A temperature-humidity index (THI) is a single value representing the combined effects of air temperature and humidity associated with the level of thermal stress. The dairy animals are thought to cope with extreme climatic conditions, especially high temperatures but fertility and milk productions are compromised during the stress period. In the present study, the mean THI values were recorded to be significantly higher during the summer than in the winter season. The present study conducted

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... e impact of THI on salivary fern patterns of 40 Water buffaloes and 40 Crossbred Jersey cattle during winter and summer seasons. This is the first study to know the THI impact on salivary fern patterns of estrus in dairy cattle. The Water buffaloes housed at both farm and field conditions showed better estrus signs and had 55% of typical salivary ferns found positive in the winter season when compared to the summer season had only 30%. The same correlation was also found in Crossbred Jersey cattle that had better estrus symptoms and 70% of typical salivary fern patterns found in the winter season compared to the summer season had only 40% typical fern patterns. The mean salivary fern pattern of Crossbred Jersey cows housed at both farm and field conditions was 40%, whereas in Water buffaloes was 30% in the summer season, may be due to the THI impact on these animals during the summer season was high. And also studied the typical salivary fern patterns at farm and field level were 60% and 37.5% respectively in both seasons, this wide difference was due to the water buffaloes and Crossbred Jersey cows were presented to the local dispensary for artificial insemination preferably on the second day of estrus, in those animals the concentrations of Estradiol was low on second day of Estrus. In conclusion, the drastic changes in salivary fern patterns results may be due to the lowered steroidogenic capacity of follicles under thermal stress is characterized by Aromatase activity of granulosa cells and lowered Estradiol concentration in the dominant follicle effect lesser amount of chloride ions secreted into the saliva, which is one of the for fern pattern initiation.