My Border Collie does not tolerate lamb well. It's not my favorite meat source for dog food, as most people say it's healthier & causes less allergies just because it's a novel protein source... when it isn't generally that digestible. Chicken, turkey, duck, etc are usually much more easily digested.
People are always recommending lamb for allergy dogs at my current store location and it drives me nuts, I rarely see dogs with legitimate issues do well on lamb. And then when they come back and say it didn't work, I have to try and tell them to switch to something that probably WILL help without making it seem like my coworkers don't know what they're doing. And in this day and age, it's NOT a novel protein source anymore. Kangaroo is novel, beaver is novel, for some dogs bison is novel, but lamb really isn't.
And if you believe in chinese medicine at all (which a lot of people don't, and that's fine) lamb is one of the WORST protein sources you can put a dog on.