Young calves require a substantial amount of energy for body maintenance. They need additional energy for maintenance when temperatures fall below or rise above their critical temperature zone.
Calf milk replacer (CMR) contains metabolic energy, which depends on its protein, fat, and lactose content, the origin and digestibility of raw materials, and the dry matter content. After meeting the maintenance energy needs the remaining energy can be used for growth.
Young calves lose heat quickly due to their large body surface area relative to their weight, minimal energy reserves in the form of body fat, and the lack of a functioning rumen that generates heat. In cold temperatures, energy shortages can cause calves to stop growing and lose weight rapidly.
Various environmental and management factors can help keep calves warm during cold weather. These can be read in the bulletin.