Border Terrier puppy and adult food in one house

A 6-month-old puppy and a 3-year-old adult in the same house — that's a lovely setup but it does create a real feeding puzzle! Border Terriers are a pretty active, lean little breed, and at 6 months your puppy is still in a key development window where getting the nutrition right genuinely matters. Puppy nutrition is one of the most important investments you'll make — the right food in the first year sets the foundation for long-term health, and the differences between puppy foods are more significant than most people realise. So before I point you in the right direction: what are they currently eating, and are you feeding them separately or is there a bit of bowl-raiding going on?

That's really common — and honestly, the bowl-swapping is the main thing worth solving here. Royal Canin puppy food is decent but it's quite highly processed and relies heavily on rice and maize as fillers. Harringtons is fine as a budget option but it's fairly low in protein for an active terrier. The bigger issue is that when a puppy regularly eats adult food, they can miss out on the higher protein, fat and DHA levels they need at this stage. And when an adult eats puppy food often, the higher calorie density can nudge their weight up over time. Has the adult Border Terrier had any weight or energy issues, or has she been pretty stable?

Good — healthy adult and a puppy who seems to be thriving is a great starting point. Here's what I'd actually recommend: switch the puppy onto Acana Heritage Puppy & Junior. It's a high-protein, low-carb dry food with around 60% meat content — free-range chicken, wild-caught fish, and cage-free eggs — plus added DHA for brain and eye development. It's genuinely one of the best puppy foods available in the UK and it's well-suited to small, active breeds like Border Terriers. The reason I'm flagging this specifically is that it's also meaningfully different in its nutritional profile from a typical adult food, which means you have a real reason to feed them separately rather than it being a bit academic. I'd keep their meals separate and supervised — even just feeding in different rooms or one in a crate. For the adult, I'd actually look at moving her off Harringtons too, but that's a separate conversation. For now, the puppy is the priority and Acana Heritage Puppy & Junior is the right call.

Yes, exactly right — smaller breeds do mature faster than large breeds. As a rough guide, most Border Terriers are ready to transition to adult food somewhere between 9 and 12 months. At 6 months your pup is about halfway through that puppy phase. I'd keep him on the Acana Heritage Puppy & Junior until around 10–12 months, then transition gradually over about two weeks onto an adult equivalent. Acana do an adult small breed formula that would be a natural next step, so you wouldn't need to completely rethink things when the time comes.

That'll make a real difference. Separate rooms is the simplest solution and most dogs adjust to the routine quickly — they learn fast when food is involved! The Acana Heritage Puppy & Junior is available on Amazon UK in 2kg and 11.4kg bags; the larger bag works out considerably better value if you've got the storage space. Good luck with both of them — sounds like they've got a great life ahead of them together.