Roughage for Diets Fed to Weaned Dairy Calves

Two trials were conducted to test the effect of low-quality roughage level, roughage source, and CP concentration in diets of 8- to 12-wk-old Holstein steer calves. In trial 1, 96 steers (initially 79 ± 2 kg) were fed daily either A) a free-choice (FC) mixture of 96.5% textured feed (13.5% CP) blended with 4.5% chopped hay, B) a FC mixture of 96.5% textured feed (16.5% CP) blended with 4.5% chopped hay, C) 2.27 kg of 13.5% CP textured feed with FC chopped grass hay, or D) 2.27 kg of 16.5% CP textured feed with FC chopped grass hay. In trial 2, 96 steers (initially 80 ± 1 kg) were fed 16.5% CP diets consisting of a textured diet containing either A) 5% chopped hay, B) 15% chopped hay, C) 5% cottonseed hulls (CSH), or D) 15% CSH. In both trials, calves fed 4.5 or 5% of either dietary roughage had greater ADG than calves fed FC hay or 15% hay or CSH because of reduced intake. In trial 1, ADG was greater for calves fed textured feeds with 16.5% CP than for calves fed feeds with 13.5% CP, regardless of the amount of roughage fed. As-fed textured feed intakes averaged 3.17 kg/d in the low-roughage diets and were more than typical recommendations to limit intake to 2.27 to 2.73 kg/d. Limiting concentrate intake to 2.27 kg/d in 8- to 12-wk-old calves in these trials reduced ADG, and ADG was maximal at 5% roughage in the diet.