Processed Pet Foods:
As vets we should focus on what and animal needs rather than what is cheap to produce or surplus to human requirements. It is easy for pet food processor to adequately satisfy the needs of pets in terms of calories, and major nutrients but not micro-nutrients such as enzymes and antioxidants. The cooking process involved when preparing Dried, tinned or semi moist foods destroy many of the major nutrients such as taurine we know animals need and so the processor will add them back. It is the minor plant chemicals I am concerned they do not replace.
Wild Diet: what do Dogs and Cats eat naturally?
Both dogs and cats eat the WHOLE or majority of the carcass they kill or scavenge. This includes bone, hair and gut content. The gut contains vegetable material and enzymes. Dogs also eat fruit, berries and of course droppings or faeces of other animals especially herbivores.
The wild diet is raw, fresh, varied and simple in most cases; although a part decomposed bone seems to attract many canines!
There are of course a wide variety of foods on the market in the developed world for pets. It is a huge industry backed by massive marketing budgets. If you look in any veterinary publication half the adverts seem to be for Pet Diets. They sponsor all sorts of conferences and give free this and that to vets. They are backed by large research departments and to be fair produce a hygienic, consistent product that meets the vast majority of an animals needs.
But no matter how conscientious some loss of nutritional content is inevitable.
There are 4 main methods of processing Pet foods:
1. Dry foods or Kibble
2. Semi moist
3. Tinned or Pouches
4. Freeze dried or Frozen
Ingredients are chopped mixed and then cooked using added water and steam injections. The mixture is then forced through an extruder at high temperature and pressure to finish the cooking process and then shaped. Meat products are mixed with grains such as wheat, maize or rice to add texture, calories and reduce cost.
The main problem as you can see is the high temperatures required often as much as 250° C as well as a pressure of 60 PSI. This denatures proteins, fatty acids, and many vitamins never mind the micro nutrients we mentioned earlier. The best (and majority) of reputable manufactures will add the major ones back in processed form, but it cannot match the original raw ingredients and many micro-nutrients are not even considered.
The other main problem is the significant grain content which is not part of a natural diet, is not appetising to many animals and leads to the finished product having to be sprayed with 'digests' to enhance flavour.
In the cases of cats the low water content is thought to be part of the cause of Urinary Tract problems, cystitis, FULTD as although they drink more the total water content of a cat on a dried diet will be less than one fed on wet foods.
Semi Moist Foods
Not often found in the UK This is mixed in a simi liar way to dried foods but extruded at lower temperatures, with less denaturing of nutrients. However it is more prone to spoilage problems in storage so inhibitors of spoilage bacteria and moulds are added such as acids and sugars.
Tinned and Pouched Foods
These products are heated to 125° or so in or to preserve the product after cooking. Meats vegetables are used but many pet foods can contain large percentages even the majority of dog foods content by weight.
Freeze Dried Food
Freeze drying is were food is flash frozen to -50° C then under reduced pressure gradually heated. Water content is then sublimated, causing evaporation without thawing. 98% of water is removed if performed correctly so that it has excellent keeping qualities.If packaged correctly to keep dry the food can be kept for long periods without additives.
The advantages of Freeze dried Foods are :
* Flavour is unaffected so enhancers are not required
* Micro and Macro nutrients are relatively unaffected as cell structure is maintained
* A wider choice of ingredients can be used
* Light weight so can reasonably economically be posted to you!
* Can be stored at room temperature
The Disadvantages are:
* Cost is greater than other more mass produced methods of production
* Less available product
For this reasons it may be as well to feed part of your pets diet as freeze dried foods such as Thrive, and/or to use the freeze dried supplements to boost poorer feeding regimes. A little of these micro nutrients can go a long way.
Of course fresh or frozen raw foods of your own can be part of this regime.
There are a number of products on our site which will help in reversing this problem :
* Thrive Cat Foods and Treats
* Pet Plus
* Udos Choice Pet Essentials
* Missing Link
All of these use freeze drying to preserve the nutrients
Saunders Wendy J. BA. DVM MRCVS, We are What we Eat (Pet Project London)
www.freeze-dry.com/tech.tech.html: Intro to freeze drying
www.mountainhouse.com/fdp.html: What is freeze drying?
Lonsdale, T. (1995). Periodontal disease and leucopenia. Journal of Small Animal Practice, 36, p542-546.
Pottenger, F.M. Jnr. (1995). Pottenger's Cats. Price-Pottenger Nutrition Foundation, San Diego, California.