Vudmaska I. Rumen metabolism and its effects on fatty acids profile of cows fed diets with different carbohydrate and lipid composition

The purpose of work were investigation of unsaturated fatty acid biohydrogenation and odd- and branched-chain fatty acids synthesis in the cows rumen and its transformation in the milk gland. Obtained results suggest that high levels of grain concentrate (40 % of DM vs. 20 % of DM in control diet) decreased trans11-18:1 and cis9,trans11-CLA and increased trans10-18:1, trans10,cis12-CLA and cis9,cis12-18:2 fatty acids in cows milk. High level of concentrate slowly reduced milk fat percentage but increased milk yield therefore fat yield was unchanged. When 10 % fiber in diet was replaced by sugar the trans-18:1 and cis9,cis12-18:2 contents in milk were increased. In cows that were fed diets with extruded sunflower cake, extruded soybeans or formaldehyde-treated rapeseed cake the content of polyunsaturated fatty acids in the milk fat was increased. The levels of milk and milk protein yield were risen to 10 %. Addition of rapeseed oil to cows diet increased contents all cis and trans 18:1 isomers in milk except for oleic acid (cis9-18:1). Milk fat of cows fed diet with rapeseed oil contained more cis9,trans11-CLA where as in cows fed diet with calcium salts of fatty acids milk fat contained more cis9,cis12-18:2. Supplementation of diet with calcium salts of fatty acids increased milk yield to 15 %.