ADDITION OF UNSATURATED FATTY ACIDS IMPROVES DIGESTION OF MID LACTATING DAIRY COWS.

The objective of the present experiment was to evaluate the effect of different unsaturated fatty acids supplementation sources on digestive metabolism, including nutrient intake and total tract digestibility, microbial protein synthesis and ruminal fermentation in lactating dairy cows. Twelve Holstein mid lactating cows (580±20 kg of body weight; mean±SD, with average of 128 days in milk, and milk yield of 25 kg/d), were assigned randomly into three 4x4 Latin squares, fed the following diets: 1) control (CO); 2) refined soybean oil (SO); 3) whole raw soybean (WS) and; 4) calcium salts of unsaturated fatty acids (CSFA). Milk yields were 26.6; 26.4; 24.1 and 25.7 for cows fed CO, SO, WS and CSFA, respectively. Cows fed SO, WS and CSFA had lesser intake of DM, OM, CP, EE, TC, NFC and TDN than cows fed CO. Animals fed unsaturated fatty acids supplementation had higher DM and EE digestibility, when compared to cows fed CO. Fatty acids supplementation increased ruminal pH and decreased NH3-N concentrations, when compared to animals fed CO. Daily allantoin excretion, uric acid, milk allantoin, total purine derivatives, absorbed purines, microbial nitrogen, and microbial efficiency did not differ among cows fed different experimental diets. Diets with whole raw soybeans and soybean oil improved digestive metabolism and increased the concentrations of unsaturated fatty acids in milk. [ABSTRACT FROM AUTHOR]