COTTONSEED MEAL OR FEATHER MEAL SUPPLEMENTATION OF AMMONIATED TROPICAL GRASS HAY FOR YEARLING CATTLE

Despite high N intake by cattle consuming ammoniated forages, improvem ents in ADG might be expected by feeding proteins that supply ruminall y available and(or) undegraded intake protein. Growth studies with 220 -kg steers were conducted to evaluate ammoniated hay plus a liquid can e molasses-based supplement containing urea or a combination of urea a nd .07, .14, or .21 kg of CP daily from cottonseed meal (CSM) or feath er 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 simil ar across years, ranging from .21 to .23 kg and .50 to .60 kg, respect ively. In all years for CSM supplementation, and in two of the three y ears for FM supplementation, increasing level of CP supplementation re sulted 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 i n FM. Improved performance by cattle fed ammoniated tropical grass hay may be obtained by feeding a protein supplement that provides preform ed protein that is either moderately or highly resistant to ruminal de gradation. Ruminal degradation characteristics of protein sources may influence efficiency of protein utilization in cattle fed ammoniated t ropical grass hay plus molasses-based supplements.