‘You couldn’t hit a cow’s arse with a banjo’ is an Irish expresion meaning ‘not a very good shot’ often applied to footballers who can’t score.
Why a banjo?
There is a shovel that is called a banjo, (because it’s shaped like the musical instrument) and there is a similar saying ‘yer couldn’t hit a cow’s arse with a shovel’
As a farmer might be more likely to have a shovel than a banjo, this is the likely derivation of the phrase, but banjo is funnier, so it stuck.
Why did I take the photograph? I ask myself the same question.
FARM ANIMALS UP CLOSE AND PERSONAL – CROPS & HARVESTS