Cold Stress in Livestock: Welfare Guide
Cold stress occurs when livestock must expend significant energy maintaining core body temperature, reducing resources available for production, growth, and immune function. Severe cold causes hypothermia and death. Young animals, newly shorn sheep, and pigs are particularly vulnerable.
Species Thermoneutral Zones
Each species has a thermoneutral zone (TNZ) — a range of ambient temperatures within which metabolic rate is minimal and thermal comfort is maintained. Below the lower critical temperature (LCT), animals must generate heat through increased metabolism, eating more, or reducing production. Understanding species-specific TNZs guides management decisions.
Cattle: Beef cattle (winter coat) LCT approximately -10°C to -15°C; dairy cows approximately -5°C to 0°C. Cold stress is less common in well-managed outdoor cattle with adequate nutrition, but wind and rain dramatically lower effective temperature.
Sheep: Shorn sheep have LCT around 20°C — dramatically higher than unshorn sheep (approximately -3°C). Freshly shorn ewes exposed to cold, wet, and windy conditions can die within hours. Timing shearing to avoid severe cold spells is a welfare imperative.
Pigs: Growing pigs have LCTs around 15-20°C depending on age and group housing. Draught is particularly harmful — air movement significantly increases heat loss even at mild temperatures. Piglets have LCT around 30°C in the first week of life.
Neonatal Cold Stress
Newborn lambs, calves, and piglets are especially vulnerable. They have high surface-area-to-volume ratios, limited brown fat reserves, and immature thermoregulatory systems. Lamb hypothermia is a leading cause of lamb mortality — affected lambs become progressively weaker, unable to suckle, and die without intervention. Warming in warm water baths or warming boxes, followed by energy supplementation (glucose injection or colostrum tube feeding), can rescue hypothermic lambs.
Neonatal housing provision — deep straw beds for lambs, heat mats or lamp zones for piglets, deep straw for calves — is essential welfare infrastructure for spring and winter births.
Nutrition During Cold Periods
Energy requirements increase significantly below the LCT. Cattle require approximately 1% more energy per degree Celsius below LCT. Feeding additional concentrates, providing ad libitum high-quality forage, and ensuring fresh water availability (ice-free drinkers) are essential cold weather management practices. Thin animals are at much greater risk — body condition monitoring and pre-winter feeding adjustments prevent welfare emergencies.
Emergency Hypothermia Management
Rectal temperature below 37°C (sheep/cattle) or 38°C (pigs) indicates hypothermia requiring immediate intervention. External warming, energy supplementation, and veterinary assessment for severe cases. Avoid warming too rapidly in severe cases — peripheral vasodilation during rapid rewarming can cause cardiovascular collapse.