An innovative approach to emulsifier use in broiler feed affects nutrient digestion and growth performance in young broilers.

1. This study evaluated the effect of oil-in-water (o/w) emulsion supplementation in feed compared to a conventional oil and emulsifier combination on fat and protein digestibility and growth performance in broiler chickens. The effects of this supplementation on macronutrient digestion kinetics were investigated through simulated in vitro digestion based on the broiler gastrointestinal tract.2. A total of 450 one-d-old Ross 308 chickens were assigned to one of the five dietary treatments consisting of nine replicates of 10 broilers each. The treatments included a control diet containing oil (3.25%) without emulsifiers, (NON-EM Low) or with a low emulsifier inclusion (0.10%), an EM Low diet supplemented with o/w emulsion using a low emulsifier concentration (3.25% oil; 0.10% emulsifier), a NON-EM High diet supplemented with oil (3.25%) and a emulsifier at high inclusion (0.65%) or a EM High diet supplemented with o/w emulsion using emulsifier at high inclusion (3.25% oil; 0.65% emulsifier). The feeding trial lasted 21 d using growing broilers.3. Body weight gain was higher in o/w emulsion diets EM Low and High compared to the other three diets. Fat digestibility at 21 d of age was not significantly different, although protein digestibility was lower in birds fed EM Low and EM High diets.4. In vitro digestion was substantially different in lipolysis, protein and starch hydrolysis kinetics. O/w emulsion supplementation reduced lag times in lipolysis and starch digestibility, and adding emulsifier altered the overall protein and lipid digestion kinetic behaviour.5. In conclusion, this study showed that o/w emulsion supplementation significantly improved broiler performance, most likely caused by differences in nutrient digestion kinetics in the starter phase. This research showed the potential of in vitro simulation to complement in vivo trials to understand digestion kinetics or to perform screening of potential diets before performing in vivo trials.