
I must say that ASDA probably son't know much about dog food, but the own brandsa arre usually produced by a company that makes food of their own, and market it under a brand name, or make lots of own brands. The formula should certainly7 be adequate, as it does have to reach a standard laid down by whoever licenses such products.
Also the most expensive does not mean the highest nutritionally speaking ingredients. Sojme very expensive foods (usually imported or vet endorsed) are still cereal based.
From a biological point of view dogs are designed to assimilate animal protein best, and the vegetable and cereal are indigestible unless highly proicessed (which takes away a lot of their goodness, which has to be replaced with synthetic vitamins and minerals).
The best complete dry foods are those where the first ingredient is meat. Actually the most digestible protein source is egg, then followed by white meat, red meat etc.
The best food s are like3ly to be dearer than the cheap ones, but the highest price does not equal the best, and some dogs do better on one food, and some on another. Try to avoid those with artificial preservatives, and go go for those preserved with viatamin c and e, or mixed tocopherols!