Wet or Dry Pet Food - Is one better than the other?

Depends who you talk to! There are passionate arguements for both sides (and that's ignoring those pet owners who prefer feeding Raw food) but the plain facts are that each can be formulated to provide a complete diet for dogs or cats.

The important criteria to consider in choosing the type of product are the place you shop, how much money you would like to spend and the level of convenience, palatability and digestibility desired.

The difference in moisture content among the various types of pet food impacts the nutrient density of the products or the amount of nutrients per pound of food. As the water content of the diet increases, the amount of protein, fat and other essential nutrients decreases. That means the animal must consume a larger portion of the high moisture products to receive the nutrition they need, but it also makes comparisons between the different types of food difficult.

Canned or pouch foods offer highest palatability and the highest cost per serving when compared to the dry and soft-moist products. However, they are less convenient to use, as once opened any unused food needs to be stored in the refrigerator.

The main advantage of dry foods is convenience, as wastage is minimal, cost is low in comparison to canned or pouch foods, and it is claimed that the grinding action of eating dry food helps to keep teeth clean (again disputed by some.)

Carbohydrates constitute between 30 percent and 40 percent of dry cat food. Some have been concerned that this unnatural diet is harmful to cats and leads to increased incidence of diabetes. Wet cat food, on the other hand, is high in protein and more similar to a natural carnivore diet.

Recent research from a University of Missouri-Columbia veterinarian, Robert Backus, assistant professor and director of the Nestle Purina Endowed Small Animal Nutrition Program at MU compared a colony of cats in California raised on dry food with a colony of cats in New Zealand raised on canned food. After comparing glucose-tolerance tests, which measures blood samples and indicates how fast glucose is being cleared from the blood after eating, researchers found no significant difference between a dry food diet and a wet food diet.

The causes of diabetes mellitus in cats remain unknown although there has been a strong debate about whether a dry food diet puts cats at greater risk for diabetes. This study suggested that weight gain, rather than the type of diet, is more important when trying to prevent diabetes in cats.

Canned or Pouch Food

Obviously it is difficult to give anything other than a guide to the production process, as methods and machinery vary. Also, some products are presented in a 'loaf' form and others as chunks in 'gravy'. But a typical processing scenario for canned or pouch food would be:

• Meat products are thawed, pre-chopped and stored in silos containing no more than half an hour's production.

• Then as soon as they enter the production chain, the ingredients required for the recipe are dosed and ground.

• An endless screw collects and weighs the components.

• The resulting mass is then sent to the thin pre-cutters and mixers. At this stage, minerals, cereals and vitamins as required are added to ensure a balanced diet for the cat or the dog.

• The product is then packed in cans, metal trays or sterilised pouches.

  
  

Bear in mind that those 'meaty chunks' in your pet's food may not be all that they seem! Much of this material is manufactured from ground up meat which is extruded to give the impression of meat fibres. Soya protein isolates can help to give these chunks more body by holding onto water.

Typical canned food process

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Dry Food

Again it is difficult to give anything other than a guide to the production process, as methods and machinery vary, but the simplified method below is common:

• The ingredients required for a given recipe are first weighed, ground and mixed.

• Production is achieved through a special technology : cooking-extrusion. This involves exposing the mixture of animal and vegetable materials to the combined effects of pressure and temperature for a short period, making the product highly digestible as it ensures the complete cooking of the starch.

• Dry foods may then be sprayed with fat in order to complete their composition and increase palatability.

Because dry foods are exposed to the air, and not sterilised in a can or pouch, they need to have anti-oxidants and preservatives added to ensure that the product does not go rancid. These can be chemical (declared as 'EU approved antioxidants' and could be BHA, BHT or Ethoxiquin for instance) or natural (Vitamin E or C, and an extract of Rosemary Oil are common), though natural antioxidants are generally less stable and more prone to degredation if subjected to high temperatures. They are also more expensive to use!

Typical dry food process

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Complete or Complementary Foods - What's the difference?

Quoting from FEDIAF

'Complete pet food means pet food which, by reason of its composition, is sufficient for a daily ration (EU Directive 79/373/EC adapted). When a complete pet food is fed for an extended period (i.e. covering the whole period of the life stage) as the only source of nutrients, it will provide all the nutritional needs of the particular animals of the given species and physiological state for which it is intended.

If a manufacturer labels a product as a complete pet food without specification of a determined life stage, it is assumed to be complete for all life stages, and should be formulated according to the levels recommended for growth and reproduction.

If the product is designed for a specific life stage, then the label must clearly state this. For example "Bloggo" is a complete pet food for breeding cats, or "Bloggo" is a complete pet food for growing puppies.'

Complementary pet food is legally defined as pet food which has a high content of certain substances but which, by reason of its composition, is sufficient for a daily ration only if used in combination with other pet foods (EU Directive 79/373/EC). Complementary pet food covers a wide range of products including:

A. Products, such as a meat and biscuit combination, where each component contributes significantly to the energy content of the mixture.

B. Products, which contain certain nutrients but are not designed to contribute significantly to the energy content of the mixture.

Treats and snacks are normally given to strengthen the human animal bond and as rewards during training.

• Tablets and conditioners often used to balance the diet when home made foods are given.

• Products, such as dog chews, that are not intended to contribute to the nutritional content of the daily ration, but are given to occupy the animal and can be eaten.

Check this particularly with some 'natural foods' which have not had proprietory vitamins and minerals added, relying instead on natural sources which may be unstable or variable. Some of these foods are not labelled as 'Complete' and this ought to be taken into consideration when feeding.

See also Pet Food Brands

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The complication of moisture content!

It can be difficult to compare foods because of the moisture content (i.e. dry diets average 10% water, but moist foods can have 80% water content) and the fact that labels list levels as an 'as fed' rather than 'dry matter' basis which would enable customers to directly compare the different foods.

If you want to convert 'as fed' to 'dry matter' a simple conversion is necessary. Are you ready?

• If a dry food is 10% moisture then it is 90% dry matter (Still with me?)

• If the declared protein content is 20%, then the maths is 20 x (100/90) which gives us the protein on a dry matter basis of 22%.

• Compare this to a canned or pouch food which declares a protein content of 5%. This food contains 80% moisture (or only 20% dry matter) so the maths is 5 x (100/20) or 25% protein on a dry matter basis.

You'll find this with the majority of canned foods, the actual protein content is higher than that of dry complete foods when compared on a dry matter basis. You can do the same for fat, fiber, etc.

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