A newborn calf has essentially no ability to fight disease. To build its immune system it must consume colostrum (first milk) from its mother. Colostrum contains immunoglobulins or more specifically immunoglobulin G (IgG) that move across the intestinal wall to build immunity. Known as passive transfer the calf’s ability to absorb IgG rapidly declines to nearly 0% at 24 hours of age. This is why it is so important that a calf nurses within a few hours of birth. In addition to building immunity, colostrum is a source of protein, energy, vitamins, minerals and natural growth promotants.

While it always preferable for the calf to get colostrum from its dam, there are situations where the quantity of maternal colostrum is insufficient, is of low quality or not available. In these situations commercial colostrum products can be substituted. However not all colostrum products are the same. Colostrum products are made from either blood serum or dried bovine colostrum. Whether made from serum or dried bovine colostrum does not seem to effect the efficacy of the colostrum product.

There is a difference, however in whether the colostrum product is intended as a supplement to or as a complete replacement of maternal colostrum. Supplements typically contain 40 g – 60 g of IgG per dose. Some research has indicated that supplements actually reduce absorption of maternal colostrum. As such colostrum replacers have been developed. Colostrum replacers provide at least 100 g of IgG per dose. Research suggests that a calf should consume at least 100 g of IgG within 4-6 hours of birth; however due to the variable efficiency in absorption of IgG, dosages of 150 g – 200 g of IgG are recommended to ensure calf health.

It’s important to read the label to determine if you are purchasing a supplement or replacer. This is sometimes indicated in the name: supplement or replacer, but also in the amount of IgG per dose. If less than 100 g IgG/dose it is a supplement; greater than 100 g IgG/dose it is a replacer. Note that some supplements can be used as a replacer by increasing the amount of powder used to provide the 100 g IgG/dose.

Colostrum replacers are more expensive but several studies have shown that these products elicit the same response in calf health as good quality maternal colostrum. Given the high price of calves, investment in the best colostrum replacer resulting in a healthy calf is a good return on investment.