NewScientist this week reports on the squeals that piglets make when their testicles are chopped off. The reference is:
Puppe B, Schon PC, Tuchscherer A, Manteuffel G, 'Castration-induced vocalisation in domestic piglets, Sus scrofa: Complex and specific alterations of the vocal quality', Applied Animal Behavior Science, 2005, 95 (1-2), 67-78.
'The observed changes of acoustical parameters during the surgical period can be interpreted as vocal indicators for experienced pain and suffering'.
For $30US you can read the whole article here. Or you need not read it but appreciate the creativity and neutrality of the study's title. Or its curiousity value. Or you can experience outrage.