Milk composition and feed intake in dairy cows selected for high or low milk fat percentage

Dairy cows, selected for high (HFI) or low (LFI) milk fat percentage but equal fat-corrected milk (FCM) yield, were studied regarding feed intake, milk production, milk composition, body weight and body condition. Forty-eight Swedish Red and Whits breed primiparous and multiparous cows from the selection lines, fed the same diet and milked twice a day, were followed during one lactation. The selection lines produced on average the same total amount of FCM, milk fat and protein. The LFI cows yielded greater milk volume and more total amount of lactose, but the HFI cows had higher percentages of milk fat, total protein and casein. Milli fat from the LFI cows had a smaller proportion of palmitic acid and larger proportions of linoleic and linolenic acids, compared with the HFI cows. No differences in body weight were found, but the LFI cows had more subcutaneous fat over the longissimus dorsi muscle, and tended to have a higher feed intake than the HFI cows. The study indicates that the selection lines differ in metabolism and partitioning of nutrients. (C) 1999 Elsevier Science BN. All rights reserved.