RESUMO
Keeping cattle outdoors year-around is considered an attractive alternative to indoor winter-housing, due to lower investment costs and better welfare. However, hair loss, attributed to lice, may impair cattle's thermal balance during harsh winters. During the winters of 2019-2021, outdoor cattle in Sweden were studied for the prevalence and development of hair loss, while surveys were conducted among the farmers on their perceptions and attitudes around hair loss. Of the 463 groups of cattle from 75 farms enrolled in a welfare control program issued by the Swedish Board of Agriculture, 25.7% (n = 119) had at least one animal with hair loss. When we followed up a subset of animals (n = 3673) which did not receive prophylactic delousing, 15.7% developed hair loss. Hair loss occurrence increased between visits within each winter in these animals, suggesting a contagious etiology. Logistic regression analyses, using the information collected in the control program and the hair loss outcome, showed that preventive delousing before November was effective, alongside keeping animals clean and the group size small. Meanwhile, being older (>2 years) and having access to bedding materials was shown to increase the risk at an animal-level. Some groups (n = 34) had no hair loss despite receiving no prophylactic delousing. Based on the survey conducted among the farmers (n = 15), groups with lower hair loss prevalence belonged to farmers who were more observant of hair loss and gave prompt treatment. This study provides knowledge useful to limit delousing interventions without compromising animal welfare.
