FACILITIES FOR FEEDING HOLSTEIN AND BEEF CATTLE

Department of Animal Science Michigan State University Lansing, MI Adverse climatic conditions impose additional restrictions and requirements on cattle. Since cattle are homeotherms, energy must be expended to maintain body temperature within a defined range (NRC, 1981; Figure 1). This range is called the thermoneutral zone. As external temperature increase or decrease outside of this range, the metabolic machinery must expend energy to maintain body temperature. Consequently, more energy is needed for maintenance and less is available for productive purposed. For growing-finishing cattle, this translates into less gain. As environmental temperatures decrease below the thermoneutral zone, the animal must generate more body heat to survive. This is accomplished by increasing dry matter intake and cellular metabolism. However, extremely cold conditions may cause a cessation of intake. As temperatures elevate above the uppermost portion of the thermoneutral zone, an animal must dissipate excess body heat. Dry matter intake and cellular activity will decrease. Figure 2 demonstrates the effects of temperature on dry matter intake. Notice the behavioral shift that can occur under extremely cold conditions. Unfavorable pen conditions such as excessive mud or frozen clods can severely impact behavior patterns and intake. Given the opportunity, cattle will seek relief from adverse conditions by moving to sheltered areas or shade. The thermoneutral zone can shift to lower or higher temperatures with adequate adaptation. Maintenance requirements at 15掳F will be 10% lower for an animal adapted to 15掳F than at 33掳F. In addition, wind, moisture, and muddy conditions can also increase maintenance requirements. In the final analysis, the animal regulates intake and metabolism to adjust to changing climatic conditions, however, there are limits. Severe environmental stresses result in lowered weight gain. The examples in Table 1 indicate the importance of temperature adaptation, shelter from the wind and dry conditions. For yearling steers and calves, maintenance requirements and dry matter consumption increase as the ambient temperature decreases. For example, a yearling steer at 15掳F needs 14 lb of DM per day to meet maintenance requirements. maintenance requirements increase, so the steer eats an additional 2 lb of DM (16 lb/d). At-30掳F, the steer needs to consume 20 lb of DM to maintain body weight; however, that level of intake exceeds the physical capacity of the digestive system. Consequently, the steer loses or gains less weight depending on the caloric density of the diet. Providing shelter and dry lot conditions will lessen many of the stresses associated with climate. Cattle have the ability to acclimate and withstand cold temperature; however, the rapid changes in temperature, wind, and moisture conditions