Effects of Breeding Systems on Hen Egg Weight: A Meta-Analysis

Abstract

In the egg production industry, egg weight is a critical parameter influencing economic viability. The objective of the present study was to determine the effect of cage, free-range, and deep litter breeding systems on hen egg weight using meta-analysis. Articles were searched using Google Scholar, PubMed, ScienceDirect, and Web of Science yielding 175 articles of which 22 articles were included in the present study. Methodological quality was assessed using Joanna Briggs Institute guidelines. A model was used to determine the effect of breeding systems on average hen egg weight. Meta-regression analysis was used to examine the effect of the following moderators, publication year, region, chicken age, and breed. The Cochran’s Q test and I2 statistic were performed for h heterogeneity across used studies. According to the obtained results, there was no significant difference between cage and free-range on average hen egg weight (standardized mean difference (SMD) = 0.08, I2 = 89%, 95%CI 0.19-0.34). The free-range breeding system had heavier hen egg weight than deep litter (SMD = 0.54, I2 = 88%, 95%CI 0.01-0.08). The findings also revealed that deep litter and free range had no significant difference in average hen egg weight (SMD = -0.05, I2 = 87%, 95%CI -0.28-0.17). Meta-regression findings showed that the origin of the used articles, the age of the chickens, and the chicken breed were observed as the main reasons for heterogeneity. This meta-analysis revealed that a free-range breeding system increased the average hen egg weight.