Effects of timing and duration of stepwise vitamin–mineral premix withdrawal on welfare indicators and trace mineral excretion in broilers

Trace mineral supplementation via vitamin–mineral premixes (VMP) is essential for broiler health and productivity but may contribute to environmental pollution through excessive mineral excretion. This study investigated the effects of time-based VMP withdrawal at different production stages on growth performance, bone mineralization, immune function, antioxidant capacity, welfare indicators, and zinc and copper excretion in broilers. A total of 500 one-day-old male Ross 308 chicks were allocated to five dietary treatments (five replicates per treatment; 20 birds/replicate) in a completely randomized design over 42days. Treatments consisted of a control group (VMP fed for 42 days) and four time-dependent withdrawal groups, where VMP was removed for the final 7, 14, 21, and 28 days of the trial. Growth performance, tibia characteristics, leg condition, serum immunoglobulins (IgM, IgG, IgA), cytokines (IL-10, IL-6, IL-1β), antioxidant enzymes (CAT, SOD, GPx), total antioxidant capacity, malondialdehyde (MDA), and fecal mineral excretion were measured. Data were analyzed using a general linear model with Tukey’s test (P < 0.05) Results showed that earlier VMP withdrawal impaired growth, bone integrity, immunity, and antioxidant status while increasing feed conversion ratio, pro-inflammatory cytokines, MDA levels, and gait abnormalities. However, zinc and copper excretion decreased progressively as withdrawal occurred earlier. These findings suggest that strategically timed VMP withdrawal during the final production phase may reduce environmental impact without compromising broiler health, offering a practical and sustainable mineral management strategy.