Evaluating net energy value of fermented citrus pulp and its effects on performance and egg quality in laying hens

Two experiments were conducted to determine the apparent metabolisable energy (AME), nitrogen-corrected apparent metabolisable energy (AMEn), and net energy (NE) values of fermented citrus pulp (FCP) for layers and to evaluate its effects on performance and egg quality. In Experiment 1, a reference diet and an FCP-containing test diet were evaluated for energy utilisation. In Experiment 2, a total of 1,080 layers were assigned to five isocaloric and isonitrogenous diets containing 0, 2.5%, 5.0%, 7.5%, or 10.0% FCP for 5 weeks. On a dry-matter basis, the AME, AMEn, and NE values of FCP were 8.76, 8.61, and 5.14 MJ/kg, respectively. Compared with the reference diet, the test diet had lower AME and AMEn (p < 0.05). Increasing FCP inclusion linearly decreased egg weight and increased the feed-to-egg ratio (p < 0.05); egg weight was lower in the 7.5% and 10% FCP groups than control group (p < 0.05). Albumen height and Haugh unit also decreased linearly (p < 0.05), and albumen height was lower in the 10% FCP group than the control and 2.5% FCP groups (p < 0.05). Yolk colour showed a quadratic response to FCP inclusion, whereas eggshell yellowness increased linearly (p < 0.05). In conclusion, FCP provided 8.76 MJ/kg AME, 8.61 MJ/kg AMEn, and 5.14 MJ/kg NE for layers, and 5% FCP was the highest tested level without significant differences in performance and egg-quality variables from the control, although increasing inclusion progressively impaired production efficiency, particularly at 7.5% or greater.