The widespread use of air conditioning has made life much better for people, but little has changed for livestock. Summer is still a high-stress time and your livestock can have serious issues when the thermometer climbs, according to Dave Sparks, DVM, Oklahoma State University food animal quality and health Extension specialist.

Males are more affected by extreme heat than females; fat animals more than thin animals; and older animals more than young. Animals with any compromise of the immune or respiratory systems are at serious risk. Some advance planning and observation of your livestock can make a big difference in their comfort and in your profits.

Unlike horses and humans, cattle, sheep, goats and pigs don’t sweat, at least not in amounts sufficient for body cooling. They maintain their body temperature at or near a constant, normal level by panting. This moves air across the highly vascular and moist mucous membranes of the mouth, tongue and nasal passages, thus cooling the blood passing through these tissues much like water in an engine is cooled as it passes through the radiator.

For this to occur, they need a lower environmental humidity and adequate water for evaporation on the surface of the membranes. If livestock are not able to maintain their normal body temperature, they start to show signs of reproductive compromise first, followed by heat exhaustion at about 105o F, and cell breakdown and death at about 107o F.”

In extremely hot weather, it’s normal for body temperatures to rise moderately above normal during the heat of the day and to cool off at night when environmental temperatures are less. It takes several hours, however, for this to occur. Although air temperatures often decline in the late afternoon or evening, the animal’s body temperature may not fully recover its normal level until 2 or 3 a.m., after several hours of cooler temperatures.

Because of this, taking an animal’s body temperature to determine if an animal is sick is best done early in the morning to get a true indication. If you must work or handle livestock during hot weather, do it as early as possible in the morning and be finished before their body temperature starts to rise.

Reproduction efficiency can suffer

In hot weather, the first thing to suffer in your herd is reproductive efficiency. In males, high core body temperature may cause suppression of libido and can result in temporary sterility if elevated body temperatures caused sperm cells to die.

Research has shown that in females, high body temperatures can result in lowered conception rates and embryonic death. Excessive heat affects embryo survival and fetal development most markedly during the first 21 to 30 days after breeding.

So what can we do? The simplest answer is shade and the easiest shade is a shade tree. Closed spaces aren’t very helpful because they restrict air movement. If you use a barn for shade, utilize a breezeway or fans.

If natural shade isn’t available, a little creativity and simple materials can provide permanent or temporary shade. On an extremely hot day, a shade structure can cause a drop of 12o to 15o F in environmental temperature. Sprinklers and misters are often used for cooling. Wetting the ground can help to reduce temperature by evaporative cooling and also helps to keep dust irritation down.

Clean, cool water

A good rule of thumb for drinking water is that if you wouldn’t drink it and enjoy it, neither will your livestock. In cool temperatures, mature livestock drink about 10% of their body weight/day in water, or about 1.25 gal./day/cwt. In summer, this doubles or even triples in order to meet body cooling requirements.

Cleaning water tanks and supplying fresh water becomes even more critical. The question isn’t “does my animal drink,” but “does my animal drink enough?” Summertime temperatures also necessitate more frequent tank cleaning because as temperature rises, bacteria and algae grow much faster.

Excessive heat can affect your livestock and your profits in several ways. Hot animals have poor appetite and growing animals that don’t eat don’t grow. Females that are trying to pick up body condition prior to breeding season or calving need to eat to capacity as well. Adequate shade, plenty of clean water, and a moratorium on handling in the afternoon and evening can limit health problems and help ensure good reproduction rates in your herd