Urea vs. urea and escape protein for finishing calves and yearlings

Abstract

Three finishing trials, two with calves and one with yearlings, were conducted to evaluate supplementing dry rolled corn-based diets with either urea or a combination of urea and escape protein. In Trial 1, 160 crossbred steer calves (285 ± 5 kg body weight (BW)) were fed (187 days) finishing diets supplemented with urea, soya-bean meal (SBM), urea and feather meal (FTH), or a combination of urea, 2 3 FTH and 1 3 blood meal (BM); (crude protein basis). The FTH and FTH/BM treatments were fed at 50% of the supplemental N with urea supplying the remaining N. Calves supplemented with SBM gained faster and more efficiently ( P < 0.10) during the first 32 days than calves supplemented with other N sources. Over the entire trial, gain and efficiency were not affected ( P > 0.10) by treatment. In Trial 2, 42 crossbred steer calves (255 ± 3 kg BW) were fed (175 days) finishing diets supplemented with SBM or urea and BM (urea and BM supplied equal amounts of supplemental N). Gain and efficiency were not affected ( P > 0.10) by treatment. In Trial 3, 400 yearling steers and heifers (342 ± 5 kg BW) were fed (117 days) diets supplemented with the following sources and percentages of supplemental N: urea 100%; urea 50%, SBM 50%; urea 75%, FTH 25%; urea 50%, FTH 50%; urea 50%, FTH 25%, meat and bone meal 25%. During the first 31 days, cattle gained faster ( P < 0.01) and more efficiently ( P < 0.10) when supplemented with SBM. Over the entire trial, gain and efficiency were not affected ( P > 0.10) by source of supplemental protein. These data indicate that young (7–10 months of age), large-framed calves may gain faster and more efficiently during the early finishing period when supplemented with a combination of escape protein and urea compared with urea alone, but not later in the finishing period. Urea supplementation alone is adequate for rapidly gaining yearling cattle.