Summer is here and so is the heat! It is my favorite time of the year. The sunshine and warmth are wonderful and feel great after a long cold winter and a chilly, wet spring. Summer brings us a new set of challenges on the farm……keeping our animals cool with the heat and humidity. Calves are not only subject to cold stress in the winter months but they can get heat stress in the summer months.

What is Heat Stress?

Heat stress happens when the temperatures outside combined with body heat are more than the amount of heat lost when sweating. The body can’t keep up with trying to regulate its internal temperatures at a comfortable level. 

This is especially difficult for young calves. Calves try to maintain a constant internal body temperature no matter what the temperature is outside. Calves use up their energy reserves to stay cool, this starts happening once the temperature outside exceeds 78°F. The stress on them increases as the temperature and the humidity rises. If you don’t recognize the first signs of heat stress or have taken measures to prevent it from occurring, a calf can die of heatstroke if its internal body temperature exceeds 108°F.

If a calf does survive heat stress, it affects them not only in the short term but in the long term as well. In the short term, they will have a lower average daily gain and are at an increased risk of diseases. In the long term, the calf’s breeding size and age at first calving will be affected. They tend to have calves prematurely and their colostrum is of lesser quality. You will need to ensure that you are testing all colostrum properly so their calves will have successful passive transfer rates.

Recognizing the Signs of Heat Stress & Dehydration

Dehydration is one of the very first signs of a calf experiencing heat stress. Recognizing those signs are critical in minimizing the effects. The signs of dehydration include:

  • Sunken eyes
  • Dry mouth and nose
  • Increased breathing rates 
  • Decreased appetite 
  • Weight loss
  • Fast or very slow pulse rates
  • Cold ears and/or legs
  • Skin pinch test performed on neck and skin stays tented for 2-6 seconds, which means that the calf is moderately dehydrated, and if the skin stays tented for more than 6 seconds, they are severely dehydrated.
Prevent Calf Sickness and Protect Future Profits: The 5-Step checklist for better calf health by Golden Calf Company

As the calf is dehydrated the symptoms of heat stress will become more significant. The common signs of a calf that is experiencing heat stress include:

  • With reduced movement, they will tend to be less active and standstill
  • Their breathing rates will continue to get faster
  • They will begin to experience open-mouth panting
  • Decreased feed intake
  • Increased water consumption
  • Their manure will be more firm
  • Their urine output will decrease
  • Their immune system will be compromised leading to other health issues

Things to do to Prevent Heat Stress

There are several steps, in a couple of different areas, that you can take to help in the prevention of heat stress during summer when the temperatures outside start surpassing 78°F. 

First, let’s address the calf housing. During the summer months, ensure that the housing is open and well ventilated. You can invest in a thermometer to monitor the temperatures inside the calf housing areas. You should be monitoring the temperatures daily. Use shade cloths and prop the hutch. Providing shade can reduce the air temp as much as 4° and gives calves a chance to get out of the sun. Using fans or opening vents helps to keep the air moving. Also, something to consider is switching the bedding to sand or sawdust, as these don’t retain as much heat as straw. But whatever the bedding choice is, it needs to stay clean and dry.

Next, you need to consider the calf’s nutritional needs as the temperatures rise. Calves will burn more energy trying to cool their bodies down. This means that there are fewer calories available for them to grow and maintain their average daily gain. You will need to increase their feed intake or even add a third feeding each day. You can reduce the fat levels in the calf milk you are providing to help increase the feed/starter intake. This will help them not only to have the calories to continue growing but have the calories to burn to ward off the heat. 

Water consumption is critical. You need to make sure there is plenty of clean fresh water available for the calf to drink. They should be drinking double the amount of water to help them stay hydrated. You can also offer electrolytes to help increase their fluid intake, improve hydration and prevent scours. However, this is NOT a replacement for fresh clean water. Keep water out of direct sunlight and change it often.

Another critical measure that you need to be taking is regarding hygiene. Remember that bacteria thrive in warm and damp conditions and this increases the chance of calf sickness. Remember to clean and sanitize all feeding equipment and buckets. Change bedding regularly so it stays fresh and clean. Throw away old feed. Have adequate drainage in the feeding and watering areas. Keep the flies at bay by eliminating hot spots-flies love spoiled feed, tall grass, and manure storage areas. Keeping calves away from those places and making sure that dirty items are properly cleaned and sanitized will help reduce the chance that the calf will get sick from the diseases flies can spread.

The last tip is to work animals early in the day to beat the heat. Finally observe the calves daily for panting, sweating, or excessive drinking as these are your first indicators that they are getting too hot. 

Prevent Calf Sickness and Protect Future Profits: The 5-Step checklist for better calf health by Golden Calf Company