Abstract
Changes in the blastogenic activity of peripheral blood lymphocytes were investigated in healthy dairy cows orally administered a Bacillus subtilis preparation. Both a 5-day repeat dose at 50g/day and single dose of 250g of the B. subtilis preparation enhanced blastogenic activity, in response to phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) stimulation, from the start of administration to 2-3 days later. Although the activity gradually declined after that, it was still higher at 7 days than before the administration (with Con A and PWM). In cows given a 28-day repeat dose at 50g/day of the B. subtilis preparation, the activity increased for 3-4 weeks from the initial administration and became significantly higher than in the control (with Con A and PWM). The activity tended to decrease more or less to the level of the control in the 5th week (the week after completion of the administration). The results suggest that the oral administration of a B. subtilis preparation could enhance the activity of T lymphocytes by stimulation with PHA or Con A and of B lymphocytes by stimulation with PWM, and that such a preparation could be useful as an immunopotentiator in long-term repeat dosing for preventing infections such as mastitis.
