Nitrogen-Fertilized Orchardgrass Compared with Alfalfa at Different Levels of Concentrate Feeding for Dairy Cows

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Abstract
N-fertilized orchardgrass and alfalfa were compared with regard to forage intake, milk yield, milk composition and weight changes, using 16 cows over three lactations. Forages were compared at four grain levels (0, 524, 1,048, and 1,572 kg in 245 days). Average forage dry matter intakes in 245 days were 13.5 kg daily on alfalfa and 10.9 kg on orchardgrass (P<0.01). Average daily yield of 4% fat-corrected-milk was 15.3 kg on alfalfa and 13.2 kg on orchardgrass (P<0.05). Average milk fat .percentages were essentially the same on the alfalfa (3.76) and grass (3.72) rations. Average solids-not-fat percentage of milk produced on the grass ration (8.44) was lower (P<0.05) than that on alfalfa (8.53). Changes in body weight indicated that cows utilized more body reserves for lactation when fed the grass ration than when fed alfalfa. Responses to grain levels were similar on both forages. Forage dry matter intake decreased 0.51 [plus or minus] 0.04 kg and yield of 4% fat-corrected-milk increased 0.92 [plus or minus] 0.09 kg for each additional kilogram of grain fed. Response in milk yield with added grain was essentially linear. Higher milk yield among cows of higher potential was primarily associated with their larger size and greater voluntary intake per unit size.