As the temperature keeps dropping and the days get shorter it’s a good indication that winter is here. As you’re gearing up to keep yourself warm on these blustery cold days, make sure you give a thought to your animals as well, especially your calves.
Whether in a barn or in hutches, calves are more susceptible to the negative effects of cold temperatures than are cows and more mature heifers. The range of temperatures where calves use no additional energy to maintain body temperature, or thermoneutral zone (TNZ), ranges from about 55°-70°F, varying slightly due to age and other factors.
In general, for every 1°F drop in temperature below the TNZ maintenance requirements of the calf increase by 1 percent. Calves are especially susceptible to the negative effects of cold due to having a larger surface-area-to-body-mass ratio than more mature animals, resulting in more body heat loss with the larger surface area. Cold stress causes calves’ energy to be used for maintenance rather than being utilized elsewhere in the body.
In more mature animals, fat can be mobilized to make up for this energy deficit. Calves, however, are born with low body fat reserves and excess energy must be supplied to avoid negative consequences.
Calves that are cold stressed right after birth have negative consequences from the start. Cold stress decreases the rate and delays the absorption of immunoglobulins from colostrum, though net absorption of colostral immunoglobulins is generally not affected.
Calves exposed to cold conditions also have a higher percentage of neutrophils and decreased percentage of lymphocytes compared to calves housed in TNZ and heat-exposed conditions between days 3 and 14 of exposure. This could be indicative of a delay in the development of the immune system in the cold-stressed calves.
Any delay in the immune system, be it the rate of absorption of colostral immunoglobulins or development of lymphocytes, puts calves even more at risk than they naturally are at this early period of life.
The more noticeable consequences of cold stress on calves, however, may be the decreased average daily gains. Unless adequate supplemented energy is provided, the energy used for growth in TNZ conditions will be used for maintenance.
Calves under cold stress will not grow as well as calves do in the TNZ; even a slight loss in growth can be detrimental to future productivity. A summary of calf data from Cornell found that a difference of 2.2 lbs. daily gain in the pre-weaning period resulted in 1,874 pounds more milk in the first lactation, and the trend continued in later lactations.