Effect of orégano oil supplementation in diets formed using either crude soybean oil or acidulated soybean oil soapstock as source of energy on the growth performance parameters of broilers

Abstract

The type of oil used in the broiler diet is mainly based on its price; in the case of soybean oil (CSO), acidulated soybean oil soapstock (ASS) is cheaper. The aim of the present study was to evaluate the effect of oregano oil dietary supplementation when the diet contains either CSO or ASS as source of energy. 320 broilers Ross 308 were assigned to four groups: (1) CSO containing diet without oregano supplementation, (2) ASS containing diet without oregano supplementation, (3) CSO containing diet with oregano supplementation (100 mg/kg), and (4) ASS containing diet with oregano supplementation (100 mg/kg). The growth performance parameters were weekly recorded during the experiment. Data were analysed with a completely randomised design with 2 X 2 factorial arrangement and the mortality rates were adjusted using the arc-sine transformation to fulfill the analysis requirements. The results showed no effect of oregano oil (containing 30.7 and 9.7 % of thymol and carvacrol, respectively) on feed intake, weight gain and feed conversion rate. A significant interaction of energy source by oregano oil supplementation was found in mortality rates (P < 0.05); mortality was higher when the diet did not contain oregano oil and was formed using ASS. It can be concluded that the addition of 100 mg of oregano oil per kg of feed did not have a positive effect on the growth performance parameters of broilers when the diet contained either crude soybean oil or acidulated soybean oil soapstock as sources of energy.