Management
Feeding for Cold Weather
By Glenn Selk, Oklahoma State University
Thus far, most of Oklahoma has experienced a relatively mild
start to winter. Nonetheless, colder weather is likely to occur
before spring time and green grass. The major effect of cold
on nutrient requirement of cows is increased need for energy.
To determine magnitude of cold, lower critical temperature for
beef cows must first be estimated. For cows with a dry winter
hair coat the lower critical temperature is considered to be 32
degrees F. In general, researchers have used the rule of thumb
that cows’ energy requirements increase 1% for each degree
the wind chill is below the 32 degree lower critical temperature.
In this example, the TV weatherman has predicted that wind
chills will average about 4 degrees F. Therefore the calculation
example for a cow with a winter dry hair coat would be:
Step 1
Step 2
Step 3
Step 4
Cow’s lower critical temperature is 32 degrees F.
Expected wind-chill from weather
reports (4 degrees wind chill in this example)
Calculate the magnitude of the cold as the
difference between the lower critical temperature
and the wind chill: 32 degrees - 4 degrees = 28 degrees
Energy adjustment is 1% for
each degree magnitude of cold or 28%.
Step 5
Feed cows 128% of daily energy amount. (if cow
was to receive 16 pounds of high quality grass/legume
hay; then feed 20.5 pounds of hay during the cold
weather event).
Research has indicated that energy requirement for
maintenance of beef cows with a wet hair coat is much
greater. Cows that are exposed to falling precipitation and
have the wet hair coats are considered to have reached
the lower critical temperature at 59 degrees F. In addition,
the requirements change twice as much for each degree
change in wind-chill factor. In other words, the energy
requirement actually increases 2% for each degree below
59 degrees F. To calculate the magnitude of the cold when
the cow is wet would be the difference between 59 degrees
minus 4 degrees = 55 degrees. True energy requirements
to maintain a wet cow in this weather would be 2% X 55
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degrees or 110 % increase in energy (which would mean
that over twice the normal energy intake is needed.)
This amount of energy change is virtually impossible to
accomplish with feedstuffs available on ranches. In addition
this amount of energy change in the diet of cows accustomed
to a high roughage diet must be made very gradually to avoid
severe digestive disorders. Therefore, the more common-
sense approach is a smaller increase in energy requirements
during wet cold weather and extending the increase into more
pleasant weather to help regain energy lost during the storm.
Cows that were consuming 16 pounds of grass hay per day
and 5 pounds of 20% range cubes could be increased to
20 pounds of grass hay offered per day plus 6 to 7 pounds
of range cubes during the severe weather event. This is
not a doubling of the energy intake but by extending
this amount for a couple of days after the storm may help
overcome some of the energy loss during the storm and
done in a manner that does not cause digestive disorders.
The fact that it is not feasible to feed a wet, very
cold cow enough to maintain her current body
condition, underscores the need for cows to be in
“good” body condition at the start of winter. I