Metabolic Adaptation Mechanisms in Heat-Stressed Dairy Cows in Tropical Nigeria: A Multi-Omics Investigation

This study investigates the metabolic adaptation mechanisms in dairy cows experiencing heat stress in tropical Nigeria, using a multi-omics integration approach to comprehensively characterise how heat stress reshapes energy metabolism, immune function, and endocrine regulation in ways relevant to developing management and breeding interventions. Dairy cows in Nigeria's hot-humid zones experience chronic heat stress that reduces milk production, impairs reproduction, and compromises immune function, but the integrated metabolic response to this stress has not been characterised at the systems level in African dairy cattle. This study monitors 60 crossbred Friesian-Bunaji dairy cows through a complete seasonal cycle in Lagos and Rivers States, collecting blood samples during mild (THI below 72), moderate (THI 72 to 79), and severe (THI above 79) heat stress periods. Multi-omics profiling includes plasma metabolomics (GC-MS and LC-MS), serum proteomics (iTRAQ), and targeted hormone quantification (IGF-1, insulin, cortisol, leptin, GH). Integration using Multi-Omics Factor Analysis identifies co-varying molecular signatures across omics layers. Causal network analysis delineates the mechanistic links from heat exposure to metabolic adaptations to production outcomes. Findings reveal a coordinated shift from glucose to fatty acid oxidation during heat stress, associated with elevated circulating NEFA and ketone bodies suggesting subacute ketosis risk. IGF-1 suppression during heat stress is identified as a primary mediator of reduced milk synthesis through insulin-like growth factor receptor pathway attenuation. The metabolomic signature 72 hours before clinical heat stress signs offers predictive early warning potential. The study contributes an original multi-omics heat stress adaptation model for tropical dairy cattle and recommends specific nutritional countermeasures targeting the identified metabolic shifts.

Keywords: heat stress, dairy cows, metabolomics, multi-omics, tropical Nigeria.