How a 6 kg dog processes small wheat portions
At this body weight, a few bites of plain cooked wheat won't overload your dog's system. The gluten content becomes relevant mainly with repeated exposure or larger servings. Since you're comparing single incidents, the difference between wheat and barley is minimal for a dog without known grain sensitivities.
Watch the next meal—if your dog shows reluctance to eat, produces unusually soft stool, or licks her lips excessively, these subtle signs might indicate mild irritation from the less familiar grain.
Why preparation method matters more than grain type
Both wheat and barley were served cooked, which significantly reduces digestive strain compared to raw grains. The heat breaks down complex carbohydrates, making them easier for canine digestion. What would worry us is if either grain had been seasoned with onion powder or other common flavor enhancers toxic to dogs.
The plain preparation you described means either grain is essentially just filler at this quantity—neither provides meaningful nutrition nor poses real danger to a healthy 6 kg adult dog in this amount.
When wheat's reputation for sensitivity actually matters
Gluten intolerance in dogs manifests through chronic exposure, not one-time ingestion. Unless your dog has a documented wheat allergy (shown by recurrent ear infections or paw licking after wheat-containing meals), this single incident won't trigger those mechanisms.
Comparatively, barley contains different gluten proteins that some dogs tolerate better—but without prior sensitivity signs, there's no reason to assume your individual dog would react to wheat more than barley at this dosage.
The 24-hour observation window for grain reactions
Monitor for any changes in bathroom habits, particularly the consistency of the next few bowel movements. Some dogs may pass grain fragments visibly in their stool when not fully digested, which looks concerning but isn't inherently problematic.
True allergic reactions—like sudden facial swelling or hives—are extremely rare from plain cooked grains and would appear within hours. Digestive upset from simple intolerance tends to be milder and delayed by 8-12 hours after ingestion.
The full verdict, portion guidance and serving notes are collected on the Wheat food facts page.