Dietary Application of Grape Waste in Laying Hens Reared Under Two Stocking Densities

A total of 224 69-week-old Nick Chick laying hens were allocated to eight treatments with eight replicate cages to investigate the effects of stocking density (SD) and dietary inclusion of different levels of grape waste (GW) on performance, some egg quality traits and yolk oxidative status of laying hens from 69 to 76 weeks of age. The experiment was conducted as a 2×4 factorial arrangement, with two levels of stocking density (3 and 4 hens/cage as normal (NSD) and high stocking density(HSD), respectively) and four dietary levels of GW (0, 1.5, 3 and 4.5 % of diet, as a corn replacement). The results indicated that rearing hens under HSD conditions resulted in a worse feed conversion ratio (FCR) and less egg production than NSD (P < 0.05). Dietary inclusion of GW had no detrimental effect on performance or egg quality traits. Increasing density had deleterious consequences on FCR, egg production, egg weight and egg mass (P < 0.05), while dietary addition of GW, particularly at the level of 4.5% alleviated those negative effects. Egg quality traits (shell weight, resistance and thickness, yolk weight, albumen height and Hague Unit) were significantly not influenced by GW, SD or their interaction. Stocking density did not affect malondialdehyde (a peroxidation indicator) level in egg yolk lipid, while all hens fed GW had lower levels of malondialdehyde than those fed diet without GW (P < 0.05). The interaction between SD and GW level significantly influenced egg albumen pH at 3 and 30 d room storage (P< 0.05). In conclusion, dietary inclusion of up to 4.5 % GW had no deleterious effect on laying hen’s egg quality and improved some performance traits and oxidative stability of egg yolk, particularly in hens reared under HSD. Thus, it could be used as a corn replacement in laying hens' diet.