Identification of a novel HSP70 SNP and heat stress biomarkers using Infrared thermography and gene expression analysis in Bos indicus

Abstract

A comparative study was conducted on three strains of Deoni cattle (Wanera, Balankya, and Shewara) in the drought-prone western region of India to evaluate their adaptability and infrared thermal profiles across seasons. Significant variation in body surface temperature was observed across different body regions. In estrus cows, rectal temperature showed positive correlation with muzzle and eye temperature, while respiration rate was positively correlated with ear, dewlap, hump, flank, vulva, and udder temperatures. In non-estrus cows, rectal temperature was positively correlated, whereas respiration and heart rates showed negative correlation with most surface temperatures. Infrared thermography revealed that hump temperature remained relatively stable (34°C), irrespective of environmental changes, indicating its reliability as an indicator of body temperature. Strong correlations were observed between body surface temperature and thorax, hump, flank, and hip regions, particularly during morning hours. Temperature-humidity index (THI) showed moderate correlation with hump temperature (0.41) in the morning but very low in the evening. Physiological parameters (heart rate, respiration rate, and rectal temperature) showed minimal variation between estrus and non-estrus cows. Genotypic differences (AA and BB) had no significant effect (p>0.05) on rectal temperature and respiration rate. A negative correlation was observed between HSP70 gene expression and body temperature, especially in the morning. Overall, infrared thermography combined with physiological and molecular parameters can serve as a reliable, non-invasive tool for estrus detection and early pregnancy diagnosis in Deoni cattle