ABSTRACT
The domestication process exerts different phenotypic plasticity between slow- and fast-growing breeds of chicken. Feed restriction has a critical role in production performance, physiological plasticity, and stress response. Our study aimed to explore how feed restriction programed the organ index, dopamine, and hippocampal transcriptome profile between slow- and fast-growing chickens, which were fed either ad libitum (SA and FA), or feed restricted to 70% of ad libitum (SR and FR), for 30 days. Results showed that feed restriction influenced the brain organ index (P < 0.05), but not the organ index of the heart, liver, and spleen. The slow-growing breed tested had a higher brain organ index than the fast-growing breed (P < 0.05). Under feed restriction conditions, both the slow- and fast-growing breeds had significantly elevated dopamine concentrations (P < 0.05) compared to those fed ad libitum. In the GO term, upregulated genes in the FA group were enriched in the mitochondria, respiratory chain, and energy metabolism compared to the SA group (P < 0.05). Membranes and ribosomes were enriched in the cellular component between the SR and FR groups (P < 0.05). In the KEGG functional pathways, upregulated DEGs in the FR group were enriched in the cardiovascular disease category and neurodegenerative disease category compared to the FA group (P < 0.05). Downregulated DEGs in the FA group were enriched in the oxidative phosphorylation and neurodegenerative disease categories (Parkinson's disease and Huntington's disease) compared with the SA group (P < 0.05). Upregulated DEGs in the FR group were enriched in the cardiovascular disease category, neurodegenerative disease category, and energy metabolism than the SR group (P < 0.05). In conclusion, feed restriction had profound effects on the brain organ index and plasma dopamine in the slow- and fast-growing chickens. Feed restriction may result in issues relating to cardiovascular and neurodegenerative diseases in the fast-growing breed tested, but not in the slow-growing breed.
ABSTRACT
In recent decades, artificial selection has contributed greatly to meeting the demands for animal meat, eggs, and milk. However, it has also resulted in changes in behavior, metabolic and digestive function, and alterations in tissue development, including the brain and skeleton. Our study aimed to profile the behavioral traits and transcriptome pattern of chickens (broilers, layers, and dual-purpose breeds) in response to artificial selection. Broilers spent less time gathered as a group in a novel arena (P < 0.01), suggesting reduced fearfulness in these birds. Broilers also showed a greater willingness to approach a model predator during a vigilance test but had a greater behavioral response when first exposed to the vocalization of the predator. Genes found to be upregulated and downregulated in previous work on chickens divergently selected for fear responses also showed consistent differences in expression between breeds in our study and indicated a reduction in fearfulness in broilers. Gene ACTB_G1 (actin) was differentially expressed between breeds and is a candidate gene involved with skeletal muscle growth and disease susceptibility in broilers. Furthermore, breed-specific alterations in the chicken domestic phenotype leading to differences in growth and egg production were associated with behavioral changes, which are probably underpinned by alterations in gene expression, gene ontology terms, and Kyoto Encyclopedia of Genes and Genomes pathways. The results highlight the change in behavior and gene expression of the broiler strain relative to the layer and a dual-purpose native breed.