# A systematic review and meta-analysis of effect of mutant traits in chickens

## TL;DR

This study reviews how mutant traits in chickens affect productivity, finding mixed results with some traits improving specific outcomes.

## Contribution

The study provides a systematic review and meta-analysis of mutant traits in chickens and their impact on productivity traits.

## Key findings

- Mutant traits in chickens showed no significant effect on most productivity outcomes like egg production and body weight.
- Dressing yield percentage and giblet yield increased significantly with mutant traits.
- Abdominal fat decreased significantly in chickens with mutant traits.

## Abstract

Mutant traits in chickens, such as naked neck, frizzle, dwarfism, and featherless, have been associated with improved adaptability, productivity, and resilience under different environmental conditions. The study aimed to evaluate the effects of mutant traits on productivity outcomes in chickens through the systematic review and meta-analysis approach. A total of 164 articles were retrieved from Scholar, PubMed, ScienceDirect, and Web of Science databases and only 28 were used for systematic review while 12 were used for meta-analysis between the year 1993 and 2025, which contained information concerning 16,821 and 4939 chickens with mutant traits and without mutant traits, respectively. The pooled analysis revealed no significant effect of mutant traits on hen day egg production (2.86; 95% CI: −2.32; 8.03), egg number (0.43; 95% CI: −0.52; 1.38), egg weight (1.19; 95% CI: −0.95; 3.33), hatchability (−3.41; 95% CI: −7.78; −0.95), shell percentage (1.42; 95% CI: −0.28; 3.13), feed intake (1.65; 95% CI: −2.88; 6.18), body weight (11.29; 95% CI: −57.48; 80.05), mortality (0.63; 95% CI: −4.30, 5.56), feed conversion ratio (−0.06; 95% CI: −0.18, −0.06), and breast yield percentage (0.65; 95% CI: −0.08, 1.38). However, a significant positive effect was observed on dressing yield percentage (2.40; 95% CI: 1.05; 3.76) and giblet yield (0.42; 95% CI: 0.17, 0.68), while a significant reduction was noted in abdominal fat (−0.54; 95% CI: −1.00, −0.08). Overall, the results indicated high heterogeneity across the findings suggesting variability among the included studies. Mutant traits can enhance poultry traits, however their impact on productivity remains variable.