Environment & Hay Quality Discussed

By Gene Schmit
Field Specialist in Livestock
University of Missouri Extension 

Wet weather also increases energy requirements for livestock. To illustrate these points, I’ve formulated some beef cow diets for varying temperatures, hair coat conditions, and hay quality.

For these examples, diets were formulated for beef cows in late gestation with a body condition score of 5 designed to maintain body weight. Good hay (54% TDN, 8% CP) and bad hay (50% TDN, 7% CP) was used for the comparison.

Let’s consider the good hay first. If the temperature is 27 degrees and the animal has a dry hair coat, free choice hay plus 1 pound of corn will meet protein and energy demands. If the cow has a wet hair coat, this ration will only meet 69% of the energy requirement and 88% of the protein requirement resulting in an estimated loss of 0.75 pounds per day.

To meet energy requirements at 27 degrees with a wet hair coat, the supplement must be increased to 8 pounds of corn and 2 pounds of distiller’s grains. If the temperature increases to 37 degrees, but the cow is still wet, a supplement consisting of 6 pounds of corn and 2 pounds of distiller’s grains is needed to keep the cow from losing weight.

For each 1 degree drop in temperature below the lower critical temperature, energy requirements increase 1 percent for dry hair coats or 2 percent for wet hair coats. For the scenarios illustrated here, if air temperature plus wind chill drops to 17 degrees, there is a subsequent increase of 10% in the cow’s energy demand. This can be overcome by feeding about 2 pounds of corn grain, for example.

Bad quality hay increases the need for supplementation. Using the hay quality numbers above, it takes 2 pounds of corn and 1 pound of distiller’s grains to meet energy and protein needs for a cow when it is 27 degrees and dry.

A wet cow will lose approximately 0.8 pounds per day at that temperature and supplement level. Eleven pounds of supplement, consisting of 9.5 pounds of corn and 1.5 pounds of distiller’s grain is necessary to maintain cow body condition under these conditions. A wet cow at 37 degrees will need a supplement of 7.5 pounds of corn and 1.5 pounds of distiller’s grains to meet energy and protein requirements.

Corn and distiller’s grains were used in these examples for ease of comparison. Other ingredients in different proportions can also be used to meet energy and protein requirements.

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Cold and wet conditions result in large increases in energy requirements for livestock. Increased grain supplementation at the rates in some of these examples is not practical nor recommended on a day-to-day basis. For this reason, it is important to have cows at an adequate body condition before extreme weather conditions exist. Then reasonable diet adjustments can be made when necessary and cows can used stored fat reserves to help make up for the energy deficits caused by cold, wet weather.

If you have questions about hay quality or would like assistance with livestock rations, please contact schmitze@missouri.edu or by calling the Pettis County Extension Center at (660) 827-0591.