As costs increase on dairy farms, many producers are looking to cut feed cost, including the cost of feeding calves. One alternative is to feed milk that would normally be discarded as unsalable, but management and careful consideration are required. Producers need to look at quality measures and how they will handle discard milk before making the switch from whole milk or milk replacer.
First, when feeding discard milk producers need to know the composition of the milk they are feeding. Discard milk may come from many sources including milk from cows too fresh for the tank, milk abnormal in composition (e.g. high SCC), or milk from treated cows with a withholding time. This variation in sources can add to the variability that may already exist within each of the sources. When looked at on a dry matter basis, discard milk can have a 20% to 36% range in fat contents and a very similar range in protein content, as well as highly variable plate counts. This variability can in turn lead to digestive upset in calves.
Milk from cows too fresh for the tank and milk from treated cows can also have antibiotic residue levels that may affect the good bacteria in the calves gut. Again this can lead to digestive issues.
Varying solid contents can be adjusted for by adding milk replacer to discard milk according to Dr. Dale Moore, Veterinary Medicine Extension, Washington State University. In her study of waste milk from 12 dairies, Dr. Moore found that most solids variation came through the inadvertent addition of water through the cleaning process. Using a brix refractometer to measure total solids in discard milk, Dr. Moore developed a chart to indicate how much milk replacer needs to be added to discard milk in order to obtain proper levels of total solids. Variations in solids have also been shown to be related to SCC numbers and may result in some components being more depressed than others. Therefore simple additions of milk replacer will not resolve this type of variation.
Because of the variation that is seen in the component levels and sources of discard milk, growers should consider having milk components tested at a regular basis. Most milk processing companies will assist with this analysis.
Producers may also choose to feed discard milk to older calves (two to eight weeks old) that are better able to handle the variability in components.