Feed Intake and Digestion by Holstein Steers Consuming Low-Protein Forage Supplemented with Different Nitrogen Sources

Abstract

Abstract Duff, G.C, Goetsch, A.L., Park, K.K., Galloway, D.L., Sr., Rinne, M. and Patil, A.R. 1995. Feed intake and digestion by Holstein steers consuming low-protein forage supplemented with different nitrogen sources. J. Appl. Anim. Res., 7: 115–128. Effects of moderate levels of supplements high in rumen undegradable protein and differing in protein quality on intake of low-protein forage by growing steers were determined. Six Holstein steers (205±4.6 and 272±17.6 kg initial and final body weight, respectively), in a 6 x 6 Latin square with 21-d periods, consumed prairie hay (4.8% crude protein, dry matter basis) ad libitum with 0.1% body weight (BW) ground corn (dry matter basis). Steers were not supplemented with additional crude protein (Control) or received (dry matter basis) 0.19% BW soybean meal (S); 0.12% BW feather meal (F); 0.12% BW feather meal plus 0.017% BW urea (F-U); a mixture of feather (0.39% BW), corn gluten (0.051% BW) and blood meals (0.39% BW; FGB); or the FGB supplement plus 0.017% BW urea (FGB-U). Total organic matter intake was increased (P<0.05) by nitrogen supplementation and similar among supplement treatments (4.69, 6.16, 5.82, 5.88, 5.89 and 6.18 kg/d for Control, S, F, f-U, FGB and FGB-U, respectively). Organic matter digestibility and digestible organic matter intake were increased (P<0.05) by supplementation and greater (P<0.05) for S than for the mean of F and FGB, and tended (P<0.09) to be increased by FGB and FGB-U compared with F and F-U (48.7, 56.5, 52.0, 53.0 and F, F-U, FGB and GB-U, respectively). In conclusion, protein quality of feedstuffs high in rumen undegradable protein and supplemented at moderate levels did not alter intake of low-protein forage by growing ruminants regardless of urea supplementation. However, digestible organic matter intake was lower for supplements high in rumen undegradable protein compared with a supplement high in rumen degradable protein.