A newborn calf has essentially no ability to fight disease. To build its immune system it must consume colostrum from its mother. Colostrum contains 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 percent at 24 hours of age. This is why it’s so important that a calf nurses within a few hours of birth. Colostrum is also a source of protein, energy, vitamins, minerals and natural growth promotants.

In situations where the quantity of maternal colostrum is insufficient, is of low quality, or it’s not available, commercial colostrum products can be substituted. However, not all colostrum products are the same. There is a difference in whether the product is intended as a supplement to or as a complete replacement of maternal colostrum.

Supplements typically contain 40 to 60 grams 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 grams of IgG per dose. Research suggests that a calf should consume at least 100 grams of IgG within four to six hours of birth; however, due to the variable efficiency in absorption of IgG, dosages of 150 to 200 grams of IgG are recommended to ensure calf health.

Read the label to determine if you’re purchasing a supplement or replacer. This is sometimes indicated in the name, but also in the amount of IgG per dose. If there’s less than 100 grams of IgG per dose it is a supplement; if there’s more than 100 grams of IgG per 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 grams of IgG per dose.