Meta-analysis of Weekly Body Weight Heritability in Japanese Quail

Heritability estimates for weekly body weight in Japanese quail vary across studies because of differences in population structure, genetic line, age at measurement, sample size, and statistical model specification. This study aimed to synthesize reported heritability (h^2 ) estimates for weekly body weight in Japanese quail from hatch to six weeks of age using a meta-analytic approach. A structured literature search was conducted on the Web of Science Core Collection, and studies were evaluated according to predefined eligibility criteria. A total of 29 studies were included in the quantitative synthesis. After data preparation and Study_ID × Age_Week-level collapsing, the analyses were conducted using 112 study-week effect sizes. Heritability estimates were analyzed on the logit(h^2 ) scale, and week-specific random-effects meta-analyses were fitted using restricted maximum likelihood. Pooled estimates were back-transformed to the original h^2 scale for reporting. The pooled h^2 estimates were 0.350 for hatch weight, 0.236 for week 1 body weight (W1), 0.265 for week 2 body weight (W2), 0.267 for week 3 body weight (W3), 0.311 for week 4 body weight (W4), 0.366 for week 5 body weight (W5), and 0.384 for week 6 body weight (W6). Between-study heterogeneity was high across all weeks, with I^2 values ranging from 84.22% to 98.63%. An exploratory meta-regression was used to examine whether heritability changed systematically with age. Leave-one-out analyses indicated that the overall pattern was not dependent on a single study. In conclusion, weekly body weight heritability in Japanese quail was generally moderate and reached numerically higher values during the later growth weeks. However, this pattern was not statistically supported as a linear age-related trend. These findings highlight the need for more transparent reporting of standard errors, confidence intervals, model information, and population structure in future genetic parameter studies.