An experiment was conducted to determine the effects of over-processing of soybean meal (SBM) and 00-rapeseed meal (RSM) on growing pig performance. The SBM and RSM were processed by secondary toasting (at 95°C for 30 min) in the presence of lignosulfonate, resulting in over-processed SBM (pSBM) and over-processed RSM (pRSM) as models for over-processed protein sources. Fifty-four growing pigs were allotted to six dietary treatments. Four of the diets contained SBM, pSBM, RSM, or pRSM as the sole protein source. The remaining two dietary treatments contained pSBM or pRSM and were supplemented with crystalline amino acids to the same standardized ileal digestible amino acids levels as the SBM or RSM diet. Pigs were slaughtered at 40 kg, and carcasses analyzed.

Diet type, comprising effects of processing and supplementing crystalline amino acids affected (P ‹ 0.05) the G:F and standardized ileal digestibility (SID) of the crude protein source. Processing reduced G:F from 0.56 to 0.38 for SBM and 0.49 to 0.40 for RSM, whereas supplementing crystalline amino acids increased G:F to the level of the SBM and RSM diets. Processing reduced the SID of crude protein from 87.2% to 69.2% for SBM and 71.0% to 52.2% for RSM. Over-processing of the protein source also significantly reduced (P ‹ 0.05) the weight of several organs, and supplementing crystalline amino acids restored organ weight. The take home message of this study is that over-processing of the protein ingredient direct affects the amino acid availability of the protein source and, therefore, impacts pig performance.