Perhaps this will help to clear up the 'sweating like a bull or pig':
according to Cassell's Dictionary of Slang, 'sweating like a bull' was a common expression in the 19th century.
'Sweating like a pig' has nothing to do with animals, according to Wikipedia: cultural references to pigs. (Pigs do not sweat, as they have inefficient sweat glands.) The term is derived from the iron smelting process. After pouring the molten iron into runners in sand, it is allowed to cool, and is seen as resembling a sow and piglets, hence 'pig iron'. As the pigs cool, the surrounding air reaches its dew point, and beads of moisture form on the surface of the pigs. 'Sweating like a pig' indicates that the pig has cooled enough to be moved in safety.