Long-Term Study Finds Herbs Boost Swine Health

Plant-based essential oils show potential as antibiotic alternatives in modern pork production.

Apr. 2, 2026 at 6:12am

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In a rare long-term public study, animal scientists at the University of Arkansas found that natural phytochemicals from rosemary and oregano provided lasting benefits for weaned pigs, supporting favorable gut health and growth performance later in life by preserving microbial diversity to improve nutrient utilization.

Why it matters

While antibiotics have their place in veterinary medicine, their extensive use has accelerated antimicrobial resistance and led to bans or restrictions in many countries. Essential oils from plants like rosemary and oregano have shown beneficial effects on animal health, but most studies have focused on short-term responses. This long-term study provides insights into the potential of natural alternatives to support sustainable and responsible pork production.

The details

The researchers randomly assigned 192 piglets to four groups after weaning: a negative control, a positive control with the antibiotic growth promoter carbadox and high dietary zinc, and two phytochemical-supplemented diets containing extracts from oregano and rosemary plants. Antibiotic and high-zinc supplementation were restricted to the immediate post-weaning period, while phytochemicals were administered continuously. The pigs that received the oregano, rosemary, and sodium humate mixture achieved the highest final body weight and best gain-to-feed ratio by day 155.

  • The study was conducted over the nursery, growing, and finishing phases, spanning a total of seven phases.
  • Piglets were randomly assigned to the four groups immediately after weaning.

The players

Tsungcheng "TC" Tsai, Ph.D.

A program associate in the department of animal science for the Arkansas Agricultural Experiment Station and the corresponding author of the study.

Ziyu Liu

The first author of the published manuscript, a graduate student in the department of animal science at the University of Arkansas.

University of Arkansas System Division of Agriculture

The research arm that conducted the study.

University of Arkansas for Medical Sciences

Collaborated on the analysis of the pigs' microbiome.

Michael Looper

Professor and Department Head of Animal Science at the University of Arkansas.

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What they’re saying

“This study allowed us to look at the lifetime impact from phytochemical exposures. 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.”

— Tsungcheng "TC" Tsai, Ph.D., Program Associate, Department of Animal Science

“These compounds may not give the instant response producers often see with antibiotics, but over time they appear to help condition the gastrointestinal tract and microbiome, so pigs handle stress better later in life.”

— Tsungcheng "TC" Tsai, Ph.D., Program Associate, Department of Animal Science

“It's an encouraging step toward more sustainable and responsible pork production. Consumers want food that's raised responsibly, and this study gives swine farmers more natural tools to do just that. It's exciting to see options that support animal health while helping produce pork that people can feel good about.”

— Michael Looper, Professor and Department Head, Animal Science

What’s next

The researchers plan to further investigate the long-term impacts of phytochemicals on swine health and productivity, as well as explore customizing treatment approaches for different production systems.

The takeaway

This long-term study suggests that natural plant-based compounds like rosemary and oregano extracts can provide lasting benefits for swine health and growth, offering promising alternatives to antibiotics and supporting more sustainable pork production practices that meet consumer demand for responsibly raised meat.