Tenant livestock farmers Judith Mudd and Nick Fielding of Station Farm in Old Dalby, Leicestershire, lost £6000 worth of hay after thieves set fire to a barm last week.
The gang responsible took 900 litres of red diesel and a trailer worth about £2700 during the attack.
It is believed they then propped a motorbike against 2,000 bales of hay before setting it alight and making their getaway. The hay and barn were destroyed in the blaze.
Neighbours helped free 17 sheep trapped in the barn after spotting the smoke and flames, with fire crews managing to stop the blaze spreading to a second barn containing straw and machinery.
The farm was also hit in July, when thieves took a motocross bike, together with other items worth around £9,000, from the farm.
“This is utterly devastating,” said Ms Mudd. “To see someone come along and do this makes you feel empty inside.
“Farming is not an easy way to make a living and we have always run the farm on a shoestring. We’ve worked so hard, but we’re noting going to give up.”