Dr. Mark A. McCann, Extension Animal Scientist, VA Tech
The first official day of winter has come and gone, but Virginia cow herds received an early dose of cold weather with many areas of the commonwealth reporting a near record cold month of December. As always winter conditions provide challenges for both man and bovine alike. The differences in calving season and climate between the coastal plains and mountains of Virginia provide very different environments through the course of the winter. Paying close attention to the winter conditions can guide the decisions related to the nutritional management and care of the beef herd.
As most cattlemen recognize, cold weather can increase the nutritional requirements of the cow as she increases metabolic and biological functions to maintain body temperature in a cold environment. Low critical temperature is the temperature at which the cow starts to use energy to stay warm. It ranges from 5 to 49 degrees Fahrenheit (F). The general rule of thumb is to increase the cow’s feed energy intake 1 percent for each degree (F) below the lower critical temperature. The only adjustment in cow rations necessitated by weather is to increase maintenance energy. Protein, mineral and vitamin requirements are not changed by weather stress.
The critical temperature also takes into consideration the insulating ability of the cattle’s hair coat as shown by the change between a wet and dry coat (Table 1). Therefore, a cold rain is more stressful due to the loss of “air insulation” in the coat of cattle that get wet versus those that are out in the snow. The air pockets between hairs are a source of insulation that is lost when hair is matted down in a cold rain. The result is that the Dry Winter Coat goes from having a critical temperature of 32 degrees F to about 59-60 degrees F of a Summer Coat.
Cattle naturally respond to cold weather with an increase in feed intake. However, feed quality many times needs to also be increased. Feeding more of poorly digestible forage will cause an accumulation of relatively indigestible feed components in the rumen due to too little energy for the bacteria to efficiently digest the feed. This will lead to a net decrease in energy intake to the cow. In order to adequately supplement cattle in winter weather, it is necessary to use quality hay and supplement as needed to balance the nutrient content of the hay.
An easy place for cold stress to adversely impact cow performance is wintering spring calving during extended adverse conditions without altering energy content. Cows can slowly lose body condition and calve thinner. Cows calving in thin body condition can have:
- Lighter birth weight and less vigorous calves
- Reduced quantity and quality of colostrums
- Slower return to estrus post-partum
- Reduced conception rate in a controlled breeding season
Other tips
- Be aware that the critical temperature of fall born calves will be greater than their dams because they will not be generating as much heat from rumen fermentation. Providing access to wind breaks and southern exposed areas can assist in providing some relief.
- Nutrient analysis of stored forages is always the foundation of a winter feeding program that can meet cow nutrient needs and be as economical as possible.
- Although supplying water in cold weather provides its own set of challenges, it is vitally important in maintaining or increasing cattle’s dry matter intake. Reduced water intake will quickly result in decreased dry matter intake and subsequent performance.
- When winter temperatures are above freezing, an often overlooked item to consider is mud. It is less clear what effect mud has on a cow’s energy requirements, but it is estimated that it can increase the maintenance requirement from 7-30{b5a992b8e63762954627fabd02ae0ce4cbdce5a7319b086354586c608f95fa42}. Moving feeding areas regularly can reduce the potential for mud and has the added benefit of better spreading nutrients in the pasture area. If cattle have to deal with mud then their ration should also be improved to help avoid the consequences listed above.
- Be sure to offer a free choice mineral that is vitamin fortified. The summer drought has forced many cattlemen to feed low quality or carry over hay in which the vitamin content is nil. Additionally, drought stressed forages and many by-products do not contain adequate levels of vitamins.
Here’s hoping that your New Year is off to good start and that spring is not too far away.
Source: Dr. Mark A. McCann, Extension Animal Scientist, VA Tech
Posted by Haylie Shipp
