Evaluation of Nutritional Factors that Influence the Efficacy of Tributyrin as a Feed Additive for Broilers

Tributyrin (TB) is a glyceride ester of butyrate that has the potential to improve broiler performance and intestinal development. Therefore, to fully evaluate this potential, three experiments were conducted to evaluate effect of tributyrin (TB) on broiler growth performance, nutrient digestibility, carcass characteristics, intestinal morphology, and gastrointestinal function in birds fed diets varying in composition reared in battery cages and floor pens. Experiment 1 explored the supplementation of graded doses of TB and its impact upon growth performance, nutrient digestibility, and carcass characteristics in a step-down program when added to a reduced energy and amino acid diet. A linear reduction in body weight gain and a quadratic response in feed conversion ratio was observed with increasing amounts of TB up to 5 times the recommended dose from d 0 – 35. In addition, a linear increase in fat pad yield and a linear reduction in breast meat yield were observed with increasing amounts of TB in the diet. When evaluating the 3 TB doses used in Experiment 1, growth performance was not negatively affected in birds fed 500 mg/kg of TB when compared to birds fed 3 to 5 times that level. Due to the differences between this study and previously published research, diet composition was subsequently evaluated as a potential source for differences observed in TB utilization among those studies. Therefore, in Experiment 2, TB supplementation, lipid source, lipid concentration, and corn particle size and their potential interactive effects on growth performance and nutrient digestibility were evaluated in 2 battery trials. Overall, TB efficacy was not consistently affected by dietary lipid source and lipid concentration. The same can be inferred regarding corn particle size as no differences were observed in broilers growth performance or gizzard function, with or without the inclusion of TB. Experiment 3 evaluated TB efficacy on growth performance, nutrient digestibility, and gastrointestinal pH in birds fed either animal or vegetable-based proteins reared in either battery cages or floor pens. Compared with diets containing animal protein, all vegetable-based diets with elevated soybean meal levels may result in increased non-starch polysaccharide content leading to increased short chain fatty acid (SCFA) production. Therefore, increasing SCFA production may confer a synergistic effect between an exogenous source of butyrate and increased production of endogenous butyrate. However, no effects of TB or interaction with diet type were observed in growth performance, nutrient digestibility, or ileal and cecal pH throughout the experiment in 15 d battery cage trial or a 42 d floor pen trial. However, birds fed animal protein-based diets did have improved growth performance compared to birds fed vegetable based diets. Additionally, growth performance of birds fed animal protein or vegetable protein diets with or without the inclusion of TB, was not significantly different between the two rearing environments