Infrared thermography to detect intramammary infections at drying off
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Mastitis is one of the most common problems in the dairy industry and is responsible for large economic losses. Mastitis is mainly caused by bacterial intramammary infections (IMI). During the dry period, especially at the start and the end of that period, mammary glands are susceptible to the invasion of udder pathogens. IMI gained during the dry period is a risk factor for the development of clinical mastitis after calving. Antibiotic treatment at drying off has a dual target: cure existing IMI and prevention of new IMI during the dry period. Currently, decisions about the dry off treatment are usually based on cow level diagnostics. To optimize antimicrobial use in dry cow treatments, a next step may be to make dry cow treatment decisions at quarter level rather than on cow level. Infrared thermography (IRT) is a simple, effective and non-invasive method that detects surface heat. In experimental settings it has been shown to be effective in diagnosing clinical mastitis. To determine if IRT is able to diagnose subclinical mastitis at drying off, a total of 53 dairy cows from 3 different dairy farms have been photographed. Somatic cell count (SCC) on cow level, on quarter level and a bacterial culture at quarter level were used to determine if IRT could be useful as a quarter level diagnostic on top of SCC on cow level to diagnose subclinical mastitis. The mean quarter temperature measured at a distance of 1 meter varied between 26°C and 36.8°C. The maximum quarter temperature varied between 29.2°C and 43.3. There is no significant association between the SCC on quarter level and the mean and maximum quarter temperature. No significant association was found between the presence of an IMI and the mean and maximum quarter temperature. Quarters with a major pathogen IMI, which could benefit from antibiotic treatment at drying off, were considered to have subclinical mastitis. No association was found between the presence of subclinical mastitis and the mean and maximum quarter temperature. The IRT pictures were taken the day after drying off. To check if a difference in quarter temperature occurred between the day of drying off and the day after, a total of 13 dairy cows were photographed using the IRT camera. There is a significant association between the quarter temperature measured at day 1 or day 2 if the environmental temperature is placed in the model (p < 0.05). This means no difference was found between the temperatures measured on day 1 and day 2. Altogether, these findings suggest that IRT is not able to diagnose subclinical mastitis and can not be used as a quarter level diagnostics method to determine dry off treatment.