Calling this song a ‘grace’ is ironic. It ‘celebrates’ the standard diet of sailors in merchant ships: old meat, tough, unidentifiable, soaked in brine and described as salt horse, but it could be anything. It was boiled for hours to make it more edible (but no less palatable) and eaten with hard ship’s biscuit without vegetables most of the time. No wonder seafarers developed scurvy.
Printed in Stan Hugill’s monumental book Shanties Of The Seven Seas, the song is unique in that it came from the quarry at Portland where horses provided the power to move huge blocks of stone that were sent by ship to London and the big cities before and since Victorian times to make the grand buildings of Empire. Not only were horses ill-used, so were the many prisoners. Both were easily replaced.
The explanation is longer than the song. Perhaps you’d better listen again.