Effect of oregano (Origanum onitesL.) essential oil on growth, lysozyme and antioxidant activity and resistance againstLactococcus garvieaein rainbow trout,Oncorhynchus mykiss(Walbaum)

Abstract

The aim of this study was to investigate the effects of different levels of Origanum onites L. essential oil as feed additives on the growth performance, antioxidant activity and disease resistance of rainbow trout. Fish (26.05 AE 0.15 g) were fed the experimental diets supplemented with four different concentrations (0.125, 1.5, 2.5 and 3.0 mL kg À1 ) of O. onites essential oil for 90 days. Fish fed diets containing essential oil of O. onites had significantly higher final weight than the control group. Feed conversion ratio in fish fed diets containing 1.5 and 3.0 mL kg À1 essential oil of O. onites was improved than other treatments (P < 0.05). The lowest feed conversion efficiency ratio was recorded in the 0.125 mL kg À1 group of O. onites. Antioxidant status of fish was assayed for levels of plasma superoxide dismutase (SOD) and plasma catalase (CAT) activity. Lysozyme activity in plasma was significantly higher in fish fed diet containing 3.0 mL kg À1 essential oil of O. onites (P < 0.05). After 8 weeks of feeding, fish were challenged with Lactococcus garvieae and cumulative mortality was recorded over 15 days. Dietary administration of 0.125, 1.5 and 2.5 mL kg À1 O. onites significantly reduced fish mortality (P < 0.05). The 3.0 mL kg À1 diet showed no mortality after challenged with L. garvieae. These results suggested that the essential oil of O. onites could be applied as growth promoter and also improved disease resistance when added to rainbow trout feed.

Evaluation of oregano essential oil as a growth promoter and resistance stimulator against Ichthyophthirius multifiliis (Protozoa, Ciliophora) in silver catfish juveniles, Rhamdia sp. (Siluriformes, Heptapteridae)

“…Similarly, in a study also with juveniles of O. mykiss fed diets containing increasing levels of oregano essential oil, both great lysozyme activity and disease resistance were observed in fish receiving the highest level tested (3 mL kg -1 ) (DILER et al, 2017). It is worth highlighting the current scarcity of studies concerning the effects of essential oils on fish immune system, especially for Neotropical species, and nonexistent in agroecological systems of production.…”

“…As well as there was no significant influence on the results in studies using supplementation with carvacrol (main active ingredient of oregano essential oil) in diets for O. niloticus (FRECCIA et al, 2014), sea bass (Dicentrarchus labrax) (VOLPATTI et al, 2014) and rainbow trout (Oncorhynchus mykiss) (YILMAZ et al, 2015). On the other hand, in contrast to the aforementioned studies, the inclusion of oregano essential oil in the diet resulted in positive effects on the performance of juvenile channel catfish (Ictalurus punctatus) (ZHENG et al, 2009), of O. mykiss (AHMADIFAR et al, 2011DILER et al, 2017), and of A. lacustres (=A. altiparanae) (FERREIRA et al, 2014).…”

Effect on Histology and Nutrient Digestibility of Supplemented Origanum onites Essential Oil to Rainbow Trout Diets (Oncorhynchus mykiss)

“…6,7 Oregano is a member of the Labiatae family of plants. Several researchers have tested the effect on growth of oregano oil on trout, 8,9 channel catfish, 10 sturgeon 11 and tilapia. 12 In the broiler researchers have…”

Effects of dietary supplementation with oregano essential oil on prevention of the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae in juvenile chum salmon Oncorhynchus keta

“…Infection with the Gram‐positive coccus Lactococcus garvieae (Collins et al ., 1984) Schleifer et al . (1986) was significantly prevented in adult O. mykiss through 8 weeks of dietary supplementation with 0.012–0.3% oregano essential oil extracted from Origanum onites , with 0.3% supplementation the most effective (Diler et al ., ). Parasitic infections with a myxozoan Myxobolus sp., the monogenean Diplectanum aequans (Wagener 1857) and the copepod Lernanthropus kroyeri were prevented in juveniles of S. aurata , D. puntazzo and D. labrax , respectively, by dietary supplementation with 0.5–1.0% oregano essential oil extracted from O. vulgare (Athanassopoulou et al ., , ).…”