As dairies increasingly turn to housing young calves indoors, ventilation, as it relates to animal health, becomes a key consideration. Outdoor calf hutches, of course, have served well and provide ample ventilation. Their exposure to weather, however, can result in stress on calves and extra labor for dairy workers. Also, calf hutches do not facilitate use of automated feeders.
The ventilation tubes in this barn provide a continuous, gentle supply of fresh outdoor air to calf pens, reducing the levels of airborne bacteria. Growing numbers of dairies are turning to calf barns with individual stalls as a lower-labor solution for providing a comfortable environment for calves. These barns typically are designed with natural ventilation that can be regulated somewhat, depending on weather conditions.
Ken Nordlund, DVM, at the University of Wisconsin (UW), has found though that even in well-ventilated barns, the individual stalls can become badly polluted microenvironments, harboring airborne pathogens. Research shows airborne bacterial counts in naturally ventilated barns can be significantly higher than those outdoors, and counts within individual calf pens can reach levels dramatically higher than in the rest of the barn. Most of the bacteria species isolated in these tests are non-pathogenic, but Nordlund says research results indicate lower total airborne bacterial counts are associated with reduced prevalence of respiratory disease in the barns. High total bacterial counts serve as an indicator of poor ventilation, and because calves spend 100 percent of their time in the pens, their exposure to the air within the microenvironment is continuous and chronic. Fields studies, he adds, have shown a relationship between airborne bacteria counts and bovine respiratory disease (BRD) in naturally ventilated barns.
Dairies frequently overlook or underestimate the incidence of BRD in calves, Nordlund says. They use appetite as an indicator, but in limitfeeding systems the calves are hungry and take their feed readily. Research from fellow UW veterinarian Sheila McGuirk, DVM, MS, PhD, ACVIM, using a clinical scoring system and ultrasound diagnostics, has shown higher rates of BRD in dairy calves than most would suspect.
So if bacterial counts reach high levels even in barns with ample natural ventilation, what can be done to reduce them? The answer lies in improving ventilation to the individual pens.
Nordlund has worked with numerous dairies, assisting in the design and use of ventilation tubes. The positive-pressure ventilation tubes are designed to drive fresh air into individual pens, he explains. These are a new generation of ventilation tubes, not the positive-pressure recirculating tube systems of the 1980s.