The impact of supplementing quebracho and chestnut tannin extracts on the growth performance in growing and finishing beef cattle: a meta-analytical assessment

Tannin extracts (TE), composed of condensed tannins from quebracho and hydrolyzable tannins from chestnut, have been studied as functional feed additives to improve growth performance in beef cattle, but reported effects vary with TE composition, dose, dietary protein, and co-additive. This meta-analysis evaluated TE supplementation effects on average daily gain (ADG), dry matter intake (DMI), and gain:feed (G:F) in growing and finishing beef cattle, using 162 treatment records from 43 published studies involving > 22,000 animals, mostly bulls and feedlot-based studies, including grazing and individually pen trials. Additional analyses included conditional independence tests for monensin use, forest and mosaic plots, and subset analyses for diets with or without monensin. Meta-regression indicated that TE supplementation was associated with increases in ADG (P < 0.001), DMI (P < 0.001), and G:F (P = 0.024). The ADG response was nonlinear; quadratic models indicated an optimal inclusion of ∼0.30% of dietary DM for maximizing weight gain. The disproportionate increase in ADG relative to DMI is consistent with improved nutrient utilization. The TE-ADG relationship was stronger at lower crude protein intake (P = 0.0525), however, because crude protein intake is not a direct proxy for rumen-degradable nitrogen supply and may co-vary with diet formulation and co-additives (e.g., ionophores and/or NPN sources), this pattern should be interpreted as context-dependent rather than as evidence of a universal mechanism. A conditional independence test also suggested that the TE-associated ADG responses were not independent of monensin use, suggesting a possible synergy effect, though additional studies are needed to confirm this pattern. Overall, TE appears to be a context-dependent additive rather than a universal growth promoter, and responses did not necessarily require doses near the model-derived optimum; benefits were also detectable at lower inclusions (e.g., ∼0.08% of dietary DM) in some contexts. Further research is needed to refine dosing strategies, better characterize TE chemistry, and evaluate environmental outcomes in dedicated studies.