ARS | Publication request: Effects of Phase Feeding of Protein on Performance, Blood Urea Nitrogen, and Carcass Characteristics of Finishing Beef Cattle: I. Individually Fed Steers

Submitted to: Beef Cattle Research In Texas
Publication Acceptance Date: July 22, 2004
Publication Date: August 4, 2004
Citation: Vasconcelos, J.T., Greene, L.W., Cole, N.A., Mccollum, F.T. 2004. Effects Of Phase Feeding Of Protein On Performance, Blood Urea Nitrogen, And Carcass Characteristics Of Finishing Beef Cattle: I. Individually Fed Steers. Beef Cattle Research In Texas. P. 129-133.

Interpretive Summary: Over the past 30 years cattle feedlots have increased in size leading to greater concentrate of manure and the nutrients within the manure. Consequently, feed nutrients such as N, P and trace minerals are being concentrated in relatively small geographic areas. Because of changes in growth rate and body composition, requirements for metabolizable protein change during the finishing period. However, feedlot cattle are usually fed one common diet with a constant level of crude protein from about d 24 until they are harvested. Consequently, protein may be underfed early in the feeding period and overfed late in the feeding period. The question becomes, whether nutrient excretion can be reduced without negatively impacting animal performance. The objective of this study was to determine the effects of decreasing dietary protein concentration late in the feeding period (ie. phase feeding) on performance, blood urea nitrogen concentration, and carcass characteristics of individually fed finishing steers. Forty five steers (BW = 935 lb) were fed three protein strategies: 1) a 13% crude protein finishing diet for 120 days,2) 13% protein for 62 then reduced to 11.5% for 56 days, or 3) 13% protein for 62 days then 10% protein for the last 56 days. Reducing the CP content of the diet did not adversely affect performance or carcass characteristics of steers. These data suggest that dietary protein levels can be reduced to conserve nitrogen during the final stages of finishing without any reduction in animal performance.

Technical Abstract: Forty five steers (BW = 935 lb) were fed three protein strategies to determine performance, blood urea nitrogen (BUN), and carcass characteristics in a randomized block design. A finishing diet containing 13% CP was fed for 62 d. On d 62, dietary CP was maintained at 13% or reduced to 11.5% or 10% CP. Reducing the CP content of the diet did not affect ADG of steers from d 62 to 108 (P = 0.51), or ADG over the 108 d feeding period (P = 0.85) regardless of dietary CP treatment. No differences were detected for BUN concentrations on d 0, 62, and 108 (P > 0.10). Carcass characteristics (P > 0.10), DMI (P = 0.81), and gain:feed ratio (P = 0.98) also did not differ. These data suggest that dietary CP levels can be reduced to conserve N during the final stages of finishing without any reduction in ADG.