Metabolic resilience and functional longevity: Insights from nutritional challenge and milk metabolomic analysis in dairy goats.

This study aimed to investigate the metabolic mechanisms and identify potential biomarkers of resilience and longevity by comparing divergent functional longevity lines and phenotypic resilience groups in dairy goats. A total of 70 Alpine goats, selected for longevity and phenotypic resilience, were subjected to a 2-d underfeeding challenge. Milk samples were collected before and at the end of the challenge and analyzed using untargeted metabolomics. Univariate and multivariate analyses revealed distinct milk metabolome changes between the divergent longevity lines and between phenotypic resilience groups during the challenge, whereas no differences were observed at prechallenge. During the challenge, phenotypic resilience groups differed in amino acid metabolism, with the low resilience group exhibiting greater reductions in branched-chain amino acids (leucine, valine, isoleucine) and tryptophan compared with the normal resilience group, supporting the previously observed decrease in total amino groups under nutritional stress. During the challenge, goats from higher functional longevity lines showed greater reductions in milk C4-DC carnitine, and this reduction was negatively correlated with their sires' EBVs for functional longevity. These findings support a biological link between metabolic resilience and functional longevity, potentially through mitochondrial efficiency. These results highlight novel milk-based biomarkers that could contribute to improved selection and management strategies aimed at enhancing resilience in dairy goats.