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Dietary Urea Influences on Digestibility and Utilization of Diets Containing Peanut Skins by Steers¹

University of Georgia^,3, Tifton 31793-0748

Abstract

Metabolism and feedlot trials were conducted to evaluate increased dietary urea as a method of reducing detrimental effects of peanut skin (PS) tannins on nutrient digestibility and finishing steer performance. The PS fed in the trials contained 17.8% crude protein and 20.1% tannin. Urea (.7%) was included in a control (C) diet without PS, and with 15% PS in low-urea (.3%; LUPS), moderate-urea (.7%; MUPS) and high-urea (1.1%; HUPS) diets that contained ground corn and 15% peanut hulls. Apparent digestibility coefficients for dry matter, organic matter and crude protein were higher (P<.05) for the C diet than for PS diets. Fecal N (g/d) was consistently higher (P<.05) for PS diets than for the C diet. Retained N (g/d) was similar for steers fed C and HUPS diets, but lower (P<.05) than C for LUPS and MUPS diets. Average daily gain at 91 d was highest (P<.05) for C steers in the feedlot, intermediate (P<.05) for MUPS and HUPS steers and lowest (P<.05) for LUPS steers. Feed:gain ratio was 97% higher (P<.05) for LUPS steers compared with C steers, but average daily feed intake was similar for all treatments. Rumen fluid propionic acid was lower (P<.05) on all PS diets compared with the C diet on d 90. Plasma urea nitrogen (d 90) was reduced (P<.05) by 48.5, 55.5 and 57.6%, respectively, on LUPS, MUPS and HUPS diets compared with the C diet. The C steers were slaughtered after 91 d with 78% of the carcasses grading USDA Choice; 75% of the steers on each PS diet graded USDA Choice after 140 d. Increasing dietary urea was not effective in overcoming detrimental effects of PS tannins on digestibility and performance of feedlot steers.

¹ Supported by State and Hatch funds allocated to the Georgia Agr. Exp. Sta.

² Dept. of Anim. Sci.

³ College of Agr., Coastal Plain Sta.