Urea in dry-rolled corn diets: finishing steer performance, nutrient digestion, and microbial protein production.
In Exp. 1, 88 yearling steers (332 kg) were fed dry-rolled corn finishing diets to evaluate effects of dietary urea level on performance and carcass characteristics. Diets contained 0, .5, 1.0, or 1.5% urea (DM basis), which supplied all supplemental N, and 10% chopped prairie hay. Gains (P = .10) and gain efficiency (G/F; P < .05) were increased by .5% urea, with little improvement by additional urea. Regression analysis estimated optimal dietary urea at .9% of DM for ADG and G/F. Fat thickness (P < .05) and yield grade (P < .10) increased linearly with dietary urea level. In Exp. 2, four ruminally and duodenally cannulated steers (557 kg) were fed the diets used in Exp. 1 to evaluate effects of dietary urea on site and extent of digestion. True ruminal OM and starch digestion were increased 25 and 37%, respectively, by .5% urea, but higher urea levels did not differ from .5%. Flows of total N and microbial N to the duodenum were not affected by urea level. In Exp. 3, 100 yearling steers (347 kg) were fed dry-rolled corn finishing diets that contained 10% alfalfa hay as the dietary roughage to evaluate effects of dietary urea level on performance and carcass characteristics. Urea levels were 0, .35, .70, 1.05, or 1.40% urea (DM basis), with no other supplemental N provided. Dry matter intake (P = .10), ADG (P < .05), and G/F (P < .05) increased with intermediate concentrations of urea but decreased with the highest concentration. Regression analysis indicated that the optimal dietary urea level was .5% of DM for ADG and G/F. Urea increased dietary energy utilization but not metabolizable protein supply.
Milton
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Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506, USA.
Brandt
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Titgemeyer
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D000818:Animals; D001823:Body Composition / Q000187:drug effects / Q000502:physiology; D002417:Cattle / Q000254:growth & development* / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004063:Digestion / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000382:microbiology; D005285:Fermentation / Q000187:drug effects / Q000502:physiology; D005511:Food Handling / Q000379:methods*; D008297:Male; D008460:Meat / Q000592:standards; D011897:Random Allocation; D012044:Regression Analysis; D012417:Rumen / Q000737:chemistry; D014481:United States; D016885:United States Department of Agriculture; D014508:Urea / Q000032:analysis* / Q000494:pharmacology*; D003313:Zea mays / Q000737:chemistry* / Q000592:standards
D014508:Urea