Abstract: The immune system of calves is immature and sensitive before weaning.However,the calves can grow rapidly after weaning.In both stages,it is necessary to provide a diet containing high quality protein to ensure the growth of calves.Considering the current situation of protein shortage in China,optimizing amino acids supply to calves is important for improving health status and utilization rate of protein in the calf stage.In addition,amino acid can play an important role in improvement of immune function in the calves.Recently,some studies found that amino acids would have some special effects on susceptible bacteria and virus in digestive tract of calves.According to the physiological characteristics of calves,such as the rapid growth,imperfect immune function,high mortality and rapid changes in physiological structure and nutritional requirements before and after weaning,the authors reviewed the effects of different levels of single amino acid and different proportions of multiple amino acids on the growth performance of calves before and after weaning.The mechanisms about the effects of amino acids on the health of calves from the aspects of improvement of autoimmunity of calves and inhibiting microbial reproduction was summarized also.The paper was to provide theoretical basis for promoting the application of amino acid in calf production.

Key words: calves; amino acid; ideal protein; growth performance; immune performance