Abstract: With the development of intensive cultivation in dairy cows,the production efficiency of dairy farms has been improved.However,issues such as animal welfare,environmental protection and product quality of dairy farm have received more attention.As judging criteria in the pattern,outdoor grazing and grass intake necessary in grass-fed farming,and its products are gradually being favored by consumers in developed countries,such as Europe and the United States.The effect of grass-fed on milk and dairy products mainly depend on the quality of forage grass.The high fiber content in forage grass maintains rumen health,high unsaturated fatty acids increase the proportion of unsaturated fatty acids in milk fat,and rich degradable proteins promote milk protein synthesis.The metabolism of fatty acids,amino acids,carbohydrates and other nutrients from forage in dairy cows may affect the sensory quality of milk and dairy products.This review focused on the actual situation and standard requirements of grass-fed in some countries,and their differences compared with organic farming,and analyzed the effects of feed composition differences on rumen metabolism of dairy cows under grazing farming and total mixed diet feeding conditions,as well as resulting differences in milk fat,protein and sensory indicators.

Key words: grass-fed; milk; protein; fat; sensory qualities