Abstract
Efficacy of the phytogenic feed additive oregano essential oil (OEO) (Origanum vulgare L.) was assessed as an alternative to an antibiotic as a growth promoter (AGP) in broiler diets. Three hundred male broiler chicks were assigned to five treatments, which consisted of diets with different levels of OEO (300, 600, and 900 mg/kg of diet), a negative control, and a positive control. Broiler performance was evaluated from 1 to 21 and 1 to 39 days old. From 1 to 39 days old, the broilers of the negative control group presented lower feed intake than those fed OEO300. No significant effect was observed on weight gain. The greatest feed conversion ratio occurred in the positive control group. Broilers treated with OEO300 had greater carcass yield than those in the positive control group. The haemogram, leukogram, and heterophil/lymphocyte ratio were positively influenced by OEO300. Red blood cell and leukocyte counts increased in a dose-dependent manner in broilers fed OEO-supplemented diets, while broilers in the positive control group had the lowest levels of haematocrit, mean corpuscular haemoglobin concentration, and plasma protein. Differential leukometry revealed lymphocyte numbers were increased with OEO treatment and reduced in the positive control group. For hepatic and renal metabolism, the broilers in the positive control group exhibited the greatest serum activities of aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, and alkaline phosphatase. Although more studies on its efficacy are needed, OEO at 300 mg/kg may be used as a phytogenic additive in broiler diets, especially those without AGP.Keywords: antibiotic as growth promoter, immune system, phytogenic feed additive
Highlights
The production of secondary compounds that are essential for plant survival and preservation depends on genetic and environmental factors
The average feed consumption was greater than that suggested for the manual feeding of Cobb 500 broilers (Cobb-Vantress-Brasil, 2008), indicating that any health challenge to which the broilers were subjected with 5% bedding mixed in the diet did not affect the variables
The performance results in the initial phase are in agreement with those obtained by Kirkpinar et al (2011) and Alp et al (2012), who found no difference for feed intake, weight gain and feed conversion at day 21 in broilers administered 300 mg oregano essential oil (OEO)/kg diet
Summary
The production of secondary compounds that are essential for plant survival and preservation depends on genetic and environmental factors Many of these compounds elicit different reactions in living organisms and are called active principles. These plants are characterized as being medicinal, since they exhibit therapeutic activities owing to the presence of one or more active principles (Martins et al, 2003). These plants can be added to animal diets as phytogenic feed additives after being dried and milled or as essential oils (Jacela et al, 2010; Madhupriya et al, 2018). Oregano essential oil has been associated with antifungal (Bedoya-Serna et al, 2018), antibacterial, and antioxidant activity in vitro (Gandra et al, 2013) and in vivo (Zanini et al, 2013; Ri et al, 2017), stimulation of enzyme secretion (He et al, 2017), and modulation of microbial colonization of the gastrointestinal tract and intestinal morphology
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