Occurrence and Determinants of Calf Mortality in Commercial Dairy Farms in Southern Highland Regions of Tanzania

Calf mortality is among the major problems hindering the success of the dairy industry throughout the world. It has a negative impact on milk production by reducing future milking herds and eroding genetic improvement. A retrospective study was conducted in Iringa and Njombe regions to estimate the magnitude and determinants of mortalities in calves up to 12 months of age. Five years data from 1st July 2017 to 30th June 2022 about calf mortality and related information were analyzed by Kaplan-Meier and Cox Proportional Hazard analysis. It was found that a total of 4,466 calves were born, out of which, 343 died at different times. The crude mortality was 7.68% while the mortality risk was 11.2% and the mortality rate was 11.9 per 100 calf-year at risk. The first month of life registered 36.15% of mortalities and at 90 days of age 63.3% of mortalities occurred. Diarrhea (27.11%), pneumonia (19.53%), and accidents (17.2%) were the most common syndrome/ factors associated with calf mortality. Calf mortality was higher in Jersey calves (HR 1.7, 95% CI 1.37-2.31) compared to other breeds. Calves born during dry season had a lower likelihood of dying (HR=0.647, 95% CI; 0.47 – 0.90) than calves born during rainy season. The major causes of early calf mortalities are managemental related and risk factors are age, breed and season. Improvement in calf management practices during the first month of life, breed selection and breeding program which allow calving in dry season may help to reduce dairy calf mortalities in Iringa and Njombe regions.