Metabolism and Nutrition: Feed Additives I

The mode of action of essential oils (EO) as growth promoters is not fully understood. One experiment was conducted to evaluate the effects of EO concentration and grain type on broiler intestinal traits. Corn (C) and wheat (W) based basal diets were formulated to have similar nutrient composition within each dietary phase. The EO containing benzoic acid (Crina Poultry Plus) was added to each basal diet to have 0, 150, or 300ppm. Starter, grower, and finisher diets were fed from 0—14d, 15—35d, and 35—47d, respectively. At hatch, 720 Ross 708 male broilers were identified and placed in 72 floor pens. At the end of each dietary phase one broiler per pen was selected, sacrificed and the length of intestines, the weights of pancreas, duodenum, jejunum, and ileum, and the pH of the proximal duodenum contents were determined. Mucus digesta content was quantified using a colorimetric procedure. Data were analyzed as a 2x3 factorial design with grain type and EO concentration as main factors. Results indicated an interaction effect (P < 0.05) on pH at 47d, with EO increasing pH in chickens fed W diets, and reducing it in broilers fed C diets. Less mucus was observed in 47d chickens fed diets with 300ppm EO than in diets without EO. An interaction effect (P ≤ 0.05) was observed at 35d with less mucus in the C diets than in W diets at 300ppm EO. At 14 and 47d, the pancreas relative weight (RW) was bigger (P < 0.05) in C than in W. At 14d the pancreas RW was larger (P < 0.05) in chickens fed 300ppm EO than in those without EO, and at 47d pancreas RW of broilers from 150ppm diets was bigger than diets without EO. At 35d, the intestine was shorter in chickens fed 300ppm diets than fed 0 and 150ppm diets. At 47d, the intestine was longer in chickens fed C diets compared with W diets. At all collections, C chickens had bigger (P < 0.05) ileum RW than W. In general, the EO increased pancreas size, reduced intestinal length, and reduced mucus production, while C diets caused increased pancreas RW and intestinal length compared with W diets. It was concluded that EO may affect intestinal development and function with different effects depending on grain type.