Evaluation of alternative feed ingredients and phytase supplementation for broiler chickens

Abstract

Modern poultry production requires nutritional strategies capable of improving productive efficiency, reducing feed costs, and promoting the sustainable use of available resources. In this context, the evaluation of alternative feed ingredients and the use of exogenous enzymes have emerged as relevant tools for optimizing broiler nutrition. Accordingly, this thesis was developed to contribute to the nutritional management of broiler chickens through two complementary approaches: the determination of the nutritional value and metabolizable energy values of alternative feed ingredients and the evaluation of phytase supplementation in diets with planned nutritional reductions. The first study aimed to determine the apparent metabolizable energy (AME) and nitrogen-corrected apparent metabolizable energy (AMEn) values of alternative feed ingredients used in broiler diets. Eight ingredients were evaluated: whole annatto seed meal, spray-dried porcine plasma, poultry viscera meal, three sources of soybean acid oil, distillers corn oil, and degummed rice bran oil. The determined AME and AMEn values were, respectively, 7,023 and 6,841 kcal/kg, 7,743 and 7,466 kcal/kg, and 8,318 and 7,913 kcal/kg for the three soybean acid oil sources; 8,554 and 8,457 kcal/kg for distillers corn oil; 8,273 and 7,910 kcal/kg for degummed rice bran oil; 999 and 975 kcal/kg for whole annatto seed meal; 3,388 and 2,753 kcal/kg for spray-dried porcine plasma; and 3,691 and 3,216 kcal/kg for poultry viscera meal. These findings demonstrated substantial variation among the evaluated ingredients, reinforcing the importance of the specific nutritional characterization of each feedstuff to improve the precision of diet formulation. The second study evaluated the effects of phytase supplementation in nutritionally deficient diets on growth performance, blood biochemical parameters, bone characteristics, and body composition of broiler chickens. Phytase supplementation restored body weight gain, feed conversion ratio, bone mineralization, serum calcium and phosphorus concentrations, as well as lean tissue and bone deposition, achieving results comparable to those obtained with nutritionally adequate diets, even under reductions in available phosphorus, calcium, sodium, metabolizable energy, crude protein, and digestible amino acids. Overall, the results demonstrate that nutritional efficiency in broiler production can be enhanced through the combination of accurate nutritional evaluation of alternative feed ingredients and the use of technologies that improve nutrient utilization. The use of alternative feed ingredients increases formulation flexibility and may reduce dependence on conventional feedstuffs, whereas phytase supplementation enhances nutrient availability and sustains productive performance in more cost-effective feeding programs. Keywords: agro-industrial coproducts; exogenous enzymes; metabolizable energy