Forest plot of the random –effect model of the effect of dietary ginger supplementation on ejaculate volume (a), sperm motility (b), sperm concentration (c), live spermatozoa (d) and abnormal spermatozoa (e) in breeder birds. Study refers to the first author and year of the publication. Standardized mean diff.
(difference) was standardized using the z-statistic. Thus, points to the left of the line indicate a reduction in the trait (spermatozoa production measures) and points to the right of the line indicate an increase in the variable (spermatozoa production measures). Each square represents the mean effect size for that study. The upper and lower limit of the line connected to the square represents the upper and lower 95% confidence interval (CI) for the effect size.
The size of the square reflects the relative weighting of the study to the overall effect size estimate, with larger squares representing greater weight. The dotted vertical line represents the overall effect size estimate. The diamond at the bottom represents the 95% CI for the overall estimate. The solid vertical line represents a mean difference of 0 or no effect. Ejaculate volume, sperm motility, sperm concentration, live spermatozoa, and abnormal spermatozoa has large heterogeneity as indicated by the I2 of 71.3%, 65.61%, 98.2%, 35.53% and 43.77% respectively.