The information on this page is courtesy of Lorraine Effa.
You have seen puppies for sale called Designer Breeds. They are usually represented as a truncation of the purebreds that have made the new ‘breed’. A Yorkie/Maltese is often called a Yorktese; a Schnauzer/Poodle will often be called a Schnoodle. These are not new breeds. These are mixed breeds. Mixes don’t always reflect the other breeds behind them, i.e., the Yorktese is not just Yorkie and Maltese; there are other breeds in the mix somewhere. The breeder you bought your puppy from cannot possibly know who or what breeds went into the grandparents, great grandparents and so on back in the family tree of that new puppy you bought.
Mixed breeds do not breed true. A Maltipoo, a mix of Maltese and Poodle, can be anywhere from very small (5 lb) to quite large (30lb.). It depends on what is behind both parents. There may be Maltese and toy Poodle but the toy Poodle might have been a small miniature poodle that goes back to larger miniature Poodles or even standard Poodles. Again, what other breeds may also be in the background of either parent?
You likely will not get the same Maltipoo that your friend or neighbour has when you want to get a Maltipoo. It can look like either parent, everything in between or neither parent. It could reflect something further back in its parentage.
Designer breeds do not have hybrid vigour. Any of the genetic problems that can occur in any of the purebreds comprising that mix can occur in the mixed breed. Genes that carry genetic problems don’t care if they have the right combination to express the disease in a purebred or a mixed breed.
An example is liver shunt, a genetic disease that can occur in Yorkies and Maltese. The disease will also potentially show up in the Yorkie Maltese mix. A Golden Doodle can still have hip dysplasia or any other genetic problems in the Golden Retriever or Poodle. A Labradoodle and Golden Doodle is a mix, not a breed. They are not always hypoallergenic. Too much Labrador or too much Golden Retriever will produce a dog that grows hair and sheds at the same time. Talk to a reputable Standard Poodle breeder and they will tell you that a Poodle also does its share of shedding.
Grooming coated mixed breeds can be more challenging than grooming a purebred because the blends of coat on a mix can mat so much more. Again, it can shed and grow coat at the same time.
Many small breed mixed breeds have severe under or overshot bites with the result that there could be additional dental problems as the puppy matures and ages.
If the preference of the buyer is a mixed breed, that certainly is up to the buyer but he should be aware of exactly what it is that he is buying.