Abstract: Small peptide can be effectively utilized by mammary gland to match the need of amino acids for milk protein synthesis. Recent researches especially showed the amount of free amino acids were not enough for milk protein synthesis. Therefore, it is necessary to study the metabolism and function of small peptide in the synthesis of milk protein for a better understanding of their utilization by ruminants. In this article, the authors have reviewed the concept of peptide, utilization of small peptide by mammary gland, uptake mechanism of small peptide by mammary gland, factors those affect small peptide use and research outlook.

Key words: small peptide; ruminant; milk protein