Effect of Diet on Behaviour

Overview

Several aspects of feeding can have an effect on behaviour:

• Dietary composition: Nutrient composition, palatability, method of preservation (raw, dried, moist).
• Timing of access: Meal-feeding, on demand feeding, ad-lib feeding.
• Type of access: Bowl, simulated foraging (activity feeding)

All of these should be taken into account when designing a feeding regime for domestic cats and dogs.

Feeding Pattern

It is particularly important to ensure appropriate timing and type of access that satisfies species-specific time and energy allocation; cats and dogs would normally spent large parts of the day on foraging behaviour. A lack of opportunity to do this can lead to welfare and behaviour problems.

• Feral and wild cats allocate 6-8 hours every day on foraging (searching for prey and hunting). They eat 10-20 small meals each day, and return to hunting dirtily after consuming a meal. Frequency of hunting is not affected by satiation; cats will hunt whether hungry or not, but latency to kill-bite delivery is reduced when cats are hungry.
• Feral dogs and wolves hunt more sporadically, as opportunities arise, but also spend several hours each day foraging (often searching for carrion and non-meat food).

For cats, the most ethologically appropriate presentation of food is ad-lib using simulated foraging (activity feeders). A cat given 2 meals per day is effectively having its feeding frequency reduced to the equivalent of a person being fed every 2nd or 3rd day.

For dogs, some opportunity for simulated foraging should also be provided, in the form of activity feeders.

Dietary Components Which Affect Behaviour

Certain dietary components have an effect on an animals behaviour, leading to the possibility that behaviour may be manipulated using a modified diet.

Protein, Tryptophan and Carbohydrate

There are several theories about how protein, tryptophan and carbohydrates may affect behaviour. These include the following:

• It is thought that very high protein diets could possibly result in a reduction in in the brain of levels of serotonin. Serotonin is formed from tryptophan and if amino acid levels are high competition for the carrier with tryptophan is increased. This means that lower quantities of tryptophan are able to cross the blood-brain barrier. Aggression has been linked to low serotonin levels in some cases and in a small percentage of dogs, diets with lower protein levels decreased territorial aggression, although other types of aggression seemed to be uninfluenced. In both dogs and cats fed a L-tryptophan supplement, lower levels of behaviours related to stress and fewer signs of anxiety were seen
• A higher carbohydrate diet is thought to be linked to tryptophan levels in the brain increasing. This as previously mentioned can be calming, which may in turn decrease the potential for aggressive behaviour. It must be noted however, that if the levels of carbohydrates are increased by reducing protein levels, the reduced protein may be the factor which causes this effect.

Pyridoxine

Pyridoxine or vitamin B₆ assists in the fabrication of serotonin, which in turn is linked to a reduction in anxiety and aggression.

Fatty Acids

For cats, cis-linoleic and arachidonic acid are essential for life.However, other fatty acids, specifically long-chain omega-3; docosahexaenoic acid (DHA), are fundamental for certain aspects of development (both neuronal and retinal) and for neurotransmission. They also help to combat oxidative stress.. Eicosapentaenoic acid (EPA) has an important anti-inflammatory effect. The conversion of alpha-linolenic acid to long-chain EPA and DHA is very inefficacious. These can be added to the diet as a supplement and may be particularly important in gestation, lactation and post-weaning. Further to the already mentioned effects DHA supplementation has been linked to an improved memory, cognitive, psychomotor and immunologic function and better problem-solving skills in puppies, this is also likely to be applicable to felines.

Behavioural Problems Related to Diet and Their Diagnosis

If it is thought that diet may be a contributing factor to behavioural problems the theory should be tested by trial and exclusion. The new diet, potentially with lower protein levels should be fed for a 1-2 weeks, taking note of any differences in behaviour and then returning the animal to the initial diet to see if behaviours which ceased or became reduced during the trial period return. Before implementing a trial diet a careful clinical examination should be performed and blood and urine samples should be taken to ensure these are normal. If a homemade diet is going to be used for the trial period, this should consist of the same amount of meat and carbohydrate, one part of each and the same quantity should be fed as of the diet it is replacing. No supplements or treats or other types of food should be fed during the trial. Alternatives to a homemade diet include using prescription diets which are already low in protein, for example a canned renal diet. It is also important to consider the difference between diets which contain additives and preservatives - dry foods, and those which don't - canned foods or homemade diets and whether this is also an influencing factor on behaviour.

Control of Diet Associated Behavioural Problems

It should be noted that a homemade diet is not a balanced diet for long-term use, and although is not likely to cause a problem for the trial period of 1-2 weeks it should not be fed long term. A nutritionist should be consulted if it is decided to continue with a home-produced diet to ensure that it is nutritionally balanced and contains all the necessary components. Prescription renal diets are a nutritionally balanced alternative. With other foods it is important to looks for those which contain a good-quality protein in conservative amounts with a carbohydrate source which is easily digestible. Canned foods generally have fewer, or no preservatives and dry foods generally have most preservatives. If behaviour deteriorates when a commercial formulation is reintroduced other problems apart from solely the protein content should be considered.

Prevention of Diet Associated Behavioural Problems

Complete prevention of diet related behavioural problems is not normally possible as they are difficult to predict. On average, most pets consume a diet which contains far higher levels of protein than are necessary to satisfy amino-acid needs. Some anecdotal evidence points to some breeds being more sensitive to certain dietary components. For example the Cavalier King Charles spaniel may be more sensitive to preservatives and Golden Retrievers to exorphines, as well as others which may react to different meat proteins affecting serotonin. However, further research is necessary to investigate these suggestions.

References

• Landsberg, G.M., Hunthausen, W.L., Ackermann, L.J. 2013. Behaviour Problems of the Dog and Cat. Third Edition. Saunders Elsevier.