Table 1 details energy requirements for calves of differing weights and average daily gains. More energy is required for heavier cattle and cattle gaining at more rapid average daily gains. For a given average daily gain, energy concentration required in the diet generally decreases as calves grow larger and intake increases. Daily energy, protein, calcium and phosphorus requirements for backgrounding steers of various weights and average daily gains. National Academy Press.
Cold weather can also impact energy requirements.
Cold temperatures cause the animal to use energy to maintain body temperature instead of using energy for growth. Factors such as wind speed, hide thickness, hair coat, and mud impact energy requirements through their effects on lower critical temperature. For example, muddy conditions raise the ambient temperature at which the animal will begin to be affected by cold stress. If high rates of gain are desired, grain or other concentrates must be added to the ration to increase energy density in the diet. However, adding cereal grains to forage based rations can decrease the digestibility of the forages.