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Cold
Stress in Calves
By Gordon
Carstens, Ph.D., and Patricia Holland, DVM MS
Calf death losses may increase if the herd
encounters a combination of inclement weather with dropping temperatures
and increasing precipitation. These factors and the stress of
maintaining body temperature during extended time periods of severe cold
exposure may interact with other causes of illness to further increase
losses of newborn calves.
Consider herd management strategies to limit the effects of cold stress
and address the factors that make newborn calves intolerant of cold.
These factors include low birth weight; inadequate nutrition of the dam;
exposure to wind and precipitation; inadequate oxygenation associated
with calving difficulty; and inadequate intake of colostrum.
Birth weight
The heavier the calves, the more resistant they are to cold. Studies
suggest light-weight calves have greater difficulties maintaining body
temperature during cold stress because they generate less heat per unit
of skin surface area than heavier calves. This may partially explain the
higher incidence of death loss reported in light-weight calves born to
first-calf heifers and mature cows as temperature decreases.
Nutrition
Protein and energy malnutrition in cows during pregnancy may make
newborn calves unable to maximize heat production during cold stress.
Malnutrition in the cow reduces energy stores in the calf’s body
required for heat production. Maternal malnutrition has been associated
with weakened labor, increased incidence of dystocia, reduced calf vigor
and impaired immune function in the calf, all of which could contribute
to increased illness and death loss in calves during cold stress.
Environmental exposure
Normal newborn calves have a remarkable ability to generate body heat
and are tolerant to cold in a dry, still-air environment. The presence
of wind or precipitation, or both, significantly increases heat loss
during cold exposure by reducing insulation provided by the calf’s hair
coat. The presence of mud and manure can further interfere with the hair
coat’s ability to insulate against heat loss.
Provide a dry, draft-free environment for calves to prevent cold stress
due to excessive heat loss. Natural wind breaks or sheds can limit the
impact of environmental stressors, but avoid excessive build up of
manure, which can also cause disease in calves. An alternative to
providing shelter for cow-calf pairs is shelter for calves only — calf
hutches.
Dystocia
Calving difficulty can make living difficult for the newborn calf
because dystocia reduces the calf’s oxygenation and causes the blood to
become acidic. Among other detrimental effects, these acidic changes may
reduce cold tolerance of newborn calves by lowering body temperature and
decreasing the calf’s ability to generate heat. Calves that withstand
calving difficulty are slower to stand. They don’t aggressively seek the
udder or nurse colostrum well. They have an apparent delay in absorbing
immunoglobulins and other important nutrients in colostrum.
Colostrum
Adequate consumption of colostrum soon after birth is critical in
providing factors that help protect calves from disease. Colostrum is a
source of energy for newborn calves. They must receive adequate
colostrum to help fuel heat production soon after birth when heat loss
is greatest. Given the limited availability of energy from the calf’s
body reserves, adequate colostral intake is essential for maintaining
body temperature during prolonged periods of cold exposure, especially
in newborn calves predisposed to cold intolerance.
Calves that cannot effectively nurse soon
after a difficult delivery should have colostrum fed to them by other
means, such as a bottle or esophageal feeder.
Strategies to consider
To limit death loss in calves due to cold stress, consider changing the
calving season to minimize exposure to inclement weather. Delaying the
start of spring-calving season, for example, will likely reduce the risk
of exposing calves to wet, cold calving conditions.
Before changing your calving season to avoid cold, wet weather, consider
the effects of this change to the ranch and herd’s calendar. Will ranch
labor be available during the new calving season? How will the change in
calving season affect when and how you market calves?
Cows and heifers should be in good body condition at calving. Ideally,
calving season should coincide with availability of high-quality forage.
Matching calving season to the forage program helps ensure dams receive
adequate energy and protein during the last trimester of pregnancy while
minimizing cost of supplemental feed. This reduces the risk of dams
giving birth to weak, light-weight calves and helps ensure the calves
are better able to resist cold and disease.
If calving season doesn’t coincide with
forage availability, hay and supplements must be fed to meet protein and
energy requirements. Provide a balanced trace mineral.
Monitor calves predisposed to cold stress
closely and provide supplemental heat. Some rewarming methods are added
thermal insulation (blankets), warming and drying boxes, heaters and
infrared lamps or warm-water baths.
Gordon Carstens is associate professor,
department of animal science; and Patricia Holland is research
specialist, department of veterinary large animal clinical sciences,
Texas A&M University.
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