Feeding Cows in Winter

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Denise Schwab
Interim Director
Iowa Beef Center
dschwab@iastate.edu

Winter is the most expensive and arguably the most important time for feeding beef cows in Iowa due to both the weather and the production stage of gestating cows. Careful planning now will help meet the needs of the cow and control feed costs at the same time.

First let’s look at the spring-calving cow. Nutrient requirements increase as the cow moves from second to third trimester. Seventy percent of the fetus weight is put on during the last trimester, or about 1.25 pounds per day. The cow needs enough energy and protein to support her own metabolic needs along with the fetal growth.  For example, a 1300-pound cow needs 1.8 pounds of crude protein (CP) and 12.5 pounds of Total Digestible Nutrients (TDN) (energy) per day. To convert this to amount of feed needed, you need to get an evaluation of the nutrients in your forage source or work with a nutritionist to estimate feed value based on plant and harvest information. Help on taking hay samples and labs to have it tested can be found at https://www.iowabeefcenter.org/forage.html in the Harvest & Storage section.

Once you receive the results you can calculate your ration needs. If your brome grass hay has 8% CP and 54% TDN and is 86% Dry Matter (DM), the rest is simple math, but remember all of our calculations are done on a dry matter basis.

If her energy requirement is 12.5 pounds of TDN she needs 23.14 pounds of hay dry matter to meet her needs (12.5lb / 54% TDN = 23.14 pounds hay DM). For CP she needs 22.5 pounds of hay (1.8lb/8% = 22.5 lb hay). So feeding 23.2 lbs DM of hay, equal to 27 lbs as fed, meets her requirements. The next question is if she can eat this much hay. A mature cow will consume about 2.25% of her body weight in dry matter per day, so a 1300# cow will consume about 29 lb of dry matter or about 34 pounds as fed. In this case, she will eat more than she needs to meet her requirements, which means if you can limit how much feed she gets per day, you can reduce costs and still meet her needs.

If you have a lower quality hay like CRP hay or corn stalks, we would go through the same calculations but would also need to consider how much of that higher fiber forage they can consume. High fiber forages move through the digestive system slower, so cows cannot consume as much as they can with lower fiber hay. In these cases we often need to provide some additional energy and protein from good hay or a supplemental feed like corn or distillers. If a low quality, high fiber forage like CRP hay or corn stalks is your main forage source, work with a nutritionist or Extension specialist to determine your ration needs.

Now let’s look at the impact winter weather has on beef cows. Typically cows in good body condition with a thick dry winter hair coat and some wind protection are pretty tolerant of cold weather, but there are limits. Three factors affect her cold tolerance: hair coat (dry or wet), wind protection, and temperature. The lower critical temperature for cattle with a dry winter hair coat is about 18oF. Below this her body compensates by metabolizing fat storage to maintain body temperature. Wind chill also factors into the formula, meaning, if there is no wind protection provided consider the wind chill as the temperature used to determine cold stress impacts. The rule of thumb is with every degree below the lower critical temperature, we need to increase TDN by 1% to meet maintenance nutritional requirements. So if we have a week of 0oF weather but the cow is dry and has wind protection she will need 18% more energy which is 2.25 additional pounds of TDN. That is an additional 4 pounds of the brome hay or 3 pounds of corn.

Notice I keep emphasizing a DRY hair coat. Dry hair provides lots of insulation from the cold, but when the hair is wet it loses the insulation effect. The lower critical temperature for a wet coat is around 53-59oF. Winter storms that start with freezing rain can have a huge impact on the nutrient needs of cows. Mud on the hair has a similar effect. In these cases, hay alone will not meet the cow’s energy requirements and high energy feeds like corn will be needed to meet nutrient demands. We can reduce the effects of winter weather on beef cows by providing wind breaks and bedding to keep the cows dry.

Tips for Winter Feeding Cows

  1. Test forages for nutrients
  2. Balance a ration to meet cow needs
  3. Install wind breaks or protection from wind
  4. Bed to keep cows off cold ground and prevent muddy, matted hair coats
Date of Publication: 
November, 2023
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