PurinaPro Plan Prime Plus Senior Salmon & Rice Dry Cat 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.

A potassium source and an electrolyte. Potassium keeps muscles and nerves working, including the heart, and cats lose more of it than dogs do. It also stands in for part of the salt in foods that are formulated lower in sodium. A routine additive with no allergy or safety concern at food levels.

A calcium source, the same compound as limestone or chalk. Meat is low in calcium and high in phosphorus, so foods add calcium to keep the two in balance, which matters for bone and for large-breed puppies in particular. Routine and safe. Not an allergen.

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.

An essential amino acid, added when the proteins in a food fall short of the required level. Meat is rich in lysine, so it is usually added when a recipe leans on plant protein, which is lower, or to replace lysine lost in cooking. In cats, lysine supplements were long given for herpesvirus flare-ups, but controlled studies found no benefit and some suggestion of harm at high doses; the small amounts in a complete food are there for nutrition and sit far below those doses.

A B-vitamin relative added to nearly every complete food because animals need more than the base ingredients supply. It supports liver function and cell membranes. Seeing it on a label is normal and reassuring rather than a concern.

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 B3. Dogs can make some from the amino acid tryptophan; cats cannot make enough and must get it from food, which is one of many reasons cat food and dog food are not interchangeable. Water-soluble and safe at food levels. Expected on every complete food label.

Essential for vision, skin and immune function. Cats cannot convert the plant form (beta-carotene) into vitamin A the way dogs can, so cat food must carry the preformed vitamin. It is fat-soluble and stored in the liver, so very high doses over time are harmful, which is why the amount is regulated. Normal on any complete food.

Vitamin B5 in its stable added form (the d- prefix just names the active version). It is needed to turn fats and carbohydrates into energy. Widely available in meats and grains, topped up to guarantee the level. Safe, expected, and irrelevant to allergies.

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.

Needed for nerve function and making red blood cells. It occurs naturally only in animal tissue, so it is added to almost every food to guarantee the level. Water-soluble, so excess passes out in urine. Cats and dogs with chronic gut disease can run low even on a good diet, which is a vet conversation rather than a food choice.

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.

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.

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.

A B vitamin tied to skin and coat quality and to fat and protein metabolism. Gut bacteria make some; food supplies the rest. Raw egg white contains a protein that binds biotin, which is the reason raw-egg diets can cause a deficiency. Safe, expected, and not an allergen.

A synthetic form of vitamin K, which is needed for blood clotting. Dogs and cats normally make enough vitamin K with help from gut bacteria, so it is not required in most foods. AAFCO's cat food profiles require a source of vitamin K, such as menadione, in complete and balanced cat foods that are more than 25% fish on a dry matter basis, where it guards against a known deficiency. It is controversial online because high doses in lab animals caused harm; at the small amounts used in pet food, no harm has been shown.

An amino acid cats cannot make in sufficient quantity and must eat, or they develop heart disease and blindness. It is in every complete cat food by law of nutrition, not by choice. Dogs make their own, but it is added to many dog foods as a precaution after a federal investigation into diet-associated heart disease in dogs. Its presence on a dog food label is a good sign, not a warning.

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 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.

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.

An iodine source. Iodine runs the thyroid, and pets cannot get enough without it being added. Calcium iodate and potassium iodide are the common forms and do the same job. Whether dietary iodine plays a role in the overactive thyroid common in older cats has been studied without a clear answer. A normal line on any complete food.

The usual source of selenium, a mineral that works alongside vitamin E as an antioxidant. Selenium has a narrow safe range, so the amount is regulated and small. Sodium selenite is the inorganic form; some brands use selenium yeast instead, which is absorbed differently, and market it as an upgrade. The evidence that it matters for a healthy pet is thin. Expected on a complete food.

A plant pigment that dogs convert to vitamin A and that also acts as an antioxidant. Cats cannot make the conversion and need preformed vitamin A from animal sources, so for cats beta carotene is an antioxidant and a colorant only. It gives kibble an orange tint. It is safe at the amounts used and appears on labels mainly as a sign that the food was formulated to a full nutrient profile.

Live bacteria added to support digestion, listed by strain name such as Lactobacillus acidophilus or Bacillus coagulans. The difficulty is that most are killed by the heat of cooking and by months on a shelf, so unless the maker coats the kibble after cooking and states a live count on the bag, the listing does not tell you much. Bacillus strains form spores and survive processing better than the others. The strains used are considered safe.

A heat-stable form of vitamin C. Dogs and cats make their own vitamin C, so it is not an essential nutrient for them. It is added as an antioxidant and, some argue, to support joints and immunity. Harmless at food levels and not a reason to choose or avoid a food.