Oklahoma State University Extension Animal Scientist Emeritus last week spelled out for Extension agents the cold-weather requirements for cow/calf producers in Oklahoma, but the article also has relevance for producers in other states.
Each winter cattle market participants wonder how cold is cold to cattle. For cattle ranchers, there is an easy-to-use formula for keeping a healthy investment healthy. For cattle owners entrusting their cow care to others, this is a good crosscheck to see if they are doing a good job.
THE FORMULA FOR DRY COWS
The major effect of cold on nutrient requirements of cows is an increased need for energy, Selk said. To determine magnitude of cold, the lower critical temperature must first be estimated.
For cows with dry winter hair, the lower critical temperature is considered to be 32 degrees Fahrenheit, he said. In general, researchers have used the rule of thumb that cows’ energy requirements increase 1% for each degree the wind chill is below this mark.
For example, if the TV weatherman has predicted average wind chills of about 4 degrees F, the calculation for a cow with a dry winter hair coat would be:
Step 1: The cow’s lower critical temperature of 32 degrees Fahrenheit.
Step 2: Expected wind-chill (4 degrees in this example).
Step 3: Calculate the magnitude of the cold as the difference between the lower critical temperature and the wind chill: 32 degrees – 4 degrees = 28 degrees.
Step 4: The energy adjustment is 1% for each degree magnitude of cold or 28%.
Step 5: Feed cows 128% of normal daily energy amount. (If the cow was to receive 16 pounds of high-quality grass/legume hay, then feed 20.5 pounds during the cold weather event).
THE ENERGY ADJUSTMENT FOR WET COWS
Research has shown that the energy requirement for maintenance of beef cows with a wet hair coat is much greater than for those with a dry coat, Selk said. Cows with wet hair 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, he said, or 2% for each degree below 59 degrees.
To calculate the magnitude of the cold when the cow is wet would be 59 degrees minus 4 degrees = 55 degrees, he said. True energy requirements to maintain a wet cow in this weather would be 2% X 55 degrees or 110% increase in energy, which would mean more than twice the normal energy intake is needed.
That much energy change is virtually impossible with the feedstuffs available on ranches, he said, and that for cows accustomed to a high roughage diet it must be made very gradually to avoid severe digestive disorders. It also underscores the need to keep cows in good condition at the start of winter.
The more common-sense approach is a smaller increase during wet, cold weather and extending the increase into more pleasant weather to help regain energy lost during the storm, Selk said.
CATTLE, BEEF RECAP
Cash cattle traded last week at $119 per cwt on a live basis, steady with the previous week, and at $190 dressed in eastern Nebraska, up $2.
The USDA choice cutout Thursday was down $0.39 per cwt at $215.30, while select was off $0.38 at $207.22. The choice/select spread narrowed to $8.08 from $8.09 with 116 loads of fabricated product sold into the spot market.
No delivery notices were served for Dec live cattle.
The CME Feeder Cattle index for the seven days ended Wednesday, was $147.20 per cwt, down $0.51. This compares with Thursday’s Jan settlement of $149.00, up $0.90.