Phytase and carbohydrase inclusion strategies to explore synergy within low-energy diets to optimize 56-day male broiler performance and processing

Research is needed to maximize the use of common feed enzymes, phytase and carbohydrase in combination. The objective was to determine effects of 2 phytase doses (PD; 250 [single dose] or 1,500 [super dose] FTU/kg) and 3 carbohydrase enzymes (xylanase [XAN]; mannanase [MAN]; or their combination [XM]) on 0- to 55-d broiler performance and processing (day 45 and 56). Enzymes were applied to a negative control (NC) diet formulated to 95% of breeder recommendations; Ca and available P reduced by 0.145%, and AME by 100 kcal/kg. A positive control diet only differing in AME was also tested, as well as NC alone; results were used for preplanned contrast comparisons. For the factorial, a 0- to 14-d interaction demonstrated optimal feed conversion ratio (FCR) for 1,500 FTU/kg + XM but worst for 250 FTU/kg + XM; feeding XAN regardless of PD brought FCR comparable to 1,500 FTU/kg + XM. Inclusion of MAN resulted in similar 0- to 14-d FCR to 250 FTU/kg + XM. Significant carbohydrase enzyme effects demonstrated maximized 0- to 44-d and 55-d BW and BW gain (BWG) for XAN. Tender yields (day 45) improved with 1,500 FTU/kg PD, but no day-56 PD significance. Foot pad dermatitis scoring was only significant for PD, with increased scores of 1 for 1,500 FTU/kg. Contrasts demonstrated improved day-0 to day-44 BWG and day-45 breast and drumstick weight for XAN + 1,500 FTU/kg vs. NC. Furthermore, feeding 1,500 FTU/kg + XAN increased day-45 scores of 0 and decreased day-56 woody breast scores of 2 when individually compared to NC and positive control. Overall data demonstrate performance/processing benefits for XAN and 1,500 FTU/kg alone and combined.