Heat stress can have a negative impact on a farm's bottom line well beyond the hot months. It's important to have strategies in place to minimise the effects on your herd.
Not only does heat stress substantially reduce milk production and income, but it also affects in-calf rates, protein and fat tests, liveweight and cow health. At temperatures of 25oC and above, dairy cows start to use energy to keep cool. Heat load is typically gained throughout the day, and lost overnight. When nighttime temperatures are above 25oC this heat load isn’t able to be dispersed, leading to more serious effects from heat stress.
Behaviours you may see in your herd during periods of high temperatures will include:
· Actively seeking shade and water
· Panting and sweating
· Standing up for increased air flow
· Reduced feed intake
· Reduction in milk production
More serious signs will include:
· Excessive drooling
· Open mouth breathing
· Group seeking of shade
If the period of excessive heat load lasts more than a few hours, the signs of heat stress will be more evident, and cows will struggle to cope. The above signs are a call for urgent attention.
There are also unseen impacts of heat stress that affect nutrition and fertility in your herd. These include hormonal changes, a rise in core body temperature and changes in blood flow distribution (reduction in blood flow to gut, uterus and other internal organs, increase blood flow to skin)
Strategies for your herd:
1. One of the best things you can provide to your herd in warm weather is shade, whether from trees or from man-made shelters, reducing the direct sun exposure.
2. The next best thing for hot days is sprinklers in the dairy yard. Evaporation is a cow's primary mechanism for heat loss. Even though cows may not spend a large amount of time in the dairy yard, even a short period of time in a hot environment will have an impact. Standing on hot concrete surrounded by other hot cows will significantly contribute to heat stress. Wetting the yard before the cows arrive can reduce the heat radiating from the yard, having sprinklers running whilst cows are waiting to be milked, and misters during milking can all reduce heat load. Having a water trough at the entry and exit of the dairy is also beneficial, particularly if the herd has a reasonable walk to and from the paddock. A trough at the exit to the dairy yard can also have a positive impact on milk production. An additional shade cloth over the dairy yard will further enhance cow cooling prior to milking.
3. During hot periods appetite is reduced and, if cows aren’t consuming enough feed, milk production will drop. It's important to keep intake up to keep production up. The best way to do this is by increasing concentrates. Cows will be chasing energy dense feeds, such as Maximize® and MaximizePlus®, as fibrous feeds will increase metabolic heat through digestion and rumination. Energy dense feeds mean they can eat less to hit their daily energy requirements, which helps during times of reduced appetite.
This will also help to maintain milk production and components.
4. Ensure your water system can cope with high demand during hot weather. Cows need between 200 – 250L of fresh drinking water during hot weather, double what they would normally consume. Flow rates to troughs should be able to provide 20L per cow per hour, waterpipes should be 75mm in diameter and ideally buried to keep lines and water cool. Large volume concrete troughs also help keep water cool.
5. Consider delaying the afternoon milking by 1-2 hours, so the herd isn’t walking to the dairy during the hottest part of the day.
Another consideration is the glucose level of your ration. Cows suffering from heat stress have a higher need for glucose. Starch is an effective source of glucose for cows, but it needs to be a slowly fermenting starch. Maize is great source of slowly digestible starch for dairy cows, but it’s hard to access and expensive in WA. Milne Feeds Maximize® and Maximize Plus® pellets have a very similar digestibility to maize, and are a great substitute.
A slowly fermenting starch source assists in a couple of ways: reducing starch fermentation in the rumen – allowing for greater glucose production in the liver, and this reduction in starch in the rumen reduces the risk of ruminal acidosis, allowing the rumen pH to remain stable even with an increased rate of pellet or grain feeding. Starch that isn’t digested in the rumen is typically digested in the small intestine, where it provides glucose for the gut tissue.
So, if you’re looking to make changes to your ration over summer or during periods of heat stress, ensure you’re aiming for an energy dense, safe, high starch feed that will maintain cow intake and provide the necessary glucose levels. Feeding Maximize® or Maximize Plus® will do this.
For more information on managing heat stress in your herd, refer to the Dairy Australia Cool Cows booklet. If you’d like to know more about Maximize and Maximize Plus to see if they are right for your herd, please get in touch with one of our team members.
