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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED PLANT GENETIC RESOURCES FOR PASTURES AND RANGELANDS IN THE TEMPERATE SEMIARID REGIONS OF THE WESTERN U.S.

Location: Forage and Range Research

Title: Growth performance, ruminal fermentation profiles, and carcass characteristics of beef steers grazing tall fescue without or with nitrogen fertilization

Authors
item Noviandi, C -
item Waldron, Blair
item Zobell, D -
item Eun, J -
item Peel, Michael

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 28, 2012
Publication Date: October 1, 2012
Citation: Noviandi, C.T., Waldron, B.L., Zobell, D.R., Eun, J.S., Peel, M. 2012. Growth performance, ruminal fermentation profiles, and carcass characteristics of beef steers grazing tall fescue without or with nitrogen fertilization. Professional Animal Scientist. 28:519-527.

Interpretive Summary: A 2-year grazing study was conducted to evaluate the effects of finishing beef cattle grazed on tall fescue (TF) pasture without or with N fertilization on growth performance, ruminal fermentation, and carcass characteristics. In each grazing season, 18 Angus crossbred steers were used with the following 2 treatments: TF without N fertilizer (TF-NF) and TF with N fertilizer (TF+NF). Three replicated pastures with 3 steers per replicate were assigned into each treatment. A total of 168 kg/ha N fertilizer was applied in 3 split applications at 56 kg/ha to the TF+NF in each grazing season. Steers rotationally grazed on 0.47-ha pasture with a 28-d rotation interval for 16 wk. Body weight data and pasture samples were collected every 4 wk, whereas ruminal fluid were collected at wk 4, 10, and 16. In response to N fertilization, 1% higher CP concentration was detected on TF+NF compared with TF-NF in 2011. Nitrogen fertilization resulted in overall higher daily gain of steers and tended to increase overall DMI. Regardless of N fertilization, daily gain peaked at wk 4 and 8 and then declined until wk 16. Higher total volatile fatty acid concentration was detected on steers grazed TF+NF with a minor effect on individual volatile fatty acids. Back fat thickness, ribeye area, and intramuscular fat concentration did not differ between treatments. Overall results of this study indicate that N fertilization on TF affected ruminal fermentation which positively influenced growth performances, but did not affect carcass characteristics of grazing beef steers. In addition, readily fermentable carbohydrate supplementation is needed to improve utilization of increased dietary CP due to N fertilization and consequently enhance growth performances of grazing steers.

Technical Abstract: A 2-year grazing study was conducted to evaluate the effects of finishing beef cattle grazed on tall fescue (TF) pasture without or with N fertilization on growth performance, ruminal fermentation, and carcass characteristics. In each grazing season, 18 Angus crossbred steers were arranged based on a completely randomized design with repeated measures on the following 2 treatments: TF without N fertilizer (TF-NF) and TF with N fertilizer (TF+NF). Three replicated pastures with 3 steers per replicate were assigned into each treatment. A total of 168 kg/ha N fertilizer was applied in 3 split applications at 56 kg/ha to the TF+NF in each grazing season. Steers rotationally grazed on 0.47-ha pasture paddocks with a 28-d rotation interval for total 16 wk. Body weight data and pasture samples were collected every 4 wk, whereas ruminal fluid were collected at wk 4, 10, and 16. After the completion of 16-wk grazing, ultrasound measurement was performed to assess carcass characteristics. In response to N fertilization, greater CP concentration was detected on TF+NF compared with TF-NF in 2011 (11.9 vs. 10.6% DM, respectively; P<0.01). Nitrogen fertilization increased overall ADG of steers grazed TF+NF (P<0.05) in 2-year grazing seasons, and tended to increase (P=0.07) overall DMI and G:F in 2010. Regardless of N fertilization, ADG was peaked at wk 4 and 8 (1.05 kg/d; P<0.01), and then declined until wk 16. Gradually decline of G:F was noticed with progression in grazing seasons (P<0.05). Higher total VFA concentration was detected on steers grazed TF+NF (P<0.01), but minor effect was showed on individual VFA (acetate, propionate, and butyrate) concentrations and acetate-to-propionate ratio. Ruminal ammonia-N (NH3-N) concentration increased (P<0.01) due to N fertilization, while NH3-N:total VFA increased (P<0.01) with the progression of grazing seasons. Back fat thickness, ribeye area, and intramuscular fat concentration did not differ between treatments. Overall results of this study indicate that N fertilization on TF affected ruminal fermentation which positively influenced growth performances, but did not affect carcass characteristics of grazing beef steers. In addition, readily fermentable carbohydrate supplementation is needed to improve utilization of increased dietary CP due to N fertilization and consequently enhance growth performances of grazing steers.

Last Modified: 9/2/2014
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