In the search to replace antibiotic growth promoters with effective alternatives in modern swine production, plant-based essential oils are showing potential to provide lasting benefits.
In a rare long-term public study that compared the effects of phytochemicals from rosemary and oregano with antibiotic growth promoters, animal scientists with the Arkansas Agricultural Experiment Station found that the natural agents given to weaned pigs supported favorable gut health and growth performance later in their lives by preserving microbial diversity to improve nutrient utilization.
“This study allowed us to look at the lifetime impact from phytochemical exposures,” says Tsungcheng “TC” Tsai, Ph.D., a program associate in the department of animal science for the experiment station, the research arm of the University of Arkansas System Division of Agriculture. “If you just look into the nursery phase — the first 43 days after weaning — and you don’t see any difference, the study is ended, and you don’t really know the true value of those phytochemicals.”
Antimicrobial resistance, and other concerns
While antibiotic medications have their time and place in veterinary medicine, Tsai says extensive use has accelerated the emergence of antimicrobial resistance and led to bans or restrictions in many countries.
Besides antibiotics, high levels of dietary zinc have also been frequently incorporated into swine diets to mitigate postweaning diarrhea. However, there are also environmental concerns associated with overreliance on excessive zinc excretion, including heavy metal accumulation in the environment, Tsai notes. Pig waste is commonly used as a fertilizer, which can lead to levels of zinc that are toxic to plants.
Essential oils from plants like rosemary and oregano have been shown in many studies, Tsai says, to have beneficial effects on animal health, including poultry, fish and swine. However, most of the studies have focused on short-term responses, often limited to the nursery phase.
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