Effect of corn processing on degradable intake protein requirements of finishing cattle

One metabolism and three finishing trials were conducted to determine the effect of corn processing on degradable intake protein requirements of feedlot cattle. Our hypothesis was that corn processing methods which increase the rate and extent of ruminal starch fermentation would increase the degradable intake protein requirement. Three corn processing/storage methods were tested: dry-rolled corn (DRC), high-moisture corn (HMC), and steam-flaked corn (SFC). All diets were 90% concentrate with an equal proportion of alfalfa hay and cottonseed hulls as the roughage source. In the metabolism trial, HMC and SFC were found to have 20.3 and 17.6%, respectively, greater ruminal starch digestibilities compared with DRC. Bacterial CP flows to the duodenum were 34.4 and 4.6%, respectively, greater for HMC and SFC compared with DRC. Microbial efficiencies were similar among treatments. Based on results from the metabolism trial, we would predict degradable intake protein requirements to be highest for HMC, followed by SFC and then DRC. In three finishing trials, urea was used to titrate degradable protein levels in DRC, HMC, and SFC-based diets. Based on breakpoint analysis of feed efficiency, our estimates of the dietary degradable intake protein requirements for finishing cattle fed dry-rolled, high-moisture, and steam-flaked corn-based diets are 6.3, 10.0, and 9.5% of DM, respectively