Prepare cows for severe weather conditions
January 12, 2018
Severe wind and cold can cause significant problems for livestock and their owners. Evidence of such problems are found in the chronicles of the South Dakota blizzard, Oct. 4-5, 2013. The wind, snow and cold resulted in major cattle loss. The storm caught many by surprise and losses were estimated to be approximately 5 percent of the region's cattle herd.
Preparing for these old-man winter visits is key to a healthy, happy herd. Planning ahead for deep snow, drifting snow and freezing temperatures is important, but so is managing the health of the animals. Moisture, high winds and cold temperatures increase an animal's energy requirements, effecting calving in unusual ways. According to veterinarians, animal health and feed play a huge role in the winter.
Ironically two studies, have shown that animal birth weights actually increase during winter. In a shorn versus unshorn ewe study, researchers found that shorn ewes actually had larger birth weight lambs. In a 1999 University of Nebraska-Lincoln calf study, researchers concluded that spring calves, born in colder winters, weighed more than those in warmer weather. The study shows that for every 1 degree F decrease in average winter temperature, there is an increase in calf birth weights by 1 pound.
The UNL beef researchers studied the effect of colder than normal temperatures on calf birth weights. The six-year study found the coldest winter (11 degrees colder than the warmest winter) resulted in calf birth weights 11 pounds heavier when compared to the warmest winter. The exception was the winter of 1995-1996 when above normal average temperatures resulted in numerically (not statistically) heavier calf birth weights. One possible reason could be the colder than normal temperatures in January when the cows were in their last trimester (the cows calved in mid-February to April 1).
“The lower critical temperature of a beef cow is the lowest temperature a cow can be exposed to before she needs to have changes metabolically to help her cope with cold stress.”
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"Colder weather may cause larger calf birth weights. Producers are encouraged to think about the impact it may have on this year's calving season," said Bethany Johnston, UNL Extension Educator.
According to Richard Randle, UNL Extension beef cattle veterinarian, producers starting out with cattle giving birth to large calves may need to increase their daily cattle checks.
"If extremely large birth weights occur at the start of calving season, then one needs to observe cows more often and intervene sooner in the rest of the cows," Randle said. "If no progress in calving is observed over a 30 to 45 minute time period, then a person should consider intervening. Heifers should definitely be observed more frequently and if a heifer appears to be struggling, don't wait more than 30 minutes to intervene."
Weaker cows, that may have gone into the winter with a lower body conditioning score (BCS), also need to be closely watched.
"Cows that are energy deficient can be weaker and therefore will take longer to calve because they don't have strong contractions and tend to fatigue quicker," Johnston said. "These prolonged calving events can lead to weak and less vigorous calves. So, cows, especially thin cows, that don't receive adequate additional feed/supplementation in cold weather will likely be weaker at calving."
Rick Rasby, beef specialist at UNL, said that cows at optimal BCS of 5 to 6 are better able to withstand adverse environmental conditions. As a risk management strategy, Rasby recommended producers reduce the number of BCS 4 cows and increase the number of BCS 5 cows in a herd, prior to winter, by being proactive with their feeding program.
Rasby said wind protection is an important management strategy. Protection may seem obvious, but wind chill can worsen stress from a cold rain. A well-ventilated building, strategically stacked big bales, wooded areas and hollows are all potential windbreaks. If the weather conditions are extremely harsh, cattle cannot be fed enough to meet the increased energy needs, and a "shelter belt" may be what helps cattle withstand these extremes in weather conditions.
Research refers to the lower critical temperature (LCT) when describing the ability of cattle to withstand cold conditions. LCT is the temperature at which maintenance requirements increase to the point where animal performance is negatively affected. This temperature is typically between 18-20 degrees F, according to research, but a fact sheet from North Dakota State University said that mature beef cows in good body condition during the middle third of gestation may have an LCT as low as minus 6 F during dry, calm conditions.
Critical temperatures for beef cattle are determined in part by the condition of the coat. Below the critical temperature, livestock must expend more energy in order to keep warm.
From Kansas State University: Coat Description Critical Temperature:
Summer coat or wet 59 degrees F
Fall coat 45 degrees F
Winter coat 32 degrees F
Heavy winter coat 18 degrees F
"The lower critical temperature of a beef cow is the lowest temperature a cow can be exposed to before she needs to have changes metabolically to help her cope with cold stress," Rasby said.
When cows begin to shiver, they require extra energy, and the lower critical temperature for beef cows is influenced by hair coat condition (dry or wet/muddy), body condition (thin, moderate, fleshy) and hair coat description heavy/winter, fall or summer, Rasby said.
"As hair coat changes from summer to winter, BCS changes from thin to fleshy, and hair coat changes from dry to wet, lower critical temperature decreases which means cows can withstand harsher conditions without an increase in energy needs. Magnitude of coldness is equal to LCT — Wind Chill Index. Energy requirement increases about 1 percent for each degree of cold stress. As an example, cows that have a heavy winter hair coat that is dry and are in condition score of 5 have a lower critical temperature of 19 degrees F," Rasby said.
The energy needs increase by as much as 30 percent when the temperature reaches 5 degrees F with a 15 mph wind, and a wind chill index at minus 10 degrees F.
Rasby recommended an increase based on total digestible nutrients (TDN):
• If the TDN requirements of the cows are 12 lb of TDN per head per day for this week, you would consider bumping the ration to 15.5 lb/hd/day. This is an increase of 3.5 pounds of TDN per head per day.
• If grass hay is 57 percent TDN, that's an increase of about 6 lb/hd/day on a dry matter basis.
• If the hay is 88 percent dry matter that would mean each cow receives an additional 7 lb/hd/day.
Producers should use caution when increasing the energy density of a diet with corn, Rasby said.
"Feeding more than 2-3 lb/hd/day of corn to cows on a forage-based diet will decrease fiber digestion. When cows are on a forage-based diet and supplemental energy is needed, consider the use of high-energy, non-starch feed stuffs such as distillers grains and soy hulls to meet the cows energy requirements. It would not be advisable to change rations daily, but if it is predicted that weather conditions will be severe over a period of time then ration changes may be warranted," Rasby said.
– Eatherton is a freelance writer from Beulah, Wyo. When she's not writing, she's riding her horse or playing with her grandson. She can be reached at firstname.lastname@example.org.