Evaluation of a Yeast Single Cell Protein in Pig Diets

Abstract

SUMMARY The value of a yeast single cell protein (SCP) as a partial replacement of dehulled soybean meal (SBM) in the diet for baby pigs and growing pigs was investigated in two experiments. In the first experiment, SCP replaced 0, 26.6, 53.2 and 79.8% of the SBM in the diet. The average daily gain response to increasing levels of SCP was quadratic and was maximized in baby pigs fed the diet in which SCP replaced 53.2% of the SBM. Response of average daily feed intake to treatments was similar to rate of gain. There was a linear improvement in feed efficiency as yeast SCP replaced soybean meal. The linear improvement suggested that palatability, not toxicity or nutrient imbalance, caused the reduced feed intake and rate of gain by pigs fed the highest level of SCP. Increasing levels of yeast SCP resulted in a linear decrease in plasma urea nitrogen, a linear increase in plasma a-amino nitrogen and no change in plasma uric acid. In experiment 2, yeast SCP replaced 0, 25 and 50% of the dehulled SBM in the diet of growing pigs (28 kg average initial weight). No significant treatment differences were observed for average daily feed and average daily gain, but gain:feed ratio increased linearly as the level of yeast SCP increased in the diets. In a third experiment, nitrogen digestibility and retention of the yeast SCP was evaluated with baby pigs. Comparisons were made between a diet with corn, SBM and dried whey as protein sources, a diet with these sources finishing half the protein and SCP furnishing the other half, and a third diet with all protein from SCP. Both nitrogen digestibility and nitrogen retention as a percentage of nitrogen