Linoleic acid in milk fat

Jahreis, G., Fritsche, J., Steinhart, H. 1997. Conjugated linoleic acid in milk fat High variation depending on production system. Nutr. Res. 17, 1479-1484. 

Collomb, M., Schmid, A., Sieber, R., Wechsler, D., Ryhanen, E. L. (2006). Conjugated linoleic acids in milk fat variation and physiological effects. International Dairy Journal, 16, 1347-1361. 

It is important to bear in mind when discussing the effect of dairy fat in association to heart disease that dairy products contain many different saturated fatty acids that do not exert the same biological response in terms of, for example, cholesterol levels. The saturated fatty acids in milk fat include shorter and medium chain fatty acids (2 0-10 0), lauric acid (12 0), myristic acid (14 0), palmitic acid (16 0), and stearic acid (18 0). Other fatty acids in milk fat are oleic acid (18 1) and linoleic acid (18 2n-6) as indicated in Table 1.2. 

Oleic acid was increased to 48% of total milk fatty acids by feeding oleamide as a rumen-protected source of oleic acid (Jenkins, 1998). The response was nearly linear up to 5% of supplement in the diet dry matter. Proportions of all de uovo-synthesized milk fatty acids, except butyric, were reduced (Jenkins, 1999). LaCount et al. (1994) abomasally infused fatty acids from canola or high oleic acid sunflower oil into lactating cows. The transfer of oleic acid to milk fat was linear (slope = 0.541 0 350 g infused/ day) the proportion of oleic acid in milk fat increased and proportions of all de novo-synthesized fatty acids, except C4 and C6 decreased. The proportion of Ci8 o also was unchanged. Linoleic acid from canola also was transferred linearly (slope = 0.527 0-90 g infused/day). These transfers from the intestine are nearly identical to that reported by Banks et al. (1976). Hagemeister et al. (1991) reported 42 to 57% transfer of abomasally-infused linolenic acid to milk fat. 

Donovan, D.C., Schingoethe, D.J., Baer, R.J., Ryali, J., Hippen, A.R., Franklin, S.T. 2000. Influence of dietary fish oil on conjugated linoleic acid and other fatty acids in milk fat from lactating dairy cows../ Dairy Sci. 83, 2620-2628. 

Polyenoic acids in milk fat (ca. 3.0% of total FA) comprise mainly linoleic acid and a-linolenic acid and its positional and geometric isomers. Milk fat contains trans- 2 isomers in average amounts of approximately 0.5%. The... 

Abu-Ghazaleh, A.A., Schingoethe, D.J., and Hippen, A.R. (2001) Conjugated Linoleic Acid and Other Beneficial Fatty Acids in Milk Fat from Cows Fed Soybean Meal, Fish Meal, or Both, J. Dairy Sci. 84, 1845-1850. 

Hansen, A. E., Wiese, H. F., Boelsche, A. N., Haggard, M. E., Adam, D.J.D. and Davis, H. 1963. Role of linoleic acid in infant nutrition. Clinical and chemical study of 428 infants fed on milk mixtures varying in kind and amount of fat. Pediatrics 31, 171 — 192. 

Cw-polyenoic acids are present at low concentrations in milk fat, because of the biohydrogenation reactions that take place in the rumen. These acids are comprised almost exclusively of linoleic acid (9c, 12c-18 2), about 1.2 to 1.7% and a-linolenic acid (9c, 12c, 15c-18 3), about 0.9 to 1.2% (Table 1.2). These two fatty acids are essential fatty acids they cannot be synthesised within the body and must be supplied by the diet. In recent times, the usage of the term essential has been extended to include derivatives of these fatty acids, which are not synthesised in significant quantities (e.g., eicosapentaenoic acid, 20 5 and docosahexaenoic acid, 22 6). The proportion of a-linolenic acid appears to be affected by the cow s diet the concentration is higher in milk from pasture-fed cows than in milk from barn-fed cows (Hebeisen et al., 1993 Wolff et al., 1995). In the case of linoleic... 

Kelsey, J.A., Corl, B.A., Collier, R.J., Bauman, D.E. 2003. The effect of breed, parity, and stage of lactation on conjugated linoleic acid (CLA) in milk fat from dairy cows. J. Dairy Sci. 86,... 

Palmquist, D.L., Mattos, W. 1978. Turnover of lipoproteins and transfer to milk fat of dietary (l-Carbon-14) linoleic acid in lactating cows. J. Dairy Sci. 61, 561-565. 

Information on the effect of diet on the production of minor isomers of CLA in the rumen and alterations in their content in milk fat is limited. Diet-induced changes in trans-10, cis-12 CLA have been best described, and its biological effects in the dairy cow will be discussed in Section 3.6.1. Griinari and Bauman (1999) presented a putative pathway for the biohydrogenation of linoleic acid where the initial isomerization involved the cis-9 double bond, thereby resulting in the production of trans-10, cis-12 CLA and trans-10 18 1 as intermediates. As discussed earlier, rumen bacteria have been identified that produce trans-10, cis-12 CLA when incubated with linoleic acid (Verhulst et al., 1987 Kim et al., 2002), and the addition of trans-10, civ-12 CLA to the rumen results in the increased formation of trans-10 18 1 (Loor and Herbein, 2001). 

Chouinard, P.Y., Corneau, L., Barbano, D.M., Metzger, L.E., Bauman, D.E. 1999a. Conjugated linoleic acids alter milk fatty acid composition and inhibit milk fat secretion in dairy cows. /. Nutr. 129, 1579-1584. 

Keeney, M. 1970. Lipid metabolism in the rumen. In Physiology of Digestion and Metabolism in the Ruminant (A.T. Phillipson, ed.), pp. 489-503, Oriel Press, Newcastle-upon-Tyne, UK. Kelly, M.L., Bauman, D.E. 1996. Conjugated linoleic acid A potent anticarcinogen found in milk fat. I roc. Cornell Nutr. Conf. 68-74. 

Offer, N.W., Marsden, M., Dixon, J., Speake, B.K., Thacker, F.E. 1999. Effect of dietary fat supplements on levels of n-3 polyunsaturated fatty acids, trans acids and conjugated linoleic acid in bovine milk. Anim. Sci. 69, 613-625. 

Piperova, L.S., Moallem, U., Teter, B.B., Sampugna, J., Yurawecz, M.P., Morehouse, K.M., Luchini, D., Erdman, R.A. 2004. Changes in milk fat in response to dietary supplementation with calcium salts of trans-18 1 or conjugated linoleic fatty acids in lactating dairy cows. J. Dairy Sci. 87, 3836-3844. 

Parodi, P.W. 1994, Conjugated linoleic acid an anticarcinogenic fatty acid present in milk fat. Aust. J. Dairy Technol. 49, 93-97. 

Milk fat is not a rich source of linoleic (co-6) and linolenic (co-3) acids however, the ratio of w-6 w-3 is close to unity, which is considered to be ideal for good health. Rats fed diets high in milk fat had a beneficial long-chain polyunsaturated fatty acid profile in plasma... 

Fatty acids with two or more conjugated double bonds are found in some plants and animals. In tissues of ruminant animals (and, hence, in meat and dairy products), fatty acids with conjugated diene system were detected as intermediates or by-products in the biohydrogenation of linoleic acid by microorganisms in the rumen. The main isomer, 9-cis, ll-fran -octadecadienoic acid, may account for up to 1% of the total fatty acids of milk fat. 9-cis, ll-fran5-15-cw-octadecatrienoic acid, derived from a-linolenic acid, is present in ruminant tissues only in trace levels. This fatty acid has been shown to have several medical properties, especially anti-cancer and anti-atherosclerosis effects. 

Chouinard, P.Y., Comeau, L., Butler, W.R., Chilliard, Y., Drackley, J.K., and Bauman, D.E. 2001. Effect of dietary lipid source on conjugated linoleic acid concentrations in milk fat. J. Dairy Sci. 

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