Abstract:
Increasing heat stress threatens livestock production especially lactating dairy cows across the world. Therefore this study was conducted to evaluate the effect of heat stress on physiological parameters, adaptation and mitigation strategies of lactating Kereyu and Hararghe cattle breeds in Bordode District, Ethiopia. Purposive sampling technique was used to select study area and respondents and Bordode district was selected based on the availability of both Kereyu and Hararge cattle breeds. Then randomly out of six agro pastoral Kebeles three kebeles namely Sirba, Funyan Ajo and Kora were selected and total 150 were selected for interview. For analyzing of physiological parameters a total of 18 lactating Kereyu and Hararghe cattle breeds were randomly selected. Physiological, blood and hormonal parameters were evaluated by factorial design thus, two cattle breeds× 3 (Stage of lactation Stages of lactation; early, middle and late) were used in completely randomized design. Breed and lactation stage were fitted to independent variables while physiological, and blood and hormonal parameters were fitted to response variables. Based on the conducted survey to overcome heat stress effects major adaptation and mitigation strategies were providing tree shade, planting trees, rearing heat-tolerant livestock, and ensuring access to cool water, and herd mobility. The respondents perceive that reduction in milk yield, increase incidence of disease and reduction in rangeland cover were the major effect of heat stress in the study area. Breed and lactation stage interaction show significance source of variation (P<0.05) on rectal temperature and white blood cell count. Likewise, breed and lactation stage interaction were highly significant (P <0.001) source of variation on hemoglobin cortisol level.. From this study, it is concluded that lactating Kereyu and Hararghe cattle breeds were good at thermoregulation at maximum THI value of 79.36. Thus, the temperature-humidity index value of 79.36 can be considered as optimum for physiological response to heat stress in lactating Kereyu and Haraghe cattle breed under their current production system. However, introducing adaptation and mitigation strategies such as better nutrition, providing shade, and routine health management practice are needed to further strengthen the resilience of the breed to heat stress in the future
