Abstract
Seventy-nine Angus x Hereford crossbred steers (avg. wt. 348 kg) were used to determine the effects of energy level, protein level and protein source on perfor-mance of growing steers. The experiment was a completely randomized 2 x 2 x 2 factorial. Diet main effects were: low energy (70% ensiled corn stover) vs high en-ergy (46% ensiled corn stover); low protein (9.5%) vs high protein (12%); and soy-bean meal vs blood meal. Steers were housed and fed individually during the 50 day growth trial. No interactions (P<0.01) were detected among energy level, protein level or protein source. High energy diets improved (P<0.01) rate of gain 62% and feed intake 21% compared to low energy diets. Increasing protein level improved (P<0.03) rate of gain by 20% and feed intake by 5.4%. Use of blood meal, which is a high ruminal escape protein supplement, increased (P <0.15) rate of gain by 9% without affecting feed intake compared to supplemental soybean meal. Results of this trial suggest that increasing protein level to 12% of the diet and the use of a ruminal escape protein source improves performance of steers when they are fed diets containing 46 to 70% corn stover.
INTRODUCTION
Effects of feeding ruminants protein sources differing in ruminal degradability have been reviewed (Chalupa, 1975; Clark, 1975). A substantial amount of research on utilization of slowly degradable protein sources has been conducted (IVIerchen et al., 1979; Stock and Klopfcnstein, 1979; Loerch et at, 1983). Performance was improved when growing cattle were. fed medium en-ergy diets supplemented with slowly degrad-able protein sources. However, when low or high energy diets were fed, cattle often did not respond to protein sources which escape ruminal degradation, Interactions of dietary
energy level and rumen protein degradation were reported by Loerch and Berger (1981). They suggested that soybean meal degrad-ability in the rumen is reduced to a level similar to that of meat and bone meal when high energy diets are fed. In another study, Loerch (1985) reported the effect of meat and bone meal supplementation of diets varying in level of energy and suggested that slowly degradable protein sources are not effective in improving cattle performance unless protein is the limiting factor for growth. Thus energy level may affect protein requirement and the requirement for aru-minal escape protein source. The objective of this study was to determine effects of
1Salaries and research support provided by Stale and Federal Funds appropriated to the Ohio Agric. Res. and Div. Center, Ohio Slate Univ: Journal No, 325-91. Research and the senior author were supported in part by a fellowship from the Food and Agriculture Organization of the United Nations.
