Roughage Amount, Source, and Processing for Diets Fed to Weaned Dairy Calves

Roughage amount, source, and processing were evaluated using Holstein steer calves initially 8 wk of age in four 56-d trials. In all trials, calves were fed a common textured grower diet (20% CP, 12% NDF) based on whole corn and oats, a protein supplement pellet, and liquid molasses. In trial 1, the treatments were 0, 3, 6, or 9% chopped wheat straw (3% CP). Average daily gain, DMI, hip width, and BCS decreased linearly as straw was increased. In trial 2, the treatments were 0, 5, 10, or 15% long alfalfa hay. Average daily gain and hip width decreased linearly as the level of alfalfa hay in the diet increased. In trial 3, the treatments were 0, 3, 6, or 9% chopped grass hay. Average dairy gain, DMI, and hip width changed quadratically as hay increased. Calf ADG, DMI, and hip width change were maximal at 3% grass hay. Calf BCS declined linearly as grass hay increased. In trial 4, the treatments were 7% alfalfa hay fed as either chopped or long hay, and there were no differences in calf performance. When the treatment means of trials 1, 2, and 3 were combined and regression analysis was performed, ADG and DMI declined quadratically as NDF intake increased, but roughage source was not significant. Dry matter intake and ADG declined the most when NDF from roughage exceeded 1.5% of DM.