159 - Effect of Dry or Temper Rolling of High or Low Protein Wheat and Its Impact on Rumen Parameters, Liver Abscesses, and Growth Performance of Feedlot Cattle

Abstract: The objective of this study was to assess the impact of low (13%, LP) or high protein (18%, HP) wheat grain subjected to dry (DR) vs temper rolling (TR) on growth performance, rumen parameters, and liver abscesses of feedlot steers. A backgrounding (BG) to finishing (FN) feedlot trial was performed using 160 302 ± 34 kg; 24 ruminally cannulated) Angus steers blocked by weight and randomly assigned to 16 pens. Cannulated steers (3 per pen) were housed within 8 pens equipped with a feed intake monitoring system. BG diets contained 35% wheat grain, 60% barley silage, and 5% supplement on a DM basis. Transition (TN) diets included sequential increases to the proportion of wheat grain in the total mixed ration to achieve a FN diet comprised of 85% wheat grain, 10% barley silage, and 5% supplement. Rumen pHs were measured with an indwelling logger and rumen samples were collected in each phase. Steers fed the HP-DR and LP-TR diets had lower (P≤0.03) ruminal pH than HP-TR during the TN phase. Tempering HP wheat reduced (P<0.001) the generation of fine particles during rolling. During BG and TN, steers fed diets containing HP wheat had higher (P<0.001) ruminal NH₃ concentrations than the LP treatments. NH₃ measurements during the FN phase were higher (P=0.01) for the LP-DR treatment compared to the LP-TR treatment. Greater (P≤0.01) C2:C3 ratios were noted for HP wheat diets during the BG and FN phases whereas the C2:C3 ratio was reduced (P<0.001) with TR wheat during the FN phase. Greater (P= 0.01) NEgs were assessed for FN steers fed LP wheat. Steers fed HP wheat had more severe (P<0.001) abscesses. Results suggest that HP wheat may limit the growth performance of FN cattle and increase the severity of liver abscesses.