Protein requirements of growing steers limit-fed corn-based diets.

R H Wessels,E C Titgemeyer

doi:10.2527/1997.75123278x

Abstract

In Exp. 1, six steers (254 kg) were used in a 6 x 4 incomplete Latin square to determine the effects of solvent-extracted soybean meal alone or in combination with rumen-protected methionine and lysine on N balance in steers limit-fed a high-corn diet to gain 1.1 kg/d. The basal diet contained (DM basis) 80% rolled corn, 15% alfalfa, and .9% urea (13.9% CP), and 2 or 4% soybean meal replaced corn to give CP concentrations of 14.8 and 15.6%, respectively. Each diet was fed with and without 5 g/d of Smartamine-ML (.75 and 2.0 g of rumen-protected methionine and lysine, respectively). Nitrogen retention increased linearly (P = .09) with level of soybean meal. Rumen-protected methionine and lysine had no effect on N balance. In Exp. 2, seven steers (233 kg) were used in a 7 x 4 incomplete Latin square experiment to investigate optimal levels and sources of CP for steers limit-fed to gain 1 kg/d. Treatments included a negative-control diet (urea; 11.7% CP) and six diets containing either 13.5, 15.4, or 17.2% CP with either solvent-extracted or expeller-processed soybean meal. Diets provided 75, 87.5, 100, or 112.5% of estimated CP requirement for a gain of 1 kg/d. The basal diet contained 83% rolled corn, 15% alfalfa, and .2% urea. Nitrogen retention increased linearly (P = .006) with soybean meal addition, and no differences were observed between CP sources. The CP system underpredicted the protein requirements of limit-fed steers under our conditions.

Highlights

Calves can be grown efficiently on highconcentrat e diets fed at restricted intakes
Because N retention increased to the highest level offered, the steers apparently required more protein than estimated by the 1984 National Research Council' s Nutrient Requirements of Beef Cattle
No significant interactions occurred between level and source of protein, and effects on N balance were similar for SSBM and Expeller-Processed Soybean Meal (ESBM)

Summary

Introduction

Calves can be grown efficiently on highconcentrat e diets fed at restricted intakes. Benefits of restrictedly feeding high-grain diets relative to ad libitum feeding of high-roughage diets include more stable intake patterns, more predictable perf ormance, and reductions in cost of gain. Growing programs aim to restrict energy-allowabl e gain without restricting other nutrients required to support that gain. Compared to a low -energy diet fed at ad libitum intake, a limit-fed high-energy diet requires higher concentrations of dietary protein. Restricted feeding alters ruminal function, which may influen ce optimal levels and sources of protein. Our objectives were to 1) investigate optimum levels of dietar y protein, and 2) compare solvent-extracte d soybean meal (SSBM) and expeller-processe d soybean meal (ESBM) as source s of supplemental protein for limit-fed steers

Objectives

Results

Conclusion