Effects of oregano oil on growth performance of nursery pigs

Objective: Two experiments were conducted to evaluate the effects on nursery pig growth performance of feeding a diet containing oregano oil (ORG), an in-feed antimicrobial, or no additive. Materials and methods: In Experiment One, a total of 224 nursery pigs were used in a 28-day trial. Dietary treatments included a control (without ORG or antimicrobial), the control diet containing neomycin and oxytetracycline (154 mg per kg of each; NT), ORG, or both NT and ORG. In Experiment Two, the five dietary treatments included the control, control diet plus NT, and control diet with ORG at 25, 50, and 100 g per tonne for 28 days. Pigs and feed were weighed to determine ADG, average daily feed intake (ADFI), and feed efficiency (gain:feed; G:F). Results: There was no differences in ADG, ADFI, or G:F in either experiment whether pigs were fed diets with or without ORG (P > .05). In Experiment One, Days 0 to 28, ADG, ADFI, G:F, and final weights were better in pigs fed diets containing NT than in pigs not fed NT (P < .05). In Experiment Two, ADG and ADFI were greater in pigs fed NT than in pigs fed the control or ORG diets (P < .01). Implication: Under the conditions of this experiment, addition of in-feed antimicrobials enhanced growth performance of nursery pigs, but addition of oregano at a range of dosages did not.