Dietary supplementation with tomato waste to improve performance and egg quality of laying hens: a meta-analysis

A meta-analysis was conducted to determine the effect of adding tomato waste to the diet of laying hens on their performance, egg quality, and blood parameters. A total of 22 articles were selected from five scientific databases such as Scopus, PubMed, ScienceDirect, Web of Science, and Directory of Open Access Journals. R software version 4.2.0, with supporting libraries, including lme4 and lsmeans (least-squares means test), was used for modelling and statistical analysis. The results of meta-analysis showed that the addition of tomato waste to laying hen rations significantly increased feed intake (P < 0.01) and tended to correlate with a quadratic pattern of hen-day egg production (HDEP) (P < 0.061) and egg mass (P < 0.075); however, eggshell strength decreased significantly (P < 0.01). Our findings also demonstrated a significant effect on egg-yolk colour, as assessed by a quadratic pattern (P < 0.01). The lycopene content in egg yolk increased significantly (P < 0.05). Tomato waste supplementation had a significant (P < 0.05) effect on total triglyceride and cholesterol levels in blood serum, which followed a quadratic pattern. This meta-analysis has confirmed that feeding tomato waste to laying hens exerts positive effects on animal performance and egg quality.