Research published in the December issue of the Journal of Dairy Science evaluated the effects of cold stress on calf growth, health and immunity. Brian Nonnecke and colleagues housed 29 calves indoors in elevated stalls at either cold (40 degrees F) or warm (60 degrees F) temperatures for seven weeks. Calves were three to 10 days old, weighed 100 pounds and had adequate passive immunity at the start of the trial. Cold housing was unheated and water was applied to calves (hair coat was saturated) and pens twice daily to maximize the impact of cold temperatures. Humidity in the warm environment was not manipulated, but temperature was controlled by thermostat. Relative humidity was about 10 percent higher in the cold environment than the warm. Calves were fed 1 pound per day of a non-medicated, 20 percent protein, 20 percent fat milk replacer and offered free-choice starter with 18 percent protein.
Temperature of the cold environment fluctuated with the weather and ranged from 34 to 51 degrees F. Heating provided a more stable temperature of 56 to 62 degrees F in the warm environment. Cold environment calves experienced more respiratory illness than warm environment calves during weeks three and six. No difference was seen in scouring or electrolyte treatment. Growth rates were not affected by the housing temperature, but cold environment calves ate more grain during weeks five to seven. Measures of immunity were not affected by environmental temperature. Researchers also noticed that cold environment calves developed thicker hair coats during the first week of the experiment. This demonstrated rapid adaptation and provided extra insulation that reduced the amount of energy used to maintain body temperature.
These results indicate that when calves receive adequate nutrition, they can tolerate considerable periods of cold without affecting growth. Some of the keys to helping calves thrive in cold weather are providing fresh, free-choice starter and clean, unfrozen water, keeping them dry and avoiding drafts.