Cold weather has major impacts for our animals, especially through increased energy to keep animals warm.
When we talk about the impact of cold weather on livestock, we have to start with understanding what a lower critical temperature is. The lower critical temperature is the threshold at which point animals need to start using energy to maintain body heat. This threshold is impacted by a variety of different factors including animal condition, hair coat condition, whether the animal is wet or dry, and wind chill.
Let’s start with body condition. Typically, animals should be going into winter at a 5 to 5.5 Body condition score. If they are lower than this, cold weather can raise up the lower critical temperature, increasing the cow’s energy requirements and causing us to burn through hay.
For example, a cow with a BCS of 5 with a dry winter coat will have a lower critical temperature of 19°F while a thinner cow with a BCS of 4, with the same dry winter coat raises that temperature to 27°F.
If you’ve ever seen a cow in a snow storm with a layer of snow on her back, you’ve seen the insulating power of body condition in action. The hair coat and fat on the animals back are trapping enough heat that snow can build up. On a thinner animal, a snowy back is a rare sight as the amount of heat leaving through their top is enough to melt snow as it accumulates.
We can also address the physical impacts of weather on lower critical temperatures. That same BCS 5 cow that with a dry coat had a lower critical temperature of 19°F will have a lower critical temperature of 53°F if their coat is wet. Providing animals shelter in bad weather can help keep coats dry and limit wind chill effects, both of which will work to minimize the impact of the cold.
Finally, know what you have to work with from an energy perspective in your feed yard. A general rule of thumb is for every degree of cold stress a cow faces, they increase their energy requirements by 1%. To put that into perspective, let’s look at the two cows in our first example again. If temperatures drop to 10°F the BCS 5 cow will need 9% more energy in her diet (remember the lower critical temperature was 19°F). The BCS 4 cow needs 17% more energy.
When we hit a stretch of cold temperatures, grass hay just doesn’t have enough energy to meet the uptick in demand. High quality alfalfa hay usually has a TDN of 58-60% and should meet requirements for dry, good condition animals at windchill temperatures down to -15°F.
When we get even colder for an extended period, we might want to look at providing some additional supplement for energy paired with free choice hay for fill. There are plenty of high energy supplement options to choose from, so pick the one that works for your operation.
Cold weather is not fun for producers or our animals, but if we know how it impacts our herd, we can do our best to mitigate its effects.
-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: email@example.com