Ecological resilience of the rectal microbiome to environmental stressors in Hulunbuir grazing sheep: response to feed restriction and extreme cold challenge.

The gut microbiota is essential for helping animals to adapt to food shortages and extreme environments. In China's Hulunbuir region, local grazing sheep endure harsh winters characterized by intense cold and limited food supply. Uncovering the adaptive mechanisms that underpin their resilience is essential for improving their productivity, breeding practices, and management strategies. This research investigated the effects of feed restriction (set at 40 % of ad libitum intake) and extreme cold stress (temperature-humidity index set at 22.27) on the dynamics of gut microbiota in Hulunbuir sheep. We employed 16S rRNA gene sequencing to investigate alterations in rectal microbial diversity, community composition, and functional pathways in response to these stressors. Our findings revealed a significant reduction in bacterial diversity and microbial community structure in response to both stressors (P < 0.05), with cold stress exerting a more pronounced impact than feed restriction. Several key bacterial genera, including Akkermansia, Christensenellaceae, Monoglobus, Bacteroides, Alistipes, and Solibacillus, were identified as major contributors to the adaptive microbiota-drives responses of Hulunbuir sheep under environmental stress. A Spearman correlation analysis revealed strong associations between these genera and essential functional pathways such as fat digestion and absorption, quorum sensing, and mineral uptake, all of which were differentially regulated in response to stress (|r| > 0.6, Padj < 0.05). These findings offer novel insights into how the gut microbiota in Hulunbuir sheep supports physiological adaptation to extreme cold and nutritional stress, laying a robust foundation for creating microbiota-targeted strategies to enhance resilience, promote animal health, and improve productivity of grazing ruminants in harsh winter environments.