Effects of the proportion of supplemental dietary crude protein supplied by urea on performance and carcass characteristics of finishing beef cattle fed steam-flaked corn-based diets with Sweet Bran® wet corn gluten feed
Richeson, John T
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An experiment was conducted to examine the effects of urea level in steam-flaked corn-based diets containing 25%) (DM basis) Sweet Bran® wet corn gluten feed (WCGF) on performance and carcass characteristics of beef steers. British x Continental steers were blocked by BW (average initial BW = 402.76 kg ± 10.75; n = 240) and assigned to one of three dietary treatments, which consisted of three different ratios (N basis) of urea:cottonseed meal provided in the supplemental CP: (1) 33%)urea:67%) cottonseed meal (33%); (2) 67%) urea:33% cottonseed meal (67%); and (3) 100%) urea:0%) cottonseed meal (100%). Eight pens per treatment were arranged in a randomized complete block design. Performance and carcass data were analyzed using mixed model procedures of S AS (SAS Institute, Cary, NC), with pen designated as the experimental unit and block as the random effect. There was a quadratic (P = 0.06) effect of the proportion of urea in supplemental CP on ADG from d 0 to 56, as steers fed the 33% diet gained less than cattle fed either the 67 or 100%) treatment. From d 0 to 112, ADG increased linearly (P = 0.09) with increasing proportion of urea provided in the supplement. For the overall feeding period, but especially early in the feeding period, ADG was numerically greatest in the steers fed the diet with 67%) urea:33%) cottonseed meal. Average daily DM intake (DMI) was affected linearly (P = 0.001), by urea level, as cattle fed the 33%) treatment consumed less than those fed the 67 or 100%> treatments from d 0 to 28. For the entire feeding period, DMI tended (P = 0.14) to increase linearly with increasing proportion of urea. There was a quadratic effect on gain:feed ratio from d 0 to end; steers fed the diet containing 67% urea:33%. cottonseed meal gained more efficiently (P = 0.09) than those fed the 33%) diet, whereas gain:feed by steers fed the 100%) treatment did not differ from that of steers in the other two treatments. Furthermore, there was a tendency for a quadratic effect (P = 0.14) of urea level relative to hot carcass weight (HCW). Average HCW was 393.0 kg for the 67% treatment, whereas the 33%) treatment averaged 384.3 kg, with an intermediate value of 390.5 kg for the 100%) treatment. Percentage of internal fat was least (P = 0.10, linear effect of urea level) for the 33%) diet. There were no treatment effects for yield grade, dressing percent, percentage of cattle grading USD A Choice, marbling score, backfat thickness, or longissimus muscle area. Incidence of liver abscess did not differ (P = 0.30) among the three treatments; however, the 33% treatment had a numerically higher rate (12.25%) than the 67% (8.26%)) and the 100% (7.50%) treatments. Results indicate that when feeding a finishing diet based on steam-flaked corn that contains 25%o (DM basis) Sweet Bran® WCGF, providing supplemental CP with a ratio of at least 67%) urea:33%o cottonseed meal improves ADG and feed efficiency compared with 33%) urea:67%> cottonseed meal.