The objective of this experimental study was to investigate the effects of essential oils of oregano, laurel and their combination on growth performance, intestinal microbiota and intestinal morphology as replacers of antibiotic growth promoters, as well as on the antioxidant capacity and mineral content of breast and thigh meat. A total of 256 day-old broiler chickens were randomized into 4 groups with 4 replicates. Control group received a basal corn-soybean diet, whereas the other experimental groups received the basal diet plus 25 mg/kg oregano essential oil, 2.5 mg/kg laurel essential oil or their combination, respectively. Chickens had free access to water and feed. Body weight gain and feed to gain ratio was calculated for the total fattening period and mortality was daily recorded. Intestinal microbiota was enumerated by conventional techniques with selective agar media at the end of the trial at both ileum and caecum. Also, evaluation of intestinal morphology was carried out in small intestine and caecum. At the end of the trial, birds were slaughtered, their carcasses were processed and samples of breast and thigh meat were analyzed for moisture, fat and protein content. Total phenolic content was determined in feeds and breast and thigh meat in order to assess its antioxidant capacity. Mineral content of breast and thigh meat was evaluated by ICP-MS. The results of the trial showed that the group that received oregano or the mixture of oregano and laurel presented better BW and FCR and mortality compared to control group. Bacterial counts for the Lactobacilli and Bifidobacteria were higher in the experimental groups compared to the control group at both ileum and caecum, and total coliforms were lower in caecum in the experimental groups compared to control. Higher values for villus height were found for the oregano supplemented groups compared to control or laurel ones. Oregano supplemented groups showed higher antioxidant capacity of breast and thigh meat compared to control and laurel groups, however no changes in mineral content were noted among the different groups. In conclusion, oregano essential oil alone or as a mixture with laurel essential oil can be used to improve growth performance and gut health in broiler chickens.
The normal distribution is considered to be one of the most important distributions, with numerous applications in various fields, including the field of agricultural sciences. The purpose of this study is to evaluate the most popular normality tests, comparing the performance in terms of the size (type I error) and the power against a large spectrum of distributions with simulations for various sample sizes and significance levels, as well as through empirical data from agricultural experiments. The simulation results show that the power of all normality tests is low for small sample size, but as the sample size increases, the power increases as well. Also, the results show that the Shapiro–Wilk test is powerful over a wide range of alternative distributions and sample sizes and especially in asymmetric distributions. Moreover the D’Agostino–Pearson Omnibus test is powerful for small sample sizes against symmetric alternative distributions, while the same is true for the Kurtosis test for moderate and large sample sizes.