At 1.36pm on Sunday 11 February crews from Kempston and Biggleswade were called to reports of an injured sheep in the river at Clifton Road, Shefford.
On arrival they found a pregnant sheep trapped in branches and in danger of falling into the flooded river. Local witnesses, who called 999 and waited for crews to arrive, reported seeing a dog chasing and attacking the animal before it panicked and ran into the vegetation on the river bank.
Once safety precautions had been put in place, the animal was rescued by crews using specialist equipment, checked for any visible injuries and returned to its flock in a nearby field.
Watch Commander Jamie Martin, an animal rescue specialist, said: "The panicked animals attempted to get away leading to one animal becoming trapped and in danger of falling into the swollen river. It is not known if the dogs were accompanied but dog owners should be aware of the need to keep their animals, regardless of how well-trained they are, on a lead when in the vicinity of other animals such as horses, cattle or sheep.
"This is particularly important as it is lambing time, with either ewes being pregnant or having lambs at foot.
"If anyone has any information relating to this incident, I would urge them to contact Bedfordshire Police on 101 or via Crimestoppers, all of which can be done confidentially."