Feeding fish oil and condensed corn distillers solubles increases conjugated linoleic acid in milk and modulates immune response in dairy cows

Dairy cows are often subjected to dietary modifications so as to increase the healthful fatty acids in milk. The important fatty acids include conjugated linoleic acid and omega-3/n-3 fatty acids. Conjugated linoleic acid, a naturally-occurring polyunsaturated fatty acid, is found preferentially in ruminant milk and meat. It has potential health benefits such as being anti-carcinogenic, anti-atherogenic, anti-obesity, and anti-diabetic as well as contributing to immune system enhancement in animal models and humans. Since the human body is unable to synthesize conjugated linoleic acid except from vaccenic acid which is also found in ruminant milk and meat, it is important to increase its production in milk. It has been observed that dietary polyunsaturated fatty acids influence the fatty acid composition of inflammatory and immune cells in humans; however, little information is available about the effects of conjugated linoleic acid on the immune system of dairy cattle. We conducted the following experiments, based on the hypothesis that feeding condensed corn distiller solubles and fish oil would increase the conjugated linoleic acid content in milk and that conjugated linoleic acid improves the immune response. Twelve lactating Holstein cows were fed diets containing either fish oil or condensed corn distiller solubles or both in a 4x4 Latin square design. Feeding fish oil or condensed corn distiller solubles resulted in decreased percentages and yield of fat in milk; however, greater concentrations of n-3 fatty acids, conjugated linoleic acid and vaccenic acid in milk were observed. Greater concentrations of vaccenic acid in milk and plasma indicated that endogenous synthesis from vaccenic acid also contributed to conjugated linoleic acid in milk. Immune response was monitored by culturing peripheral blood mononuclear cells with mitogens to measure the proliferation response and cell surface phenotyping by flowcytometry for specific bovine leukocyte markers. Feeding the diet containing both fish oil and condensed corn distiller solubles resulted in decreased T cell mediated immunity and enhanced innate immune response. These results will help dairy producers to establish a nutritional practice for the production of milk rich in beneficial fatty acids resulting in increased net returns and also aid in the development of nutritionally-based therapeutic applications to augment host resistance.