Sunflower Meal in Broiler Diets: A Dose–Response Meta-Analysis of Inclusion Rate, Residual Fibre, and Bird Age
Abstract
Sunflower meal offers a route to diversify the protein ingredients used in broiler diets, but recommendations expressed as a single inclusion ceiling obscure variation in meal composition, formulation and exposure history. This exploratory dose–response meta-analysis used performance data from three independent broiler experiments covering days 22–42. Fifteen treatment arms, representing 80 pens and 2,176 initially allocated birds, provided 12 sunflower-meal versus control contrasts. Correlated log response ratios were summarised by within-study generalised least-squares dose slopes and pooled using restricted maximum likelihood with modified Knapp–Hartung confidence intervals. Variances in two studies were reconstructed from reported coefficients of variation under an explicit residual-variance assumption. Pooled linear projections per 10 percentage points of inclusion corresponded to +1.04% for body-weight gain (95% confidence interval −5.80% to +8.37%), −0.25% for feed intake (−1.94% to +1.47%) and −1.15% for feed conversion ratio (−7.11% to +5.20%). Growth and feed-conversion slopes were heterogeneous, and some within-study responses were nonlinear. These results neither demonstrate equivalence nor identify an optimum. Reported meal crude fibre occupied a narrow range, approximately 21–22%, while dose and sunflower-derived fibre were inseparable within individual experiments. Repeated starter observations and changing feeding programmes also prevented an independent estimate of age modification. The evidence therefore supports composition-specific formulation and explicit treatment of exposure history, rather than a universal maximum inclusion rate. The analysis is a reproducible, retrieval-limited quantitative synthesis, not a comprehensive systematic review or a validated three-moderator prediction model.
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