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Managing heat stress in heifers

heat stress in heifers

All dairy farmers know that, once the summer months arrive and the weather starts to get a bit warmer, it is time to start implementing their heat stress management strategy. Without a plan in place, your dairy cows are at risk of reduced performance and health issues. Of course, with these challenges come negative impacts on your production profitability. 

To help you make the most of your heat stress management strategy, we have compiled a series of blogs focussing on the five key heat stress risk areas on every dairy farm: 

1. Feed and Forages

2. Calves 

3. Heifers 

4. Milking cows

5. Transition cows 

Where most farmers see the impact of heat stress is in their milk production and the decreasing numbers when their cows’ performance is inhibited. Because of this, it is easy to research and gather plenty of advice, both good and bad, on combatting the effects of heat stress in your mature animals. However, information regarding how heat stress affects heifers is less easily found, but that does not mean that it is any less vital. 

Heifers are an investment in the dairy farm’s future, so neglecting their needs now will lead to problems for your production later. So, to ensure that you are taking the best care of your younger animals and optimising their potential, here is some information on signs of heat stress in heifers and how you can best address the issue. 

Signs of heat stress 

Some of the first indications of heat stress in heifers that you are likely to observe are changes in behaviour. You will notice the animals standing for longer periods and congregating more. This can be due to their bedding being too heat-absorbent and, therefore, uncomfortable. 

The next obvious sign is a drop in dry matter intake, which can be as much as 9%. The immediate effect of this can be a reduction in weight gain of up to 22%, but there are further, long-term implications too. A decreased dry matter intake impacts the animal’s overall digestion and, subsequently, the cow’s growth and development. This results in undersized animals with small udders that produce less milk. 

Other notable signs of heat stress include: 

  • Reduced bulling activity and conception rate. 
  • Blood acid-base imbalance, which can lead to ruminal  (it is metabolic not ruminal) acidosis. 
  • Higher respiratory alkalosis risk. 

Housing and environment 

There are many small adjustments that can be made to your dairy heifer housing and environment that can alleviate some of the stress that elevated temperatures can cause. You should make sure to: 

  • Provide adequate shade using tarps or roofing over resting area. 
  • Optimise ventilation and cooling. 
  • Ensure access to natural shade if the heifers are outside. 

Management of group sizes is also advised. Housing the animals in smaller groups can go a long way to minimising stress and competition at the feed bunk. 

Feeding and nutrition 

What you feed your heifers plays a huge role in managing the effects of heat stress. As mentioned above, your animals’ digestion can be impacted during this time, so it is essential that you optimise their diet so they can still get the nutrient content and energy they need to not only reduce heat stress effects but continue growing at the desired rate. 

When feeding, you should: 

  • Always feed ad libitum, ensuring the animals always have enough to eat. 
  • Ensure uniformity of mixed and delivered rations to help reduce sorting, lowering the risk of SARA. 
  • Never restrict access to feed or water. 
  • Shift feeding time to cooler parts of the day, mainly evening and night. 

As always, you should be using high-quality forage and digestible feed ingredients. Be sure to: 

  • Add dietary live yeast to improve rumen function. 
  • Use corn grain or fermentable starch. 
  • Have sugar at 6–7% dry matter. 
  • Eliminate any visibly mouldy of poorly fermented forage to mitigate any challenge from mycotoxins. 
  • Ensure ammonia supply for rumen bacteria to satisfy their requirements to maintain a consistent rumen NH3 level throughout the day. 
  • Provide pre-pubertal dietary CP of 14–15%. 
  • Provide post-pubertal dietary CP of 13–14%. 
  • Have overall soluble protein of >30–35% of the CP. 

Finally, you should make sure to satisfy the heifers’ requirement for minerals. These include: 

  • Calcium. 
  • Magnesium. 
  • Sodium. 
  • Potassium. 
  • Iodine. 
  • Manganese. 
  • Zinc. 

To make the most of your heifer diet, you can avail of some Alltech products that can help. Yea-Sacc® helps to stabilise the rumen environment and optimise function, while feeding Optigen® can increase dietary nitrogen density while maintaining consistent rumen NH3 levels and intake levels. 

To make all of the above advice even more accessible, we have laid out the key points on a one-page document that you can download here

Efficiently managing heat stress on your dairy farm, whether it be in your heifers or another area of your production, requires you to have the best insights and advice.

To help you become fully informed, we brought together a team of experts to create educational materials, including a series of expert advice videos, that will provide you with all the knowledge you need. Learn more here.

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