ZIWI PeakAir-Dried Beef Dog Food

A root added for its inulin, a fiber that gut bacteria ferment. A prebiotic feeds the beneficial bacteria in the gut, and the pet gets the benefit second-hand. Studies in dogs show modest changes in gut bacteria and stool quality at the levels used in food. It is safe, and in large amounts can loosen stools, so it appears near the bottom of the list.

An essential mineral for muscle, nerve and bone function, added to guarantee the required level. The amount matters more than the form. In cats, higher magnesium combined with alkaline urine is linked to struvite crystals, which is why urinary foods keep it low; most foods list it far down because only small amounts are needed. Oxide and sulfate are the usual forms; proteinate is a chelated form marketed as better absorbed.

A zinc source. Zinc is essential for skin, coat, immunity and wound healing, and deficiency shows up first as crusty skin. Some Arctic breeds absorb it poorly and need more. Sulfate and oxide are inorganic; proteinate or chelate is bound to protein, which brands present as better absorbed. Any of them is normal. Not an allergen.

An iron source. Iron carries oxygen in the blood, and meat supplies much of it, with the mineral supplement making up the rest. Ferrous sulfate is the inorganic form; iron proteinate or chelate is the same mineral bound to a protein fragment, which brands describe as more absorbable. Either is normal. Not an allergen.

A copper source. Copper is essential in small amounts for blood, connective tissue and coat color. Some veterinary nutritionists have questioned whether modern dog foods carry more copper than dogs need, and a few breeds (Bedlington Terriers, Labradors among them) are prone to storing it in the liver. For most pets it is a routine additive. If your dog has a diagnosed liver condition, copper level is worth a vet conversation.

A manganese source. Manganese is needed in tiny amounts for bone, cartilage and enzyme function. Sulfate is the inorganic form; proteinate is the mineral bound to protein. The choice between them is a marketing distinction more than a health one for a healthy pet. Expected, safe, not an allergen.

Yeast grown in a selenium-rich medium so the mineral is bound into the yeast's proteins, which is the form found in meat. Selenium is an essential antioxidant mineral that pets need in tiny amounts and that is toxic in large ones. Selenium yeast is absorbed more steadily than sodium selenite, the inorganic alternative, and is the form many nutritionists prefer. Either form is safe at label levels.

A dried seaweed added as a natural source of iodine and trace minerals. Iodine is needed for thyroid function, and kelp is one of the few whole-food sources of it. The iodine content of kelp varies a great deal between harvests, so it has to be tested and dosed carefully, and the label will not tell you whether it was. Pets with thyroid disease should get the vet's view on foods that use kelp as the main iodine source.

Sodium and chloride, both essential, plus a palatability boost. Pets need less than people, and the minimum is set in the nutrient profiles the food is formulated to. Salt high on the list of a treat is a flavor choice; salt near the end of a complete food is nutrition. Ask your vet before choosing a low-sodium food for heart or kidney disease rather than reading labels alone.

A fat-soluble antioxidant that protects cells and the fats in the food itself. It is in nearly every complete food, both as a nutrient and, under the name mixed tocopherols, as the natural preservative that keeps fat from going rancid. Deficiency is rare in pets eating a complete diet. Nothing to worry about on a label, and a sign the maker is preserving with vitamin E rather than synthetic chemicals.

Vitamin B1, essential for nerves and energy metabolism, and the vitamin most often behind cat food recalls. It is destroyed by heat and by some preservatives, so canned foods in particular must add it back. Cats are especially sensitive to running short. Its presence is expected; its absence from a cooked food would be a red flag.

Vitamin B2, used to turn food into energy. Present in meat and dairy but partly lost in cooking, so manufacturers top it up. Water-soluble and safe at the levels used in food. Its presence tells you the food was formulated to a complete nutrient profile, not that anything unusual is going on.

Vitamin B6 in its stable, added form. It is central to protein metabolism, and cats need proportionally more of it than dogs because their diet runs so high in protein. Water-soluble and safe at food levels. A normal line on any complete food.

Dogs and cats cannot make useful amounts of vitamin D from sunlight, so it has to be in the food. It governs calcium and bone health. It is also one of the few vitamins where too much is dangerous: excess vitamin D has caused pet food recalls. The amount is regulated and the presence of D3 on a label is expected. What matters is that the maker gets the dose right, which is a quality-control question, not an ingredient question.

Vitamin B9, needed for cell division and healthy blood. Standard fortification in complete foods for dogs and cats. Water-soluble, no toxicity concern at food levels. Its main relevance to a shopper is none: it is there because the recipe was balanced properly.