Heat stress in dairy cows - podcast transcription
Heat stress in dairy cows
Greg: Welcome to Dairy News brought to you by the Department of Industry and Investment.
I’m Greg Mills and I have with me today, Kerry Kempton who’s our Dairy Officer based at Tocal to talk through some of the issues of heat stress in dairy cows. Welcome to the program Kerry.
Kerry: Thanks Greg.
Greg: Kerry, heat stress. If I’m a dairy farmer why should I be concerned about heat stress?
Kerry: Well, it can have a big impact on your cows and on your production on your farm Greg. We probably tend to underestimate sometimes the impact that heat stress can have on cows. We can get a lot of milk production which is pretty easily seen, you know, in the vat the next day but there’s other things that we don’t see so readily that are the impacts of cows getting hot. These can be things like lower fertility of cows, a higher abortion rate, weight loss in cows and sometimes more health problems with cows, particularly metabolic problems such as acidosis.
Dairy cows particularly feel the heat in summer because they’re high performance animals, they’re producing a lot of milk, they’re having to walk to the dairy building twice a day, usually in the hot part of the day to be milked. The effects of a hot spell can build up a head load in a cow that can take several days and sometimes weeks to really dissipate and for the effects to be lessened.
Greg: So does it matter what type of cows I have, where I am? What sort of things impact on heat stress on my cows?
Kerry: Breed of cow does have an impact. We generally find that Holstein Friesian cows which are the most common dairy cow in New South Wales are probably the most susceptible of all our dairy breeds and probably Jersey cows are our least susceptible. They can tolerate the hot weather a bit more than Friesian cows can and probably our Illawarra cows and brown Swiss cows are somewhere in between the two.
Pretty much anywhere you milk in New South Wales is susceptible to hot periods, hot summers and heat stress on cows.
Greg: What sort of temperatures do you need to be looking for when we see heat stress?
Kerry: Dairy cows can get stressed over and above about 25 degrees Celsius, so it doesn’t have to be a really stinking hot day to make cows feel stressed. Also the humidity of the day has a big effect too Greg and the more humid the day is, the worse the cows feel it. So even what we might think a milder day of mid to low 20s, if the humidity’s high, that can be pretty stressful for a cow.
Greg: So there’d be lots of places in New South Wales that would see 25 degrees for a large proportion of the year. So, if my cows are showing signs of heat stress, what can I do about it?
Kerry: Yeah there’s some short term strategies that you can do that are fairly easy to implement - wetting your cows with water, sprinklers at the dairy are a really good way to cool cows down quickly. You want to wet the cows and then have good air movement around them so that they can evaporate some of their heat. Making sure your cows have plenty of water is a really crucial thing in hot weather. Cows’ water intake goes up in the heat and they do need access to good quality drinking water.
Wetting the dairy yard down before the cows come in for milking can also help take the heat out of the concrete so that they’re not standing on hot concrete. Providing shade wherever you can. Trees are the ideal access to shade but also you can have temporary shade shelters, shade cloth over your dairy yard and also sheds where you can provide feed for cows and they can get out of the sun is another option.
You can change your diet to make sure that the cows are getting really good quality forage in the cooler parts of the day when they’re wanting to eat and also possibly increase your grain ration so that you can keep the energy content of the diet up in the hot weather because a cow’s appetite is effected in the hot weather. They don’t really want to eat as much. So you really need to make sure that what they area eating is high quality.
Greg: Should I also look at how I’m rotating around my paddocks because if I’ve got paddocks with more trees in them, should I perhaps be using them during the hotter parts of the day?
Kerry: Yes definitely and that’s something that you can do in the cooler months is to just take a look at your farm. Ideally, if you’ve got an aerial photograph and a farm map, just look at all your paddocks where your cows go in the hot months. You can rate your paddocks according to how much shade there is in the paddock, whether there’s good water access in the paddock and how far they are away from the dairy where the cows will have to walk back to.
So those paddocks that are furthest from the dairy and that have limited amounts of shade, you wouldn’t consider putting the cows in those paddocks on the really hot days. Keep them closer to the dairy, keep them near shade and make sure they’ve got plenty of water.
Greg: So if a dairy producer would like to find out more about managing heat stress in their cows, what sort of resources and information are out there for them?
Kerry: Yes Greg. There’s a really good website that has been set up recently called www.coolcows.com.au and this is part of the Grains to Milk Project that Dairy Australia is running. There’s some terrific resources there that farmers can go and have a look. They can assess their own herd’s susceptibility to heat stress and they can get some really good tips about how to minimise heat stress on dairy cows and what are some of the things they can do in the short term, as well as in the longer term to minimise the effects on their cows.
Greg: It sounds like a great resource because while trees may take some time in building shade it sounds like there’s some low cost options that farmers could implement almost immediately to have some impact.
Kerry: Yes that’s right and these tweaks to management don’t really cost you anything. It’s just a matter of changing your thinking. Yeah, whilst you can also look at some of the longer term sort of infrastructure modifications to your farm that can be done, you know, as and when finances permit, but certainly you really need to make sure that your cows aren’t suffering during these hot spells and that you’re doing all you can to keep them cool.
Greg: Is there a way of knowing that these hot spells are actually coming our way? Can we prepare a few days in advance?
Kerry: We can and if you go to the Cool Cows website, there’s actually a weather forecasting tool on that website which is linked to the Bureau of Meteorology. So you can find out for various sites around Australia what the weather forecast is and what the heat stress levels on cows are going to be for the next five days. So that’s a great site just to go and have a look and be able to predict when the really high stress days are likely to hit. You can have a few days to prepare for that.
Greg: It sounds like a great resource given the impact that heat stress can have on the bottom line. It sounds like something that could be of great use to the industry.
Kerry: Yes I think it definitely is Greg. We’ve had a fairly hot summer in 2009 so far and chances are we’re going to have more of these extended hot spells are going to become a more common feature of our climate and whilst we’re trying to milk cows in these sort of climatic zones, heat stress is going to continue to be a big factor.
Greg: Thanks Kerry. Thanks for joining us on Dairy News today. If people would like to talk to you a bit more about heat stress in cows where can they contact you?
Kerry: Yes Greg. They can call their nearest DPI Dairy Officer. I’m based in the Hunter Valley and my phone number is 02 4939 8945.
Greg: Can you just mention that cool cows website again for our listeners?
Kerry: Yes. It’s www.coolcows.com.au
Greg: Thank you for joining us today on Dairy News.
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