Cold weather cattle care important
By Miles Dabovich
Texas AgriLife Extension Service agent, agriculture, Wichita County
Cattle need care during cold or wet weather to make sure they stay healthy and perform well. A well-managed program to prepare cattle for winter and minimize cold stress can save money and reduce the number of problems. Thin cows suffer more cold stress and rob body fat stores to keep warm. Calves may be born weak, cows may not produce adequate colostrum, calf survivability is lowered, as is the cow's ability to breed back on time.
How much feed or supplement a cow needs depends on weather, body condition, available pasture or crop residue (quantity and quality), age of cows, whether they are still nursing calves, dry, or ready to calve again soon, or fall calved and need extra nutrition to milk well and breed back again.
Closely monitor condition of cows as they go through winter. If some start to lose weight, you have time to correct this by feeding hay to supplement dwindling posters or increase the hay rations if weather turns cold.
If weather is cold and windy, cows need extra feed just to keep warm. They may stand around or huddle behind windbreaks instead of grazing. Even if pasture is available, they may not graze until mid-day when temperatures are warmest--losing weight because they don't eat enough. This problem can be solved by giving some hay or supplement early in the day to get them going then they will start grazing.
A cow needs to eat more roughage in cold weather to give her the calories for heat energy. If she doesn't have enough roughage, the pounds will melt off her as she robs body fat to create energy for warmth. More total pounds of roughage in her diet (extra grass hay,) can keep her warm, since the fermentation and breakdown of cellulose creates heat energy. Cattle who have a chance to acclimate gradually to winter will develop a good hair coat, and put on body fat if feed sources are adequate. Hair and fat serve as good insulation against cold. With a summer hair coat the typical beef cow may chill when temperature drops below the mid 50s; whereas, with a heavy winter coat she can stay comfortable at much lower temperatures. She can also adjust by increasing her metabolic rate to increase heat production, which also increases her appetite. But, if she gets too cold, heat loss and cold stress reduces appetite and efficiency of feed conversion since the body's metabolism is adversely affected (mammals must maintain a constant body temperature to keep up the proper metabolic processes).
If a cow has good winter hair, she does fine until temperatures drop below 20 to 30 degrees F. Below that, she compensates for heat loss by increasing energy intake; she must increase heat production to maintain body temperature. Healthy cows, in average body condition and acclimated to cold weather have a "lower critical temperature point" (point at which maintenance requirements increase and you need to feed them more) of about 20 degrees F. Lower critical temperature is defined as the lower limit of the "comfort zone" (below which the animal must increase its rate of heat production; it's also the temperature at which performance begins to decline as temperatures become colder).
For example, a 1,100 pound pregnant cow needs 11.2 pounds of TDN per day when temperatures are above freezing. If temperature drops 20 degrees below her lower critical temperature, she needs 20 percent more MN or 2.2 more pounds of digestible nutrients. To supply that, you can feed her 3 pounds of grain, or 5 pounds of hay containing 50 percent TDN.
Cows with normal winter hair coats need about one-third more feed when exposed to wind chill temperatures at or near zero. Critical temperature for any cow or calf will vary according to a hair coat, moisture conditions, age, size of animal, fatness (fat under the satin is good insulation against cold), length of time exposed to adverse conditions, and amount of wind. Feedlot steers, with their extra fat and access to windbreaks, are usually more tolerant of cold weather than grazing cows. Cold stress is also less severe if a storm is brief, compared with the wind chill and stress of continuous bad weather.
A rough rule of thumb to compensate for cold is to increase the amount of feed (energy source) by 1 percent for each two degrees F of cold stress. For thin cows with poor hair coats, or in wet condition (wet hair coat) figure a 1 percent increase for each degree of temperature drop. A wet storm is worse than dry cold. Wet hair loses insulating quality; the cow will chill sooner. When hair coat is wet, the critical temperature is about 50 degrees F.