Egg storage longer than 7 days is associated with negative effects on hatchability traits. Pre-storage incubation has been a suggested method to reduce the negative effects of long-term storage times by enhancing the developmental stage of the embryo and probably reducing the embryonic stress. The objective of the present study was to investigate the effects of pre-storage incubation and storage time on hatchability characteristics, chick quality and serum thyroid hormones, antioxidative properties and immunoglobulin Y (IgY) concentrations of newly hatched chicks at two breeder flock ages. A total of 8000 fertile eggs were obtained from two different ages of chicken breeder hens (Egyptian local cross, Inshas). Half of the eggs were collected from young breeder hens (28 weeks old) and the other half from old breeder hens (50 weeks old). In each breeder flock age, eggs were distributed in a completely randomized experimental design in a 2×4 factorial arrangement, with two storage periods (4 or 14 days) and four pre-storage incubation durations (0, 4, 6 or 8 h at 37.5°C). At 28 and 50 weeks of age, pre-storage incubation and its interaction with storage period influenced significantly the apparent fertility, hatchability of set eggs and hatchability of fertile eggs and this improvement in hatchability is attributed to the reduction in embryonic mortality (early, intermediate and late). Pre-storage incubation for 6 or 8 h elevated significantly the grade A chicks and reduced the grade B chicks in comparison with non-heated controls. Interestingly, for eggs stored for 14 days, pre-storage incubation for 6 or 8 h enhanced serum triiodothyronine, thyroxine, glutathione peroxidase activity, total antioxidant capacity and IgY concentrations significantly and decreased serum malondialdehyde concentration significantly in the newly hatched chicks. It could be concluded that pre-storage incubation enhanced the hatching results, improved the antioxidative properties, reduced lipid peroxidation and elevated the humoral immunity in the newly hatched chicks. Hence, several benefits might be gained by pre-storage incubation when fertilized eggs will be stored for long periods.

The objectives of this study were to investigate the effects of different dietary sources of unsaturated fatty acids (fish oil (FO) and/or linseed oil (LO)) on laying performance, egg yolk fatty acid composition, ovarian follicular development, antioxidative properties, immune response and tibial bone characteristics in aged laying hens. A total of 100 Hisex Brown hens at 56 weeks of age were housed individually in laying cages in an open-sided building under a 16 h light:8 h dark lighting schedule. Hens were randomly divided into four experimental treatments (n = 25 each). Birds were fed ad libitum diets containing 2.5% vegetable oil (C, control), 2.5% FO, 2.5% LO and a mixture of 1.25% LO +1.25% FO (LO + FO) from 56 to 68 weeks of age. Egg production, egg quality characteristics and yolk lipid profile were analyzed. At 68 weeks of age, ovarian follicles were classified and tibial bone characteristics were determined. Serum thiobarbituric acid reactive substance (TBARS), glutathione peroxidase (GSH-Px) activity and total antioxidant capacity were measured. Incorporation of n-3 polyunsaturated fatty acids (n-3PUFA) into the egg yolks has been successful by using dietary FO and/or LO. There were no significant effects of treatments on hen-day egg production, feed intake, egg weight, egg shape index, albumen height, Haugh units and yolk height. However, dietary FO and/or LO supplementation had a significantly positive effect on eggshell percentage, eggshell thickness and yolk color. At 68 weeks of age, there was no significant difference among dietary treatments for tibial bone measurements. Also, no negative effects were detected in ovarian follicular development and weights of the ovary and oviduct, expressed in both absolute terms and relative to body weight. Dietary 2.5% LO, 2.5% FO and a mixture of 1.25% FO + 1.25% LO enhanced GSH-Px activity, total antioxidant capacity and antibody titers significantly in comparison with control. It could be concluded that inclusion of mixed sources of n-3PUFA in diets at moderate levels (2.5%) increased the n-3PUFA content and decreased the n-6/n-3 ratio content in the yolk, improved the antioxidative status, reduced lipid peroxidation, enhanced the antibody response and did not have any negative influence on ovarian follicular development and tibial bone characteristics in aged laying hens.