Effect of dry and rainy environments on the Ethology of dairy cows

Bioclimatic production conditions and the responses of animals under production were evaluated in the Meio Norte region of Brazil. Lactating dairy cows, crossbreeds (Gir x Holstein) and zebu (Gyr) during the dry and rainy season. Collected air temperature data in the dry and wet bulbs, minimum and maximum temperature, relative humidity, respiratory rate (RR), heart rate (HR), and rectal temperature (TR) converged to the bioclimatic indicator Temperature and Humidity Index (THI) and the etiological indicator Heat Tolerance Coefficient (CA). Analysis of variance to assess significant differences accompanied by post-hoc analyses indicate significant effects (p-value <= 0.05) of season effects (Rains and Droughts) and/or genetic group (Girolanda/Gir). Higher temperatures (T) and lower relative humidity (RH) were identified during droughts: 30.5(degrees) and 47.5%; in relation to the rainy season: 26.7degree celsius and 86.5%. Bioclimatic conditions were mostly unsuitable for cattle. Ethological responses varied mainly depending on breed and only HR significantly differed depending on season. Gir animals, despite having a smaller thoracic perimeter (PT), are more adept at promoting thermolysis and/or producing less endogenous heat, presenting significantly lower AC, RR, HR, and TR (p-value < 0.05). Production conditions are challenging with high THI and animal responses that indicate discomfort, especially during dry periods in the Meio Norte region.