Cottonseed meal or feather meal supplementation of ammoniated tropical grass hay for yearling cattle.

Despite high N intake by cattle consuming ammoniated forages, improvements in ADG might be expected be feeding proteins that supply ruminally available and(or) undegraded intake protein. Growth studies with 220-kg steers were conducted to evaluate ammoniated hay plus a liquid cane molasses-based supplement containing urea or a combination of urea and .07, .14, or .21 kg of CP daily from cottonseed meal (CSM) or feather meal (FM). Steers grazed dormant pasture and were fed hay plus 1.36 kg of DM daily per steer of the supplement. In each of 3 yr, total DM intake was similar (P > .60) among treatments, averaging 3.0% of BW. Daily gain by steers supplemented with urea and maximum ADG were similar across years, ranging from .21 to .23 kg and .50 to .60 kg, respectively. In all years for CSM supplementation, and in two of the three years for FM supplementation, increasing level of CP supplementation resulted in linear (P < .01) increases in ADG and gain:feed ratio (GF), with no differences (P > .10) between the protein sources. In one year, ADG and GF by steers supplemented with FM were maximized at the .07 kg of CP level, suggesting greater efficiency of protein utilization in FM. Improved performance by cattle fed ammoniated tropical grass hay may be obtained by feeding a protein supplement that provides preformed protein that is either moderately or highly resistant to ruminal degradation. Ruminal degradation characteristics of protein sources may influence efficiency of protein utilization in cattle fed ammoniated tropical grass hay plus molasses-based supplements.