Differences in meat and wool quality and gastrointestinal/hypothalamic functions in Dexin fine-wool meat sheep with divergent residual feed intake

Residual feed intake (RFI) is an important indicator for measuring feed efficiency and can be used to screen sheep populations with low feed consumption and excellent growth performance. Its mechanism is closely related to the hypothalamus, which regulates animal feeding behavior, as well as the rumen and duodenum, which are responsible for the main digestive and absorptive functions. In theory, the hypothalamus-gastrointestinal axis is one of the key pathways affecting feed efficiency in ruminants. However, existing research has focused on the gastrointestinal microbiota and lacks systematic research on the interaction mechanism and functional expression differences between the hypothalamus and the gastrointestinal axis. The results indicate that Residual Feed Intake (RFI) significantly influences livestock quality in sheep. Regarding meat characteristics, the low-RFI (L-RFI) group exhibited a significantly higher cooking percentage in the longissimus dorsi muscle compared to the high-RFI (H-RFI) group. In terms of wool quality, L-RFI sheep were characterized by finer fiber diameters, shorter staple lengths, and an increased straight fiber rate. Mechanistically, RFI affected glutamatergic synapses, calcium signaling, and neurotransmitter receptor activity in the hypothalamus. Transcriptomic profiling further revealed that high-intake sheep showed upregulated lysosomal function, ATP metabolism, and cell cycle pathways in the rumen. Similarly, the duodenum of H-RFI sheep displayed marked activation of DNA replication and B-cell receptor signaling, alongside enhanced cholesterol transport and epithelial cell proliferation. In summary, this study, through a multi-dimensional analysis from the hypothalamus to the gastrointestinal tract, systematically reveals the physiological and molecular basis of RFI’s influence on sheep feed efficiency, providing a new research paradigm for further exploring the role of the brain-gut axis in the regulation of animal feed efficiency.