What substance from the mother is crucial for the health and immunity of young sheep?

The correct answer is colostrum, which is the first milk produced by the mother sheep, or ewe, shortly after giving birth. This substance is crucial for the health and immunity of young sheep, known as lambs. Colostrum is rich in antibodies, vitamins, and essential nutrients that are vital for a lamb’s development, particularly in providing passive immunity. This immunity is essential because newborn lambs are born with an immature immune system and rely on the antibodies in colostrum to protect them from infections and diseases until their immune systems mature and can function independently.

The significance of colostrum cannot be overstated; it is necessary for a lamb's survival and health in the early days of life. A properly timed intake—ideally within the first few hours after birth—is critical to maximizing the benefits of the antibodies it contains.

While milk is generally important for the growth and nourishment of lambs, it is colostrum in particular that delivers the immediate immune benefits. Protein is also important for growth, but it does not specifically address the immunity aspect needed in newborns. The term "foal" refers to a young horse, not a sheep, and is therefore not relevant to this context.