To concur with Jim - gallowa is a generic term for pit pony as the Galloway breed is long extinct; see WIKI. Jez Lowe sings of gallowas grazing and the small ponies common in the fields around the old pit villages of Co. Durham are still referred to as gallowas by the locals (most recently in back of the Chester-le-Street Travelodge up at Chester Moor on the A167). In many old songs, pit ponies were simply called horses. Famously, and most anciently : The Collier's Rant; obscurely (and probably just as anciently given the imagery & terminology) : Ca' the Horse Me Marra.

Though cows were never used in collieries*, I did hear of a pig being introduced in a drift by way of a prank. Couldn't say what breed it was, though Pinterest gives us a Belted Galloway which looks more like a Hampshire to me...

* I'd REALLY love to proved wrong on this.