Abstract
This meta-analysis aimed to evaluate the effects of amino acid supplementation on the growth performance of broiler chicks challenged with coccidiosis. Data were collected on authorship, publication year, study sample characteristics and outcomes of interest related to growth performance. Effect sizes were calculated for both overall effects and the individual effects of each amino acid. The effects of moderator factors, such as supplementation levels and duration, were also assessed, and bias was calculated. Works were obtained from PubMed, Elsevier, ScienceDirect, Wiley, Springer Link and Scopus databases, with the help of search engines like Google Scholar and ResearchGate, covering the period from 2013 to 2023. A random-effects model was used. Thirteen works were included in the current analysis, examining the effects of arginine (n = 4), methionine (n = 6), threonine (n = 3) and glutamine (n = 3). Amino acid supplementation [0.326, CI 95% (0.297-0.355); p = 0.000], arginine [0.430, CI 95% (0.293-0.568); p = 0.000] and threonine [0.793, CI 95% (0.193-1.38); p = 0.009] significantly increased body weight. Amino acid supplementation [0.052, CI 95% (0.022-0.081); p = 0.000] and arginine [0.317, CI 95% (0.049-0.585); p = 0.000] also significantly increased feed intake. Higher levels of amino acids (≥1.50%) and longer supplementation periods (≥15 days) significantly increased body weight and feed intake, while reducing the feed conversion ratio. Funnel plots, fail-safe N and Egger tests showed no evidence of bias. In conclusion, arginine supplementation has the potential to increase body weight and feed intake in poultry challenged with coccidiosis. Higher doses of amino acids and longer supplementation periods are recommended in such cases.