Short communication: Identification of diseased calves by use of data from automatic milk feeders

Housing calves in large groups is associated with a higher risk of respiratory disease and with increased difficulties in identifying diseased animals compared with single housing. The aim of the present study was to investigate the effect of clinical disease on some behaviors recorded by automatic milk feeders in pre-weaned dairy calves. The experiment included 27 calves from a Danish research farm and 41 calves from a Swedish research farm. The calves were fed restrictively from a computer-controlled milk feeder, and all calves were subjected to daily clinical examinations for 3 to 26 d, with information gathered on general condition, nasal discharge, lung auscultation findings, coughing, signs of dehydration, naval status, rectal temperature, fecal consistency, and presence of chin abscess, arthritis, umbilical hernia, poor body condition, and poor hair coat. Calves suffering from diarrhea, respiratory disease, fever, or unspecific decreased general condition for more than 2 d were considered to be diseased and were declared to have recovered when they had been free of clinical signs of the disease for at least 2 d. The effects of clinical status (healthy, diseased) on the number of rewarded and unrewarded visits to the calf feeder and drinking rate, respectively, were analyzed by variance component analysis using a mixed model. Milk consumption on diseased and nondiseased days within calves was compared using a Wilcoxon signed rank test. In total, 53 of the calves were diagnosed as diseased during the study period. All cases of diseases were mild and were associated with an unaffected or only mildly affected general condition. Diarrhea was diagnosed in 51 calves, 6 of which also had respiratory disease. In 2 calves, respiratory disease was the only diagnosis. Eleven calves had an unspecific decreased general condition. The number of unrewarded visits was significantly reduced when calves were diseased. In Swedish calves, there was also a tendency for rewarded visits to be reduced during diseased days. Drinking rate and number of rewarded visits increased with increasing age. No effect of clinical status on milk consumption was detected. The number of unrewarded visits was the most sensitive of the 4 feeding behaviors monitored to indicate clinical disease in calves fed restricted milk volumes.