Twenty four dairy cows at 7 d after calving were randomly assigned to four groups（three immunized group and one control group）, the three immunized group of cows were primarily immunized（injection day as 0 d） with 3 mL（per cattle cow） of recombinant bacterium C500（pXAIS） delivering the inhibin gene vaccine（a kind of DNA vaccine without antibiotic resistance gene） in a high（1010 CFU/mL）, middle（109 CFU/mL） or low（108 CFU/mL） dosage, the control group of cows were intramuscularly immunized with physiological saline（3 mL per cattl...
