R. E. James
Extension Dairy Scientist
It is not uncommon to evaluate milk replacers on a cost/bag basis in an effort to control cost. The standby has been the 20 percent protein/20 percent fat milk replacer fed at a rate of 1.0 pound of powder fed in 4 quarts of total liquid per day. Attempts to improve growth have lead many companies to offer replacers containing 22 percent protein, 24 percent fat and up to 28 percent protein. Naturally these higher protein milk replacers are more expensive. Research has shown that greater lean tissue growth occurs with the higher protein milk replacers. Similarly, there are varying levels of fat in milk replacers from 10 percent to as much as 25 percent. The lower levels of fat are probably adequate for summer time feeding, while the 20 percent fat levels are more appropriate for winter when energy requirements are higher. Replacers with 25 percent fat are recommended for smaller breeds such as Jerseys with higher maintenance requirements.
However the most important concept to remember in feeding calves is that the percentages are not as important as the total amount of protein or fat consumed. Following is a comparison of the amount of protein consumed with a 20 or 28 percent CP milk replacer containing 20 percent fat fed at two different rates.
Feeding the higher protein milk replacer at a low feeding rate only changes the amount of protein consumed by 0.08 pound per day and provides enough energy to increase gain by 0.06 pound and enough protein to increase gain by 0.3 pound One can expect much better gains from the higher feeding rate. At 68 F increasing both nutrient content and amount per day fed to a calf supports better tissue gain and overall growth rate. Feeding a low level of milk replacer is usually insufficient to support any growth at all, especially during all seasons but the summer.
Responses to fat level are interpreted differently. Lower fat levels may be adequate during the summer when energy needs are lower. However, as temperatures drop below 50 F, increased energy is required and there will be responses to higher fat percent milk replacers when fed at higher levels. This is especially critical for the calf during the first two weeks of life when calf starter intake is negligible. More efficient gain is achieved by feeding higher component milk replacers at higher levels of intake. Nutrient demands for growth demand higher levels of intake from milk replacers, especially during winter and in adverse housing conditions.