Research suggests that owners who overfeed treats to their dogs risk their pets becoming overweight
Many treats available in supermarkets exceed dogs' daily energy allowance guides and fail to properly specify ingredients, experts say.
Owners who overfeed treats to their dogs risk their pets becoming overweight and suffering from illnesses like diabetes, the study showed.
It revealed many biscuits, chewable and dental sticks contained well above the recommended ten per cent of a dog's daily energy needs.
Companies which make the treats have now been urged to produce clearer packaging which prevents owners overfeeding their pets.
Lead author Giada Morelli, a PhD researcher at the University of Padua in Italy, analysed 32 popular dog treats sold in Britain and other countries, with brands including Pedigree and Purina.
She said: "First of all we wanted to study the labels, because they are very vague about the composition of the ingredients.
"It's difficult to understand the actual ingredients.
"In more than half of products sugar was contained and sometimes it was in a position which showed it was contained in a great amount."
She explained guidelines means ingredients must be listed in order of quantity and sugar was prominent in many.
The study, published in the journal Vet Record, then looked at levels of minerals, starch, simple sugars like glucose, fructose and sucrose, and the amino acid hydroxyproline, a component of collagen.
It showed three quarters (76 per cent) of treats contained between four to nine ingredients but they were not precisely described on the label.
This included biscuits and dental sticks listing 'cereals' as the first ingredient, while tenders, meat strips, rawhides and chewable sticks had 'meat and animal derivatives' listed first.
Many treats available in supermarkets exceed dogs' daily allowance, experts say
Almost half of the products mentioned 'sugars' on the label's ingredient list and all contained varying amounts of minerals.
Miss Morelli said: "European regulations allow producers to make the labels like that.
"They are not doing anything wrong unfortunately, but for vets and owners more information would be very helpful, because it would prevent owners from making their dogs obese and overweight."
The most calorie-dense treats were biscuits, whereas the least dense were dental sticks.
When caloric density was expressed as kcal/treat, rawhides were the most energy-dense products, followed by chewable sticks and dental sticks.
Human foods that dogs can and cannot eat
Meanwhile when manufacturers' feeding instructions of the number of treats per day were followed, only dental sticks remained below the MER for every dog size.
Biscuits accounted for 16 per cent of MER for dogs of any size, rawhides exceeded 25 per cent small-sized dogs and 18 per cent for medium-sized dogs.
Chewable sticks surpassed 10 per cent for all size dogs, reaching 16.9 per cent MER in small-sized dogs.
Miss Morelli said: "It was very surprising because it appeared that most of the treats given in the recommended quantities go far beyond this ten per cent, especially for dogs of a smaller size."
Pet owners explain why they abandoned their Christmas dogs
The researchers also urged caution when considering treats for dogs with specific ingredient sensitivities or in dogs with conditions such as heart failure and kidney disease due to their potential high mineral content.
They also said future studies should sample a greater number of products to provide more precise data.