Validation of preventive routines and diagnostics in hairloss in free ranging beef herds

Keeping cattle outdoor year-around is an attractive alternative for farmers due to low investment costs. Furthermore, keeping the animals outside can promote animal health and welfare compared to confined settings. In the Nordic countries, the climate can be a challenge though, as extreme cold and harsh wind can negatively affect an animal's thermal balance. The hair is an important parameter in the thermal retention capacity of an animal. Thus, if the hair thins out and bald spots appear, the welfare of the animal can get negatively affected along with the production value of the animal. Therefore, we conducted a repeated cross-sectional study to examine the epidemiology of hair loss in outdoor cattle in Sweden during the winters of 2019-2021. The three main objectives were (1) to describe the prevalence of hair loss in outdoor cattle, (2) to examine the development of hair loss in animals when there was no prophylactic ectoparasite treatment (delousing) applied, and (3) to investigate the associated factors for the hair loss outcome.

During January-February of 2019-2021, each group of outdoor cattle had an annual visit where they were inspected for hair loss, and group-level data, such as size, breed, and information on delousing treatment (date, drug), was collected along with the inspection parameters in the Swedish control program for outdoor cattle. A subset of the study population, among groups with no prophylactic delousing treatment, was followed up for investigating development of hair loss in animal level. Logistic regression was used to examine the association between collected animal- and group-level factors and status of hair loss with group and farm added as random effects when relevant. All the analyses were done using R.

A total of 463 groups from 75 farms were included in the study. The median size of the groups was 30 animals (range 2-698). 25.7% (n=119) of all the groups had at least one animal with hair loss. Prevalence of hair loss within group varied from 0.6% to 47.9% (mean 8.2%). Thirty-one farms had no hair loss observed. In the final model, group size (p<0.01) remained to be significantly associated with the hair loss outcome with the small groups (<14 animals) having lower odds. Also, having at least one dirty cow in the group significantly increased the odds for hair loss (OR=4.34, p<0.01), while delousing treatment significantly lowered the likelihood for hair loss in a group (OR=0.43, p<0.05). Among the groups with delousing treatment (n= 336), having at least one dirty animal in the group significantly increased the odds to have hair loss outcome (OR=12.64, p<0.00001), while delousing the animals before November significantly decreased the odds (OR=0.26, p>0.05). For the groups that did not have any prophylactic delousing treatment (n=127), only the big group size (>68 animals) was associated with the hair loss outcome (OR=3.64, p<0.05) in the final model.

A total of 3673 animals were included in the groups in which no prophylactic delousing was performed for the study. At the first visit, 249 animals showed hair loss (6.78%) while the proportion increased to 12.02% at the second visit and 18.22% on the third visit, suggesting spread of hair loss within the group over time. In the final model, being >2 years old (OR=11.89, p<0.001) and having bedding (OR=4.13, p<0.001) were significantly associated with higher likelihood of hair loss in an animal. Also in the final model, compared to Hereford, Angus had significantly higher odds to develop hair loss (OR=8.59, p<0.05).

In conclusion, the study showed a wide range of hair loss prevalence between farms and groups. Applying prophylactic delousing treatment significantly decreased the likelihood to develop hair loss in a group while increase in the proportion of animals with hair loss was observed among animals without delousing treatment in the follow-up visits. Along with the statements of veterinarians in the field, these findings suggest ectoparasites, i.e., lice, as a significant cause for the hair loss in these outdoor cattle. Yet, there were farms which had no cows with hair loss during all three years without any delousing treatment, indicating good farm management, like having no dirty cows, and keeping the group size more manageable can also be effective measures against hair loss.

Publication

Prevalence and risk factors for hair loss in outdoor-wintered beef cattle under cold weather conditions (2024)