A nutrigenomics approach to study the effects of ω-3 fatty acids in laying hens under physiological stress.

Supplement of ω-3 fatty acids can decrease the harmful effects of stress. However, the potential molecular mechanisms that are modulated by dietary ω-3 fatty acids in laying hens under stress remain unknown. Hence, RNA-sequencing (RNA-Seq) technology was used to gain new insights into different gene expression profiles and potential pathways involved in response to stress in the liver of 35-week-old Lohmann LSL-Lite laying hens supplemented with ω-3. Three groups including control (non-stress), stress, and stress_ω-3 fatty acids (three layers per each group) were applied. A total of 1,321 genes were detected as differentially expressed genes of which 701, 1,049, and 86 DEGs belonged to stress vs. control, stress_ω-3 vs. control, and stress vs. stress_ω-3 pairwise comparisons, respectively. Gene ontology and KEGG pathway analysis indicated that the DEGs were enriched in particular regulation of steroid and cholesterol biosynthetic process, fatty acid degradation, AMPK signaling pathway, fatty acid biosynthesis, and immune response. Our data represented a promising approach regarding the importance of ω-3 as anxiolytic and anti-stress. In this context, UNC13B and ADRA1B genes were downregulated in the stress_ω-3 group compared to the stress group, which are associated with decreased activity of glutamatergic stimulatory neurons and probably play important role in facilitating the response to stress. This study extends the current understanding of the liver transcriptome response to physiological stress, and provides new insights into the molecular responses to stress in laying hens fed a diet supplemented with ω-3 fatty acids.

Omega-3 fatty acids reduce the negative effects of dexamethasone-induced physiological stress in laying hens by acting through the nutrient digestibility and gut morphometry.

In this study, the effects of omega-3 fatty acids on egg production, nutrients digestibility, eggs yolk lipid peroxidation, and intestinal morphology in laying hens under physiological stress were investigated. Ninety-six 35-wk-old Lohmann LSL-Lite laying hens were used in 2 × 3 factorial arrangement with 2 levels of dexamethasone (DEX) (0 and 1.5 mg/kg of the diet) and 3 levels of omega-3 fatty acids (0, 0.24, or 0.48% of the diet) in a completely randomized design. At 41 wk of age, the stress groups were continuously fed with a DEX 1.5 mg/kg diet for 1 wk. Egg production, egg mass, feed intake, egg weight, and feed conversion ratio were recorded. In addition, the AME, digestibility of CP, crude fat (CF), and organic matter were measured during the stress induction period. At the end of 41 wk of age, malondialdehyde and cholesterol concentrations in the egg yolk and intestinal morphology were investigated. The results showed that egg production, egg mass (P < 0.0001), egg weight (P = 0.043), and BW (P = 0.0005) were lower in DEX layers. Feed intake was reduced by the interaction between DEX and omega-3 fatty acid (P = 0.042). Malondialdehyde value (P = 0.002) and cholesterol concentration (P = 0.001) in egg yolk increased by DEX administration. The combination of DEX administration and omega-3 fatty acids supplementation was found in the indices of intestinal morphology such as villus height and width and crypt depth (P < 0.05). Administration of DEX decreased the CP digestibility (P < 0.0001) and AME (P = 0.006). Digestibility of CF and AME in the group of 0.48% omega-3 fatty acids were higher (P < 0.05) than those of 0 and 0.24%. In conclusion, we found that dietary omega-3 fatty acids had beneficial effects on gut morphology and nutrient digestibility in laying hens under physiological stress. However, they could not alleviate the negative effects of physiological stress on performance.

Effect of Chromium Nanoparticles on Physiological Stress Induced by Exogenous Dexamethasone in Japanese Quails.

Chromium (Cr), as an essential trace element, plays a critical role in carbohydrate, protein, and lipid metabolism in animals. It has been suggested that the beneficial effects of Cr increase by environmental stresses, which lead to greater Cr effects on stressed animals. The objective of the present study was to evaluate the response of physiologically stressed Japanese quails (Coturnix japonica) to dietary chromium nanoparticle (Nano-Cr) supplementation. The stress was induced by adding dexamethasone (0.6 mg/kg BW) to Japanese quails' diet from 17 to 22 days of age. A total of 360 birds were randomly allocated to six dietary treatments with four replicates each having 15 birds: negative control diet (no-stress, no-additive; NC), positive control diet (stress, no-additive; PC), and stress additive diets including four diets containing 200, 400, 800, and 1200 µg/kg of Nano-Cr. Performance and haematological parameters were affected (P < 0.05) by physiological stress though they were not affected by adding Nano-Cr. Comparison of diets containing Nano-Cr levels and stress no-additive diets, at 23 days of age, was indicative of a positive linear relationship (P < 0.05) between dietary Nano-Cr levels and feed intake and average daily gain. Furthermore, white blood cell (WBC) count as well as haematocrit level increased (P < 0.05) as the level of supplied Nano-Cr increased. A negative relationship (P < 0.05) was observed between Nano-Cr levels and heterophil percentage and heterophil/lymphocyte ratio. On day 35, increased dietary Nano-Cr improved (P < 0.05) weight gain, live body weight, energy/protein utilization efficiency, and WBC count. In conclusion, supplementation of diet with optimum concentration of Nano-Cr revealed alleviation of negative effects of physiological stress in quails.