DOGS bred on intensive puppy farms grow up to be more aggressive, fearful and anxious than pets from reputable breeders, a North-East study has found.

Animal behaviour experts conducted the first UK study of how the first few weeks of a dog's life in a puppy farm can have a serious effect on its temperament as an adult.

The Newcastle University team assessed pugs, Chihuahuas and Jack Russells from reputable breeders and from puppy farms.

The puppies' backgrounds were assessed by asking owners questions such as if they saw the mother, if health documents were available and the age at which they got the puppy.

They were then asked to assess their adult dog using a test called the Canine Behaviour and Research Questionnaire. This included whether their dog was aggressive; afraid of new things or loud noises and whether it suffered separation-related problems plus obedience.

Dr Catherine Douglas, lecturer in animal science and research supervisor said puppy farms were usually businesses that produced a lot of dogs for sale, but the study considered smaller breeders with poor welfare standards.

"We found that across all behaviour categories, including trainability, dogs from less responsible breeders had significantly less favourable behaviour and temperament scores than puppies from responsible breeders."

That was likely to be down to the poor environment both before and after birth.

"Early separation from the mother has been found to be detrimental and the direct effect on the puppies of their early experiences in these less-than-ideal environments is also likely to be a factor."

The research will be presented at Universities Federation for Animal Welfare's Recent Advances in Animal Welfare Science in York next month.