Abstract: To investigate the variation of dairy cows'milk performance and plasma biochemical index in different farms between spring and summer， milk and plasma samples in spring and summer were collected from dairycows in early lactation( DIM， 50 － 90 d) ， which were screened from dairy farms in Beijing， Chuzhou， Harbin， Hohhot， Urumqi and Xi'an． Milk property， such as milk yield， protein， fat， total solid， lactose content in milk， and biochemical index in plasma， β-hydroxybutyrate ( β-HA) ， nonesterified fatty acid ( NEFA) ， cholesterol ( CHOL) ， totalprotein(TP) ， albumin( ALB) ， blood urea nitrogen( BUN) ， alkaline phosphatase ( ALP) ， aspartate amino transferase(AST) ， alanine amino transferase (ALT) ， for instance， were examined in this study． And data were processed by SAS8． 1 ． Results showed， dairy cows from different dairy farms had significant variation in milk performance (P ＜ 0． 01 ) ，only milk fat content was influenced by season transition significantly ( P ＜ 0． 01 ) ， prominent interaction betweenseason and dairy farm also existed in milk performance ( P ＜ 0． 01 ) ． Biochemical parameters in plasma， all butCHOL were affected by dairy farm ( P ＜ 0． 01 ) ， most of items ( except ALP， AST) varied remarkably ( P ＜ 0. 05) asseason changed， NEFA and other 7 indexes were obedient to interaction of season and dairy farm ( P ＜ 0. 05) ． It wassuggested that milk fat and dairy cow plasma biochemical parameters were subjected to season remarkably， but in consistent variation emerged on corresponding parameters of dairy cows from different farms．

Key words: Dairy farm, Season, Milk performance, Plasma biochemical index

CLC Number: 

• S823