Even in early spring, cow-house temperatures and humidity can impact herd performance. So what can producers do to create a cooler environment that’s more conducive to good welfare and supporting yields?
TEXT RACHAEL PORTER
Reduced dry matter intakes and yields, restless cows, panting – all tell-tale signs of heat stress. And they could signal that producers have been a little late off the mark in tackling it. “Some may not even see these signs, but will see a dip in herd fertility a few months later,” says Harper Adams University’s dairy specialist Emma Bleach. This is because heat stress experienced by a cow depends on both temperature and relative humidity. The temperature humidity index (THI) reflects the effect of the two. A THI of 68 or above indicates that a high-yielding dairy cow will typically experience heat stress. This THI is already reached with a combination of an ambient temperature of 22°C and a relative humidity of 60% (see Figure 1).
Figure 1: Temperature humidity index (THI) chart for dairy cows (Source: OMAFRA)
“This THI may only be for a couple of days – and not severe enough for cows to show the obvious signs of stress, but fertility can still be affected.”
Data loggers, which measure and monitor temperature and humidity in cow housing, are being installed on some UK units to help producers better manage the environment, as well as feeding, to help mitigate heat stress.
So how can producers improve cow housing to keep cows cool? AHDB’s building specialist David Ball says ventilation is king. “It’s all about air movement and drawing fresh air into cow buildings,” he says.
“Most herds, to a greater or lesser degree, will experience heat stress every year. And, due to the role played by humidity, cows can actually start feeling the effects of heat in the spring when temperatures are relatively low. “The first thing a cow does when heat stressed is to stop eating. The second thing she’ll do is spend more time standing – she won’t lie down, and this puts additional pressure on her feet. She’ll move to find shade or the coolest part of the shed to create an updraft of air movement around her body.
This is why heat stress is such a huge problem – particularly for transitioning and early lactation cows – and lost milk yield is just the tip of the iceberg. Mr Ball says a good way to check ventilation is a smoke-bomb test. “Smoke should quickly dissipate – within a minute – ideally up through the roof ridge. If not, open up more roof ridges and look at the sides of the building. Do they allow fresh air to be drawn in? Modifications may be required – to improve airflow in, out and around the building. Always take some advice, particularly if you’re considering investing in fans and other cow-housing improvements.”
Cowcare System’s John Sharkey agrees, adding that no cow house is perfect and it’s a case of ‘working with what you have and spending wisely’. “Producers are now more aware of the impact of heat stress and are looking to take steps to mitigate it. We’ve seen many installing louvred sides to existing buildings and some have fitted fans.”
He says louvred sides are underrated. “They’re compared to curtains, but they’re much better for cow housing. Curtains can’t cope in a storm or wet weather. Whereas a louvred side can remain open even if it’s pouring outside. The building will be well ventilated, without water ingress being an issue.”
Fans are also growing in popularity, particularly the high-volume-low-speed (HVLS) models. “Traditional box fans are losing favour compared to the HVLS design, which looks like a helicopter rotor and is ideal for positioning above the cows. They are effective at moving air both in and out of, as well as around the building.”
Mr Robertson sells low-energy Italian Evel HVLS fans, powered by a DC motor, which are quiet and efficient to run. These are equipped with sensors and can be programmed to kick in as temperatures and humidity begin to creep up. The widest model has a diameter of 7.2 metres – sufficient to ‘cool’ an area four times its width. “So, depending on the shed size, two or more may need to be fitted to have an impact. But talk to your dealer and get some advice.”
Herefordshire-based producer Henry Lewis runs a 900-cow herd, on a high-welfare indoor system, in partnership with his wife Sue and son James. Herd average yield is around 12,000 litres, at 4.12% butterfat and 3.25% protein. Henry is only too aware of the importance of cow comfort and mitigating the impact of heat stress.
“Cow health and welfare is paramount in our business. Keeping cows cool is vital and, for our unit, fans are key to ensuring housing is comfortable and conducive to achieving high yields,” he says.
Prior to installation, it was typical to see intakes and milk yields drop, reduced bulling activity and signs of oestrus, and even cases of acidosis as spring and summer temperatures took their toll on the herd.
Air movement: high-volume-low-speed fans can help to keep cow housing cool
Now the unit’s older buildings have traditional box fans, which Mr Lewis says ‘do their job’. But it’s the HVLS fans in the newer cow housing that are really making a difference, keeping cows cool, comfortable and milking efficiently.
“I hate to see heat stress in cows and it was a problem on our unit as soon as temperatures hit the mid-20s. At 22°C we saw cows standing around, particularly close to water troughs, so we knew they were feeling it.”
Lewis has several HVLS CMP fans in cow housing, mounted on the roof. They also have temperature-control sensors and his are set to kick in at just 8°C. “Just turning slowly, but enough to help move air around the building. They’re working almost all year round.” Fan speed increases in line with temperature and humidity. “They’ve made a huge difference but they’re extremely quiet, so the cows are not disturbed but can enjoy the cooling benefits,” says Mr Lewis. “We’ve also noticed how much more pleasant and airy the buildings are to work in.”