As winter approaches, nutritional needs and increased stress on cattle are becoming a concern. Winter feeding plays a very important role in the profitability of a beef cowherd because it can comprise a large percentage of your cost of production.
Cold stress occurs when cattle are exposed to weather conditions that put them below their lower critical temperature. If cattle have a dry winter coat, the lower critical temperature is 32 degrees Fahrenheit. If the coat is very heavy and thick, they can withstand lower temperatures and the critical temperature drops to 18 degrees Fahrenheit. If the coat is wet, however, the lower critical temperature may increase up to 60 degrees Fahrenheit.
When the environment results in an effective temperature below the animal’s lower critical temperature, the animal must increase heat production to maintain a constant body temperature and performance. To produce more heat, the animal must either receive an increase in energy from the ration or draw on body stores.
To compensate for the energy deficit created by the cold stress, follow this rule of thumb: Increase the amount of feed 1 percent for each degree of cold stress. If you have the wind-chill temperature, use that temperature.
Keeping hay in front of the cattle may not take care of meeting the extra nutrient needs. If the hay is good, meaning it was harvested before it matured or was rained on, cattle can probably make it through the cold weather and still maintain good body condition. If the quality of the hay is poor, the cattle may not perform as well. This is where it is important to have your hay tested, which can be done through our office.
A 1,200-pound cow in good body condition (BCS of 5) needs a ration that has a minimum Total Digestible Nutrients (TDN) value of 55% and crude protein (CP) value of 10% under neutral environmental conditions. The TDN value is a rough estimate of the total energy content of a feed. Concentrates have higher TDN and CP values than forages, but do not generate as much heat when being broken down in the rumen. In comparison, shelled corn has a TDN value of 90% and soybean hulls, 80%. If hay falls below the 50% TDN minimum, producers should consider supplementing with an energy-dense feed.