Meta-analysis of the influence of phytobiotic (pepper) supplementation in broiler chicken performance

The aim of the study is to use meta-analytical procedure to resolve uncertainty, identify knowledge gaps, and create new insights using published data on the phytobiotic effect of dietary pepper intervention on daily feed intake (DFI), average daily gain (ADG), and feed conversion ratio (FCR) in broiler chickens. The authors accessed AGORA, Scopus, ScienceDirect, and Google Scholar databases for primary studies published between 2011 and 2018 using combinations of different search terms. Fifteen studies were included to assess phytobiotic effect of pepper on DFI, FCR, and ADG in broiler chickens. Random-effects model (REM) was used to generate pooled effect estimates at 95% confidence intervals (CI). Analysis was performed using Open Meta-analyst for Ecology and Evolution (OpenMEE) software, while publication bias and source of heterogeneity were assessed using standard methods. Dietary pepper supplementation enhanced ADG (standardized mean difference (SMD) = 0.576, 95% CI 0.444 to 0.707, p < 0.001) and FCR (SMD = 0.325, 95% CI − 0.453 to − 0.196, p < 0.001) considering the presence of heterogeneity and publication bias. DFI (SMD = 0.052, 95%CI − 0.069 to 0.173, p = 0.403) was not significantly influenced by dietary pepper supplementation. Restricted subgroup analysis revealed that both black and red pepper increased ADG (p < 0.001). Broilers on black pepper intervention had better FCR (p = 0.002) than broilers on red pepper treatment. Higher (p < 0.05) DFI was obtained on broilers fed pepper-based diet at the rate of > 6 g/kg feed for 35 days. There was no association between DFI and explanatory variables (broiler strain used and number of broilers used), whereas study country influenced DFI (p < 0.001). Furthermore, there was an association between outcome of interests (ADG and FCR) and explanatory variables (supplementation level, study country, number of broilers used per treatment group, and broiler strain used). Broilers on dietary pepper intervention for 42 days had higher ADG (SMD = 62.2 g/bird/day, p < 0.001) than those on dietary pepper intervention for 56 days (SMD = 35.7 g/bird/day, p = 0.002). There is evidence of heterogeneity, and meta-regression analysis showed that study country, supplementation level, and broiler strain used explained most of the sources of heterogeneity. The results of the present study revealed the potential of dietary pepper intervention to improve production efficiency in broiler chickens. The current meta-analysis also set the steps for standardized experimental designs on the use of dietary pepper intervention in broiler feeding trials in the future.