In beef feedlot steers with marginal liver copper status (42 mg/kg dry matter), supplementation with lubabegron fumarate (36 mg/day) for 37 days improves feed efficiency by 29%, whereas steers with adequate copper status (193 mg/kg dry matter) show only a 6% improvement in feed efficiency during the same period, indicating that copper status modulates the metabolic response to beta-agonist growth promoters.

When copper levels are low, the body responds to the beta-agonist drug by increasing signals that promote fat tissue changes and blood vessel growth. This attracts immune cells that help the fat tissue adapt to shifting energy use, making the animal more sensitive to insulin. As a result, more energy goes to muscle growth instead of fat storage, improving how efficiently feed is turned into body weight. When copper is normal, these signals are suppressed, so the drug has little effect.