Nitrogen-Fertilized Orchardgrass Compared with Alfalfa at Different Levels of Concentrate Feeding for Dairy Cows1,2

Abstract

Nitrogen-fertilized orchardgrass and alfalfa were compared with regard to forage intake, milk production, milk composition, and weight changes, using 16 cows over three lactations. Forages were compared at four grain levels (0, 524, 1,048, and 1,572kg in 245 days).Average forage dry matter intakes in 245 days were 13.5kg daily on alfalfa and 10.9kg on orchardgrass. Corresponding average daily FCM production was 15.3kg on alfalfa and 13.2kg on orchardgrass. Average milk fat percentages were essentially the same on the alfalfa (3.76) and grass (3.72) rations. Lower intake of the grass forage was associated with a significantly lower SNF percentage in milk produced on that ration (alfalfa 8.53 and grass 8.44). 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±0.04kg and FCM production increased 0.92±0.09kg 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 of forage per unit size.