Milk fat percentage

Akerlind, M., Holtenius, K., Bertilsson, J. and Emanuelson, M. (1999) Milk composition and feed intake in dairy cows selected for high or low milk fat percentage. Livestock Prod. Sci., 59, 1-11. 

In addition to modifying the diets of cows, feeding exogenous CLA directly to cows has also been evaluated to increase the CLA content of milk. However, adverse effects of CLA on milk fat yield were observed. Baumgard et al. (42) reported that specific CLA isomers markedly reduced milk fat synthesis. When cows were given 10 g/d of the c9,Hl or H0,cl2 isomer, the 10,12 CLA supplement caused a 42 and 44% reduction in milk fat percentage and yield, respectively. Not only was de novo milk fat synthesis extensively reduced, but the activity of the A9-desaturase was lowered as evidenced by the increased ratios of 14 0 to 14 1 and... 

The addition of sugar required a different formulation for MCSM from the proportions stipulated by the commodity specification (11). Also, in lieu of the usual procedure of mixing commodities in a given proportion to formulate corn-soy-milk, protein and fat percentage levels of MCSM were set identically to those specified for CC. Cornmeal, defatted soy flour and soy oil proportions were then adjusted by computer to meet these constraints. The vitamin premix provided the antioxidants B.H.A. and B.H.T., each at a level of 0.0022 percent (11) in both blends. 

Hay and Morrison (1970) identified the monoenoic positional and geometric isomers in milk fat and determined the amounts of each total acid class and percentage of trans isomers. The geometric and positional isomers of the monoenes are primarily the result of biohydrogenation of polyunsaturated fatty acids in the rumen. Stearate is also produced, and cis-9-18 l accounts for most of the monoenes. The several positional isomers in trans 16 1 and 18 1 are due to the positional isomerization of double bonds which accompanies elaidinization. 

Many different kinds of milk and milk products are available (USDA 1978 NDC 1976,1983A, 1983B). Milk has two major components fat, including fat-soluble vitamins, and milk-solids-not-fat (MSNF), which contain protein, carbohydrate, water-soluble vitamins, and minerals. The specific nutrient contribution of each of these milk products is related largely to the concentrations of milk fat and MSNF of the product. If the percentages of milk fat and MSNF are known, the values in Table 7.2 may be used to determine the nutrient contribution of a particular milk product. 

Minzner, R. A., Jr. and Kroger, M. 1974. Physicochemical and bacteriological aspects of preserved milk samples and their effect on fat percentages as determined with the Milko-tester. J. Milk Food Technol. 37, 123-128. 

TABLE 1.2 Percentages of the different fatty acids in milk fat... 

The saturated fatty acids that are present in significant quantities in milk fat are molecules with un-branched hydrocarbon chains, which vary in length from 4 to 18 carbon atoms. These fatty acids account for approximately 70 to 75% of the total fatty acids. The most important saturated fatty acid from a quantitative viewpoint is 16 0, which accounts for about 25 to 30% of the total, while two other fatty acids, 14 0 and 18 0 have values in the region 10 to 13% (Table 1.2). The amounts of the short-chain fatty acids, 4 0 and 6 0, are reasonably high when their proportions are expressed as molar percentages (approximately 10 and 5%, respectively—Table 1.2) appreciable amounts of medium-chain length fatty acids (Cs to C12) are also present. 

Giesy, J.G., McGuire, M.A., Shafii, B., Hanson, T.W. 2002. Effect of dose of calcium salts of conjugated linoleic acid (CLA) on percentage and fatty acid content of milk fat in midlactation Holstein cows. J. Dairy Sci. 85, 2023-2029. 

Vallance, W.S., McClymont, G.L. 1959. Depression in percentage of milk fat by parenteral glucose infusion and glycerol feeding. Nature 183, 466-467. 

Figure 8.3. Fatty acid composition of anhydrous milk fat and selected milk fat fractions grouped in short chain, medium chain and long chain saturated fatty acids and unsaturated fatty acids. For definition of fractions, see Figure 8.1. The numbers in the bars give the percentage of the group of fatty acids. Data from Deffense (1987, Table 3).

Fat is a major component in most cheese types, but its level and importance differ markedly with variety. Inter- and intra-variety differences in fat content are affected by a number of factors, including milk composition (particularly ratio of protein to fat), and the cheesemaking process (recipe, manufacturing procedure and technology), which control the levels of milk fat and moisture retained in the cheese curd and the moisture content of the cheese. The ratio of protein-to-fat in the cheese milk is probably the principal factor influencing fat content, as it controls the relative proportions of two of the three major compositional components in cheese, namely protein and fat the third major component is moisture. Owing to the inverse relationship between the percentage of moisture and fat in cheese, as discussed in Section... 

Variations in rate of loss may perhaps be explained or understood by using the percentage of the dose which is secreted. Some workers (10,17) found anywhere from 3 to 30% of the dose excreted in the milk. Our study had a variation in the recovered dose in the milk of from 0.78% in one of the intratracheal one-dose exposures to 32.2% in one of the intravenous six-dose exposures. No correlation was noted between recovered dose and milk fat production, lactation number, stage of lactation, or weight of the cow. There was, of course, a correlation between level of residue in the milk and length of time the residue can be followed in the milk. 

Although nutrition specialists object to excessive consumption of animal fat, this component constitutes a considerable percentage in the global consumption balance. To improve its nutritional value, it is modified with respect to animal lipid composition and properties. The fat present in milk, eggs, and poultry meat is of particular interest. Nutritional modification of the amount and quality of cows milk fat plays an important role and can be effectively performed. However, fat modification by feeding is limited due to the biohydrogenation in rumen, resulting in a lower supply of unsaturated FA from feed. 

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