Effects of isopropyl alcohol treatment of soya bean meal on nitrogen utilization by ruminants

Abstract

Soya bean meal (SBM) treated with isopropyl alcohol (IPA) or n-propyl alcohol (NPA) was used to study effects of alcohol treatments on SBM nitrogen (N) utilization by ruminants. The IPA treatments simulated removal of oil from whole soya beans normally extracted with hexane. In an in situ experiment comparing 85.0, 87.7 or 90.5% (w/w) IPA, a hexane (H) control and an untreated SBM control, less soluble N was washed from the bags at 0 h for the 3 IPA and H treatments compared to untreated SBM. At 2, 4 and 6 h, more N remained in the 85% (74.4, 67.5 and 46.0% of the original N at 2, 4 and 6 h, respectively) and 87.7% IPA bags (72.6, 64.4 and 46.9%) than for the H (66.2, 58.8 and 38.8%) or control SBM bags (61.1, 52.2 and 33.4%). No difference was noted among treatments in the rate of N disappearance between 2 and 12 h. A chick bioassay revealed that N availability in the small intestine was not affected by alcohol treatment. Average daily gain, feed intake and feed :gain were not reduced for 85, 87.7 or 90.5% IPA or 40% NPA treatments compared to control SBM. A lamb metabolism trial using 20-kg lambs was conducted using 85 or 87.7% IPA-treated SBM, 40% NPA-treated SBM, untreated SBM or urea as protein supplements to a corncob basal diet. No differences in N retention, absorption or digestion were observed among treatments. The same protein sources were used to study rumen ammonia (NH 3) levels in relation to time after feeding. At 4 and 8 h, 40% NPA resulted in lower rumen NH 3 levels (11.2 and 4.8 mg %, respectively) than did control SBM (16.3 and 9.1 mg %) and urea (17.6 and 10.1 mg %). At 6 h, both 85% IPA and 40% NPA resulted in lower (7.4 and 4.9 mg %, respectively) NH 3 levels than did control SBM or urea (11.8 and 13.4 mg %, respectively).