Phenotype and multi-tissue transcriptome response to diet changes in laying hens

Adaptation to feed changes in laying hens is particularly important to promote innovation, in selection schemes and in dietary solutions, for the sustainability of the egg-production sector. In Europe and USA poultry feed is rich in cereals, while Asian countries privilege by-products to soybean meal, resulting in low energy diets.In this study, we investigated the effects of a sub-optimal low energy diet on different traits and multi-tissue transcriptomes of brown egg layers of 2 divergent lines selected for low (R-) and high (R+) residual feed intake. The 2 diets had a similar protein content, while the energy content was reduced by 15% as compared to the standard diet (2450 Kcal versus 2800 Kcal). The R+ and R- hens were fed ad libitum, with the standard diet until 17 wk of age; half of the birds were fed with the low energy feed until 33 wk of age when a subset of birds was slaughtered for tissue sampling (8 per line and diet). Food intake was increased in response to the suboptimal diet whereas egg number was unchanged showing that birds were able to adjust their energy intake by modifying feed intake. Nevertheless, hens fed the low energy diet had a higher feed efficiency (pval < 5%) and a higher residual feed intake (P-value <1%). No diet × line interaction was observed for these traits. PolyA+ RNA from different tissues were sequenced resulting in 90 M reads per sample. After bioinformatics treatment and differential analysis, we observed in liver and adipose tissue only few differentiallyexpressed genes (DEG) between diets (16 and 21 respectively). In contrast, we observed in blood 1179 DEG out of 17123 expressed genes with 463 and 716 over and under expressed in the suboptimal diet compared to the standard diet. No diet × line interaction was observed in the three tissues. GObp term enrichment revealed that under expressed DEG in blood were associated with glucose catabolism, cholesterol biosynthesis, mitotic cell cycle and protein catabolic process. Taken together, these results indicate an adaptation of birds to diet changes by increasing feed intake to maintain egg production, and a tissue-specific response with a limited role of metabolic tissues as liver and adipose tissue compared to the blood.