Effect of a commercial essential oil on growth performance, digestive enzyme activity and intestinal microflora population in broiler chickens

The present study was designed to evaluate whether a blend of essential oils (EO) extracted from herbs could affect growth performance, digestive enzymes and antimicrobial activity of the gut in growing broiler chickens. A total of one hundred and twenty, 3-day-old male broiler chickens were assigned to the basal diet (CON) and the basal diet supplemented with 10mg antibiotics/kg diet (ANTI), 25mgEO/kgdiet (EO I) and 50mgEO/kg diet (EO II) until 35 days of age. Through-out the entire feeding period (3-35 days), there were no differences in body weight, feed intake, total gain and feed:gain ratio among the birds fed the basal diet and the diet supplemented with antibiotics, either low (EO I) or high level of EO (EO H). Weights of digestive organs including the liver, pancreas, intestine and mucosal tissues were not affected by the dietary treatments. Total and specific activities of pancreatic trypsin significantly (P < 0.05) increased in birds fed EO II diet compared with those fed CON and ANTI diets. It was also observed that the total activities of pancreatic alpha-amylase and intestinal maltase significantly (P < 0.05) elevated in birds fed EO II diet compared with those fed CON diet. The colony forming units (CFU) of Escherichia coli in the digesta of ileo-cecum in the ANTI group showed a significantly lower number compared with that in the CON group. However, there was no difference in the CFU of E. coli between the ANTI and EO groups. The CFU of lactobacilli was unaffected by dietary supplementation of either EO or antibiotics. In summary, dietary addition of EO showed a decreased E. coli population in ileo-cecal digesta. Furthermore, a high dose of EO resulted in a significant increase in certain digestive enzyme activities of the pancreas and intestine in growing broiler chickens. (c) 2006 Elsevier B.V. All rights reserved.