Calf coats: A necessary winter accessory

By Dr. Jodi Wallace DVM, MSc, Ormstown Veterinary Hospital

In our harsh Canadian climate, cold weather can take its toll on everyone, including calves. Whether your calves are inside or outside, cold weather is very stressful for them. Calf coats are a simple, inexpensive accessory for your calf health management program.

When the temperature drops, calves require more energy for maintenance and growth. Calves will use their own fat reserves for energy if the extra energy is not supplied. Newborns have low brown fat reserves (one to three per cent of bodyweight for a 45 kg (99.2 lb.) calf). Brown fat is a rapid energy source used to keep calves warm. Once the fat deposits are used up, the calf starts to break down muscle for energy and heat production. In addition, cold-stressed calves will divert energy away from digestion. Consequently, there is decreased fluid absorption and less energy for growth, resulting in reduced average daily gains. Calves will lose weight and have a weakened immune system. This will make them more susceptible to diarrhea and pneumonia.

Calves are more sensitive to cold. They are monogastric, meaning they have yet to develop a rumen. Therefore, they are unable to generate heat through rumen fermentation. Also, they have a large surface area per bodyweight ratio, which means they lose heat faster.

When do calves need coats?

The thermoneutral zone (TNZ) is the temperature range where calves can easily maintain their body temperature. The TNZ for calves is 12 to 20°C (53.6 to 68°F). The LCT (low critical temperature) is the temperature that calves begin to require extra energy to maintain body temperature. The LCT ranges from nine to 15°C (48.2 to 59°F) with younger calves feeling cold-stressed at the upper temperature range as compared to calves older than three weeks. The actual temperature of the calf will depend on multiple factors including wind speed, relative humidity, hair coat, sunlight, bedding, and rumination. A good rule of thumb: below 10°C (50°F), cover them up with a calf coat.

Calf coat considerations

• Dry: The calves’ hair coat must be dry before fitting the coat. For newborns, make sure the hair coat is dry to touch. Dry hair traps air creating a natural insulation. I like placing calves in a warm room or an incubator to air-dry immediately after birth. This also is a good time to feed colostrum. Once the coat is on, verify that calf is not sweating or that the coat does not get wet from rain or snow. If so, remove or replace the coat. Choose a coat that is water resistant and breathable.
• Adjust: Coats are not a one-size-fits-all. Coats should fit snuggly and cover from shoulder to rump. Coats range in size from XS to XXL. Be sure to adjust straps as the calf grows to make it a comfortable fit.
• Clean: Make sure coats are clean. Coats need to be disinfected and washed. Soiled coats can be a source of infection for diarrhea pathogens (bacterial, viral, and protozoal), especially if they are moved from calf to calf. Cleaning is key to kill these pathogens. Cryptosporidium is the most fastidious pathogen. To kill Crypto oocysts, coats must be disinfected and washed. Coats can be disinfected with chlorine dioxide, which is a product known to kill crypto oocysts and then washed in a commercial washer with water over 60°C (140°F). Coats can go into a dryer or hang to dry. Ensure coats are completely dry before placing on the calf.

Calf coats work great to combat cold stress, but they need to be combined with, proper bedding, ventilation, and increased energy at feeding.

Bedding management is an extremely important aspect. Ensure that calves have enough bedding to keep them warm and dry. Calves lose heat by conduction. That means heat is transferred down through the bedding. Cold concrete, gravel, and sand increase conduction losses. The best bedding for calves outside in hutches is wood shavings covered with straw. Calves lie down a lot. Newborn calves will spend approximately 80 per cent of their time lying down, and six-week-old calves will spend 75 per cent. That translates into upwards of 19 hours lying down per day! Calves should be able to ‘nest’ in the bedding which helps reduce heat loss. The legs of the calf should be covered by the bedding when lying down (nesting score 3). A score of 2, the calf is nestled slightly into bedding, part of legs visible above bedding. A nesting score of 1, is when calves lie on the bedding and their legs are visible. Calf coats can increase the nesting score by 1.

Coats will not protect calves from cold drafts. Indoor barns need to be properly ventilated. With outdoor housing, calves need to be protected from the wind.

As the temperature drops, calves need more calories to maintain the same growth. Calves will need more milk. It is best to increase the milk volume and not change the concentration. Milk replacer fed too concentrated, over 180 g/L, can cause nutritional diarrhea. Adding a mid-day feeding can help to increase the energy intake. Calves should also have access to fresh starter and water daily. If calves are outside in extreme weather, water should be offered at least three times a day for a minimum of 30 minutes. Calves cannot drink ice. Research has shown calves, that have free choice water versus no water, have a 45 per cent increase in starter intake and a 60 per cent increase in weight gain in the first four weeks of life. Starter intake is important because it increases rumen development. A functional rumen is a fermentation vat that produces heat and helps to keep the calf warm. In addition, starter intake helps meet the energy requirements in cold weather. Even calves one week of age should be offered a small amount of calf starter.

With winter upon us, just remember that the colder it gets, the more energy a calf needs to maintain heat, stay healthy, and keep growing. Calf coats help protect the calf from cold stress caused by extreme weather and daily environmental variations. Calf coats along with proper calf care management will help improve calf health on your farm.