Effects of Moisture and a Saponin-Based Surfactant During Barley Processing on Growth Performance and Carcass Quality of Feedlot Steers and on in Vitro Ruminal Fermentation (Report‪)‬

INTRODUCTION In feedlot beef production, feed efficiency is typically improved and cost per unit of gain is decreased with increasing dietary energy levels. Due to their highly digestible starch content, grains are typically the cheapest source of energy in ruminant diets and therefore are usually included at levels greater than 85% in finishing diets in North America. Barley grain is the major grain source for feedlot cattle in western Canada. It must be processed prior to feeding so that endosperm encased within the indigestible pericarp and hull can be utilized (Wang and McAllister, 2000), with rolling being the most common form of processing for this purpose. However, the variation in kernel size of barley grain can dramatically influence the efficacy of rolling as a processing method. Therefore, tempering grain prior to rolling has been used to standardize this inherent variation and to reduce mechanical wear on processing equipment (Mathison et al., 1997). However, the effects of tempering on animal performance have been inconsistent (Hinman and Combs, 1983; Combs and Hinman, 1989; Mathison et al., 1997). Some of these discrepancies may have arisen from variations in the rate and extent of moisture uptake by the kernels during tempering. Surfactants have been used to enhance hydration in a variety of applications (Cairns, 1972; Aksenova et al., 1993; Coret and Chamel, 1993). However, there is little information on the effects of these compounds on the processing and utilization of barley grain. Wang et al. (2003), using cattle individually fed barley grain and barley silage, showed that inclusion of saponin-based surfactant at 60 ppm during tempering increased average daily gain and feed efficiency by 7 and 6%, respectively. This growth promotion effect of the surfactant appeared to be mediated by the feed particle size, but the mechanism was not clear. Their subsequent study (Wang et al., 2005) revealed that although this surfactant increased water absorption of barley grain up to 2 h of tempering it did not affect the particle size distribution after rolling. It is not known if the surfactant would produce a similar response under conditions that are more indicative of a commercial feedlot.