Diameter Of Milk Fat Globules Research Articles

The Effect of Milking Frequency, Breed, and Stage of Lactation on the Milk Fat Globule Size and Fatty Acid Composition in Sheep's Milk.

This study examined the effects of milking frequency, breed, and stage of lactation on the milk fat globules (MFG) size and fatty acids (FA) composition of sheep milk. Milk from Karagouniko (n = 13) and Chios (n = 13) ewes was sampled postpartum on the 93rd, 101st, 108th, 121st, 156th, and 188th days of lactation. On the 108th day, the ewes were divided randomly into two milking groups: Once daily at 06:00 a.m. or twice daily at 06:00 a.m. and 16:00 p.m. Morphometric characteristics of MFG and FA composition were determined for each sample. Once versus twice daily milking had no effect on MFG dimensions, which tended to vary according to breed (smaller MFG were secreted from Chios with p = 0.065), while the stage of lactation had a significant effect (p < 0.001). FA composition differed significantly according to the stage of lactation and breed. The FA profile of the Karagouniko breed showed higher concentrations of short-chain FA. The milk samples from late lactation were characterized by higher concentrations of mono-unsaturated FA (MUFA) compared to early and mid-lactation. Moreover, correlations were found between the average diameter of MFG and FA concentrations, where the size of MFG was positively correlated with saturated FA (SFA) and negatively correlated with MUFA.

Feed restriction as a tool for further studies describing the mechanisms underlying lipolysis in milk in dairy cows

Milk lipolysis is defined as the hydrolysis of triglycerides, which are the main component of milk fat. Short-chain fatty acids (FAs) released in milk are responsible for rancid flavour. In addition, the presence of partial glycerides impairs the functional properties of milk, such as foaming and creaming abilities. Milk lipolysis, a key criterion used to assess milk quality, depends on animal parameters and breeding factors. Low-energy diets are associated with higher levels of spontaneous lipolysis, particularly in late lactation. In this study, dairy cows were fed a restricted diet (i.e. 65% of their ad libitum DM intake (DMI)) to induce spontaneous lipolysis in milk and to study milk composition associated with lipolysis. Two groups of 22 cows each received a control diet (100% of ad libitum DMI) or the restricted diet according to a 2 × 2 crossover design. The restricted diet was fed for five days. As expected, feed restriction increased milk spontaneous lipolysis which was associated with an increase in lipoprotein lipase activity. At the same time, milk yield and protein content decreased and no effect was observed on milk fat content. The increase in spontaneous lipolysis was associated with an increase in milk fat globules diameter, without influencing casein micelles diameter. Feed restriction altered the parameters of dairy cow metabolism, with increases in plasma non-esterified FAs, triglycerides and urea, indicating body fat mobilisation and protein catabolism associated with feed restriction. Feed restriction also altered hormonal parameters, with decreases in plasma insulin, insulin-like growth factor 1 and prolactin. As expected, lipolysis was higher in evening milk and was associated with a larger diameter of milk fat globules. This zootechnical approach will be completed with proteomic, lipidomic and transcriptomic studies of milk and/or mammary gland of animals selected for their extreme lipolysis.

Short communication: A decrease in diameter of milk fat globules accompanies milk fat depression induced by conjugated linoleic acid supplementation in lactating dairy cows

Milk fat is secreted from the mammary gland in the form of milk fat globules (MFG). Although milk fat depression has been studied since the beginning of the last century, the extent to which this phenomenon alters MFG synthesis is not fully understood. The aim of this study was to evaluate the effect of conjugated linoleic acid (CLA) on the size and distribution of MFG during milk fat depression in dairy cows. Twelve Holstein cows in mid lactation (145 ± 31 d in milk, 583 ± 34.6 kg of body weight, and 27.2 ± 2.4 kg of milk/d) were randomly assigned to a control diet or control plus Ca-protected CLA at 15 g/kg of dry matter for a 6-d period. The average diameter and particle size distribution of MFG were measured using a Mastersizer 3000 laser particle size analyzer (Malvern Instruments Ltd., Malvern, UK). Feeding CLA did not affect dry matter intake (16.2 ± 0.4 kg/d), milk production (28.4 ± 0.4 kg/d), milk protein, or lactose, but it decreased milk fat content (3.46 vs. 2.52%). In addition, surface area-related mean diameter of fat globules in cows fed CLA was lower compared with controls (3.02 vs. 3.45 μm). The percentage of large fat globules decreased and that of small fat globules increased in response to CLA. Overall, the data suggest that the milk fat depression induced by CLA is accompanied by a decrease in average diameter of MFG.

Phospholipid Composition and Fat Globule Structure I: Comparison of Human Milk Fat from Different Gestational Ages, Lactation Stages, and Infant Formulas.

We compared phospholipids (PLs), PL fatty acid (FA) composition, and milk fat globule size and structure in human milk (n = 120) from mothers of full-term and preterm infants during lactation (colostrum, transition, 1 mo, 2 mo, and 3 mo) and 8 brands of infant formulas. The absolute quantification of PLs was analyzed using 31P NMR spectroscopy. Sphingomyelin was the dominant PLs (35.01 ± 3.31%) in human milk, whereas phosphatidylcholine and phosphatidylethanolamine were the dominant PLs in infant formulas. The PL content in preterm milk increased during lactation, whereas that in term milk remained stable. Saturated FAs (mainly 16:0 and 18:0) were the most abundant (>60%) PL FA in both preterm and term milk and increased throughout lactation. The mean diameter of milk fat globules in infant formulas was much smaller than that found in human milk (200 nm vs 5.63 μm). Significant differences were observed between human milk and infant formulas with regard to PLs, suggesting that more research is needed to mimic the PL profile in infant formulas.

Elevated concentrate-to-forage ratio in dairy cow rations is associated with a shift in the diameter of milk fat globules and remodeling of their membranes

We examined the effects of concentrate-to-forage ratio in dairy cow rations on milk-fat composition, with a specific focus on the structure of milk fat globules (MFG). Twenty-four Holstein cows, 153 d in milk, were assigned to 2 dietary treatments in a crossover design study. Treatments were (1) high-concentrate (65%), low-forage (35%; HCLF) diet and (2) low-concentrate (35%), high-forage (65%; LCHF) diet. The mean diameter of the MFG; plasma concentrations of insulin, glucose, and nonesterified fatty acids (FA); and the composition and concentrations of milk FA and polar lipids were determined. Concentrations of insulin were 56% higher, and those of nonesterified FA 46% lower, in the HCLF than in the LCHF diet. The milk yield was 8.5kg/d higher and yields of fat, protein, and lactose were 180, 350, and 403g/d higher, respectively, in the HCLF versus LCHF diet. Milk FA composition differed between treatments, with 1.5 and 1.0 percentage units higher saturated and polyunsaturated FA concentrations, respectively, in the HCLF versus LCHF diet. Mean MFG diameter tended to be smaller (0.2μm) in the HCLF diet than in the LCHF diet, associated with increased daily phospholipids yield (34%), lower phosphatidylserine and higher phosphatidylcholine concentrations. In conclusion, the decreased milk and fat yields in the LCHF diet were associated with remodeling of the MFG membrane and with the secretion of larger MFG. Membrane remodeling of the mammary epithelium membranes seems to play a role in regulating MFG size.

Body Measures and Milk Production, Milk Fat Globules Granulometry and Milk Fatty Acid Content in Cabannina Cattle Breed

Aim of the study was to achieve scientific information about body measures and milk production of Cabannina cattle, a local breed reared in northern Italy. Fourteen body measures and five morphologic indexes were recorded from 86 heads enrolled in the herd book. Low differences between males and females of the same age-class were shown. Body measures were generally greater than those reported in previous studies, probably due to recent crosses. With reference to milk production, 991 test-day records from 128 lactations of 59 cows were analysed. Average milk daily production was 8 kg/d in 1st lactation to 10.61 in 3rd (P<0.05); the parameters of the Wood equation draw atypical curves with the exception of curves from spring calving cows. Only 74.5% of lactations with an adjusted R2>0.75 showed a standard curve, with low persistence (7.7%), high value of d at peak (103 d) and peak production of 20.18 kg of milk. Moreover, 100 milk samples (40 to 220 d of lactation) were submitted to a granulometric survey by laser scatter technique in order to evaluate the dimensions of fat globules; then milk fat was analyzed by gas chromatography, and desaturase indexes were determined. Cabannina cows showed small fat globules with high specific surface. Furthermore mean diameter of milk fat globules decreased during lactation then rose. Milk fat contained high levels of cis-MUFA, and high desaturase indexes. In conclusion, the low size of Cabannina cattle orients for a limited meat production. Instead milk production has a higher economic potential, aimed at cheese production and human nutrition.

Fat globule membranes in ewes' milk: The main enzyme activities during lactation

A trial was carried out on seven Massese ewes, from which individual milk samples were taken during lactation. All the enzyme activities investigated (oxidase activity of xanthine oxidoreductase, gamma-glutamyltranspeptidase, alkaline phosphatase and 5′-nucleotidase) were affected by the lactation phase, with the exception of the dehydrogenase activity of xanthine oxidoreductase (XOR). A higher oxidase activity (XO) of XOR was found when the diameter of milk fat globules was smaller. In addition, the absence of XO in colostrum led to the hypothesis that its antibacterial role is independent of its activity. The increase in alkaline phosphatase activity during lactation requires further research to better define the criteria for pasteurised sheep milk.

Relationship between the nutritional value of fatty acid profile and the morphometric characteristics of milk fat globules in ewe's milk

Over the last few years the interest of scientists in the nutritional value of milk and dairy products has been increasing as a result of the role of specific components such as individual fatty acids (FAs) in health maintenance and chronic diseases. Milk fatty acid composition has been reported to change with the morphometric characteristics of milk fat globules. Although some studies have investigated the relationship between milk fatty acids and the morphometric characteristics of milk fat globules in cows, this relationship has not been sufficiently explored in ewe's milk.The aim of this study was to check how the nutritional value of fatty acid profile in ewe's milk is linked to changes in the morphometric characteristics of milk fat globules (MFGs).The study involved sampling and analyzing bulk milk from a dairy that collects and manufactures milk from six flocks of Massese ewes. All the ewes were reared in the same area of Tuscany (Italy) and were fed according to a grazing system. Milk samples were taken over a month.Results highlighted a negative correlation between the number of milk fat globules/mL and the average diameter of the MFGs. In addition, the number of MFGs was positively related with n-3 docosapentaenoic acid, long chain FAs, monounsaturated FAs, and the n-3/n-6 ratio. It was negatively related on the other hand, with polyunsaturated fatty acids (PUFAs), n-6 FAs, thrombogenic index and the linoleic/linolenic acid ratio.MFGs >5μm were positively related with lauric and vaccenic acids, with short chain FAs, PUFAs, n-6 FAs, and the linoleic/linolenic ratio; whereas MFGs <2μm were negatively related with PUFAs, n-6 and the linoleic/linolenic ratio.In conclusion, adjusting the average diameter of MFGs could modify the nutritional value of ewe's milk and dairy products, favoring better health effects.

The use of sedimentation field-flow fractionation in the size characterization of bovine milk fat globules as affected by heat treatment

Abstract Size distribution of fat globules affects the appearance, taste and stability of milk and milk-based products. Full-fat, semi-fat and chocolate bovine milk were subjected to heat treatment within a temperature range of 50–125 °C for 1 h. Sedimentation field-flow fractionation was employed to determine the changes in mean particle diameter of milk fat globules as affected by heat treatment. The mean particle diameter of fat droplets increased with increasing heating temperature for most samples. The particle size of fat globules increased on average 40 nm (4.65%) for full-fat and 72 nm (8.52%) for semi-fat milk following the heat treatment (50–125 °C). Chocolate milk exhibited considerable increase in particle size (104 nm, 12.53%) within a certain temperature range (50–110 °C), followed by a decrease in particle size when heated at 125 °C for 1 h. Heat-induced flocculation due to attractive interactions between hydrophobic sites on denatured protein molecules on different droplets was assumed to be mainly responsible for the increases in particle size observed in this study. Extensive heat-induced denaturation of milk proteins was also indicated by Native PAGE. Sedimentation field-flow fractionation proved to be a useful technique for adequately monitoring heat-induced changes in particle size distributions in milk.

Transfer of Dietary Zinc and Fat to Milk—Evaluation of Milk Fat Quality, Milk Fat Precursors, and Mastitis Indicators

The present study demonstrated that the zinc concentration in bovine milk and blood plasma is significantly affected by the intake of saturated fat supplements. Sixteen Holstein cows were used in a 4×4 Latin square design with 4 periods of 12 d, and 4 dietary treatments were conducted. A total mixed ration based on corn silage, grass-clover silages, and pelleted sugar beet pulp was used on all treatments. A high de novo milk fat diet was formulated by adding rapeseed meal and molasses in the total mixed ration [39mg of Zn/kg of dry matter (DM)], and a low de novo diet by adding saturated fat, fat-rich rapeseed cake, and corn (34mg of Zn/kg of DM). Dietary Zn levels were increased by addition of ZnO to 83 and 80mg of Zn/kg of DM. Treatments did not affect daily DM intake, or yield of energy-corrected milk, milk fat, or milk protein. The high de novo diet significantly increased milk fat percentage and milk content of fatty acids with chain length from C6 to C16, and decreased content of C18 and C18:1. Treatments did not influence milk free fatty acids at 4°C at 0 or 28h after milking. The average diameter of milk fat globules was significantly greater in milk from cows offered low de novo diets. Furthermore, the low de novo diet significantly increased the concentration of nonesterified fatty acids and d-β-hydroxybutyrate in blood plasma, the latter was also increased in milk. Treatments did not affect the enzyme activity of lactate dehydrogenase and N-acetyl-β-d-glucosaminidase in milk or the activity of isocitrate dehydrogenase and malate dehydrogenase in blood plasma. The low de novo diet significantly increased plasma Zn and milk Zn content, whereas dietary Zn level did not in itself influence these parameters. This indicates that the transfer of fat from diet to milk might facilitate transfer of Zn from diet to milk.

Relationship between morphometric characteristics of milk fat globules and the cheese making aptitude of sheep's milk

The morphometric characteristics of fat globules from sheep's milk were investigated in order to determine their relationship in terms of milk composition and cheese yield. Bulk milk samples from 13 flocks of Massese ewes were collected and analysed for size and number mL −1 of milk fat globules, and the physico-chemical, hygienic and rheological parameters ( r, k 20, a 30) of milk. Cheese yield (g of cheese per 100 g −1 of milk) and the weight loss of the cheese at 10, 30 and 60 days of ripening were also determined. Negative and significant correlations were found between the value of the average diameter of milk fat globules and the number of fat globules per mL −1 of milk. The morphometric characteristics of milk fat globules were significantly correlated with the percentage of protein, casein, non-fat dry matter, calcium, phosphorus, the value of density, casein to fat ratio, clotting parameters and cheese yield. Worst milk chemical composition, rheological parameters and lower cheese yield were found to be associated with an increased percentage of milk fat globules with a diameter greater than 5 μm.