Response of Ruminants to Diets Containing Sodium Hydroxide or Ammonia Treated Rice Straw

Abstract

Comparative slaughter feeding trials (sheep and cattle) with concurrent digestion experiments (lambs) were conducted to determine the value of alkali treated (NaOH or NH3) rice straw in diets for ruminants. The diets contained 72 or 36% rice straw (as-fed basis). All NaOH treatments used 4% NaOH by weight of straw. The NH3 treatments (4.7, 5.0 or 7.0% NH3 by weight of straw) were by an ambient temperature ammoniation process in which aqueous ammonia was applied to baled straw kept sealed in plastic envelopes for at least 30 days. The general pattern of response was the same for lambs and steers. The diets containing 72% treated rice straw were consumed in larger quantities and less feed was required per unit of gain when compared to results with untreated straw diets. The treated straw diets also had higher net energy values. Digestibility of the organic matter, cellulose and energy was higher for most 72% treated rice straw diets although differences were not always statistically significant. Nitrogen digestibility was lower for those diets containing the treated straw at the 72% level. There were no significant changes in digestibility or animal response between control and treated rice straw diets when 36% of the diet was straw. This observation could indicate an important practical limitation to the use of alkali treated roughage in higher concentrate diets. Rumen pH was not different due to the consumption of alkali treated straw and the percentages of the volatile fatty acids were similar for comparable diets. The NH3 treatment approximately doubled the nitrogen content of the straw from .7% in the control to 1.49 ± .12 for all NH3 straws, but the availability of this added nitrogen is not known.