Barley Silage or Corn Silage Fed in Combination with Barley Grain, Corn Grain, or a Blend of Barley and Corn Grain to Backgrounding Beef Cattle

Abstract

The objective of this study was to determine the effect of either barley (BS) or corn (CS) silage fed with dry-rolled barley (BG), dry-rolled corn (CG), or a blend of barley and corn grain (BCG) on predicted nutrient digestibility and growth performance of backgrounding cattle (Study 1) and dry matter intake, ruminal fermentation, total tract digestibility and nitrogen balance (Study 2).In study 1, Steers (n = 288) were stratified by BW into 24 pens and pens were randomly assigned to one of six treatments (n = 4) in a two  three factorial design. For Study 2 five ruminally cannulated heifers were used in an incomplete 6  6 Latin square design. Periods were 25-d including five days of dietary transition, 13 days of dietary adaptation, and seven days of sample collection. Treatments contained (DM basis) either BS or CS included at 55% in combination with 30% BG, CG, or BCG, 8% canola meal, varying amounts of urea to balance CP, and 5% of a mineral and vitamin supplement. There were no interactions among silage or grain source and no differences in ADG (1.01 kg/d) or G:F (0.10 kg/kg) among diets. However, DMI was 0.8 kg/d greater for steers fed CS (P = 0.018) than BS. Final BW was 8.4 kg greater for steers fed CS (P = 0.004) compared to steers fed BS. Fecal starch was greatest for CG, intermediate for BCG, and least for BG (P < 0.01). Whole barley kernels appearing in feces were greatest in BG compared to BCG while partial corn kernels in feces were greater in CG compared BCG (P < 0.01). Fine fibre particles in feces were greatest in BG diets with CG and BCG being least (P < 0.01 In study 2 Acetate concentrations were greatest for the CG and BCG diets (P < 0.01) while propionate was greatest for BS-BG and the least for CS-BCG (P < 0.05). Rumen ammonia concentrations were greatest for CG treatments (P < 0.01). Barley grain had greater DM, OM, starch and GE digestibility comparted to CG with BCG being intermediate (P < 0.05). Fecal nitrogen excretion was greatest for cattle fed CS (P < 0.05) as wells as for CG (P < 0.01). Use of CS improved DMI, ending BW and nutrient digestibility; while dry-rolled BG improved nutrient digestibility and reduced fecal starch concentration as compared to CG or BCG in diets for backgrounding cattle.