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Adjusting Rations with Temperature Changes

The lower critical temperature for mature beef cattle is -20 degrees Celsius. This is the point where the heat produced when consumed feed is digested matches what is required to keep the animal warm. Smaller animals that have a larger body surface area : body weight ratio loose heat more rapidly and have less ability to withstand cold. Their lower critical temperature is above -20 degrees Celsius and ration adjustments must be made sooner for these animals than what is done for mature animals . As a survival mechanism, animals increase their feed intake when it is colder than the lower critical temperature.

Increasing the amount of the total ration provided is recommended. It is not advisable for animals eat extra straw to meet their appetite. Straw is a low energy, low protein feed that lowers overall ration quality. If protein levels are reduced, this can reduce the amount of feed an animal can consume in a day due to slower digestion of the high fibre feeds. Adding extra grain to the ration is the best option to increase heat production.

It requires one to three days for feed to pass through the digestive system. Grains and low fibre feeds are easily digested and pass through more rapidly than hay or silage. Straw requires the most time to be digested.

When temperatures moderate, energy required to keep an animal warm, decreases. Two to three days prior to temperatures moderating, start adjusting the ration. Remove one pound of grain per day from the ration so that when temperatures reach -20 degrees Celsius, the cattle are back onto the normal ration. If the extra grain remains in the ration, the animal may become “heat stressed” and go off feed. Timing is critical when removing the extra grain.

For additional information on adjusting rations, contact Barry at 403-741-6032 or


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