Mutual fund managers pumped in over Rs40,000 crore in debt markets during April-May this fiscal primarily on account of improved business sentiments. This follows a fund infusion of nearly Rs6 lakh crore in debt market in the last financial year. As per the Sebi, fund managers invested net sum of Rs17,389 crore in May and Rs22,650 crore in April, taking the total amount to Rs 40,039 crore.