She said that lamb has particularly dark blood, so it goes bad much more quickly than other meat. Veal is similar. We don't really eat veal at all, so we hadn't encountered this, but we do eat lamb frequently and have trouble finding the cuts we like. We just assumed that this was because lamb is less popular in the United States than pork and beef, but apparently the shelf life is also an issue.
The butcher told us that the dark blood causes the meat to spoil much more quickly and so they keep much less lamb in stock. We did some cursory research and found some references to a different pH levels in lamb and veal, as well as wild game like deer. We also researched in Harold McGee's tome, but didn't find any references to this.
We're curious - what do you know about dark blood, shelf life, and lamb and veal?