Effects of dry matter content on trypsin inhibitors and urease activity inheat treated soya beans fed to weaned piglets

A nutrition study was conducted to evaluate the growth response of weaned p iglets fed diets containing soya beans that had been processed into protein supplements at two different levels of dry matter (DM) and temperature. Fo ur diets contained protein supplements prepared from whole full-fat soya be ans equilibrated at 800 or 900 g kg(-1) DM prior to being heated to 110 or 125 degreesC. An additional diet contained a protein supplement prepared fr om raw whole full-fat soya beans at 900 g kg(-1) DM; i.e. an unheated soya bean protein supplement. The experimental control diet was supplemented wit h a solvent extracted commercially processed soya bean meal (900 g kg(-1) D M) containing 480 g crude protein kg(-1). Soya beans at 900 g kg(-1) DM pri or to heat treatment at 110 degreesC produced protein supplements, after he at treatment, that had higher residual levels of trypsin inhibitors and ure ase activity than measured in soya beans at 800 g kg(-1) DM prior to the sa me heat treatment. The moisture content of soya beans prior to heat treatme nt affected the level of heat necessary to lower values for trypsin inhibit ors and urease activity. Soya beans at 800 g kg(-1) DM prior to heating at 110 degreesC, produced a protein supplement with similar residual concentra tions of trypsin inhibitors and urease activity to soya beans at 900 g kg(- 1) DM prior to heating at 125 degreesC. This observation suggested that the soya beans with higher moisture content required lower heat energy to inac tivate trypsin inhibitors and urease. The pen unit response of piglets fed The diet containing the soya bean protein supplement prepared from soybeans processed at 900 g kg(-1) DM and heated to 110 degreesC was not improved w hen compared to piglets fed the diet containing the unheated soya bean prot ein supplement. Soya beans at 800 or 900 g kg(-1) DM prior to heating to 11 0 degreesC, or soybeans at 900 g kg(-1) DM heated to 125 degreesC, produced protein supplements that were inadequately heat processed as indicated by the values for residual trypsin inhibitors and urease activity, and, the de pressed pen unit response of Piglets when compared to those fed the control diet. In contrast, piglets fed the protein supplement prepared from soya b eans at 800 g kg(-1) DM prior to heating to 125 degreesC, displayed an aver age daily feed intake and feed-to-gain ratio that did not differ significan tly from piglets fed the control diet. These data indicate that when whole full-fat soya beans were processed by the dry roasting method, their initia l DM content of 800 or 900 g kg(-1) affected the processing temperature nec essary to denature or otherwise inactivate inherent trypsin inhibitors and urease activity. (C) 2000 Elsevier Science B.V. All rights reserved.