Early detection of disease onset through changes in appearance of pre-weaning calves.

The onset of diseases in pre-weaning calves can lead to changes in their appearance, which can aid early disease detection. This study measured the changes in appearance that led to disease onset in 66 pre-weaning Holstein calves. The appearance scores of the calves were recorded for 7 days before the onset of digestive or respiratory diseases. Appearance features (ear position, head position, topline curve, hair coat length, hair coat gloss, eye opening, and sunken eyes) were recorded using video camera images and scored from 0 (healthy) to 2 (poor). Among the calves with respiratory diseases, the proportion of calves with a score of 0 for ear position decreased linearly over time (p = 0.0437). Among the calves with digestive diseases, the proportion of calves with a score of 2 for hair coat length increased linearly over time (p = 0.0197). Among the calves with both respiratory and digestive diseases, the proportion of calves with scores of 1 for the topline curve and 2 for eye opening increased linearly over time (p = 0.0191). Therefore, early signs of disease manifest as different appearance features depending on the type of disease before its onset.