It’s easy to focus on heat stress and its impact on herd health during the dog days of summer, but one often-overlooked area is cold stress and how it compromises herd productivity and performance.
The Old Farmer’s Almanac is predicting colder temperatures for the coming season in much of the eastern two-thirds of the nation from North Dakota to Maine and into Canada. Pacific states are projected to experience below-normal temperatures.
Snowfall is predicted to be above normal for southern New England, western New York, eastern parts of several Midwestern states and in Canada. Precipitation is slated to be above-average for areas of northern California and southern Oregon.
Combating cold stress from the inside – at the cellular level – is an essential part of maintaining dairy herd reproductive health and production gains.
Whether you’re operating in a cold, snowy climate or in a damp, cold, rainy climate, early detection of cold stress and procedures to combat it will keep your herd healthy and productive. There are a few things dairy producers should keep in mind when it comes to the effects cold stress can have on their herds.
Hypothermia begins at 32ºF
A number of factors contribute to cold stress, but the most significant is temperature. Mild hypothermia can happen beginning at just 30 to 32ºF, moderate hypothermia occurs at temperatures of 22 to 29ºF and severe hypothermia at temperatures below 20ºF. Other contributing factors include wind, rain and mud.
Signs of cold stress include behavior changes, huddling, reduced body condition, decreased water consumption, decreased movement to feedbunks and water tanks, or matted hair covered with mud or ice.
Cows experiencing cold stress have lower respiration and heart rates and even delayed return to estrus. Blood is diverted from body extremities to protect vital organs.
It’s imperative to factor in actual temperature and wind speed. Wind speeds ranging from 5 to 30 mph can typically lower actual air temperatures by 6 to 30ºF, increasing herd energy requirements.
Researchers at South Dakota State University estimate that for every degree the effective temperature is below the lower critical temperature, herd energy needs increase by 1 to 2 percent. If the effective temperature is 17 degrees, energy needs jump by 15 percent.
Dry matter intake and body condition score
Cold stress can negatively affect dry matter intake. Decreased dry matter intake, coupled with increased energy requirements necessary to maintain basal body temperatures, work in opposing directions and can negatively impact gut health and production parameters.
Energy requirements for both bodyweight maintenance and production add to dietary energy requirements (up to 40 percent more during extreme cold) and create a necessity for higher feed intake. Therefore, any interruptions in feed intake can adversely affect production along with body condition.
Another factor impacting cold stress is body condition score, a subjective measure used to indirectly estimate body fat percentage and its ability to insulate cattle.
Cows with low body condition scores can also have more difficulty with calving, lower colostrum quality, and longer recovery and breed-backs. Calves born from cows with lower body condition scores are weaker and more susceptible to illness.
Transition cows, in particular, will rapidly metabolize fat tissue to support milk production and are most susceptible to cold stress challenges. Many symptoms can compound into bigger issues.
Fat deposits from the digital footpad (responsible for cushioning bodyweight when walking or standing) are also mobilized during the transition period. As such, sore feet can reduce a cow’s willingness or ability to access feed and adequate fluids, resulting in reduced intake and potentially contributing to other health-related challenges.
Cattle with a higher body condition score are less severely impacted by cold stress. While body fat is the primary insulating element, a thick, dry coat allows heat to be trapped, creating an insulating blanket.
Wet and matted coats tend to lie flat, allowing heat to escape, thereby increasing animal susceptibility to cold stress.
Keep cattle drinking during the winter
Cattle drink less during the winter; however, they have to eat more to maintain body temperature. Respiration and urination leave them susceptible to dehydration. Dehydrated cows experience increased levels of adrenalin, cortisol and hepatic glycose. They also have decreased rumen volume, dry matter digestibility and decreased insulin response.
Their electrolyte balances can quickly become out of balance, just as they can when animals are experiencing heat stress. Adding osmolyte-enriched hydration products to either feed rations or water will help support energy requirements and maintain essential electrolyte balance.
Practical herd comfort tips
So what can you do from a practical perspective to combat cold stress? We focus on the following:
- Provide plenty of clean, fresh water
- Provide adequate dry bedding
- Ensure proper air circulation ventilation
- Feed higher-energy diets (feed intakes increase during winter weather)
- Keep cows dry and clean
- Provide shelter from the wind
PHOTO: Heat isn’t the only thing that causes stress for dairy cattle. Cold weather can, too. Discover how chilly temperatures put a strain on animal health and productivity, and learn what you can do to prevent the cold from stressing your cows. Courtesy photo.
Tammy Howe is a marketing lead with TechMix Global. Email Tammy Howe.
