The effect of inclusion in drinking water, either singly or alternating, of oregano oil and a probiotic Enterococcus faecium strain on gut health characteristics of growing broiler chickens

The hypothesis of this study was that, during a 42-day growth period, the inclusion of oregano oil and a probiotic Enterococcus faecium strain in drinking water, either singly or alternating, would positively impact on gut health characteristics of growing broiler chickens such as excreta pH and dry matter content, and selected histomorphological parameters, i.e, villus height, crypt depth, villus height to crypt depth ratio, and crypt width. Four-hundred Ross 308 chicks (mixed-sex; mean body weight 45.1 g (standard deviation 1.04 g)) were randomly assigned to four experimental groups during the 42-day growth period: control (without supplement), probiotic (continuous supply of an E. faecium commodity [minimum activity per kg: 3.3 × 10¹² colony forming units] with drinking water at 200 mg/L), oregano oil (75,000 mg/kg of product; first three days of each week at 0.2 mL/L drinking water), and oregano oil-probiotic (addition of oregano oil (0.2 mL/L) for three days and E. faecium commodity (200 mg/L) for four days to drinking water), each group with 10 replicates and each replicate with 10 broilers. Excreta pH and dry matter content were unaffected by dietary treatment. Only in the finisher phase of the growth period, the oregano oil group had slightly higher excreta dry matter content. However, the probiotic and oregano oil-probiotic supplements affected histomorphological parameters; the villus height in the ileum was higher compared with the other experimental groups. Moreover, in the ileum of broilers in the oregano oil-probiotic group, the crypt depth was deeper and the villus height to crypt depth ratio was wider than for the other experimental groups. Yet, crypt width in the ileum was not influenced by additives. Overall, the oregano oil-probiotic administration in drinking water positively affected selected histomorphological gut characteristics in growing broiler chickens. Consequently, the administration with drinking water may be a viable way to supply these types of feed additives to diets of growing broiler chickens. Future studies should be conducted applying varying concentrations of the additives supplied with drinking water.