Heat shock proteins (HSPs) are highly conserved proteins, shown to protect organisms against physical and physiological stress. TEX-OE(®) is a patented total extract of the fruit of Opuntia ficus indica, which has been demonstrated to accelerate the development of HSPs in several animal species. One-day-old commercial broiler chicks were treated with TEX-OE(®); HSP was measured by enzyme-linked immunosorbent assay (ELISA), and a large commercial field trial investigated key performance indicators (KPIs) in treated versus untreated controls chicks. TEX-OE(®) significantly increased HSP concentrations in treated chicks versus controls. Final cumulative mortality, liveweight and percentage factory-rejects were better than in controls. The accelerated HSP response may enable chicks to cope with early stressors, which is reflected in improved KPIs.