Author
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BROWN, M. - WTAMU |
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GREENE, L. - TAES |
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Cole, Noel |
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Submitted to: Meeting Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 7/1/2004 Publication Date: 8/1/2004 Citation: Brown, M.S., Greene, L.W., Cole, N.A. 2004. Recent feedlot cattle research in the Texas Panhandle. In: Proceedings of the 50th Annual Texas A&M University Beef Cattle Short Course, August 2-4, 2004, College Station, Texas. p. H-30. Interpretive Summary: Scientists from multiple disciplines at the Amarillo Experiment Station, USDA laboratory in Bushland, and West Texas A&M are actively engaged in research addressing areas of importance to feedlot cattle production. These areas generally encompass animal health, food safety, waste and pest management, and nutrition. The scope of this update will be limited to the nutrition area, and specific experiments will be discussed that relate to evaluating nutrient requirements and the fate of excreted nitrogen. Nutrient requirements. An increasing emphasis has been placed on refining dietary protein and phosphorus needs for optimum performance because of greater regulatory requirements. The nitrogen (N):phosphorus (P) ratio in manure scraped from the pen is typically lower than that needed for crop production. Consequently, applying manure to meet the N needs of the crop supplies an excess of P. We conducted a study at the WTAMU feedlot to evaluate the effects of dietary protein and degradable protein (degraded in the rumen) on feedlot performance and carcass characteristics. Yearling steers (315 hd, 45 pens total, 827 lb initial weight) were fed a finishing diet with one of three CP concentrations (11.5, 13. or 14.5% of DM) provided by one of three ratios of urea and cottonseed meal (100:0, 50:50, and 0:100, N basis) for 135 days. Diet CP and protein degradability did not interact (P > 0.15) for performance or carcass data. Steer ADG increased (P < 0.01) with diet CP (4.21, 4.48, and 4.92 lb/d for 11.5, 13.0, and 14.5%, respectively), and feed efficiency was improved as both diet CP and degradable protein increased (P < 0.07) during the first 28 days after reimplanting (Revalor S after Ralgro). However, ADG tended (P = 0.14) to decrease as diet CP increased from day 85 to 112, and feed efficiency increased as dietary CP decreased and as degradable protein increased (P < 0.09) from d 85 to 112. Thus, overall ADG, DMI, and feed efficiency did not differ and carcass yield grade characteristics were similar among treatments. A related study conducted at TAES ' Amarillo examined withdrawing supplemental protein later in the feeding period as protein gain declines. Yearling steers (184 hd, 21 pens total, 895 lb initial wt) were fed a 13% CP finishing diet until reaching 1050 lb, and fed either 13% CP, 11.5% CP, or 10% CP thereafter until slaughter. Overall DMI was reduced (P < 0.10) by the 10% CP diet. Overall ADG was greater (P < 0.10) for 11.5% CP (4.10 lb/day) than for 10% CP (3.73 lb/day), and ADG by 13.0% CP was intermediate (3.84 lb/day). Feed efficiency was improved (P < 0.10) by reducing CP to 11.5%. Fate of excreted nitrogen. It has long been recognized that the N:P ratio of manure is reduced between the time that feces is excreted and the time that manure is scraped from the pen surface. Only recently have nutritionists and environmental scientists begun to explore the fate of excreted N. Andy Cole evaluated potential ammonia emissions from feedlot cattle feces and urine in a laboratory study at the USDA ARS laboratory. Feces and urine were applied to soil in enclosed chambers and volatilized ammonia was measured over 7 days. Treatments used on the cattle providing the excreta were similar to the first study reported here, and feces and urine were added to the soil in the same relative amounts as excreted (e.g., chambers for treatments on which the cattle excreted more urine or feces received more feces or urine). Treatments did not differ in the percentage of total N (urine + feces) that disappeared (average of approximately 15%), but more total N was lost (P < 0.05) by cattle fed 13 or 14.5% CP than for 11.5% CP. Although the percentage of total N lost as ammonia was similar (average of approximately 43%), more urinary N was lost as ammonia (P < 0.05) for 13.0 and 14.5% CP (4.34 and 4.32%, respectively) th Technical Abstract: Scientists from multiple disciplines at the Amarillo Experiment Station, USDA laboratory in Bushland, and West Texas A&M are actively engaged in research addressing areas of importance to feedlot cattle production. These areas generally encompass animal health, food safety, waste and pest management, and nutrition. The scope of this update will be limited to the nutrition area, and specific experiments will be discussed that relate to evaluating nutrient requirements and the fate of excreted nitrogen. Nutrient requirements. An increasing emphasis has been placed on refining dietary protein and phosphorus needs for optimum performance because of greater regulatory requirements. The nitrogen (N):phosphorus (P) ratio in manure scraped from the pen is typically lower than that needed for crop production. Consequently, applying manure to meet the N needs of the crop supplies an excess of P. We conducted a study at the WTAMU feedlot to evaluate the effects of dietary protein and degradable protein (degraded in the rumen) on feedlot performance and carcass characteristics. Yearling steers (315 hd, 45 pens total, 827 lb initial weight) were fed a finishing diet with one of three CP concentrations (11.5, 13. or 14.5% of DM) provided by one of three ratios of urea and cottonseed meal (100:0, 50:50, and 0:100, N basis) for 135 days. Diet CP and protein degradability did not interact (P > 0.15) for performance or carcass data. Steer ADG increased (P < 0.01) with diet CP (4.21, 4.48, and 4.92 lb/d for 11.5, 13.0, and 14.5%, respectively), and feed efficiency was improved as both diet CP and degradable protein increased (P < 0.07) during the first 28 days after reimplanting (Revalor S after Ralgro). However, ADG tended (P = 0.14) to decrease as diet CP increased from day 85 to 112, and feed efficiency increased as dietary CP decreased and as degradable protein increased (P < 0.09) from d 85 to 112. Thus, overall ADG, DMI, and feed efficiency did not differ and carcass yield grade characteristics were similar among treatments. A related study conducted at TAES ' Amarillo examined withdrawing supplemental protein later in the feeding period as protein gain declines. Yearling steers (184 hd, 21 pens total, 895 lb initial wt) were fed a 13% CP finishing diet until reaching 1050 lb, and fed either 13% CP, 11.5% CP, or 10% CP thereafter until slaughter. Overall DMI was reduced (P < 0.10) by the 10% CP diet. Overall ADG was greater (P < 0.10) for 11.5% CP (4.10 lb/day) than for 10% CP (3.73 lb/day), and ADG by 13.0% CP was intermediate (3.84 lb/day). Feed efficiency was improved (P < 0.10) by reducing CP to 11.5%. Fate of excreted nitrogen. It has long been recognized that the N:P ratio of manure is reduced between the time that feces is excreted and the time that manure is scraped from the pen surface. Only recently have nutritionists and environmental scientists begun to explore the fate of excreted N. Andy Cole evaluated potential ammonia emissions from feedlot cattle feces and urine in a laboratory study at the USDA ARS laboratory. Feces and urine were applied to soil in enclosed chambers and volatilized ammonia was measured over 7 days. Treatments used on the cattle providing the excreta were similar to the first study reported here, and feces and urine were added to the soil in the same relative amounts as excreted (e.g., chambers for treatments on which the cattle excreted more urine or feces received more feces or urine). Treatments did not differ in the percentage of total N (urine + feces) that disappeared (average of approximately 15%), but more total N was lost (P < 0.05) by cattle fed 13 or 14.5% CP than for 11.5% CP. Although the percentage of total N lost as ammonia was similar (average of approximately 43%), more urinary N was lost as ammonia (P < 0.05) for 13.0 and 14.5% CP (4.34 and 4.32%, respectively) th |
