Effects of Aldehyde Treatments of Soybean Meal on in vitro Ammonia Release, Solubility and Lamb Performance

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Abstract
The uniqueness of the symbiotic relationship between the ruminant and its intestinal microbiological flora and fauna is not generally appreciated or fully understood. Under many feeding regimes most of the dietary nitrogenous compounds are degraded in the rumen and the nitrogen used in the synthesis of microbial protein. Consequently, nitrogenous compounds with low biological values are upgraded to the biological value level of rumen microbial protein. Conversely, a protein having a high availability and biological value in the nonruminant may be altered in the rumen to microbial protein which may have a lower availability or biological value, or both. Thus it would seem desirable to use this biological system (the ruminant and its intestinal microflora and fauna) advantageously by “protecting” high quality dietary proteins from rumen degradation and alteration while permitting the low quality nitrogenous compounds to be upgraded to microbial protein. A series of studies were conducted to determine if aldehyde treatment of solvent-extracted soybean meal (SBM) would prevent or reduce its degradation in the rumen, affect its in vitro or in vivo solubility, or enhance its utilization by the ruminant. Solvent-extracted SBM was treated with different concentrations of acetaldehyde (ethanal), acrolein (2-propenal), butyraldehyde (butanal), formaldehyde (methanal), glutaraldehyde (pentanedial), glyoxal (ethanedial), propionaldehyde (propanal) or 1,3,5-trioxane. Incubation of the treated SBM with rumen fluid was used to determine ammonia production from the various treatments. Ammonia production in the in vitro system was significantly reduced (P < 0.01) by acrolein, formaldehyde, glyoxal or glutaraldehyde treatment of the SBM. At the concentrations used and at the time sampled, the other aldehydes had no significant effect on ammonia production. Effect of aldehyde treatment on solubility of SBM was determined. Treatment of SBM with formaldehyde, glutaraldehyde or glyoxal significantly (P < 0.01) depressed protein solubility. Sixty lambs were used in a 2 × 3 factorially designed experiment to study effect on performance of formaldehyde (0.6% of SBM) or glyoxal (1.5% of SBM) treatment of SBM used as supplemental dietary protein and to observe the effect of dietary methionine hydroxy analog (MHA). SBM treated with either aldehyde supported improved gains (P < 0.01) and feed conversion (P < 0.01) and glyoxal lowered plasma urea nitrogen (PUN) level (P < 0.05) as compared to lambs receiving the control (water-treated) SBM. MHA addition depressed rate of gain (P < 0.05) and PUN (P < 0.05).