Farmers will be up the walls this week trying to get field work done while the sun shines, but as things die down, they may notice a drop in milk production.

As of Friday last week, just as the weather was turning good, the average milk kg/cow was 27.6, according to national milk recording data from the Irish Cattle Breeding Federation (ICBF).

However, with temperatures hitting as high as 30℃ in places during the week, many farmers saw milk production fall.

According to data from Moonsyst rumen bolus technology, heat stress was detected in 20-30% of dairy cows currently being monitored with its technology in Ireland during the week.

The smart rumen bolus technologies consistently reported 'high rumen temperatures' throughout the week, with temperatures rising in the late afternoon and dropping off in the evening.

The technology also reported increased drinking events and higher activity levels.

Director at Moonsyst, Desmond Savage said these spikes could arise from cows seeking access to water troughs and shade.

Savage noted that this is the first time there has been clear signals of heat stress in Ireland.

He stated that Moonsyst is well adapted when it comes to reporting these events. With the technology deployed in over 40 countries, it commonly identifies these issues in regions such as Australia and Argentina when temperatures exceed 35℃.

Despite the rapid increase in temperature and humidity this week, Savage highlighted that the same level of stress was not seen in beef and suckler herds using the technology.

Heat stress

Although peak milk production is just beginning to slip away, cows are still producing strong yields.

This paired with the stress of breeding can leave the dairy herd quite susceptible to heat stress when temperatures climb above 20°C with moderate humidity.

Once cows begins to feel the impact of heat stress, feed intake will be reduced and ultimately cause a reduction in milk yield and solids, which can be quite costly considering the year we are having.

To make matters worse, fertility can be severely impacted by heat stress, which could prove disastrous considering how we are in the midst of the breeding season.

To top it all off, heat stress can be a root cause of additional health issues, such as mastitis, lameness, and acidosis.

That is why it is important to identify heat stress early, and take measures to prevent it.

Spotting heat stress

The water trough is often the best place to spot heat stress, as animals will be bunched around it with drinking activity increased.

You may also notice cows splashing water onto their body using their head.

A farmer might also observe a cow's refusal to lie down if she is under stress, which can ultimately lead to claw horn lesions such as heel ulcers.

During heat stress, cattle's body language may display open-mouth breathing; head extended, tongue protruding, front legs separated, and excess saliva production.

In a worst case scenario, the animal's body temperature remains high and under stress, leading to fatality.

This something you must be aware of when it comes to sick cows, as they may need to be supplemented with oral fluids or even electrolytes.

Prevention

It goes without saying that one of the most important things farmers need to be on top of during these warm fronts is water supply.

Water intake can nearly double in hot weather, so ensure troughs are big enough and have a strong enough pressure to keep them filled.

If signs of heat stress are presenting, farmers can cool cattle down by using a water sprinkler system to wet their coats.

Provide shade to cattle during the heatwave, and consider giving the herd open access to enter a well-ventilated shed voluntarily.

This option may prevent animals from huddling under trees and hedges for shade, which is a fine option but does come with the risk of mastitis, as these areas are often a favourable environment for the bacteria.

If feeding concentrates or forage to your herd, aim to do so in the late afternoon or evening rather than the morning to allow fermentation to peak during the night when cooler.

Try to avoid moving cattle during the heatwaves - obviously this is not possible for dairy herds, but the system should be managed to avoid walking them in peak daylight hours, while keeping them relatively close to the parlour.