Rayner Reckons

Jul 17

Prepare for the cold fronts!

Posted on Wednesday, July 17, 2019

The impact of cold weather on your livestock isn’t to be underestimated.  So far this July we have already seen several strong cold fronts sweep across southern and eastern Australia.  These fronts have been accompanied by strong winds, snow and sleet and then days of intense frosts.  

These events have a big impact on your livestock.  The demand to stay warm requires extra energy.  At present the intense drought conditions mean many livestock are low in body condition and surviving on minimal rations.  The combination of low body reserves and reduced energy intake means your stock is less able to cope with the cold, and at greater risk of dying. 

How does cold affect your cattle?

We often assume cattle can cope with cold conditions more easily than other species like sheep.  However, cattle can be just as impacted by the cold as any other species.  As a warm-blooded animal, cattle have a normal temperature of 380C. Under most circumstances cattle can cope with some temperature fluctuations without needing to expend too much extra energy.  As the season changes they grow thicker coats, and in periods of cold weather they change their grazing patterns to find shelter.  

However this behaviour can only go so far.  If temperatures fall to what is known as the ‘lower critical temperature” your cattle will start to be cold stressed.  To cope they start to require more energy to stay warm.  And in this situation they need to have more energy in their diets. 

Some research by the Ontario Ministry of Agriculture in Canada identified the differing levels of lower critical temperature, depending on cattle coat thickness.  These levels do vary depending on coat thickness.

Coat Description 

Lower Critical Temperature

°C

Summer coat or wet coat

15

Autumn coat 

7

Winter coat 

0

Heavy winter coat 

-8

These temperatures don’t take into account the impact of wind speed.  Wind has the biggest impact on the lower critical temperature.  This can be seen below

Looking at the table, if the wind was only 8km /hour on a 40c Day, the actual air temperature is really 10C.  

This is close to the Lower Critical Level for cattle with a dry winter coat.  But a wet coat after rain means your animals are at real risk of cold stress.

Cold and wet conditions have a massive impact on sheep programs.  At greatest risk are lambs that are often unable to cope with the impact of cold weather.  Rain and moisture significantly increases the risk of mortality.  As with cattle, sheep manage to cope to some degree with cold by changing behaviour and seeking shelter.  They also have a fleece that will offer some protection.  

However its important not to overestimate how effective a fleece may be.  The table below highlights the Lower Critical Temperatures of Sheep 

  

Lower Critical Temperature (ºC) 

5-mm fleece (fixed) 

  

    Fasting 

31 

    Maintenance 

25 

    Full-fed 

18 

Maintenance 

  

    1-mm fleece 

28 

    10-mm fleece 

22 

    50-mm fleece 

    100-mm fleece 

-3

As with cattle, when wind speed increases, the impact on Lower Critical Temperature is much greater. And for lambs with no fleece and a large surface area and low body mass, their energy loss is very high.  

Managing the Risk

In practical terms it's impossible to avoid cold fronts.  However we can manage for them.  The options that are available to help your stock cope with cold conditions include:

 

  • Increasing rations ahead of the cold front:  Hay is a very good option to increase a ration.  It is more slowly digested and the process of digestion helps stock stay warmer as well as getting more energy.  However it’s no good just offering a bit!  You need to increase your rations by 10 – 20%.  If your stock are light in condition or slick coated cattle I’d definitely be increasing to 20% ahead of and during the cold period.

 

  • Provide shelter.  Breaking the wind speed up can have a dramatic effect on improving conditions for your stock.  Moving them to sheltered paddocks that have trees and shrubs that break up the wind will be vital.  There are plenty of well proven strategies and studies that show the role shelter has in livestock survival

 

  • Longer term, consider developing shelterbelts and wind breaks to moderate the wind across the farm.  You certainly can’t grow shelter over night, so in the short term consider what other options you have to shelter your stock.

Cold fronts often only last for a few days, and with adequate warning you can prepare your stock to cope with the challenge.  It is important to make your plans happen when the fronts are forecast.  Don’t leave it to the day of the windy and snow to start doing something.  Often moving stock in those conditions makes it worse not better!  Pre preparation is everything to give your stock a chance!


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