Protect the Cow Herd From Winter Weather
During the fall and winter, cattle typically adapt to cold temperatures by growing a longer, thicker hair coat, which provides more insulation.
However, many cattle have not had an opportunity to fully acclimate to cold weather this year due to unseasonably warm conditions and an open winter, according to Janna Block, Extension livestock systems specialist based at North Dakota State University’s Hettinger Research Extension Center. This can reduce the animals’ ability to tolerate cold, even on a short-term basis.
With extreme cold temperatures, wind and moisture predicted for many areas of North Dakota during the next few days, livestock grazing on pasture may not have adequate protection. Producers should make plans to help reduce the effects of cold stress on livestock, Block says.
Cattle have a certain environmental temperature range in which they can function without using extra energy to maintain their core body temperature. This is referred to as the “thermoneutral zone” and includes a range of temperatures from approximately 40 to 90 F for cattle.
Lower Critical Temperature
The lower limit of the thermoneutral zone is referred to as the lower critical temperature, or LCT. When the temperature drops below the lower limit of the thermoneutral zone, livestock will experience cold stress. The LCT will vary depending on thickness of the hide and hair coat, whether the animal is wet or dry, and factors such as age, stage of production and body condition of the animal. In general, an LCT of 18 F commonly is used for animals with a dry, heavy coat.
“Like people, cattle experience the effective temperature, which includes air temperature, humidity and wind chill,” Block says. “Wind can increase heat losses much more quickly than when air is still at the same temperature.”
Several charts are available to help producers calculate the effective temperature. For one example, refer to the chart at https://www.ag.ndsu.edu/livestockextension/lower-critical-temperature-for-beef-cattle.
Below the LCT, the maintenance energy requirement of cattle will increase as cows divert more energy to maintaining body temperature. To compensate, additional energy must be provided in the diet.
The general rule of thumb is to provide an additional 1% of total digestible nutrients (TDN) for each degree below the LCT. For example, a temperature of 25 F with a 20 mph wind results in an effective temperature of 4 F (14 degrees below the LCT).
Under normal conditions, 1,300-pound cows require approximately 12.7 pounds TDN in late gestation. In this example, energy requirements would increase by 1.78 pounds (12.7 × 1.14 = 14.48 pounds TDN required) due to cold stress. For forage containing 56% TDN, cows would require an additional 3.2 pounds (1.78 pounds TDN needed ÷ 0.56) on a dry-matter basis.
During extended cold temperatures, particularly when cattle are wet and cold, meeting additional energy needs with forage can be difficult, and high-energy supplements such as grain or byproducts may be necessary.
Windbreaks and Bedding
Providing access to windbreaks and using bedding to help keep cattle clean and provide insulation from mud or frozen ground are two other effective strategies to reduce cold stress. Low spots and trees that offer natural protection from wind and snow are not available in every situation, so producers may need to provide portable solutions such as large round bales or panels covered with a tarp or canvas. Also, feeding late in the afternoon will help ensure that heat from fermentation will be maximized during the coldest part of the night.
If additional feed and protection from elements are not provided, cows will burn body stores to produce heat and maintain the function of vital organs. If extreme weather conditions are short-lived, effects on body condition losses may be minimal.
However, extended cold conditions without additional energy provided will result in weight loss that will further reduce body condition and insulation and reduce the cow’s ability to deal with cold stress. Losing weight in late gestation and/or early lactation has a variety of negative impacts, including increased calving difficulty, weak calves, impacts on colostrum and milk production, and even rebreeding.
In the case of severe cold stress, cattle may experience hypothermia, which slows metabolic and physiological processes and diverts blood away from extremities. This can result in frostbite to teats, ears and testes. Therefore, producers must consider potential negative impacts not only on cows but also on herd bulls.
During normal winter conditions, frostbite is not a common problem with breeding bulls, but prolonged exposure to extreme cold and wind increases the likelihood of frostbite. It is a problem producers must consider when planning for the breeding season. Lack of wind protection and lack of bedding will increase the chance of frost damage to the scrotum and testicles.
“The future reproductive success of the herd could suffer if herd bulls are not prepared for or protected from winter weather,” says Karl Hoppe, Extension livestock systems specialist based at NDSU’s Carrington Research Extension Center.
Evidence of frostbite to the scrotum - noticeable inflammation and swelling - usually is apparent a few days after frostbite occurred. The heat generated from the inflammation directly affects the sperm that are maturing and stored in the epididymis, which surrounds the testicle at the lower end of the scrotum.
The resulting damage may cause temporary or, in more severe cases, permanent sterility in the bull. A scab may appear on the lower portion of the scrotum as healing occurs.
However, the absence of a scab does not indicate that frostbite injury did not occur. Severe frost damage to the testicles and epididymis may cause fibrous bands that affect mobility and circulation in the scrotum.
To determine if a bull suffered frostbite damage, a trained veterinarian should perform a breeding soundness examination prior to the breeding season, Block says. The process of spermatogenesis takes approximately 60 days, so damage occurring at this time from frostbite or other injuries still may be evident in early April.
An examination normally includes a physical evaluation of the entire reproductive tract, including the testicles and epididymis, as well as a microscopic semen evaluation.
“Producers should ensure that breeding soundness exams allow adequate time for bulls to recover from winter injuries but also give themselves time to source new bulls if necessary,” Block says.
Check out the NDSU Extension publication “Winter Management of the Beef Cow Herd” (https://tinyurl.com/WinterHerdManagement) for information on winter management of cattle.
K. William Boyer is the Managing Editor of the Devils Lake News Journal. He can be reached at email@example.com, or by phone at (701) 662-2127.
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