Growth and body composition goals should be considered when choosing both milk powder composition as well as feed rate. The protein and energy requirements for maintenance (i.e. normal calf activities) will differ when compared to the requirements for growth. Farms should aim to match their growth objectives with their feeding regime.
Conventional feeding
Restrictive feed rates i.e. <600g of calf milk replacer per day are not going to meet requirements for growth as well as maintenance. In this scenario, feeding a high protein milk powder is wasteful as limited energy intake will limit growth. Therefore milk powders with a modest 20% protein composition should be considered. If wanting to optimise growth rates and feed for success, consider moderate or higher feeding plans.
Moderate feeding
Moderate feeding plans aim to achieve adequate growth rates, and will generally be feeding ~ 700-800g of calf milk replacer per day. These will likely meet energy requirements, however protein requirements will increase to meet the demands for growth. Therefore a milk replacer of ~24% protein should be considered.
Intensive/full potential feeding
Intensive feeding plans aim to achieve high growth rates during the calf's most feed efficient period (pre-weaning). These feed plans usually deliver >1kg of calf milk replacer per day. For these to achieve the best growth rates in these calves protein requirements will be higher still and milk replacers of 26-28% should be considered.
Summary
Feeding high protein milk powders at low feed rates will be wasteful of an expensive component of the milk powder. At lower feed rates protein will not be utilized effectively for growth. However, when aiming for high growth rates protein requirements will be much higher and so, higher protein levels should be used. As a rule, the protein requirement for maintenance is relatively low, but the requirement for growth is relatively high. The opposite is true for energy.
Always remember to analyse milk powder protein sources as well as overall crude protein % as plant proteins are less easily digested than milk proteins in calves <3 weeks old.