Relationship Between Higher Estrus-Associated Temperatures (HEAT) and the Bovine Preovulatory Follicular Fluid Metabolome

A higher estrus-associated temperature (HEAT) is a hallmark feature in sexually-active females, functional relevance is unclear. Objective was to examine relationship between HEAT and the preovulatory follicular fluid metabolome to test hypothesis-HEAT is functionally important to affect fertility related components in the preovulatory follicle. Estrus was synchronized in nonlactating Jersey cows using 7-day CIDR protocol. Thermochron iButton temperature data logger was affixed to blank CIDR and intravaginally inserted after CIDR removal. Onsite ambient temperature and relative humidity were recorded. Follicular fluid was aspirated 14.9 + 3.3 h after an animal first stood to be mounted. Eighty-six metabolites were identified in follicular fluid samples from cows with varying levels of HEAT. Mixed model regression was performed using metabolite abundance and HEAT variables. Best fit models were determined using backwards manual selection (P < 0.05). Vaginal temperature at first mount, change from baseline, was positively related to abundance of 20 metabolites, and negatively related to 1 metabolite. Enriched pathways included 'Aminoacyl-tRNA biosynthesis', 'Phenylalanine, tyrosine, and tryptophan biosynthesis', 'Thiamine metabolism', 'Glutathione metabolism', 'Taurine and hypotaurine metabolism', 'Pyrimidine metabolism', and 'Phenylalanine metabolism' (FDR < 0.1). Vaginal temperature at first standing mount was related to the differential abundance of two metabolites (Jasmonate, N-Carbamoyl-Laspartate). Three metabolites were related to maximum vaginal temperature (N-Carbamoyl-Laspartate, Uracil, Glycodeoxycholate). When expressed as a change from baseline, maximum vaginal temperature was related to differential abundance of Uracil, Uric Acid, 6-Phospho-D-gluconate. The time to maximum vaginal temperature was related to N-Carbamoyl-L-aspartate, Glycodeoxycholate, Jasmonate, and Tricarballylic Acid. Pertaining to the combination of HEAT and its duration, area under the curve from first initial vaginal temperature increase to maximum vaginal temperature related to 6-Phospho-D-gluconate, Sulfolactate, Guanidoacetic Acid, and Aspartate. Area under the curve from initial vaginal temperature increase and up to 10 h after a cow first stood to be mounted or when cow temperature returned to baseline related to the differential abundance of Uracil, sn-Glycerol 3-Phosphate, Methionine Sulfoxide, and Taurodeoxycholate. These findings support the notion for HEAT to relate to marked changes in the preovulatory follicular fluid metabolome which may be involved in energy metabolism, thermoregulation, and oxidative stress management.