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 <i>in vitro</i> 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. <i>In vitro</i> 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 <i>in vitro</i> simulation to complement <i>in vivo</i> trials to understand digestion kinetics or to perform screening of potential diets before performing <i>in vivo</i> trials.