Dietary supplementation with orange pulp (Citrus sinensis) improves egg yolk oxidative stability in laying hens

The aim of the present study was to evaluate the effects of dietary supplementation with dried orange pulp on antioxidant capacity of egg yolk and the possible side effects on performance and egg quality of laying hens. A total of 189 animals, reared in 21 replicate enriched cages with 9 hens each, were randomly allocated into 3 treatment groups: control group (C) that was offered a basal diet without orange pulp addition, group (OP) that was offered a diet supplemented with dried orange pulp (Citrus sinensis) at 9% and group EN that was offered the basal diet further supplemented with 0.767 g hesperidin and 0.002 g naringin per kg of feed (levels of hesperidin and naringin that are contained in dried orange pulp of OP group). The diets were offered for 30 days and were isocaloric and isonitrogenous. Oxidative stability of egg, expressed as ng malondialdehyde (MDA) per g of yolk, performance and egg quality parameters were determined throughout the 30 d experimental period. Oxidative stability of fresh and stored eggs for 30 and 90 d was improved when hens were fed a diet supplemented with OP in comparison with controls (P < 0.05). Ten days of dietary supplementation with OP were enough for apparent beneficial effects on yolk oxidative stability and consequently egg shelf life. However, feed intake and laying rate were decreased whereas feed conversion ratio (FCR) was increased in group of hens supplemented with OP in comparison with both controls and hens fed with hesperidin and naringin (P < 0.05). The reduced values of feed intake may be attributed to the low palatability of OP and not only negatively affected performance but also resulted in deterioration of egg quality parameters. Hens fed with OP produced slightly lighter eggs with a lower eggshell percentage, thickness and strength and a less orange yolk color in comparison with controls (P < 0.05). The negative effects of dietary supplementation with OP on egg production and quality may be alleviated by a gradual increase of OP levels in hens' diet that could offer an adaptation to OP incorporation in the diet.