Final answer:
Lysine is often the first limiting amino acid in most livestock species because it is essential and cannot be synthesized in sufficient quantities by the animals. Supplementing livestock diets with essential amino acids, particularly lysine, supports their health and productivity.
Step-by-step explanation:
The first limiting amino acid in most livestock species is lysine. This is due to the fact that lysine is one of the nine essential amino acids that animals must obtain from their diet. These essential amino acids are crucial for protein synthesis and overall health, and cannot be synthesized by the animal's body in sufficient quantities. In particular, diets based on various plant proteins may not provide enough lysine, thus making it the limiting amino acid that can affect the growth and productivity of livestock.
To ensure that livestock receives all the necessary amino acids, their diets can be supplemented with essential amino acids, with a focus on increasing lysine content. This ensures that the diet is not limiting in terms of protein quality and supports the animals' well-being and performance.