Milk fat as a source of bioactive compounds

One type of large and intricate post-translational modification of milk proteins that has significant biological implications is phosphorylation. The characterization of phosphoproteins found in the bovine milk fat globule membrane (MFGM) is still mostly unknown. Here, label-free phosphoproteomics was used to identify 94 phosphorylation sites from 54 MFGM phosphoproteins in bovine colostrum (BC) and 136 phosphorylation sites from 91 MFGM phosphoproteins in bovine mature milk (BM). αs1-Casein and β-casein were the most phosphorylated proteins in bovine colostrum. In bovine mature milk, perilipin-2 was the protein with the greatest number of phosphorylation sites. The results show that bovine colostrum MFGM phosphoproteins were mainly involved in immune function, whereas bovine mature MFGM phosphoproteins were mainly involved in metabolic function. Plasminogen and osteopontin were the most strongly interacting proteins in colostrum, whereas perilipin-2 was the most strongly interacting protein in bovine mature milk. This work demonstrates the unique alterations in the phosphorylation manner of the bovine MFGM protein during lactation and further expands our knowledge of the site characteristics of bovine MFGM phosphoproteins. This result confirms the value of MFGM as a reference ingredient for infant formula during different stages.

Calcium salts of polyunsaturated fatty acids deliver more essential fatty acids to the lactating dairy cow

Milk fat globule membrane (MFGM) proteins surround the triacylglycerol core comprising milk fat globules (MFG). We previously detected a decrease in the size of fat globules during conjugated linoleic acid (CLA)-induced milk fat depression (MFD), and other studies have reported that some MFGM proteins play a central role in regulating mammary cellular lipid droplet size. However, little is known about the relationship between MFD, MFG size, and MFGM proteins in bovine milk. The aim of this study was to investigate the profile of MFGM proteins during MFD induced by CLA. Sixteen mid-lactating Holstein cows (145 ± 24 d in milk) with similar body condition and parity were divided into control and CLA groups over a 10-d period. Cows were fed a basal diet (control, n = 8) or control plus 15 g/kg of dry matter (DM) CLA (n = 8) to induce MFD. Cow performance, milk composition, and MFG size were measured daily. On d 10, MFGM proteins were extracted and identified by quantitative proteomic analysis, and western blotting was used to verify a subset of the identified MFGM proteins. Compared with controls, supplemental CLA did not affect milk production, DM intake, or milk protein and lactose contents. However, CLA reduced milk fat content (3.73 g/100 mL vs. 2.47 g/100 mL) and the size parameters volume-related diameter D[4,3] (3.72 μm vs. 3.35 μm) and surface area-related diameter D[3,2] (3.13 μm vs. 2.80 μm), but increased specific surface area of MFG (1,905 m2/kg vs. 2,188 m2/kg). In total, 177 differentially expressed proteins were detected in milk from cows with CLA-induced MFD, 60 of which were upregulated and 117 downregulated. Correlation analysis showed that MFG size was negatively correlated with various proteins, including XDH and FABP3, and positively correlated with MFG-E8, RAB19, and APOA1. The results provide evidence for an important role of MFGM proteins in regulating MFG diameter, and they facilitate a mechanistic understanding of diet-induced MFD.

Canine pancreatic responses to intestinally perfused fat and products of fat digestion.

Effect of dietary fat supplements on levels of n-3 poly-unsaturated fatty acids,<i>trans</i>acids and conjugated linoleic acid in bovine milk

Location of glycoproteins on milk fat globule membrane by scanning and transmission electron microscopy, using lectin-labelled gold granules

Similarity index and soap forming capacity in milk fat- and OPO-containing infant formulas

Effectiveness of extruded rapeseed associated with an alfalfa protein concentrate in enhancing the bovine milk fatty acid composition

Annual rhythms of milk and milk fat and protein production in dairy cattle in the United States

Cardiovascular diseases (CVD) are the leading cause of mortality worldwide, with impaired lipids levels being a significant risk factor (1). This meta-analysis provides comprehensive insights on the impact of bovine dairy-derived milk fat globule membrane (MFGM) supplementation on blood lipid profiles in adults. A systematic search was conducted across various databases (including PubMed, Scopus, Web of Science, the Cochrane Library, Google Scholar, ACS Publications, Academic Search Index, BMJ Journals, BNP Media, and others) up until March 2024, resulting in the inclusion of six trials with a total of 464 participants. The findings indicate that MFGM phospholipid supplementation may significantly reduce total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol levels. A combined analysis of the effects on TC, LDL and triglycerides (TG) revealed a significant overall reduction in these markers (SMDs = −0.174; 95% CI: −0.328~−0.021; p = 0.026; I2 = 0%). However, no significant increase or reduction was observed for high-density lipoprotein (HDL) (SMDs = 0.019; 95% CI: −0.289~0.326; p = 0.906; I2 = 95.5%) and TG levels (SMDs = −0.083; 95% CI: −0.198~0.033; p = 0.160; I2 = 0%). Overall, these results suggest that MFGM supplementation could be a promising dietary intervention for improving lipid profiles in adults. Nonetheless, further research is warranted to confirm these results and to better understand the potential variability in the impact of MFGM on blood lipid levels.

Cardiovascular diseases (CVDs) are the leading cause of mortality worldwide, with dyslipidemia being a significant risk factor. This meta-analysis provides a comprehensive evaluation of the impact of bovine dairy-derived milk fat globule membrane (MFGM) supplementation on blood lipid profiles in adults. A systematic search was conducted across various databases up until March 2024, resulting in the inclusion of 6 trials with a total of 464 participants. The findings indicated that MFGM phospholipid supplementation may significantly reduce total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol levels. A combined analysis of the effects on TC, LDL, and triglycerides (TG) revealed a significant overall reduction in these markers. However, no significant increase or reduction was observed on high-density lipoprotein (HDL) and TG levels. Overall, MFGM phospholipid intake may significantly decrease the level of TC and LDL, while no significant changes in TG and HDL were observed. These results suggest that MFGM supplementation could be a promising dietary intervention for improving lipid profiles in adults. Nonetheless, further research is warranted to confirm these results and to better understand the potential variability in the impact of MFGM on blood lipid levels.

Milk composition and flavor under different feeding systems: A survey of dairy farms

A review was made of the literature concerning the metabolism of fatty acids in the dairy cow, and the potential of increasing the content of the essential fatty acids eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C22:6) in cows' milk. EPA and DHA are two n-3 polyunsaturated fatty acids, which can be synthesised from a-linolenic acid (LNA, C18:3). Both EPA and DHA have anti-thrombotic and anti-carcinogenic effects. The UK Department of Health has recommended that the daily human intake of total n-3 PUFA should be 0.2 g/d, which is approximately double the current average intake. The richest source of dietary EPA and DHA is marine products, but the consumption of fish in the UK is declining. Milk fat consumption constitutes 30% of total fat consumption in the UK diet, and so enhancing the concentration of EPA and DHA in milk fat could be an effective means of increasing the consumption of these fatty acids in the UK. Grass and linseed are rich sources of LNA for dairy cows, while fish oil or marine algae are the richest sources of EPA and DHA. However, a large proportion of these fatty acids ( ca 0.9) are hydrogenated to more saturated fatty acids by the microorganisms in the rumen. The proportion of absorbed n-3 PUFA is therefore only about 7 g/kg ingested n-3 PUFA. Absorbed EPA and DHA are transported around the body as phospholipids, associated with the high-density lipoprotein fraction of the plasma. This fraction is not a good substrate for lipoprotein lipase, which is the enzyme in the mammary gland that removes fatty acids from the circulation for incorporation into milk fat. The uptake by the mammary gland of absorbed EPA and DHA is therefore extremely low. The concentration of EPA and DHA in milk fat therefore remains low even when the diet is enriched with these fatty acids. It is possible that the EPA and DHA present in the milk arise from de novo synthesis of these acids from LNA in the mammary gland. However, while EPA is synthesised from LNA, there appears to be a block on the subsequent synthesis of DHA from EPA. EPA and DHA are not stored in adipose tissue triacylglycerols, and they are not used for oxidative metabolism. There is therefore little competition for circulating EPA and DHA between the mammary gland and adipose tissue, or between secretion and oxidation. There is some potential storage of these acids in the phospholipids of muscle tissue and adipose tissue. Grass is a rich source of LNA, and the LNA content of milk can be enhanced by increasing the herbage content of the diet. This potentially provides more precursors of EPA and DHA. However, increasing the proportion of forage in the diet also tends to increase the extent of rumen biohydrogenation of PUFA as this process is encouraged by higher rumen pH and reduced propionate production. Including either fish oil or some species of marine microalgae in the diet increases the EPA and DHA content of milk. However, these oils can adversely affect rumen function, so that total dry matter intake and milk fat content are reduced. Feeding fish oils to ruminant animals may also not be a sustainable practice in the longer-term. Protecting marine oils from rumen biohydrogenation should prevent the adverse effects on rumen function. However, the evaluation of a protected marine microalgae product suggested that the protection was far from complete, and a reliable means of treating algae to protect it from rumen metabolism still awaits development. Further enhancement of the EPA and DHA content of cows' milk requires more research. Issues, which need to be addressed, are the development of a suitable oil supplement, and a reliable means of protecting it from rumen biohydrogenation. A means of transporting the absorbed EPA and DHA in the circulation so that it is readily taken up by the mammary gland for incorporation into the milk fat also needs to be developed. Changes in the marketing of milk that has been improved in this way would also be required to meet the increased cost of producing this nutritionally enhanced milk.

Breast ovarian cancer susceptibility (BRCA) proteins appear to be involved in cell cycle regulation, DNA repair or genome integrity and induction of apoptosis in a variety of cells from humans and laboratory animals. The BRCA gene and protein have not been identified in cattle. The pattern of BRCA1 gene expression during normal mammary gland development and involution has not been examined in detail in any mammalian species. Therefore, the purpose of the present study was to clone the BRCA1 gene in Holstein dairy cattle and determine if the BRCA1 gene is differentially expressed through various stages of mammary gland development. We also localized immunoreactive BRCA1 protein in bovine mammary cells and milk fat globule membrane. Bovine BRCA1 cDNA was highly conserved to the human. Five hundred base pairs of exon 11 (+3384/ + 3866, human BRCA1 cDNA position) and the C-terminus 1 kb were identical to the human. Seven hundred base pairs of the N-terminus, which contain two ring domains, showed 90 % homology to human BRCA1. In bovine tissues, the degree of BRCA1 gene expression, from highest to lowest , was as follows: liver, spleen, mammary tissues and kidney. The mammary tissues of early pregnancy heifers (3 months) showed much higher mammary gland BRCA1 mRNA expression than other mammary developmental stages. BRCA1 expression declined during the remainder of pregnancy and remained low for lactating cows. However, its expression increased when involution proceeded. Immunohistochemical studies showed that immunoreactive BRCA1 was localized in the nucleus and cytoplasm of mammary epithelial cells from lactating cows. It was not present in myoepithelial cells. The protein was also localized in the milk fat globule membranes. Our data suggest that BRCA1 is involved in bovine mammary gland development and/or differentiation, is specifically localized in secretary epithelial cells and is likely a secreted protein during normal lactation.

Bovine milk fat contains ∼400 different fatty acids, with their relative concentration being highly variable and influenced by (or associated with) intrinsic and extrinsic factors such as diet, breed, and lactation stage. Using predicted fatty acids from milk mid-infrared spectra, the objectives of the present study were to (1) quantify the association between cow parity, lactation stage, breed, heterosis, and recombination loss with milk fatty acid composition, and (2) quantify the association between parental average genetic merit for both milk fat concentration and yield with a series of different fatty acids. The dataset used included 644,752 milk test-day records from 303,089 cows across 2,406 commercial dairy farms. The concentration of 16 individual fatty acids as well as 16 fatty acid indices were predicted from spectral analyses of milk samples. Factors associated with all the investigated traits were individually explored using linear mixed models. The fixed effects considered in all models were the interaction between parity and stage of lactation, the calendar month of test, breed composition, heterosis, and recombination; the random effects were contemporary group and a within-lactation repeated effect. In a separate series of analyses, cow genetic merit for fat yield and fat percentage were separately included in the model as linear covariates. The concentration of the different fatty acids changed throughout lactation and across calendar months, coinciding with the seasonal profile in pasture quality, especially during the summer months. Multiparous cows were characterized by milk with a higher concentration of saturated and short-chain fatty acids, along with a lower concentration of unsaturated, medium-chain, and long-chain fatty acids. Jersey bloodline was associated with a higher concentration of milk saturated and short-chain fatty acids, along with a lower concentration of unsaturated, medium-chain, and long-chain fatty acids compared with Holstein-Friesians. Genetic merit for fat yield or fat percentage was associated with a higher concentration of saturated fatty acids and a lower concentration of unsaturated fatty acids.