Oregano (Origanum vulgare L.) aqueous extract diet supplementation enhances defense ability of pig gut

Conjugated Linoleic Acid supplementation of pig diet showed to have positive effects on the saturated and monounsaturated fatty acids/monounsaturated FA ratio in meat products and that its antioxidative properties can be transferred to derivated products used for human nutrition [1]; in addition, Oregano aqueous extract showed to enable good growth performance, enhancing both the quantity and quality of glycoconjugates involved in indirect defence actions in broiler chickens [2]. This work is aimed to recognize the glycoconjugates and to evaluate the oxidative stress in duodenum and colon of pigs fed as finisher stage for 84 days with different diets represented by: (1) degermed corn-barley-soybean-based diet supplemented (0,5 g/kg) with conjugated linoleic acid which included cis9-trans11 and trans10-cis12 isomers in equal parts (CLA); (2) CLA diet supplemented (2 g/kg) with an oregano aqueous extract (O). Glycohistochemistry was performed by staining with Periodic acid-Schiff (PAS), Alcian blue (AB) pH 2.5, AB-PAS, AB pH 1, AB pH 0.5, low iron diamine, high iron diamine. Adjacent serial sections were pre-treated with Sialidase V before staining with AB pH 2.5 (Sial-AB) preceded or not by saponification with 1% KOH in 70% ethanol to remove the acetyl groups (KOH-Sial-AB) [3]. For the study of the oxidative stress, two proteins were tested by immunohistochemistry, BAX and p53. The reaction was visualized on 5 µm serial sections, utilising the primary mouse monoclonal antibodies anti-BAX and anti-p53, the secondary corresponding antibody, the avidin-biotin-complex and the DAB as the chromogen. The samples tested were positive with histochemical treatments at the goblet cell level in both colon and duodenum, where also duodenal glands were reactive. Data analysis evidenced significant differences to the histochemical treatment reactivity among the dietary treatments. The most noticeable difference regarded the response to Sial-AB and KOH-Sial-AB histochemical treatments that induced differentiated behavior of goblet cells in both duodenum and colon of samples derived from O diets. In particular O diets that enhanced the gut production of highly acid glycoconjugates which improve the mucosae lubrication and the formation of a viscoelastic barrier, with an unspecific defence mean. O diet also induced the sialilated glycoconjugate production by goblet cells, particularly at duodenum level, with specific defence action. Immunohistochemical results showed a very low expression of BAX in the duodenum and colon of O group (+/-) vs CLA group (++), while for p53 its expression was evident in animals of O groups (+) while it was very low in animals of CLA group (+/-). In conclusion, oregano aqueous extract seems to strongly improve the defence ability, in addition to decrease the oxidative stress of pig gut.