(Reuters) -Union Pacific reported a fourth-quarter profit on Thursday that rose 7% on the back of higher grain and fertilizer shipments and core pricing gains, sending the railroad operator's shares up more than 4% before the bell.

Union Pacific on Thursday posted a better-than-expected profit for the fourth quarter helped by improving volumes and robust pricing, which was partially offset by lower fuel surcharge and less profitable cargo mix.

Operating revenue of $6.1 billion was down 1% from a year ago, driven by lower fuel surcharge revenue, unfavorable business mix, and lower other revenue, partially offset by increased volume and core pricing gains. Revenue carloads were up 5% for the quarter.