This is book number 21 in the Commissario Guido Brunetti Mysteries (Audio) series.
“When Brunetti begins to investigate a murder, the corpse turns out to have been a veterinarian beloved by all whose animals he treated. Why, then, did such a man work in a slaughterhouse? And what exactly was his role there? As in many of the excellent Venetian mysteries of Leon, ethics are the true subject under investigation: the ethics of the abattoir and of the consumption of meat; the ethics of decent people who, when threatened, test the waters of illegality; and the ethics of the police - always a subject for dissection in the mind of Brunetti. This may be Leon's best yet - high praise indeed.”
— Betsy Burton, The King's English, Salt Lake City, UT