Slipping on cow shit while walking down a cobbled farmyard in the pitch dark carrying an exercise bike, and landing flat on your back/arse in the aforementioned cow shit with the exercise bike on top of you.
(Don’t ask.)
Gruts
keep your ear to the grindstone
Never trust those bastard cows (ibid).
Presumably, in a nearby shippon, a maligned cow was rubbing its hooves together with glee as you fell into its crusty trap.