Effects of Different Energy Levels on the Milk Performance and Blood Chemistry in Jersey Cows in Tibet

Background: Owing to the extreme cold and hight elevation, demand for fat by people in the plateau is great than those on the plains Butter were used to supply of fat to the herders in areas as remote as rural Tibet and as one of the traditional food, it occupied an importan place in the diet. Therefore, there is a significance in improving butter production in Tibet. Methods: To explore the effects of energy levels on milk performance, blood chemstryand milk hydrolysis amino acid in Jersey cows in Tibet. Forty late-lactation Jersey cows were randomly assigned into 4 groups equally according to the level of energy: E1 (11.50 MJ/kg); E2 (12.0 MJ/kg); E3 (12.5 MJ/kg) and E4 (13.0 MJ/kg). Result: The results indicated milk yield, milk fat content, total soilds content, lactose contentand soilds-not-fat content increased in response to higher levels of dietary energy, whereas the greater (P less than 0.0001) value of milk protein content was observed at the lower levels of dietary energy. The greater plasma GPT content was obtained in group E4 (P less than 0.0001), whereas, the greater plasma TG and GLU were observed in group E3 (P less than 0.01). Plasma TG and LDH of group E2 were greater than those of another treatments (P less than 0.0001) and the plasma UN of group E1 was significant higher among treatments (P less than 0.0001). The greater values of most hydrolysis amino acid and total AA in milk were observed at the lower level of group E1.