Effects of housing conditions on egg characteristics. A review

Abstract

During the last fifteen years, twenty five studies have been conducted in order to determine whether the housing conditions of laying hens (free range, deep litter or cages) affect egg composition and/or egg quality. The results indicate that neither egg weight nor gross egg composition are permanently modified by housing conditions. Small increases (rarely significant) in linoleic acid and cholesterol content were the only permanently recorded modifications when laying hens were not kept in cages. Similarly, albumen quality, yolk color and blood and meat spot incidence did not seem to be directly controlled by housing conditions. The percentage of broken eggs was sometimes slightly lower in deep litter than in cages but without any important increase in the shell strength itself. No variation in organoleptic traits of eggs was recorded between deep litter and cage eggs. True « farm eggs were potentially more variable (and not necessarily better) than eggs produced in more controlled housing conditions. The use of nests instead of cages could easily increase dirty egg incidence and the bacterial contamination of eggshells. One of the most important factors in limiting this problem is to collect eggs from the nests within 6 hours after laying. In conclusion eggs produced on deep litter or in free range conditions do not present objective advantages for the consumer. Modifications of egg characteristics are not the arguments which might be used to change the usual system of cage housing of hens.