Optimizing low-crude protein diets with essential oils and sodium butyrate to maintain productive performance and improve intestinal integrity in 58- to 69-wk-old laying hens.
Abstract
This study evaluated the effects of supplementation with saponified essential oils (EOs) and sodium butyrate (SB) on production performance, egg quality, gastrointestinal organ characteristics, jejunal morphology, intestinal barrier function, inflammatory responses, and antioxidant-related gene expression in late-phase laying hens fed a low crude protein (LCP) diet. A total of 150 ISA Brown laying hens aged 58 wk were assigned to 5 dietary treatments: a standard crude protein diet (SCP, 18.12% CP), LCP (15.89% CP), LCP + EOs (750 mg/kg), LCP + SB (750 mg/kg), and LCP + EOs + SB (each at 750 mg/kg). Each treatment had 6 replicates of 5 hens, and the experiment lasted 12 wk. Dietary treatments did not affect overall laying performance (P > 0.05), although feed conversion ratio differed during wk 58-61 (P = 0.010). The LCP diet reduced albumen height and Haugh unit (P < 0.05). Feeding LCP altered gastrointestinal organ characteristics by decreasing jejunal weight and cecal weight (P < 0.05). LCP increased crypt depth and reduced the villus height-to-crypt depth ratio (VH:CD) (P < 0.05). It also downregulated zonula occludens-1 (ZO-1), occludin (OCLN), interleukin-10 (IL-10), interleukin-13 (IL-13), superoxide dismutase 1 (SOD-1), and glutathione peroxidase 1 (GPx-1), while upregulating tumor necrosis factor-α (TNF-α) and interleukin-18 (IL-18) (P < 0.001). EOs improved internal egg quality, reduced crypt depth, increased the VH:CD ratio, and attenuated pro-inflammatory gene expression (P < 0.05). Sodium butyrate increased ZO-1 and IL-13 expression and reduced TNF-α and IL-18 expression (P < 0.05). The combined EOs + SB treatment produced the broadest improvement in gastrointestinal and jejunal responses. In conclusion, reducing dietary CP by 2.23 percentage points maintained laying performance but impaired internal egg quality and intestinal barrier-related gene expression, whereas combined EOs and SB supplementation may mitigate these responses in late-phase laying hens.