Cold weather and cattle nutrient requirements
November 14, 2008
Sometime during the last week, almost everyone in the Tri-State Livestock News readership area has seen some form of winter weather. It was severe, with blizzard conditions here in the western Dakotas. This of course has lead to a lot of discussion and concern about what this winter will be like and whether this is the start of a long, hard winter. It is too soon to know if that will be the case, but it is not too soon to be prepared for winter conditions. Today’s column will be about feeding the cow herd so they can deal with the increased energy requirements associated with cold stress. Credit for the following needs to be shared with Cody Wright, one of my partner Beef Cattle Extension Specialists at SDSU, who recently wrote an article on the topic. Much of the following is from that article.
“A good rule of thumb is that for every degree below 32 degrees, including wind chill, a cow’s energy requirements increase by one percent,” Wright said. “How you manage your cows between now and calving may have the single largest impact on how your cows breed back next summer.”
The bottom line is that cows need to be managed to be in moderate body condition when they calve next spring, and feeding adequate energy to allow them to maintain body condition during cold weather is necessary to meet that goal.
Remember that maintenance energy requirements will increase as temperatures fall below “lower critical temperature,” or in other words, become cold stressed. The lower critical temperature depends on hair coat, wind, wetness and body condition. The lower critical temperature for a cow in moderate condition with dry winter coat is around 30 degrees Fahrenheit. However, this lower critical temperature is based on wind chill, so as wind speed increases, the lower critical temperature also increases, meaning that a cow will become cold stressed at higher temperatures if she can’t find shelter from the wind. Also, “the energy requirements of wet cattle generally increase by two percent for every degree below 59 degrees Fahrenheit,” Wright said. “It becomes imperative to practice good animal husbandry and provide bedding and shelter from the wind and precipitation if possible.” Thus, keep animals dry and sheltered from wind, if possible. If cattle have wet hair coats or it is very windy, the cattle will feel much colder and thus have increased requirements.
Take special care with thinner cows (those with a body condition score of less than 5). They have less insulation from fat and so are more susceptible to colder temperatures. Thus, they may need special care and higher quality feeds to gain adequate energy to both maintain body temperature and gain body condition before calving. If they are still thin at calving, it will be very difficult for them to gain, or maybe even maintain body condition once they calve and start to lactate.
Cattle will eat more when it is cold. As temperatures get very cold, increase the feeding rate above maintenance. Assuming cows are fed a diet to just meet requirements with moderate winter weather, feed three to four pounds more hay (i.e. alfalfa hay) or two to three pounds more grain to account for the increased requirements. An exception to this is grazing cattle. If grazing, cattle spend less time grazing in extreme cold, so supplemental feeding may become necessary. Generally, a 1,200-pound cow can be fed up to three pounds of grain without any negative consequences. If more grain is fed, additional degradable protein will be necessary to reduce the negative effects of the grain on forage digestion.
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Use of fiber-based alternative feeds such as wheat middlings, soybean hulls, corn gluten feed, and distiller’s grains will allow producers to supplement energy and protein to the cow’s diet without sacrificing forage digestion. Each of these feeds can be easily fed at up to 15 pounds per cow per day. The high fat content of distiller’s grains limits their inclusion to 10 pounds of dry distiller’s grains, 17 pounds of modified distillers grains, or 25 pounds of wet distiller’s grains per cow per day.
Free-choice access to forage during severe winter conditions is one simple way to help cows cope with cold stress. At extremely cold temperatures, it is unlikely that the cows will be able to consume enough forage to meet their requirements. However, heat generated during the digestive process, especially fermentation in the rumen, helps maintain core body temperatures. Feeding the better quality forages that a producer has available may be a good idea during severe winter weather. Because it will digest more rapidly, the cows will be able to consume more. It is also probably more palatable, so the cows will be willing to consume more.
Keep in mind that cows’ nutrition demands are greatest in the late stages of gestation, when most fetal growth and development takes place. Providing proper nutrition during this time can have a dramatic impact on the health and vigor of the calf as well as the cow’s rebreeding.
Cows will handle one or two days of very cold weather fairly well – but sustained periods of three to five days or more are harder on the animals. “When Mother Nature unleashes a cold snap or a blizzard, providing adequate nutrients can be challenging,” Wright said. “In the short term, nutrient deficiencies are not likely to cause problems. However, once the weather breaks, care should be taken to provide the necessary nutrients to get the cows back in shape.”
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