Performance and carcass characteristics of feedlot cattle fed ensiled soybean straw treated with various alkalis

A beef growing-finishing study was conducted to determine the effects of feeding ensiled chopped soybean straw (SBS) (35% dry matter) treated with various alkalis on performance carcass characteristics. Concentrations of alkalis used in the diets were either 0 (control) or 4% (w/w) of the straw dry matter. A fescue hay (FH) diet was used as a positive control. Thirty-five Angus and Hereford steer and heifer calves averaging 202 kg body weight were randomly assigned to 5 treatment groups. Treatments were: (1) water, (2) NaOH, (3) Ca(OH)(2), (4) NH4OH, and (5) FH. The diets were fed 141 days including a 21-day adaptation period. Sodium hydroxide and Ca(OH)(2) treatments decreased (P <0.05) the organic matter concentration while the NH4OH increased (P <0.05) the nitrogen level of the straw. Alkali treatments decreased (P <0.05) the acid detergent fiber (ADF) and increased (P <0.05) the hemicellulose contents of the straw compared to the water treatment. There were no significant (P >0.05) differences among final weights and average daily gain of animals fed alkali treated forage and those fed fescue hay. Average dry matter intake and feed:grain ratio did not differ (P >0.05) among treatments. Also, alkali treatments increased (P <0.05) carcass weight compared the water treatment, whereas other carcass characteristics did not differ (P >0.05) among treatments. Cattle fed the NH4OH treated SBS had the highest (P <0.05) plasma urea-N (PUN) and ruminal ammonia-N concentrations than those fed the other treatments. Plasma urea-N did not differ (P > 0.05) among cattle fed SBS treated with NaOH, Ca(OH)(2) or water and those fed FH diets. Ruminal ammonia-N concentrations were the lowest (P <0.05) for cattle fed NaOH treated SBS. Ruminal pH value was the lowest (P <0.05) for cattle fed the ensiled control compared to the other treatment groups. Alkali treatments did not (P >0.05) affect the molar concentrations of VFAs. Molar proportion of acetate was higher (P <0.05) for animals fed NaOH treated SBS than for those fed the water treatment. Molar proportion of propionate, butyrare, valerate, as well as acetate:propionate ratio did not differ (P >0.05) among treatments.