Oregano: Not Just for Pizza Anymore | Dairy Herd

Move over, pizza and pasta. Oregano – specifically, its essential oil – is finding its way into calf diets.

Oregano essential oil has been shown to have antibacterial properties against Gram-negative bacteria, especially E. coli. It also has been shown to have antiviral and anticryptosporidial effects in laboratory settings.

Two recent studies examined the effects of oregano essential oil in calf diets.

The first study, led by researchers at Aristotle University of Thessaloniki in Greece, examined the effects on early life diarrhea by supplementing newborn calves with Greek oregano essential oil. A total of 91 Holstein calves from three dairy farmers were included.

Half of the calves received a drench of oregano essential oil at 12.5 mg/kg of bodyweight for the first 10 days of life. The other half received no treatment. The researchers noted that, because oregano oil has a strong flavor, they opted for a drench delivery to avoid affecting milk intakes. The oil was diluted with saline solution up to 60 mL.

Results included:

· The overall incidence of diarrhea was significantly lower in the calves receiving oregano oil. That difference was the result of a dramatically lower incidence at one of the farms, which had outstanding hygiene, leading the researchers to speculate that diarrhea incidence was reduced most effectively by oregano oil when pathogen loads were low.

· For calves from all farms, the severity of diarrhea was appreciably lower in the oregano-oil-treated calves. This was the result of a lower number of days with diarrhea, lower diarrhea index, shorter duration of sickness, and fewer calves requiring treatment (antibiotic and supportive therapy).

The researchers speculated that reduced severity of diarrhea in calves treated with oregano oils was due to inhibition of coliform bacteria overgrowth in the small intestine of diarrheic calves, leading to lower incidence of bacteremia.

The second study, conducted at the Gansu Academy of Agricultural Sciences in China, examined the potential of replacing monensin with oregano essential oil in the grower diet of weaned Holstein bull calves. The research team speculated that oregano could provide the same benefits to rumen fermentation as monensin, modulating rumen fermentation and potentially lowering acidosis.

One of four treatments was assigned to three calves each, for a total of 12 calves in the study. Starting at 70 days of age, calves were followed for the next 240 days, receiving (1) no treatment (control); (2) oregano essential oil at 36 mg/kg of dry matter (DM)in the TMR; (3) monensin at 25 mg/kg of DM; and (4) a combination therapy including both the same dose of oregano oil and monensin.

Both the oregano essential oil group and the monensin group had significantly higher weight gain than the other two groups. Interestingly, the lowest weight gain was in the combination therapy group, leading the researchers to believe that the two treatments had an antagonistic effect on one another.

They concluded that using oregano essential oil alone could be a valid alternative to monensin, providing a non-antibiotic alternative that still yielded growth promotion benefits.