Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

A reader sent in a letter asking if there was a problem because her two dogs, both Labradors and true brother and sister, behaved differently around food. The female was less food oriented, would eat slowly and was on the thin side, although healthy, whereas the boy was a voracious eater in good condition - gaining weight and also healthy.

The first point I want to make here is that all animals should be seen as individuals; just like people. Even though they are related they will not carry identical genes and will have different metabolisms.
They are siblings, not identical twins. It is inherent in their behaviour how they approach food – greedily in the case of the male and slowly in the case of the female. These factors can be modified by the environment, such as competition for food with other dogs.

Breed definitely plays a role in risk of weight gain and often in eating habits. Larger breeds generally eat more greedily than the smaller toy breeds. Labradors are predisposed to putting on weight whereas dogs such as pointers and weimaraners are less so.

There is no info regarding the sterilisation status of these two Labradors. The caloric requirement of sterilised (spayed or castrated) dogs drops by up to 30%. The sex hormones – testosterone in the male and oestrogen in the female – have an effect on the basal metabolic rate and these drop after sterilisation, decreasing food requirements. All sterilised animals are prone to weight gain, but this is an entirely manageable condition.

Proper portion control, measuring out the required food twice a day and restriction of snacking is generally all that is required in addition to moderate exercise. In some animals a ‘light’ diet may be required to maintain goal weight. In animals where weight gain has already occurred, a proper prescription diet is generally the best way to get the kilos off before maintaining on a light diet.

However, what is considered thin and what is considered normal? Because dogs are of so many sizes and breeds and even within breeds there is a variation in size, the term ‘body condition scoring’ (BCS) is often used instead of ‘weight’. A large-boned male German shepherd may be normal at 45 kg, but a smaller female may be obese at that weight. I prefer the 1-5 scoring system where 1 is emaciated, 2 is thin, 3 is normal, 4 is overweight and 5 is obese.

Dogs should have a waist as seen from the top and from the side. You should be able to easily feel their ribs, but not see them. This places them in BCS 3. Most owners, myself included, are inclined to want their pets a little overweight. In our reader’s situation I would not be surprised if the male is not slightly overweight and the female at the perfect condition score.

In the long run excess weight will negatively affect your pet, as the joints have to carry more weight, especially in large breed dogs which often have arthritis. In fact, when weight is normalised the clinical signs of arthritis will often disappear. Especially in smaller dogs the lungs and heart really take strain with all that extra body fat.