In a guinea pig, hay is not one menu item among many. Long hay fiber keeps the gut moving and the constant chewing wears teeth that grow throughout life, so a senior pig who eats less hay and starts leaving pellets unfinished is showing a change that deserves prompt attention, not weeks of hopeful experimenting at home.
Book the Vet Check Promptly
Make the vet appointment first, before changing everything else. Eating less hay is not a watch-and-wait item, because the possible causes a vet will want to examine, such as tooth problems, mouth pain, gut slowdown, or other illness, tend to worsen while an owner experiments, and a guinea pig who eats too little can decline quickly. This article cannot tell you which cause applies to your pig; only an examination can, and arriving promptly gives the vet the best chance to help.
Prepare for that visit while you wait. Write down when the hay intake dropped, how much pellet food is left each day, whether the pig still eats vegetables eagerly, how droppings look and how many there are, and whether chewing looks uneven or slower than usual. Take that record with you, because a clear timeline of appetite change is genuinely useful clinical information, not worrying over nothing.
Meanwhile, treat appetite as the daily headline. A pig who stops eating altogether, produces very few droppings, sits hunched and quiet, or loses interest in favorite vegetables needs to be seen urgently, the same day, rather than waiting for the booked appointment. Senior guinea pigs hide illness well, and reduced hay intake may be the earliest visible sign you get.
Make the Hay Easier to Eat
Change the hay offer itself: offer fresher, softer, leafier hay alongside the usual hay, in several low piles on the floor and in a low-entry rack. Coarse, stemmy hay asks hard work of aging teeth and jaws, while softer leafy material can be gathered and chewed with less effort. Low piles matter because a senior pig with stiff movement should not have to rear up or wrestle hay through high rack bars to eat.
Check the basics around the hay with equal care. Confirm water flows freely from the bottle or that a bowl is clean and reachable, because a pig who cannot drink comfortably eats less dry food. Smell the hay itself; dusty or stale hay is refused by sensible pigs of any age. In a pair or group, watch whether a bolder pig guards the rack or the best pile, and add another low pile out of that pig's sight line if so. An older pig quietly displaced from food will eat less without ever making a scene.
Keep vitamin C vegetables coming daily, as before, because guinea pigs cannot make their own vitamin C and a reduced appetite is the worst moment to let that intake slip. Do not compensate for uneaten hay with larger pellet portions or sugary treats; the point is to restore hay eating with veterinary help, not to fill the pig with foods that do neither the gut's nor the teeth's work.
Weigh Weekly and Watch the Trend
Weigh the pig weekly, on the same scales, at the same time of day, and write the result down. Weight is the honest measure underneath daily impressions: a stable weight while intake looks lower is reassuring information for the vet, while a steady slide confirms the urgency and shows whether changes are helping after treatment begins. Hands-on weekly handling also lets you feel ribs, check feet and coat, and notice lumps or soreness early.
Bringing a clear eating history matters, and KinsLe keeps it ready in the Pet Passport, so a clinician sees trends instead of a worried summary from memory.