Walk into any pet shop or supermarket and you will find an array of different cat foods – wet, dry, complete, complementary – so much to choose from, but what does it all mean?
There are many classifications of cat food according to their:
- nutritional adequacy (complete vs complementary)
- life stage (kittens, adult, senior/geriatric)
- sensitivities and lifestyle (hairball prevention, neutered, indoor, sensitive skin, etc.)
- price (economic, premium, super premium).
Complete foods give your cat all the nutrients it needs (with the exception of water) and are designed to be the main part of your cat’s diet. Complementary foods are typically treats and are nutritionally incomplete – they should form no more than 10% of your cat’s diet.
Life stage diets are nutritionally balanced for your cat’s age and lifestyle. For example, growing kittens require more protein and calories, neutered/indoor cats require fewer calories and in senior cat diets, phosphorus levels are reduced to help support ageing kidneys. On top of this, some diets are also adapted for specific requirements, for example, fibres such as psyllium can be added to help prevent hairball formation, and diets can be enhanced with fatty acids to help with skin and coat condition. You know how old your cat is and if they have any specific requirements, but should you feed wet or dry food (or a combination of the two)? Let’s look at the facts.
Wet vs dry
Cat food can be classified according to its water content:
- dry food (<14%),
- wet food (>60%), and
- semi-moist (14–59%). This latter category is mostly restricted to treats.
Wet food is cooked at high temperatures for sterilisation, which results in longer shelf life than dry diets before opening, but once opened, is more perishable. There are several textures available in wet food, such as mousse, loaf, chunks in gravy or in jelly.Dry food is mostly extruded but can also be baked. Wet food is more expensive than dry on a per calorie basis.
Benefits of wet food
Cats have evolved from arid geographical locations and their response to low moisture foods is to concentrate their urine rather than drink more water. Typical prey of the cat has a moisture content of >60% and it has been suggested that feeding wet food would be a more appropriate way to provide water to cats rather than relying on drinking water.
Dehydration in cats has been proposed as a risk factor for several diseases, including kidney disease. However, it is not clear if feeding dry food results in inadequate or worse hydration compared to feeding wet. There are several studies that assess the effect of feeding dry vs wet foods in the water status of cats, and the results are conflicting.
Wet foods are particularly useful for:
- Urinary health – Wet foods are useful to promote more urine that is more diluted, which is useful for prevention of urinary tract problems – the hypothesis is that wet food will promote a more dilute urine that could result in a lower concentration of inflammatory components in the bladder.
- Weight management – Water does not provide calories, therefore, wet food always has a lower energy density (calories) than dry food. Typical dry diets provide more than 3–4 kcal/g (some diets even higher), whereas wet food provides 0.8–1.5 kcal/g, with some weight loss diets providing even less. For this reason, wet food is bulkier and can help with weight loss or weight prevention plans.
- Constipation – Dehydration is a risk factor for constipation and feeding wet food can be beneficial in these cases, and it is a common recommendation to feed canned food to cats suffering from this problem.
Benefits of dry food
The main benefit of dry food is its ease, convenience and cost. Millions of cats over the world are fed dry food (either exclusively or in combination) and can live long healthy lives. Dry food allows for free- feeding and the food can be left out for prolonged periods of time. Some cats prefer grazing their food over the day rather than at specific mealtimes, which is the main feeding method when wet food is used.
Dry food is easier to use with food dispenser toys, as a means of environmental enrichment and to provide mental stimulation.
There are some dry diets that can have beneficial dental effects either reducing tartar formation or slowing down plaque accumulation, the latter achieved mainly by mechanical scraping of the tooth. However, not all dry diets will have adequate kibble texture to address plaque and, even if they do, they might not act on all tooth surfaces. There is a dearth of conclusive data supporting the superiority of dry food over wet on oral health. In any case, the gold standard to promote adequate dental health is tooth brushing. If you want to use a diet that slows down plaque accumulation you should use products assessed as effective by the Veterinary Oral Health Council seal (www.vohc.org).
Dry food has a higher energy density than wet.
This can be a problem in cats that cannot self- regulate their energy intake, and obesity/overweight prevalence in cats is high enough to suggest that many cats are not able to do so. However, in cats that are thin and/or have a picky appetite, which happens in some healthy cats but is also associated with the disease, dry food will provide energy
and nutrients in a concentrated, small volume, maximising the nutritional supply.
My cat only eats dry food – how can I make sure she’s getting enough water?
In cats fed dry (or mostly dry) food, it is important to promote water intake, especially to prevent urinary problems. A constant supply of fresh clean water should always be available. Other factors that can influence water intake include:
- Location of water bowls: keep the water station separate from both food and litterboxes. Choose a quiet place where your cat will not be disturbed while it drinks.
- Choice of water bowl: cats seem to prefer ceramic or steel, since plastic can give water an after taste. Use a wide, flat bowl, since some cats prefer their whiskers do not touch the container.
- Multiple drinking stations: multiple stations can help promote water intake and are indicated in multi-cat households to ensure this resource is not restricted due to conflict.
- Water fountains: some cats prefer running water, so the use of water fountains is a good alternative in these cases. These should be cleaned often, and the filters changed as recommended by the manufacturer.
- Add water to the dry food: to achieve similar moisture to wet food, the ratio is 2–3 cups of water to 1 cup of dry food.
Flavoured water: chicken broth (without garlic or onion) or tuna ‘water’ can be added to the cat’s drinking water to encourage fluid uptake.
Both dry and wet food have pros and cons. Wet food is more expensive and less easy to use but can be beneficial in cats prone to lower urinary tract disease, constipation and that are overweight. Dry food can be a very efficient way to provide calories in thin cats with food volume limitations and allows for the use of food puzzles and food toy dispensers. In order to decide which is best, a complete nutritional evaluation, including diet history and body condition score, should be carried by your vet – this is often carried out during routine check-ups (eg. at time of vaccination).