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Effect of Cattle Size and Protein Level on the Utilization of High Corn Silage or High Grain Rations¹

Michigan State University, East Lansing 48824

Abstract

Two feeding trials were conducted to compare feedlot performance and carcass characteristics when cattle were fed corn silage (HS) or high grain (HG) rations. In trial 1 equal numbers of small (SA) and average framed (AA) Angus, crossbred Chianina (CH), and Holstein (HO) calves were fed HS or HG rations in which supplemental protein requirements were determined by two methods. System 1 (N.R.C.) involved supplementing rations according to National Research Council crude protein recommendations. In System 2 protein supplementation was based on requirements estimated from stage of growth, composition of gain, and estimated growth rate. In trial 2 unselected (UH) and selected Hereford (SH), Charolais x Angus x Hereford crossbred (CAH), and Holstein x Angus x Hereford crossbred (HAH) calves were used to compare HS and HG rations. In trial 2 protein supplementation (System 3) was calculated similarly to System 2, with the exception that estimates of protein utilization efficiency for corn silage and corn grain were lower and higher, respectively, than in System 2.

High grain fed cattle, compared to HS cattle, had higher (P<.05) daily carcass gains, fatter carcasses, and lower cutability. Daily protein and fat gains were greater (P<.05) for HG cattle than for HS cattle.

Daily carcass, fat, and protein gains were higher (P<.05) with NRC than with System 2 supplementation, but carcass quality and cutability were not influenced by protein system (trial 1). High grain steers used ME 34 and 18% more efficiently than HS steers, respectively, with NRC and System 3 supplementation. In System 2 HG steers were 67% more efficient in use of ME than were HS steers. This suggests a protein x energy level interaction on efficiency of ME utilization.

Daily protein gain tended to be greater and daily fat gain less for the larger cattle types compared to average or small framed steers. Only small differences in energetic efficiency were observed among the beef breeds or crosses, but Holsteins were less efficient than beef breeds.

¹ Michigan Agricultural Experiment Station Journal Article No. 8133.

² Present address: Department of Animal Science, North Carolina State University, Raleigh.

³ Present address: Department of Animal Science, Cornell University, Ithaca, NY.

⁴ Department of Animal Husbandry, Michigan State University, East Lansing.