Phytase and protease improved growth performance by enhancing nutrient utilisation of broilers reared under challenge conditions

Abstract

A total of 720 broilers at day old were allocated to 9 treatments to study the influence of enzymes in a P-deficient (NC) diet. The treatments were NC diet without or with phytase, protease or phytase plus protease. The diets were fed to birds reared on clean or used litter thus producing a 2×2×2 factorial plus a P-adequate diet for reference. Each treat-ment had 8 replicates and 10 birds per replicate. Birds and feed were weighed on d 0 and 21. Three birds per pen were transferred to cages on d 16, and ileal digesta and excreta were collected on d 21. There were no interactions for any of the growth performance response but there were 3-way interactions for total tract retention. Birds raised on used litter (P < 0.01) gained 31% less weight, consumed 10% less feed and were poorer in FCR by 33%. Phytase increased (P < 0.01) weight gain (24%) and decreased FCR (18%). Birds reared on used litter had lower (P < 0.05) ileal DM and N digestibility. DM and energy retention was lower (P < 0.05) in NC diets for birds reared on used litter. The enzymes, individually, improved (P < 0.05) DM and energy retention in both litter types but the enzyme effect was greater for birds reared on used litter. It was concluded that the enzymes improved growth performance of the birds reared on used litter by enhancing nutrient utilisation to a greater extent in these birds thus helping to partially offset some of the negative consequences of depressed feed intake in birds raised on the used litter.