Exogenous enzyme strategies in broiler diets: impacts on performance, nutrient utilisation and metabolic efficiency

Abstract

This thesis investigated the effects of different exogenous enzyme supplementation strategies on the nutritional and metabolic efficiency of broiler chickens. Two complementary studies were conducted to evaluate phytase superdosing and multi- enzyme supplementation in nutritionally reduced diets containing plant- and animal- derived ingredients. In the first study, the effects of phytase superdosing were evaluated in diets formulated with corn, soybean meal, and meat and bone meal. Increasing phytase inclusion levels improved feed conversion ratio and enhanced bone mineralisation, with linear increases observed in metabolisable energy and nutrient metabolizability coefficients. Supplementation with 2000 and 2500 FTU/kg resulted in greater calcium and phosphorus deposition in bones, increased nutrient utilization by up to 29%, and reduced phosphorus excretion by more than 30%, demonstrating that phytase superdosing remains effective even in diets containing mixed phosphorus sources. The second study evaluated exogenous enzyme supplementation in nutritionally reduced diets, focusing on growth performance, metabolisable energy, and amino acid digestibility. Enzyme inclusion promoted nutritional recovery, increased metabolisable energy values, and improved amino acid digestibility, demonstrating that enzymatic strategies can mitigate the effects of dietary nutrient reduction without compromising bird performance. Collectively, the results demonstrate that exogenous enzyme supplementation, whether through phytase superdosing or multi-enzyme complexes, improves nutrient utilization, metabolic efficiency, and sustainability in broiler production systems. These findings reinforce the role of enzyme technology as a multifunctional nutritional tool capable of optimizing feed efficiency and reducing the environmental impact of modern poultry production. Keywords: exogenous enzymes; phytase; broiler chickens; nutrient utilization; metabolisable energy; amino acid digestibility; bone mineralisation; sustainability