Provide Cold Cows More Energy
The New Year historically brings with it some of the coldest and most extreme conditions of the year. Weather can be one of the greatest challenges of managing cows during the winter, especially for spring-calving herds on the verge of calving. Most cattle producers appreciate that cold weather increases nutrient requirements. However, the more common questions are “When or under what conditions should we respond to a cold weather event?” and “How should we respond?”
How cold is too cold?
According to Justin Waggoner, K-State beef systems specialist, cattle are most comfortable within the thermonuetral zone when temperatures are neither too warm nor too cold. During the winter months cattle experience cold stress anytime the effective ambient temperature, which takes into account wind chill, humidity, etc., drops below the lower critical temperature. The lower critical temperature is influenced by both environmental and animal factors including hair coat and tissue insulation (body condition). In wet conditions cattle can begin experiencing cold stress at 59°F, which would be a relatively mild winter day. However, if cattle have time to develop a sufficient winter coat the estimated lower critical temperature under dry conditions is 18°F.
Energy requirements during cold stress
Cold stress increases maintenance energy requirements but does not impact protein, mineral or vitamin requirements. The general rule of thumb (for a cow in good body condition, BCS = 5 or greater) is to increase the energy density of the ration by 1% for each degree (Fahrenheit) below the lower critical temperature. The classic response to cold stress in confinement situations is an increase in voluntary intake. However, it has been documented that grazing beef cows may spend less time grazing as temperatures decline below freezing, which reduces forage intake and makes the challenge of meeting the cow’s nutrient requirements even greater.
Feed needs: energy VS protein
The traditional response to a cold weather event on many operations is to feed more of the current supplement being used or offer a greater amount of low-quality hay. Although the additional supplement and hay may provide some additional energy it may not be sufficient to meet the energy requirements of a third trimester cow, experiencing cold stress. In many situations (depending on the supplement being used), the additional supplement offered supplies more protein and not necessarily energy; and the additional hay offered simply replaces grazed forage. In this situation energy is likely limiting. An alternative response would be to offer a relatively higher-quality hay than the current forage being grazed or a small amount of grain combination with the normal amount of (protein) supplement being used. Circumstances, supplements and forages will vary.
In a cold weather event, cold stress increases energy requirements and not protein. More information on cold stress and nutrition may be found in Beef Cow Nutrition Guide, Publication C-735 which may be accessed online at http://www.ksre.ksu.edu/bookstore/pubs/C735.pdf