Effects of dietary dried Greek Oregano (Origanum vulgare ssp. hirtum) supplementation on blood and milk enzymatic antioxidant indices, on milk total antioxidant capacity and on productivity in goats

• The effects of oregano supplementation on antioxidant system's performance were studied.
• Glutathione peroxidase activity was increased in both blood plasma and milk.
• Glutathione reductase activity was increased in both blood plasma and milk.
• FRAP values of milk were improved.
• Oregano supplementation can improve the antioxidant system performance in goats.

The aim of the present study was to evaluate the effects of the dietary supplementation of dried Greek oregano (Origanum vulgare ssp. hirtum) as a whole plant on various blood and milk oxidative stress enzymatic indices, on milk total antioxidant capacity and on productivity in dairy goats. Twelve Alpine goats were used in a 4-week experiment and were allocated to 1 of 2 groups (CON, OR). The animals were fed 1.2 kg of alfalfa hay and 1.2 kg of concentrate mixtures (50% basal and 50% lactation ration) daily. The concentrate mixtures for the CON group were not supplemented with oregano, while oregano plants were incorporated into the lactation ration of the OR group, at a level of 30 g equivalent to a daily dosage of 1 ml of essential oil per animal. The goats were milked twice per day and the milk yield was recorded. At the end of each week of the experimental period, individual milk samples were obtained and analyzed for fat, milk and protein contents. Additional blood and milk samples were taken during the 3rd and the 4th week of the experimental period. The activities of the following antioxidant enzymatic indices were measured: superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase in blood and milk, glutathione transferase in blood and lactoperoxidase in milk. The OR group showed a significant increase in glutathione peroxidase and glutathione reductase both in blood (P < 0.01 and P < 0.001, respectively) and milk (P < 0.001 and P < 0.001, respectively). In addition, the dietary oregano supplementation effectively enhanced FRAP values (P < 0.001) of the milk. It can be concluded that the dietary intake of dried oregano plants positively affected at least partially, some enzymatic and non enzymatic antioxidant defenses of blood and milk and thus, contributed to enhanced antioxidant capacity of milk.