The effect of cold stress on a cow herd cannot be ignored
Now that we are a few months into winter, it can be easy to fall into a routine and assume cows are acclimated to the cold weather by now and do not need additional help.
However, this may not be the case as cold stress can occur at higher temperatures than you may realize.
To understand cold stress, first we need to understand the thermoneutral zone.
This is the range of environmental temperatures where an animal’s metabolism is normal, they do not need any extra energy for maintenance and normal metabolic processes supply enough heat to maintain a regular temperature.
As the environmental temperature starts to drop to the bottom end of the thermoneutral zone, animals may begin to seek shelter from the wind or grow a thicker hair coat, but their nutrient requirements will not change until the temperature reaches the lower critical temperature.
The lower critical temperature can vary based on how acclimated an animal is to the wintery conditions, but we generally assume 0 C for a cow with a normal winter coat and -8 C for one with a heavy winter coat.
This means that as winter goes on and your cows adapt and grow a thicker coat, they can handle colder temperatures. Conversely, if their coat is wet or muddy, the lower critical temperature jumps up to 16 C, meaning wet cows will enter cold stress at warmer temperatures.
When an animal enters a cold stress situation, energy and nutrients needed for growth will be diverted towards maintaining their body heat. The body will increase blood flow as well as gut passage rate, which results in lower digestibility of feed. Their body will begin to mobilize fat stores for energy, leading to a decrease in body condition.
For cattle that are nursing calves, cold stress can lead to a decreased milk supply. Several changes will occur at the hormonal level, including a drop in insulin levels, increase in stress hormones and decreased leptin, which will stimulate an increase in appetite.
The changes in hormones will also contribute to a weakening in the immune response.
Aside from having to feed more, can cold stress really impact your operation? Cattle experiencing cold stress can have quite the negative spiral.
While initially you may not be too concerned by a slight drop in body condition, it does mean a reduction in the fat stores that are used for insulation. Less fat means higher susceptibility to negative effects from cold stress.
Cattle who lose weight prior to calving can have more calving difficulties, weaker, lighter calves and higher chance of calf mortality.
As the cow is attempting to produce milk through cold stress, she will produce less colostrum that is lower quality and continue to have a low milk production. Calves that get less colostrum and nurse off a dam with low milk production will be, at best, lighter at weaning and at worst, die.
Furthermore, once the cows have weaned their calves, they will also have less reproductive success unless they can return to good condition on pasture. All these things put together can result in a significant impact on your cow herd and your bottom line.
As gloomy as cold stress sounds, minimizing the effects is possible. Making sure your cows are in good body condition going into winter will help immensely, as that will provide them with a layer of insulation. It is also important to provide extra feed when it is cold out.
Remember, as cattle get cold, they need more energy. A good rule of thumb is to increase grain by about two pounds for every 10 C drop below -10 C to a maximum of five pounds of grain.
It is also important to make sure your cattle have good shelter to avoid wind and are well bedded. Keep in mind, when a cow gets muddy, her lower critical temperature gets higher and she becomes cold stressed easier.
Clean, dry bedding will go a long way in preventing cold stress.
Making sure your cattle have access to clean, fresh water is also important as when their water intake drops, so does their feed intake.
Also important, but not often thought of regarding cold stress, is to make sure your cattle are up-todate on their vaccination schedule and are meeting their mineral requirements.
Since cold stress can limit their immune system, it is important to help them out however you can. Implementing biosecurity measures on your farm can also help your herd’s immune systems. Controlling the weather is not possible, so cold stress will continue to be a reality for Saskatchewan livestock. Cold stress can be hard on cattle, but with careful management, the effects can be mitigated.
If you are concerned your cows are beginning to suffer from cold stress related problems, contact your local livestock and feed extension specialist or call the Agriculture Knowledge Centre at 1-866-457-2377 for more information.