Wheat

Wheat is classified as non-toxic to dogs and cats by the ASPCA Animal Poison Control Center (APCC). That mention appears in an article about fall decorations (alongside pumpkins, hay and corn) and uses the common name "wheat" — it is not a species entry on the plant list. Note also that the article is about dried decorative wheat, while this page is about fresh wheatgrass: the same species, but a different form.

Wheat shoots are sold as "cat grass" alongside oat and barley shoots. The three are different species, and unlike wheat, oat and barley still have no confirmed cat-specific verdict.

Separately from toxicity, the same article flags two things: mold on grains can cause significant effects on the nervous system even in small amounts, and large ingestions of leaves or seeds can lodge in the intestinal tract and cause a blockage. It also notes that grains can trigger allergies in pets with a sensitivity to them.

So replace the whole tray if water pools in it or the shoots turn soggy, and offer small amounts at about 10–15 cm, before the blades toughen. Contact your vet if anything seems off.