Morbidity in 3-7-month-old dairy calves in south-western Sweden, and risk factors for diarrhoea and respiratory disease.

The health status of 2947 heifer calves born in 1998 and raised in 122 Swedish dairy herds was monitored from birth to 210 days of age. Disease occurrence was recorded by farmers and by veterinarians who visited the farms six times yearly, examined the calves clinically and auscultated their lungs. The incidence risks of diarrhoea, ringworm and clinical respiratory-tract disease (CRTD) in calves from 3 to 7 months of age were 2.7%, 5.6% and 5.7%, respectively. The herd-level incidence risks of the three diseases were zero in 63.1%, 76.2% and 48.4%, respectively, of the herds. In positive herds incidence risks were 2.2-46.4%, 2.6-47.0% and 2.2-53.3%, respectively. The associations between the potential risk factors age at first grazing, air quality, birth place, feeding of colostrum, hygiene, number of animals, age range within the pen or building, pen area, pen location, previous housing type, present housing type, previous disease and season, and each of three binary outcome variables (diarrhoea, increased respiratory sounds and CRTD) were evaluated using two-level (calf; herd) variance component logistic models. Predictors significantly associated (P<0.05) with diarrhoea were pen area, season and the interaction between pen location and previous CRTD. Previous CRTD, season and heart girth at weaning were significantly associated with moderately to severely increased respiratory sounds. Predictors significantly associated with CRTD were previous diarrhoea, previous housing and season. It was concluded that the incidence of diarrhoea and CRTD in 91-210-day-old Swedish dairy calves is higher than previously reported from dairy herds in Sweden and the USA, and that diarrhoea, increased respiratory sounds and CRTD are associated with season, a history of disease during the first 90 days of age and, to some extent, housing factors.