“Climate is an issue when it comes to managing animals,” Michael Westendorf, Extension Specialist, Department of Animal Science at Rutgers University, said in a recent webinar presentation.
Every species handles temperature extremes in a different manner. All mammals have a thermoneutral zone. Outside of this zone, extra energy is required to heat or cool the body. Some livestock species are better at thermoregulating than are others. And each species of livestock has a different thermoneutral range, so they all have different requirements for housing, cooling, and body temperature control.
The temperature humidity index (THI) takes into account the relative humidity level’s effect on the actual degree of warmth. As relative humidity levels rise, any given temperature becomes more of a concern, and heat stress symptoms are exacerbated. The symptoms of overheating include: decreased feed efficiency; decreased weight gain; a loss of milk; a decline in feed intake; and decreased reproduction.
Livestock species have several innate ways of coping with temperatures outside of their thermoneutral zone. Panting cools the body by moving air across the mouth, causing salivation. This process transfers heat, which then evaporates from the saliva, resulting in a cooling effect on the body. Sweating changes water to gas, which vaporizes, and removes body heat.
Cows, however, don’t really sweat. When the body requires cooling, cows pant. They will also seek out a cool location – in the shade, or in mud or water. Cows in mud or water can cause disease concerns. Producers should provide alternative ways to keep cows cool.
Mitigating heat stress can be achieved in several different manners. Conduction, or direct contact; convection, via wind; radiation – either directly from the sun or to and from an animal and its environment; and evaporation, which occurs from panting or sweating. These are the primary tools to manage temperature extremes.
Misting cows, housing them in well-ventilated areas with fans, providing a cool environment on which they can lie down, and decreasing body-to-body contact will all decrease the effects of heat stress. Cows on pasture benefit from shaded areas, or shade shelters. Avoid handling or transporting cattle in heat stress situations.
Signs of heat stress include increased respiration rates; a rise in body temperature; lethargy; and lack of feeding. Increased salivation occurs as the animal desperately tries to remove heat via evaporation. Death can quickly result. Symptoms of severe heat stress can begin to occur in temperatures of about 82 degrees, if the relative humidity level reaches 80 percent. As the temperature rises, severe heat stress begins to occur at lower relative humidity levels. At 100 degrees, a relative humidity level of a mere 20 percent becomes a major concern.
When temperatures are in the thermoneutral zone, animals do not have to expend energy to stay cool, or generate extra warmth. This range differs not only amongst species, but amongst classes of animals within a species. Calves, for example, have a much more limited thermoneutral range than mature cattle. Reproductive stage, size, nutrition level, age, hair coverage and breed all impact the precise comfort zone.
Mature cattle have a thermoneutral zone which ranges roughly between freezing and 75 degrees Fahrenheit. Calves, however, cannot tolerate the lower or upper temperature ranges, and have a much shorter thermoneutral range, of 50-68 degrees Fahrenheit.
In cattle, the Brangus breed is a heat-tolerant cross of 5/8 Angus and 3/8 Brahmin. It is commonly used in the southern United States, to combat heat and humidity levels that cause heat stress in other breeds. Selective breeding can be used as a management tool to assist with particular environmental challenges.
When temperature fall below the thermoneutral zone, animals will shiver, huddle together, and eat more in an attempt to take in enough energy to keep them warm. Animals can also acclimate via increased hair growth, helping to maintain body heat.
An energy-rich diet, shelter, or external heat sources, for very cold or windy days, assists cattle in maintaining their body temperatures during cold spells. Adding energy in the diet will assist with rumination, and lowers digestive heat loss, too.
One often overlooked issue with cold temperature stress is the need for adequate water. Cows require a large amount of water, in the range of 30-40 gallons per day for lactating dairy cows, or 15-25 gallons for beef cattle. While this is often recognized as important during heat stress events, water is just a crucial when it is cold.
“Animals will stop eating if they don’t have enough water,” Westendorf said. If they don’t eat, they won’t have enough energy to devote to staying warm. They will suffer from the cold, lose body condition, or both.
Pigs have a very limited ability to thermoregulate. Wallowing in mud is one strategy they can employ. They don’t sweat as they have no sweat glands, and can only pant minimally. Hogs are particularly vulnerable to heat stress.
Sheep and goats both primarily pant, like cattle. And goats don’t sweat, either. Sheep sweat minimally, and do have a wider thermoneutral range than goats.
The thermoneutral range for swine is 55 – 78 degrees Fahrenheit, while goats are the same as calves. Sheep, however, do fine in extremes. Their thermoneutral zone ranges from 30 degrees up to 88 degrees Fahrenheit, and possibly higher.
Chickens pant as a cooling mechanism. They are fine in temperature into the low 80s, but don’t do so well below a moderate 63 degrees Fahrenheit, Westendorf said.
All livestock require water daily, no matter the temperature. Daily water needs for other species are much less than for cattle, but are no less important whatever the temperature.
Chickens require a pint of water per day. Swine require three to five gallons. Sheep and goats are in the three gallons per day range. During cold events, keeping water unfrozen is critical. Keeping it clean at all times, no matter the species, is also prudent.
As climate change causes more severe weather extremes to occur, livestock producers may be coping with unprecedented heat, or levels of cold, not normally seen in their regions. In addition, events which place animals outside of their thermoneutral zones may occur more frequently, and last for longer periods of time, making proactive measures crucial to curtail livestock losses.
The webinar is available here: www.climatewebinars.net/webinars/climate-change-and-its-effects-on-animal-agriculture