Effects of dietary supplementation of encapsulated essential oils on growth performance, intestinal morphology and bacterial population of Japanese broiler quails

The aim of this study was to determine the effects of adding encapsulated thyme and fennel essential oils to the compound feed of broiler quail (Coturnix coturnix japonica) on growth performance, intestinal morphology, and bacterial population. A total of 160 one-day-old quail chicks were used. The quails were divided into 4 groups, each arranged with 10 replicates and 4 chicks per replicate, and quails were fed experimental diets for 5 weeks. While the control group was fed a normal basal diet, the treatment group's diet included 250 mg of encapsulated fennel essential oil, thyme essential oil, and a combination of these oils per kg of feed. At the end of the study, there was no significant difference in body weight gain between the groups (P>0.05). Encapsulated thyme essential oil added to the diets reduced feed intake and improved feed efficiency (P<0.05). In female quails, there was no significant difference between the groups in terms of Clostridium perfringens and Escherichia coli presence (P>0.05), but an increase in Lactobacillus spp. was observed in those fed diets containing encapsulated thyme essential oil (P<0.05). In male quails, no significant difference was found between groups in the presence of Clostridium perfringens, Escherichia coli, and Lactobacillus spp. (P>0.05). Encapsulated fennel essential oil added to the diets increased the duodenum villus height, width, area, and villus height/crypt depth ratio (P<0.05). However, quails fed with the combined essential oil diets showed a reduction in jejunum and ileum villus height and width (P<0.05). Additionally, an increase in ileum villus height and villus area was observed in animals fed with diets containing encapsulated thyme essential oil (P<0.05). In conclusion, we determined that dietary supplementation of the encapsulated fennel and thyme essential oils individually, rather than in combination, to the diets is more appropriate. Future studies are recommended to investigate different levels of these oils and their combinations with various phytogenics.