wait until you find out about kirkland canned chicken breast 
Discussion
Pet food often contains dl-methionine. D-methionine is an essential amino acid found in animal products. Your carnivore pet needs it. It is expensive, so manufacturers use a synthetic version. Labs are VERY bad at selecting a specific handedness, so you get a mixture of both isomers. Unfortunately, l-methionine is toxic to the liver.
interesting
In a similar vein, human and animal Vit E supplements often use dl-alpha tocopherols. Natural sources provide d-alpha tocopherol. The synthetic version is cheaper, but is a mixture of D and L. The L-alpha tocopherol is ineffective, but seems to be innocuous. So far. That I have noticed in research.
Isaac Asimov wrote a short sci-fi story about a guy that is stranded on an alien planet, that looks just like earth, has delicious food, beautiful girls, all in all a paradise. He even marries an alien girl. But his health rapidly deteriorates. Spoiler **** It turns out that all the chiral organic molecules on this planet were the opposite of Earth. ****
This story made me more aware than most of chirality in supplements.
