Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/26/2007
Publication Date: 6/1/2007
Citation: Archibeque, S.L., Miller, D.N., Freetly, H.C., Berry, E.D., Ferrell, C.L. 2007. The influence of oscillating dietary protein concentrations on finishing cattle. I. Feedlot performance and odorous compound production. Journal of Animal Science. 85(6):1487-1495. Interpretive Summary: Feeding livestock in confined areas can lead to an accumulation of nutrients, which may have negative environmental impacts within and around the livestock operation. The challenge is to develop methods to reduce possible environmental impacts without impairing feedlot productivity. The present study suggests that such a strategy may have some undesirable side effects, such as increased production of odorous compounds in manure. However, the present study also demonstrates such a strategy allows feedlot productivity to remain at a high level.
Technical Abstract: We hypothesized that oscillating dietary CP concentration, which may improve N retention of finishing beef steers, would reduce manure odor compound production and total N inputs while yielding comparable performance. Charolais-sired steers (n = 144; 303 +/- 5 kg initial BW) were used in a completely randomized block design (six pens/treatment). The steers were fed to 567 kg (averaged across treatments on two occasions) on the following dry-rolled corn-based, finishing diets: 1) Low (9.11% CP), 2) Medium (Med; 11.80% CP), 3) High (14.95% CP), or 4) Low and High oscillated on a 48 h interval (Osc). Steers fed the Low diet (7.80 kg x d-1) tended (P = 0.08) to have a lower feed intake than steers fed either the Med (8.60 kg x d-1) or Osc (8.67 kg x d-1) diets, but not the steers fed the High diet (8.12 kg x d-1). Daily N intake was greatest (P < 0.01) for steers fed the High diet (189 g), intermediate for the Med (160 g) and Osc (164 g) diets, and smallest for the Low (113 g) diet. The ADG was reduced (P < 0.01) in steers fed the Low (1.03 kg) diet, compared to those fed either the Med (1.45 kg), High (1.45 kg), or Osc (1.43 kg) diets. Similarly, steers fed the Low diet had a lower adjusted fat thickness (P < 0.01) and yield grade (P = 0.05), and tended (P = 0.10) to have less marbling than steers fed the other three diets. In slurries with feces, urine, soil, and water, incubated for 35 d, nonsoluble CP was similar between slurries from steers fed either the Med, High, or Osc diets, yet was reduced (P < 0.01) in slurries from steers fed the Low diet. However, throughout the incubation period, slurries from steers fed either the High or Osc diets had greater (P < 0.01) concentrations of total aromatics and NH4 than those from steers fed either the Low or Med diets. Also, the slurries from steers fed the Osc diet had an increase (P < 0.01) in the concentration of branched-chain VFA that was not apparent in manure slurries from steers fed any of the other diets. These data indicate that while there is no apparent alteration in the performance of finishing steers fed diets with oscillating dietary protein, there may be undesirable increases in the production of compounds associated with malodor.