# Effects of Fermented Feed Supplementation on Production Performance and Egg Quality Parameters in Laying Hens: A Meta-Analysis

## TL;DR

Fermented feed improves egg production and quality in hens, but results vary based on feed type and inclusion level.

## Contribution

A meta-analysis showing fermented feed's specific benefits on egg-laying rate, Haugh unit, and eggshell thickness in laying hens.

## Key findings

- Fermented feed increased egg-laying rate by 2.11 percentage points.
- Haugh unit improved by 1.99, indicating better albumen quality.
- Eggshell thickness increased by 0.0081 mm, though feed-to-egg ratio showed no significant change.

## Abstract

Efficient egg production is crucial for a consistent supply of nutritious feed. However, laying hens often experience nutritional limitations, including reduced nutrient digestibility and bioavailability caused by anti-nutritional factors and suboptimal gut microbial balance that negatively impact productivity and egg quality. Fermented feeds, produced by treating feed components with beneficial microorganisms, have been proposed as a practical nutritional strategy to improve feed value and performance. This study systematically analyzed 24 controlled experiments to evaluate the effects of fermented feed supplementation on egg production and egg quality in laying hens. Overall, fermented feed supplementation was associated with a statistically significant increase in egg-laying rate (MD = 2.11 percentage points; 95% CI: 0.92 to 3.30) and Haugh unit (MD = 1.99; 95% CI: 0.61 to 3.38), indicating improved internal egg quality. A small but statistically significant increase in eggshell thickness (MD = 0.0081 mm; 95% CI: 0.0037 to 0.0124) was also observed, which may contribute to reduced egg breakage during handling and transport. In contrast, fermented feed supplementation was not associated with a statistically significant change in feed-to-egg ratio (MD = −0.0384 g feed/g egg; 95% CI: −0.0871 to 0.0103), and substantial heterogeneity was observed across studies, indicating variability in feed efficiency responses. Importantly, the magnitude of the benefits varied depending on the type of fermented feed and the level of its inclusion in the diet. These findings demonstrate that fermented feeds can contribute to improving laying performance and egg quality, but their effectiveness depends on careful selection and application.

Fermentation-based feed processing has been proposed as a nutritional approach to improve nutrient availability and metabolic efficiency in laying hens. However, information on its impact on production performance and egg quality remains limited. This meta-analysis statistically assessed the impact of fermented feed supplementation on the production performance and egg quality parameters of laying hens while investigating potential sources of heterogeneity across studies. A comprehensive literature search was performed in PubMed, Scopus, and Web of Science using the PRISMA 2020 guidelines. The inclusion criteria were randomized controlled trials and controlled intervention studies with non-fermented control diets. Two primary outcomes were examined: (1) production performance and (2) egg quality. Multilevel random-effects meta-analyses employing restricted maximum likelihood were conducted to address multiple effect sizes. Heterogeneity was evaluated using Cochran’s Q statistic and I2 estimates. Meta-regression analyses were performed considering dietary inclusion level, trial duration, and total hens, with subgroup analyses based on fermented feed type, assessment of publication bias using Egger’s test and trim-and-fill methods, and leave-one-study-out sensitivity analysis. Twenty-four studies were included in the quantitative synthesis. Supplementation with fermented feed markedly enhanced the egg-laying rate (MD = 2.11 percentage points; 95% CI: 0.92–3.30; p = 0.0005), Haugh unit (MD = 1.99; 95% CI: 0.61–3.38; p = 0.0048), and eggshell thickness (MD = 0.0081 mm; 95% CI: 0.0037–0.0124; p = 0.0003), whereas no significant overall effect was noted on the feed-to-egg ratio (MD = −0.0384 g feed/g egg; 95% CI: −0.0871–0.0103; p = 0.1218). Significant heterogeneity was observed across outcomes (I2 ≈ 73–93%). Subgroup analyses revealed notable feed-type-specific effects, whereas meta-regression indicated that dietary inclusion level is a significant moderator of the feed-to-egg ratio. Sensitivity analysis validated the robustness of the pooled estimates, and publication bias did not significantly influence the results. Supplementation with fermented feed was associated with improvements in egg-laying rate, albumen quality (Haugh unit), and eggshell thickness in laying hens. However, substantial heterogeneity across studies and variability in effect sizes indicate that responses may depend on feed type, inclusion level, and study conditions. These findings should therefore be interpreted with caution, and further well-designed and standardized trials are needed to confirm the consistency and magnitude of these effects.