Meta-analysis of the effect of oregan as a dietary additive for broiler chickens on growth performance and nutrient digestibility

Abstract

Phytogenic additives are characterized as an alternative to increase the efficiency of diets for broilers, modulating intestinal microbiota. Moreover, they have several other benefits, such as, the stimulation of digestive enzymes, resulting in feed digestibility improvement and higher productive performance. In the literature, there is a large amount of work that evaluated the use of phytogenic additives in the diet of broiler chickens, with oregano being the most investigated. The use of oregano as a dietary additive seems promising, however, the different evaluation conditions (heterogeneity among studies) result in inconsistent evidence. Oregano can be used as a plant extract (dehydrated and ground) or processed (e.g. aqueous extract or essential oil), it may vary in quality, and can be included in the diet in different doses, making it difficult to interpret this subject in the literature. Furthermore, there are other factors which can interfere in this additive effectiveness, such as the health challenge in which the experiment is conducted (microbial challenge), the genetics and physiology of the chickens, the feed composition, and others. At the same time, so far, we have not identified any meta-analysis work that proposed to organize the subject. Thus, the objective of this project will be to evaluate the effect of oregano as an additive in diets for broiler chickens on the performance and nutrient digestibility through a meta-analytical study, identifying the factors that may interfere in the results. (AU)