In vitro degradation of non-starch polysaccharide residues in the digesta of broilers offered wheat-soy or maize-soy diets by feed enzymes

The present study evaluated the in vitro efficacy of different feed enzymes on degrading non-starch polysaccharide (NSP) residues present in digesta collected from broilers’ gastrointestinal tract. Two dietary treatments, wheat-soy or maize-soy based diets, were assigned to broilers (12 replicates per treatment; 10 birds per replicate pen) from d 0 to 35. At 35 d of age, digesta was collected from the gizzard, jejunum and ileum from three birds per replicate and pooled. The digesta samples were digested in vitro with one of nine enzymes; GH10, GH11 and GH8 xylanase, arabinofuranosidase, a combination of GH10 xylanase and β-glucanase (XYN+BG), β-mannanase, protease, cellulase cocktail and pectate lyase. When using the gizzard digesta as substrate, GH8 xylanase reduced (P<0.005) both insoluble and soluble NSP levels compared to the control, regardless of diet type. Analysis of NSP degradation in jejunal digesta from birds fed the wheat-soy diet revealed that the three xylanases and arabinofuranosidase reduced (P<0.001) insoluble NSP level compared to the control, but the soluble NSP level was not affected by the enzyme treatments. All enzymes, except the cellulase cocktail and pectate lyase, reduced (P=0.005) the insoluble NSP level in the jejunal digesta collected from birds fed the maize-soy diet. Similarly, all enzyme preparations reduced (P<0.001) the insoluble NSP level in ileal digesta obtained from birds fed the maize-soy diet. The GH10 and GH11 xylanase, XYN+BG, cellulase cocktail and pectate lyase reduced (P<0.001) the insoluble NSP level in the ileal digesta from birds fed the wheat-soy diet compared to the control, with XYN+BG exhibiting the greatest reduction. Collectively, the present in vitro study indicated that the in vitro efficacy of enzyme preparations was dictated by the amount and type of NSP remaining undigested in various parts of the gut, which perhaps affect the in vivo efficacy.

Evaluation of increasing levels of a microbial phytase in phosphorus deficient broiler diets via live broiler performance, tibia bone ash, apparent metabolizable energy, and amino acid digestibility

The objective was to investigate increasing concentrations of an evolved microbial phytase on male broiler performance, tibia bone ash, AME, and amino acid digestibility when fed diets deficient in available phosphorus (aP). Experiment 1 evaluated the effects of phytase during a 21 d battery cage study and Experiment 2 was a 42 d grow-out. Experiment 1 included six treatments; negative control (NC) with an aP level of 0.23% (starter) and 0.19% (grower), two positive controls (PC) consisting of an additional 0.12% and 0.22% aP (PC 1 and PC 2), and the NC supplemented with three levels of phytase (250, 500, and 2,000 U/kg). The NC diet reduced (P < 0.05) FC, BW, and bone ash. Phytase increased (P < 0.05) BW with 2,000 U/kg phytase yielding similar results to the PC2, and improved FCR and increased bone ash was observed at all phytase levels. Amino acid digestibility coefficients were increased (P < 0.05) with phytase at 250 U/kg. Phytase at all rates increased (P < 0.05) AME to levels similar level as PC diets. Linear regression analysis indicated average P equivalency values for BW and bone ash of 0.137, 0.147, and 0.226 for phytase inclusion of 250, 500, and 2000 U/kg, respectively. Experiment 2 included a PC consisting of 0.45%, 0.41%, and 0.38% aP for the starter, grower, and finisher, respectively; NC with reduced aP of 0.17%; and phytase at 500 and 2,000 U/kg. Phytase increased BW (P < 0.05) compared to the NC as 2,000 U/kg phytase resulted in further BW increases compared to the PC (starter and grower). Phytase improved FCR to levels comparable to the PC, with supplementation at 2,000 U/kg resulting in improvements beyond the PC in the starter phase. Amino acid digestibility coefficients were increased with phytase at 2,000 U/kg to levels comparable to that of the PC. These data confirm that the inclusion of phytase improves broiler performance and bone mineralization in aP reduced diets and levels beyond the traditional 500 U/kg can result in further improvements.