Comparative assessment of thermoadaptibility between Tharparkar and Sahiwal based on biochemical profile and gene expression pattern under heat stress

Abstract

Heat stress impact on Tharparkar and Sahiwal breed cattle can be quantified by measuring physiological variables and biochemical responses and observing gene expression at the molecular level. The experiment was conducted on two groups consisting of Tharparkar and Sahiwal animals (5 in each group), and the experimental period involved 7 days acclimatization period, a heat exposure period of 21 days at moderate (35 °C) and severe (42 °C) heat stress and 9–10 days recovery period between each exposure. Blood samples were cumulated weekly for serum and PBMC isolation for gene expression analysis. The physiological responses, i.e., rectal temperature (RT) and respiratory rate (RR) elevated as the temperature exposure increased. The AST, ALT, ALP and Cholesterol levels in serum were significantly (p<0.05) elevated in Sahiwal than in Tharparkar breed during heat exposure. However, no significant (p>0.05) difference was observed between breeds while assessing serum total protein levels. Relative mRNA expression of HSP 70, TLR 2, TLR 4, IL 1, IL 10 and TNF- α was comparatively up-regulated (p<0.05) in Sahiwal as correlated to Tharparkar, but HSP 90 and eNOS relative mRNA expression was (p<0.05) significantly elevated in Tharparkar animals. Given response sensitivity due to thermal stress representing the decrease in the immune status of animals, it can be concluded that the indigenous breed Tharparkar showed more tolerance to thermal stress than the Sahiwal during the heat exposure period.