In the March 2009 issue of Dairy Herd Management  we reported on a field trial conducted by the University of Wisconsin’s School of Veterinary Medicine. In the trial, they measured the air quality within 13 nurseries on Wisconsin dairy farms during winter months. Their measures were quite startling. Air quality as determined by measuring the concentration of bacteria in the air of the nurseries varied a lot — from very low to too many bacteria too accurately measure. Several factors were indentified that contributed to air quality, and solid recommendations were made from the research that can be applied to calf nursery management to reduce the incidence of respiratory infection. 

Key recommendations were:

  • Only have solid panels between calf pens but not in the front and rear of pens to allow for better air circulation.
  • Maintain deep straw bedding.
  • Lower the barn temperature.
  • Maintain at least 30 square feet of pen space.

More recent research on housing for dairy calves was presented in this week at the American Dairy Science Association annual meeting by researchers at the Nurture Research Center (formerly Akey Nutrition and Research Center) in Southwest Ohio. That research was a multi-year project evaluating three main concepts:

  • Housing type (poly hutches vs. wire mesh pens within a well-ventilated nursery).
  • Bedding type (sand vs. straw bedding).
  • Cooling calves with fans during summer months.

In measures made from September to March, calves weighed 5 pounds less at 8 weeks of age when housed the poly hutches vs. in wire mesh pens (32 square feet per calf) in the nursery using straw bedding. All calves were bedded with straw.

During the months of May through September, calves bedded with straw were 6 pounds to 9 pounds heavier at 8 weeks of age than calves bedded with sand. Additionally, calves in wire pens within the nursery on straw bedding had the least days with scours, while calves housed in hutches on sand had the most days with scours. “These data compare well to previous research that we have published during winter months” comments Mark Hill, lead researcher at the unit. “In those winter trials, calves were bedded either on straw or hardwood shavings and fed various amounts and types of milk replacers. Calves bedded with straw gained 5 pounds to 9 pounds more body weight by eight weeks of age compared to calves bedded with shavings. Additionally, in these trials increasing the amount of a conventional 20 percent protein, 20 percent fat milk replacer by 50 percent did not change weight gain, while the bedding type did, demonstrating the importance and effectiveness of deep straw bedding.”

Calves in poly hutches, bedded with sand had significantly greater concentrations of airborne bacteria than calves within the nursery bedded with either sand or straw. Airborne bacteria concentrations were also measured in several types of poly hutches on several other farms and were all very high (over 300,000 colony forming units per cubic meter of air). This compares to an average of 30,000 colony forming units per cubic meter of air within the well-ventilated nursery pens in the Nurture Research Center. A possible management strategy to improve the air quality in hutches is to elevate the rear of hutches with thick boards or blocks. A simple 1.5 inch gap at the rear of hutches reduced the concentration of airborne bacteria within the hutches to under 100,000 colony forming units per cubic meter.

These hutches were not shaded. In the 1990s, researchers at both Auburn University and the University of Missouri reported benefits from shading calf hutches in their southern climates.

Airborne bacteria concentrations increased with calf age in the nursery. The range was 5,000 to 50,000 colony forming units per cubic meter of air in the calf pens. This makes it more difficult to ventilate nurseries with calf age and it increases the chances of respiratory infection in calves with age. To this point, the University of Wisconsin research observed the highest incidence of respiratory infection in 7-week old calves. Also, extending the time calves are housed in nurseries or hutches could increase their chances of respiratory infection.

Fans operated during the hours of 8 a.m. to 5 p.m. to cool calves within the nursery during summer months supported approximately 11 pounds more body weight of calves and better feed efficiency at 8 weeks of age compared to calves that were not cooled. Calves cooled with fans had fewer breaths per minute than calves not cooled. The panting or faster breathing in the calves that were not cooled with fans likely used more energy to reduce calf weight gain.

Take to the farm messages:

Benefit:

Use straw bedding
Deep straw during cold weather

Less respiratory infection
Less scouring
More body weight gain

Ventilate nurseries well

Less respiratory infections
More body weight gain

Elevate rear of hutches in summer
(bedding can block vent from elevation)

Less airborne bacteria than can contribute to respiratory infections

Cool calves in nurseries with fans during hot weather

More body weight gain

Source: Provimi North America (formerly Akey Nutrition and Research Center)