevé que les brebis CCS+. Cette caractéristique pourrait conférer aux brebis de la lignée CCS-, une meilleure aptitude à limiter les infections. Par ailleurs, l'analyse des photographies numériques indique que les brebis de la lignée CCS-présentent des mamelles plus hautes et moins décrochées que les brebis de la lignée CCS+. Les relations directes de ces caractéristiques physiologiques et anatomiques avec la fréquence et la durée des infections n'ont toutefois pas pu être clairement établies dans cette étude et doivent être étayées par un plus grand nombre de données. Milk flow patterns and udder anatomy are associated with mastitis resistance: results from a divergent experiment in dairy sheep selected on milk somatic cell counts ALLAIN C. SUMMARY Mastitis is a major health problem in dairy ruminants because of their high frequency and economic importance. Selection programmes based on milk somatic cell counts have been implemented worldwide to improve mastitis resistance. To evaluate the response to such a selection, we studied two divergent lines of ewes (SCC+ and SCC-) created at the INRA experimental unit of La Fage. Resistance to natural intra mammary infections was evaluated based on regular measures of milk SCC, milk bacteriological analyses and clinical mammary examinations. Correlated response of SCC-based selection on milk flow patterns was evaluated with an automatic milk-recording device, designed by INRA. Correlated response on udder anatomy was evaluated using digital photography. Regarding cell counts, the difference between lines was equal to 3 genetic standard deviations for the SCS trait. Infected milk samples were significantly more frequent in the SCC+ line than the SCC-line (OR=3.3 [2.5 ; 4.4] on average). The difference was even higher at lambing (OR=7.0 [4.2 ; 11.7]). Most of the clinical cases (25 out of 31) occurred in the SCC+ line. Also, the majority of persistent infections were observed in SCC+ ewes (24 out of 30) whereas SCC-ewes were often infected only briefly. SCC-ewes are therefore more resistant to mastitis than SCC+ ewes. Analysis of milk flow patterns indicated that the latency time was significantly higher in SCC-than in the SCC+ line. This result might reflect better ability of SCC-ewes to limit intra mammary infections. Analysis of digital photography indicated that SCC-ewes exhibited higher and better attached udders. However, significant relationships of milk flow patterns and udder anatomy with infection status of the udder could not be established. An increased number of records is needed for final conclusions.
[Show abstract][Hide abstract] ABSTRACT: Fat is present in milk as droplets of triglycerides surrounded by a complex membrane derived from the mammary epithelial cell called milk fat globule membrane (MFGM). Although numerous studies have been published on human or bovine MFGM proteins, to date few studies exist on MFGM proteins from goat milk. The objective of this study was thus to investigate the protein composition of the goat MFGM. Milk fat globule membrane proteins from goat milk were separated by 6% and 10% sodium dodecyl sulfate-PAGE and were Coomassie or periodic acid-Schiff stained. Most of MFGM proteins [mucin-1, fatty acid synthase, xanthine oxidase, butyrophilin, lactadherin (MFG EGF-8, MFG-E8), and adipophilin] already described in cow milk were identified in goat milk using peptide mass fingerprinting. In addition, lectin staining provided a preliminary characterization of carbohydrate structures occurring on MFGM proteins from goat milk depending on alpha(S1)-casein genotype and lactation stage. We provide here first evidence of the presence of O-glycans on fatty acid synthase and xanthine oxidase from goat milk. A prominent difference between the cow and the goat species was demonstrated for lactadherin. Indeed, whereas 2 polypeptide chains were easily identified by peptide mass fingerprinting matrix-assisted laser desorption/ionization-time of flight analysis within bovine MFGM proteins, lactadherin from goat milk consisted of a single polypeptide chain. Another striking observation was the presence of caseins associated with MFGM preparations from goat milk, whereas virtually no caseins were found in MFGM extracts from bovine milk. Taken together, these observations strongly support the existence of a singular secretion mode previously hypothesized in the goat.
No preview · Article · Mar 2010 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: In sheep, susceptibility to scrapie is mainly influenced by polymorphisms of the PrP gene. In goats, there are to date few data related to scrapie susceptibility association with PrP gene polymorphisms. In this study, we first investigated PrP gene polymorphisms of the French Alpine and Saanen breeds. Based on PrP gene open reading frame sequencing of artificial insemination bucks (n=404), six encoding mutations were identified at codons 127, 142, 154, 211, 222 and 240. However, only seven haplotypes could be detected: four (GIH(154)RQS, GIRQ(211)QS, GIRRK(222)S and GIRRQP(240)) derived from the wild-type allele (G(127)I(142)R(154)R(211)Q(222)S(240)) by a single-codon mutation, and two (S(127)IRRQP(240) and GM(142)RRQP(240)) by a double-codon mutation. A case-control study was then implemented in a highly affected Alpine and Saanen breed herd (90 cases/164 controls). Mutations at codon 142 (I/M), 154 (R/H), 211 (R/Q) and 222 (Q/K) were found to induce a significant degree of protection towards natural scrapie infection. Compared with the baseline homozygote wild-type genotype I(142)R(154)R(211)Q(222)/IRRQ goats, the odds of scrapie cases in IRQ(211)Q/IRRQ and IRRK(222)/IRRQ heterozygous animals were significantly lower [odds ratio (OR)=0.133, P<0.0001; and OR=0.048, P<0.0001, respectively]. The heterozygote M(142)RRQ/IRRQ genotype was only protective (OR=0.243, P=0.0186) in goats also PP(240) homozygous at codon 240. However, mutated allele frequencies in French Alpine and Saanen breeds were low (0.5-18.5 %), which prevent us from assessing the influence of all the possible genotypes in natural exposure conditions.
Full-text · Article · Mar 2009 · Journal of General Virology