APP and infection: Some physiological measures that merit further study include, acute phase proteins (APP), including pig major acute phase proteins (Pig-MAP), haptoglobin, serum amyloid A (SAA), and C-reactive protein (CRP), which have recently been suggested as a good means of measuring animal welfare [60,61] and are said to increase in response to inflammation due to tissue damage, infections, immunological disorders, or stress [62,63].