Effects of Treatment of Whole Fat Soybeans or Soy Flour with Formaldehyde to Protect the Polyunsaturated Fatty Acids from Biohydrogenation in the Rumen.

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Abstract
Full-fat, ground soy flour (GSF) was treated with 37% formaldehyde (HCHO) and evaluated by in vitro and in vivo criteria to determine the protection afforded linoleic acid against ruminal biohydrogenation when the materials described above were fed as a protein supplement to rations for growing lambs. The supplements compared were soybean meal (SBM), untreated GSF and GSF treated with 10.2 ml HCHO/100 g GSF and soaked for 2 hours. Organoleptic evaluations were conducted to determine if any flavor differences in meat from lambs fed these supplements could be detected. Excellent protection of linoleic acid, the major polyunsaturated fatty acid in soybeans, was noted both in vitro and in vivo. Rump, shoulder, kidney knob and omental fat depots of lambs fed the HCHO treated GSF ration had significantly more linoleic acid than lambs fed untreated GSF while lambs fed untreated GSF had significantly more linoleic acid in their fat depots than lambs fed SBM. Linoleic acid content of intramuscular (loin) fat from lambs fed HCHO treated GSF was not significantly different from lambs fed untreated GSF, but lambs fed untreated GSF had significantly more loin linoleic acid than lambs fed SBM. No significant differences were noted in daily feed intake, feed efficiency or average daily gain for lambs fed growing-finishing rations containing any of the products tested as the protein supplement. A taste panel could not detect any differences in flavor of ground loin among any of the treatments.