Environmental Enrichments in Laying Hen Production Systems with Emphasis on Welfare and Egg Quality

Abstract

This paper reviews the effects of environmental enrichments in different laying hen production systems on hen welfare and egg quality. To improve hen welfare, several studies have investigated various environmental enrichments that suit different laying hen production systems. The positive results of these studies can enable such environmental enrichments to be utilized in commercial laying hen production. In this review, the most studied environmental enrichments in the free-range production system include forage, shelterbelt, and artificial shade in the outdoor area and novel objects and H-shaped perching structures in the indoor. These are associated with increased range use that positively affects hen welfare. In the aviary system, perches, and litter materials (e.g., straw, sand) as environmental enrichments are linked to improved behavioral expression, reduced stress, and enhanced immune system. Under the litter system, environmental enrichment with substrates (e.g., pecking stones, alfalfa blocks, silage, straw, barley) has been found to increase the foraging behavior of laying hens. This reduces severe feather pecking thus improving the plumage condition of hens. Although the effects of environmental enrichments on hen welfare have been assessed and scientifically proven in the reviewed studies, enough progress of their impact on egg quality traits has not been reported. The studies have shown that environmental enrichments have no significant effect on egg quality traits. On the other hand, appropriate pasture plants as environmental enrichments in the free-range production system in relation to hen welfare and egg quality have not been identified. Therefore, it is important to continue studies on environmental enrichments while emphasizing their influence on egg quality since it is a major performance trait in the egg industry. In addition, there is a need for studies to determine the ideal pasture species in the free-range production system that positively affects hen welfare and egg quality.