If it breathing
These are diaphragm and externa intercostal muscles in quiet breathing and sternocliedomastoid ,sclene muscles,anterior serrati in heavy breathing
It is not called humming, guinea pigs do that type of sound because they are breathing.
The breathing will be steady, the babies will kick out of scync.
Wild pigs should be able to swim. But I don't think farm pigs can swim because of how heavy they are.
heavy breathing occurs to breathe out the acid (CO2) in an attempt to correct the acidosis.
heavy breathing as you call it , in an engine would mostly be caused by a filthy air cleaner or a blocked air intake
they weigh about 700-900g
Yes, breathing heavy is the body trying to recover more oxygen. It happens during exercise such as running as your body tries to recover the lost oxygen.
aches in the muscles and heavy breathing
lactation of the nipples and heavy breathing.
dying