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.

(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.

Shares of Union Pacific were gaining after the railroad easily beat quarterly earnings estimates, but missed on the top line. Union Pacific stock rose 5% to $247.50 in early trading Thursday. For its fourth quarter,