As described in Table 1, protein maintenance needs (used to replace proteins in body tissues) are relatively small (less than 0.1 pounds per day). Amino acids for growth represent the major portion of total protein requirements (0.3 pounds per pound of bodyweight gain). As bodyweight and rate-of-gain increase, the crude protein needed to achieve this growth also increases.
Table 1. Prediction of protein requirements based on calf size and averaged daily gain (NRC 2001).
Research has demonstrated higher protein feeding amounts (both concentration and feeding rate) result in greater lean body growth and less deposition in body fat. Matching energy and protein intake are impacted by the feeding rate, calf bodyweight, and impact of the environment. The impact of the protein-to-fat ratio and feeding rate are described in Figure 1. The key is to select a milk replacer and a feeding rate that most closely matches the desired calf performance.
Figure 1. Estimates of energy and protein allowable gain for calves fed milk replacer varying in protein to fat content as well as feeding rate of 1.5 or 1.75 pounds of powder per calf per day.