
Beacause all dogs are different.
Your youngsters are they the sor twho keep weight on, or seem to be skinny all the time even when eating enough? If the former get them on the Adult/summer diet. If the latter keep them on the Spring one.
I have been using the Summer on my lot with 100g of raw tripe on tope. Am still undecided whether to stick with it or get them back on the Arden Grange Adult (with no additives) need to see how their coats are when they ahve all finished their moult, and to see if the old girl holds condition on it!