Feed quantitative restriction effect on performance, carcass quality, blood parameters and immunity of broiler chickens

This study investigated the effects of early-age, short-term quantitative feed restriction followed by compensatory refeeding with energy and protein-dense diets on the performance, carcass traits, blood biochemistry, and immune response of broiler chickens. A total of 270 Ross 308 chicks were allocated to a 2 × 4 factorial design plus a control group. Treatments included two restriction durations (days 8-12 and 8-17) and four feed restriction intensities (22.5%, 25.0%, 27.5%, and 30.0%) based on standard nutritional recommendations, along with a control group fed ad libitum. Growth performance was recorded weekly, and carcass characteristics, organ weights, blood metabolites, and antibody titers (HI and SRBC) were assessed at day 42. Data were analyzed using two-way ANOVA under a completely randomized design, and treatment means were compared using Duncan's multiple range test at a significance level of P < 0.05. Feed restriction temporarily reduced feed intake, weight gain, and efficiency parameters during the restriction period especially in the 10-day and higher intensity groups (P < 0.05). However, birds exhibited compensatory growth during refeeding, with final body weights and carcass yields comparable to controls. Abdominal fat percentage was significantly lower in restricted birds, particularly in the 10-day, 30% group (P < 0.05). Triglyceride and VLDL levels were reduced in the 25% restriction group, while other blood lipids and glucose remained unaffected. HI antibody titers against Newcastle disease were significantly higher in some restricted groups, notably the 5-day, 30% group (P < 0.05), with no adverse effects on SRBC responses. These findings suggest that early short-term feed restriction, when followed by nutrient-dense refeeding, can improve feed efficiency and reduce fat deposition without compromising carcass yield or humoral immunity.