Best calming supplement for anxious Australian Shepherds

That's actually a really useful starting point — your vet has already done the hard work of ruling out pain, which means you're not guessing. Anxiety in dogs takes a few distinct forms: separation anxiety, noise phobia, and generalised anxiety that's just baked into their temperament. The right product depends on which pattern you're dealing with and how intense it is. So tell me: what does the anxiety actually look like in day-to-day life? When does it tend to flare up, and does it happen in specific situations or pretty much all the time?

That tracks perfectly with the breed. Australian Shepherds are wired to work and make decisions constantly, and when that drive has nowhere to go it often manifests exactly as you're describing — not fear of something specific, just a nervous system that won't idle properly. A few quick questions before I point you at anything: is he getting plenty of physical exercise and some kind of mental stimulation — training, puzzles, that sort of thing? And has the vet mentioned any particular approach they'd like you to try first, or are you coming to this fairly open?

Your vet is thinking along exactly the right lines, and casein is the one I'd go with first for a dog like yours. I'd recommend Zylkene 450mg — it's a hydrolysed milk protein (alpha-casozepine) that works on the same GABA receptors as some prescription anti-anxiety drugs, but gently and without sedation. It has a solid evidence base, it's widely used in veterinary practice, and crucially it won't blunt his drive or make him dopey — which matters a lot with a working breed you're actively training. The 450mg dose is right for his size. You'd give one capsule daily, and most dogs show a meaningful response within two to four weeks. It also comes as a capsule you can open and mix into food, which makes it straightforward. It won't fix everything on its own, but as a first-line supplement trial with a dog who's already well-exercised, it's the most sensible place to start — and your vet will recognise it immediately if you mention it at your follow-up.

Give it a full four weeks at minimum before making a judgement call. The first two weeks can be subtle — you might notice he settles slightly faster after exercise, or that he's a bit less reactive to movement around the house. By weeks three and four you should have a clearer picture. It helps to keep a simple log: score his restlessness on a 1–10 scale each evening for the first month. That gives you something concrete to bring back to the vet rather than relying on memory, and it makes the decision about next steps much easier if you're not seeing enough improvement.

Good plan. Zylkene is easy to find on Amazon UK — search for Zylkene 450mg and make sure you're getting the Vetoquinol branded version, which is the one with the clinical data behind it. Keep your vet in the loop at the four-week mark either way. If it's working well, great. If it's not moved the needle enough, they'll have a clearer sense of whether to increase the dose, add something like L-theanine alongside it, or consider a prescription route. You're approaching this in exactly the right order.