| Popis: |
Sixteen dairy cows over two consecutive 305-day lactations were used to evaluate a diet containing urea, corncobs, and other by-products unsuitable for human consumption. The control ration contained mostly soybean meal, corn, corn silage, and alfalfa. Dry matter digestibilities were 55.4 and 68.6% for urea-cob and standard diets. Apparent digestibility of cobs fed as 87 to 94% of total dry matter intake was 50.2%. Cows on the urea-cob diet produced less total milk (5,940 kg versus 7,307 kg), fat (228 kg, 267 kg), and protein (189 kg, 246 kg) than cows fed soybean meal and corn silage. Dry matter intake was similar (5,432 kg, 5,395 kg) but digestible dry matter intake was lower for the urea-cob diet (3,011 kg, 3,707 kg). From day 40 to day 240 of lactation, essential amino acids tended to increase whereas non-essential amino acids decreased in plasma of cows fed either diet. The upgrading of feed protein already suitable for human consumption to milk protein was 340% for the urea-cob diet whereas there was a possible loss of 30% with the diet containing soybean meal and corn silage. |
