Wisconsin study identifies key management considerations to help keep young animals healthy in calf barns
If you house your calves in hutches like most dairy farmers and you've fed them during a January snowstorm, you may have wondered about moving them into a well-protected barn. If so, you're not alone.
Although individual hutches have long been the standard housing recommendation for raising healthy calves, the number of requests for practical calf barn plans have increased dramatically the last two years. Barns offer a much less labour-intensive-not to mention less bone-chilling-alternative to caring for calves in hutches.
Practical studies on calf barn design and its impact on calf health and growth are scarce. However, a recent University of Wisconsin field study of 13 naturally ventilated cold calf barns sheds light on the design and management decisions we face in constructing these facilities. The study's authors include some of North America's most highly regarded dairy management experts.
The barns studied had open ridges, curtain sidewalls and individual pens bedded with either straw or shavings. Individual pen sizes, proportion of pen area versus alley space, number of solid partitions, quantity of bedding and ventilation rate varied widely. Calves were scored for respiratory disease, based on a system combining rectal temperature, presence of a cough, nasal discharges and condition of eyes and ears. Airborne bacteria counts were measured in calf pens and alleys.
Among the 225 calves studied, 14 per cent showed signs of respiratory disease, with incidence ranging from zero to 37 per cent. Incidence was lowest in barns with low airborne bacteria counts in the pens, solid dividers between calves and bedding that let calves nest.
Solid side walls on the pens prevent calf-to-calf contact and also create some separation of air space. Both of these factors logically reduce disease pressure.
The value of calves nesting is perhaps less well recognized but was one of the biggest factors in reducing respiratory disease. Calves bedded with enough fresh straw in such a way that "they could nestle deeply into the bedding material and legs were not visible" had a much lower incidence of respiratory problems. Since the study was done when barn temperatures averaged four degrees C, calves that could nest were more protected from drafts and better able to keep warm.
Factors associated with higher airborne bacteria counts in the pens, and higher disease incidence, included smaller pen sizes, use of straw versus shavings and additional solid partitions in locations other than the sides of the pen.
Pen size ranged from 2.3 to 4.1 square metres. While observations associated straw with more bacteria in the air, deep straw was associated with lower disease incidence. This suggests the beneficial effect of nesting in cold weather outweighs the negative effect of increased bacteria load.
The last observation about additional solid partitions points out a flaw in current design practices. To keep drafts away from calves it has become common to add solid back and front panels, and partial roofs or covers to individual pens. By comparing air quality in the alleys and pens, this study established that these panels trap bacteria-laden air in pens, resulting in higher airborne bacteria counts and higher disease incidence.
While part of the interest in calf barns stems from wanting to save labour and improve operator comfort by moving calves inside, another factor is group housing and automated feeding. From a design standpoint, this study points us toward naturally ventilated calf barns housing individual pens with solid sides to prevent calf-to-calf contact. This study and others suggest calves touching each other is still a disease risk, a warning that group housing barns and their management will have to be even better than barns designed for individual pens.
Regardless of whether structures are for individual pens or groups, it is noteworthy that the study's results don't support limiting air flow with a partial roof or solid front and back panels. According to this study, providing lots of long straw that lets calves nest and keep warm is the preferred way to protect young animals from the cold. While not addressed here, controlling the speed of inflowing winter air with windbreak cloth may also help. Although straw is the preferred winter bedding for nesting, its association with greater bacterial growth suggests shavings might be a better choice in summer weather.
As in any field study, the study's authors point out, management factors that were not measurable can affect results, making it hard to draw clear conclusions. In this case, however, they have included and addressed an impressive number of variables that add new insight into important calf housing and management concerns.
Reference: A. Lago, S.M. McGuirk, T.B. Bennett, N.B. Cook, and K.V. Nordlund, 2006, "Calf Respiratory Disease and Pen Microenvironments in Naturally Ventilated Calf Barns in Winter." Journal of Dairy Science 89:4014-4025.
This article first appeared in the Ruminations column of The Milk Producer Magazine, January, 2007.
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