ARTICLE 60 FEED & ADDITIVE MAGAZINE May 2023 fast digestibility kinetics and only 9.5% is slow and resistant. The proteins from YELA PROSECURE are, therefore, highly bioavailable for the animals. • Effect of the yeast process on the protein digestibility kinetic The protein digestibility kinetic of YELA PROSECURE was compared to a whole-cell inactivated yeast (Figure 4) with a focus on the three first hours of the intestinal phase as the process of digestion is already quite complete at that time for young animals. In whole-cell inactivated yeasts, no lysis process is applied, and most nutrients (including the proteins) are in the cytoplasm of the yeast cell making them less accessible. As shown in Figure 5, their protein digestibility is low right after the stomach (46%) and increases slowly, up to 60% after 3 hours. Thanks to the oriented and controlled hydrolysis process used to produce YELA PROSECURE, proteins and nucleic acids are fragmented into small size peptides offering highly digestible nutrients. We can conclude the yeast lysis process strongly benefits protein digestibility and therefore nutrient bioavailability in the gut. • Hydrolyzed yeast protein digestibility compared to other feed materials Eight feed materials were assessed for protein digestibility and kinetics of absorption based on the Boisen method. Figure 5 shows that the digestibility kinetics of the protein sources is specific to the different feed materials: - The whey protein concentrate (WPC) reaches its maximum digestibility level right after the stomach. It is a high-quality protein source even if the crude protein content is low (35%). Additionally, WPC volumes are limited and prices are high. - Blood plasma also shows fast kinetics of protein digestibility, close to 100 % after 1 hour 30 minutes in the intestine. - Soybean meal starts with a 50% protein digestibility after the stomach and increases up to 70% after 3 hours of the intestinal phase. - The kinetics of protein digestibility for fish meal is between YELA PROSECURE and soybean meal, starting with 56% digestibility after the stomach to 81% after 3 hours in the intestine. - Soy protein concentrate (SPC) reaches the same protein digestibility as soybean meal after 3 hours but starts with a lower digestibility after the stomach (41%). This lower initial digestibility may be explained by the process applied to the SPC to reduce the antinutritional factors, which possibly makes the protein more complex and reduces its bioavailability. It is also important to keep in mind Figure 4. Kinetic of protein digestibility: YELA PROSECURE vs. a whole-cell inactivated yeast
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