Which immunoglobulin is primarily transferred to a newborn calf via colostrum?

• A. Immunoglobulin A (IgA)
• B. Immunoglobulin M (IgM)
• C. Immunoglobulin E (IgE)
• D. Immunoglobulin G (IgG)

Answer: (D)

The key idea is passive transfer of maternal antibodies through colostrum. Calves are born with an immature immune system and, in cattle, the placenta doesn’t pass large antibodies to the fetus, so the calf relies on colostrum right after birth to gain immunity. The immunoglobulin that is absorbed into the bloodstream from colostrum in the largest amount is Immunoglobulin G (IgG). This provides systemic, whole-body protection during the early life period. Other antibodies in colostrum, like IgA, mainly protect mucosal surfaces such as the gut, and IgM and IgE have different roles and are not the primary systemic transfer. The window for absorption is brief—most IgG uptake occurs in the first day of life before the gut “closes.”