Performance and nutrient metabolism by nursing calves supplemented with limited or unlimited corn or soyhulls.

Five-month-old Angus x Hereford reciprocal crossbred nursing steer calves on fescue pasture were used to determine the effects of 1) limiting supplemental feed intake and 2) soyhulls and corn as sources of supplemental (creep) feed in an 84-d study. The treatments were 1) control (no creep feed), 2) limited intake of corn (1 kg/d), 3) unlimited intake of corn, 4) limited intake of soyhulls (1 kg/d), and 5) unlimited intake of soyhulls. Before weaning, there were no differences in supplemental feed efficiency ([supplemented gain--control gain]/supplement intake) or calf gain between corn or soyhulls. Calf gain before weaning increased linearly (P < .05) as intake of creep feed increased, but supplemental feed efficiency did not differ between limited and unlimited supplements. Feedlot performance by the calves was not affected by any of the previous treatments. Calves that consumed an unlimited level of creep feed had greater (P < .05) quality grades than the control group that did not consume creep feed, but no other carcass traits were influenced by treatment. In a metabolism study, fescue DM intake decreased linearly (P < .001) with increasing levels of creep feed, whereas milk DM intake was not affected by level of creep feed. Digestible DM intake increased linearly (P < .001) with increasing intake of creep feed. No differences (P < .18) were observed in digestible DM intake as a result of creep feed source. Apparent total tract DM digestibility increased (P < .05) with increasing level of creep feed intake but did not differ between sources.(ABSTRACT TRUNCATED AT 250 WORDS)