Milk nucleotides have received little attention compared with other metabolite classes, despite their central role in rumen microbial activity and potential value as markers of nutritional and environmental dynamics.This study applied untargeted metabolomics to screen purine-and pyrimidine-related metabolites in bulk-tank milk collected from dairy herds in the Po Valley (Italy) across 4 seasons under a standardized corn silage-based total mixed ration.A total of 82 metabolites were annotated, with purine and pyrimidine metabolism emerging as central hubs in the milk metabolome and showing connections with amino acid and nitrogen pathways.Multivariate analyses revealed that summer and fall samples had more distinctive nucleotide profiles than spring and winter, with adenosine-and guanosine-related compounds being the main discriminants.Phosphoribosyl pyrophosphate was identified as a key intermediate linking purine and pyrimidine metabolism, while carbamoyl phosphate accumulation in summer highlighted the sensitivity of pyrimidine pathways to environmental stressors.Semiquantitative evaluation of known markers showed stable levels of uric acid and allantoin across seasons, whereas -aminoisobutyric acid, a pyrimidine catabolite, increased in summer.These findings suggest that both pyrimidine and purine metabolism are responsive to seasonal influences under controlled feeding, positioning -aminoisobutyric acid, and potentially carbamoyl phosphate, as candidate tracers of summer-related metabolic adaptations in dairy cows.
Errico et al. (2026) studied this question.