Have you ever taken care of someone’s animals or been to a farm that uses a different scoop for each grain or milk replacer they have? I know that I have and it even happens at my own farm. We use whatever is convenient and we make it work, right? A concern with this is that the scoop used to measure out milk replacer on one farm is not necessarily the same scoop as another farm down the road; they may be feeding different weights of milk replacer when they should be feeding the same.
When you look on any milk replacer tag it generally provides instructions for mixing based on weight. We do not often think about milk replacer as the amount of total energy or protein provided in a calf’s daily allotment but rather in the total volume that is given to each calf. Consequently, it is important to make sure we know how much each cup or scoop is measuring out so we are better able to target our calf raising goals.
A common goal in calf raising systems is to support good health and high average daily gains. Calves require energy and protein to support maintenance and growth. Maintenance in the calf includes basic functions of thermal regulation (in hot and cold conditions), immune responses, and stress responses. Requirements for maintenance of a 100-lb. calf, less than 21 days old, are 1.75 Mcal/d under thermoneutral conditions (59-77°F) using Cornell-Illinois modifications of NRC (2001). For example, if a 100-lb. calf under thermoneutral conditions was fed either a 20:20 milk replacer or a 24:20, how much would the calf have to consume just to meet maintenance requirements?
The amount of milk replacer that is needed might be more than you would expect. For the 20/20 milk replacer there would be 0.27 Mcal/L from protein and 0.12 Mcal/L from fat for a total of 0.39 Mcal/L provided, while the 24:20 milk replacer will provide 0.32 Mcal/L from protein and 0.12 Mcal/L from fat for a total of 0.44 Mcal/L. In order to meet the maintenance requirement on the 20:20 milk replacer the calf would have to consume 4.49 L (4.74 qt.) per day.
On the other hand, the same calf fed the 24:20 would only have to consume 3.98 L (4.21 qt.) per day to meet maintenance requirements under thermoneutral conditions. Once the requirement for maintenance has been met then additional Mcals can be partitioned toward growth. Therefore, a calf eating a similar volume of 24:20 milk replacer to a 20:20 milk replacer has an increased potential for gain because of the increased energy density of the milk replacer offered in a smaller volume of milk.