Maintaining a stable body temperature is important for sheep health. Their ability to keep their internal temperature within a narrow range directly impacts their immune function, disease resistance, and overall productivity, including growth and reproductive performance. Deviations from this stable temperature can indicate underlying health issues, such as infection, inflammation, heat stress, or hypothermia.
Normal Body Temperature and How to Measure It
A healthy sheep maintains a rectal body temperature between 101.5°F and 103.5°F (38.6°C to 39.7°C). This range can vary slightly depending on factors like age, breed, environmental conditions, and individual differences among sheep. Lambs may have a slightly higher normal temperature.
To accurately measure a sheep’s temperature, a digital rectal thermometer is recommended. Gently move the sheep’s tail to the side. Insert the thermometer carefully into the anus, aiming for it to touch the rectal wall to ensure an accurate reading, as taking the temperature of feces can result in a falsely low result.
Maintain a firm, yet gentle, grip on the thermometer for about 30 seconds until the reading stabilizes. After removing the thermometer, wipe it clean and read the displayed temperature. Clean and disinfect the thermometer with cold water and soap after each use.
How Sheep Regulate Their Temperature
Sheep use physiological and behavioral mechanisms to regulate their core body temperature, a process known as thermoregulation. These adaptations allow them to cope with different environmental conditions, helping them dissipate heat when it is hot and conserve it when it is cold.
To dissipate heat, sheep use several strategies. They may increase their respiration rate, leading to panting, which cools their bodies through evaporative cooling. Seeking shade and reducing activity, such as grazing during the hottest parts of the day, are common behavioral responses. They also increase water consumption to aid in cooling.
When faced with cold, sheep use different mechanisms to conserve body heat. Their wool acts as a natural insulator, trapping a layer of warm air close to their bodies and protecting them from both cold and heat. Shivering generates heat through muscle contractions, and huddling together with other sheep reduces individual heat loss to the environment. Sheep may also increase feed intake, as digestion and metabolism produce internal heat.
Recognizing and Addressing Temperature Extremes
Recognizing signs of heat stress and cold stress in sheep is important for their well-being. Heat stress occurs when a sheep’s body generates or absorbs more heat than it can dissipate, causing its core temperature to rise.
Signs include rapid breathing or panting, often with an open mouth and extended tongue, and profuse salivation. Affected sheep may also appear lethargic, refuse to lie down, increase water intake, and seek shade or crowd around water sources. In severe cases, they might exhibit a wide stance or stagger. A rectal temperature above 105°F (40.6°C) indicates heat stress, and temperatures exceeding 107°F (41.7°C) can be life-threatening.
To address heat stress, immediately move affected sheep to a cool, shaded area with good air circulation. Provide access to clean, cool water, and consider electrolytes. For sheep with short wool or hair, gently sprinkling them with room-temperature water on their lower legs and inner flanks can promote evaporative cooling, but avoid soaking sheep with long wool as wet wool can trap heat. Avoid handling or transporting sheep during the hottest parts of the day; if necessary, schedule these activities for early mornings or late evenings.
Cold stress and hypothermia, a dangerously low body temperature, can occur when sheep lose more heat than they can produce. Lambs and recently shorn sheep are especially vulnerable.
Signs of cold stress include shivering, a hunched posture, hollowed-out sides, and seeking shelter or huddling together. The sheep may appear weak, gaunt, or lethargic, and their mouth and ears might feel cold. If the skin over their spine remains tented after a gentle pinch, it indicates dehydration, a common issue with cold stress. A lamb’s rectal temperature below 37°C indicates severe hypothermia.
For sheep experiencing cold stress, move them to a warm, dry, and protected area with plenty of feed. For hypothermic lambs, warming methods include a warming box or a water bath followed by immediate drying. Heat lamps can be used, but ensure they are not too close to prevent burns.
Providing warmed colostrum or milk replacement can help. If a lamb cannot swallow or has very low blood sugar, energy may be needed via a glucose injection before warming to prevent convulsions. Ensure water troughs are not frozen in cold weather and provide alternative water sources if needed.