Wintertime Feeding For Reducing Cattle Stress

GROWING BEEF

It’s too early to tell what the winter will be like, but we likely will have a few extreme cold snaps. Preparing the cow herd for these can have an impact on the success of the  calving season as well as breeding cows for the next calf crop.

Factors that create stress and increase the energy requirements during the winter months are cold, wind, precipitation and mud.  Cows with a dry winter hair coat have a lower critical temperature of about 32˚F Below this the cow’s energy needs increase. A general rule of thumb is that for every one degree (F) the temperature drops below 32˚F, increase the ration energy by 1%. This is based on the effective ambient temperature or wind chill index, so providing wind breaks is important to  reducing winter cold stress.

A mature 1350 lb. dry British bred type cow, requires 14.5 megacalories of NEm and about 3.1 lb CP at 32˚F. This requirement is met by approximately 31lb. of first cutting grass hay. At 12˚F an additional three pounds of hay is needed to meet her energy requirements. In both cases the protein requirements are exceeded. If cattle have wet hair coats, the lower critical temperature is increased. The energy requirements of wet cattle generally increase by two percent for every degree below 59˚F. Mud is another major consideration in cold stress. It is estimated that mud can increase the maintenance requirement from 7-30%. The simple practice of providing bedding helps to reduce the stress from precipitation and mud.

One tool to manage cold snaps is to increase access to forage. Heat generated during the digestive process (fermentation in the rumen) helps maintain core body temperatures. Cattle will also eat more when it is cold, so increase feeding rate above maintenance - three to four pounds more hay or two to three pounds more grain. Remember that cows will handle one or two days of very cold weather fairly well, but sustained periods probably warrant a ration modification. Cows should be monitored throughout the winter feeding period to ensure adequate nutrition. The goal should be a body condition score of five or six at calving time to prevent calving problems and ensure the best results for conception and pregnancy the following summer. Thin cows have a higher risk of calving problems, weak calves and poor colostrums quality. Missouri research shows that only  66% of cows with a body condition score (BCS) of three to four at calving are cycling 90 days after calving, while 92% of cows with a BCS of five to six are cycling within

90 days.   Body condition during the winter is not only a challenge with Iowa winters,  but it is also very expensive. Increase body condition on thin cows in the fall before winter weather hits. Additionally, requirements for vitamins  and minerals must not be neglected. Free choice salt and mineral should be provided at all times. Water also needs to be monitored to ensure adequate water intake,  since water intake drives feed intake.

Cold Stress Tips

1. Provide plenty of fresh water - snow and ice don’t count

2. Provide for animal comfort with wind breaks and bedding

3. Meet their increased energy requirements

4. Separate cow herd based on feed requirements, mature cows separate   from young, old or thin cows.

January 2009 • Volume 1 Issue 6 • www.iowabeefcenter.org • beefcenter@iastate.edu

Iowa Beef Center’s monthly newsletter

@ Iowa State University