Evaluation of ammoniated wheat straw during a receiving and growing period for beef cattle1

Two experiments were conducted to determine the effects of including ammoniated wheat straw in diets for beef cattle on growth performance and digestibility. Treatments consisted of diets containing 70% (DM basis) concentrate containing 40% (DM basis) wet corn gluten feed with 30% (DM basis) roughage from wheat straw (STRW), anhydrous ammonia-treated wheat straw (AMMN), or a 50:50 prairie hay and alfalfa hay blend (CONT). Experiment 1 used 288 crossbred steer calves (271 ± 28 kg) in a randomized complete block design in which steers were fed their experimental diets for 56 d. Final BW, ADG, and G:F were greater for calves fed CONT than for those fed either STRW or AMMN (P < 0.05). Experiment 2 used 6 ruminally fistulated Holstein heifers (288 kg) in a 3 × 3 Latin square design. Heifers fed CONT consumed less (P < 0.05) DM, OM, and ADF compared with those fed AMMN and STRW. Feeding heifers CONT improved (P < 0.05) digestibility of DM and OM but decreased (P < 0.05) digestibility of ADF. Ruminal pH was lowest (P < 0.05) for heifers fed CONT. The results of this experiment suggest that wheat straw and ammoniated wheat straw are equivalent roughage sources but inferior to a 50:50 blend of alfalfa hay and prairie hay when fed to growing calves at 30% of the dietary DM.