Market players said slackness in demand amid steady inflow of supplies reflected downtrend in mustard seed futures.
Apart from lower demand for mustard cake from animal feed makers as well as reports of good crops to weighed on prices, they added.
At the National Commodity and Derivative Exchange, mustard seed delivery for May contracts slipped by Rs 39, or 0.93 per cent, to Rs 4,168 per quintal with an open interest of 7,100 lots.