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Seeking to improve cognitive function in the senior dog

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01 March 2010, at 12:00am

Veterinary Practice reports on a recent international symposium where advances in managing ageing in the canine brain were discussed.

NEARLY 100 veterinary surgeons, animal behaviourists, neurologists and specialist journalists from 17 countries attended a symposium hosted by Nestlé Purina in Vevey, Switzerland, last month to hear about canine cognitive function. 

Eight speakers addressed aspects of Advances in managing canine brain ageing, covering topics including geriatric medicine, brain physiology, diet and canine cognitive dysfunction (CCD). 

The audience also heard about a new nutritional intervention using a specific fat source – medium chain triglycerides (MCTs) – which has been proven to improve significantly cognitive function in the senior dog, resulting in increased attention, memory and learning capacity. 

The meeting was chaired by Professor Adám Miklósi, a Hungarian behaviourist renowned for his research with wolves, and addressed by, among others, British veterinary surgeon Sarah Heath, president of the European Society for Veterinary Clinical Ethology, who spoke on CCD and highlighted the need for practitioners to incorporate a programme for the early detection of canine dementia into their geriatric clinics.

Dr Jill Cline, senior research scientist at Nestlé Purina in Saint Louis, USA, reported on efficacy studies which had shown that when senior dogs were fed with a natural source of MCTs that provide metabolites readily used by the ageing brain, they demonstrated improved attention, memory, learning capacity and an ability to adapt to novel situations. 

Claire Guest, CEO of the UK charity, Cancer & Biodetection Dogs, based in Aylesbury, Bucks., presented a case study showing that feeding a diet with MCTs had enabled a cancer detection dog to extend its working life.

A paper soon to be published in the British Journal of Nutrition indicates that incorporating MCTs in the diet of a senior is an effective way to help delay the cognitive effects of ageing and improve the quality of life for both the dog and its owner. Although further studies are needed to confirm this, it is also possible, Dr Cline said, that feeding MCTs will have positive effects on dogs with mild to moderate CCD. 

Dr Lizzie Parker, Nestlé Purina’s head of the veterinary channel, Europe, said that, similar to trends seen within the human population, and thanks to improvements in veterinary medicine, nutrition and preventive health- care, the European canine population is becoming older with up to an estimated 50% of dogs now regarded as “senior”.

As a result, there is an increasing diagnosis of age- related diseases and also a higher incidence of behavioural problems related to ageing.

Dr Xavier Manteca Vilanova, from the Barcelona veterinary school, said that from the perspective of owners, more than 40% of dogs and cats suffered from behavioural problems, adding: “Behavioural medicine should be seen as a fundamental part of our professional activity.”

He said that the relationship between nutrition and behaviour was two-fold: nutritional factors had a significant effect on behaviour; and the nutritional status and health of animals could be affected by their behaviour.

With increasing age, some dogs develop a neurogenerative disease that is characterised by a gradual decline in cognitive function (CCD). Interest in this has grown rapidly as it has been realised that it has many similarities with Alzheimer’s disease in humans. Clinically, CCD may cause disorientation, altered interactions with people or other animals, alterations in the sleep- wake cycle, changes in activity level and house- soiling. 

Dietary treatment has been based on the use of antioxidants and mitochondrial co- factors that may decrease the deleterious effects of free radicals. There is ample evidence, he continued, suggesting that free radicals play an important role in ageing; the brain is particularly susceptible to the effects of free radicals, as it has a high rate of oxidative metabolism, a high content of lipids and a limited ability for regeneration.

There are several studies showing that an antioxidant-enriched diet improves cognitive performance in senior dogs and recent work has shown that long-term supplementation with medium chain triglycerides can improve cognitive function in aged dogs.

The underlying mechanism appears to be an increase in the circulating levels of ketones which provide the brain with an alternative energy source.

Pressures

Dr Gérard Muller, a French veterinary surgeon who specialises in pet behaviour, said that ageing animals were subject to two types of pressure: that caused by their physical ailments and that caused by their lack of motivation.

“Motivation is a reaction by the body to restore its equilibrium,” he said. “The degree of motivation depends on how strong the imbalance is, whilst the search for a solution is informed by past experience. 

“Thus, when an animal is hungry, its body is no longer in a state of equilibrium, and foraging mechanisms will be triggered until the sensation of imbalance disappears, i.e. until its hunger has been sated. Likewise, when an animal feels insecure, it gears its behaviour toward seeking shelter and restoring its sense of safety. 

“Ageing individuals gradually learn to resign themselves to minor imbalances. As the ageing process progresses, the imbalances they tolerate become more and more severe. Powerless to react to ever more serious physical ailments, they grow increasingly resigned. This is one of the mechanisms of pathological inhibition classically observed in depression. It is thus easy to understand how physical ailments can exacerbate ageing.”

Stating that cognitive disorders could often lead owners to react in less than sympathetic ways, he said that the ageing dog often saw its environment becoming more and more hostile. “Its social relationships deteriorate and it finds fewer and fewer reasons to motivate itself.” 

Cognitive creatures

Dr Karen Overall, from the University of Pennsylvania school of medicine, discussed advances in understanding canine learning, memory and cognition and also the impact of diet on brain metabolism.

Urging caution in labelling behaviours, she said that dogs were not wolves and hadn’t been for a long time. “They are cognitive creatures and by understanding the factors that affect how dogs learn, we can contribute to preventing behavioural problems and provide data-based humane care.”

Dr Overall said dogs could do “observational learning” by watching both humans and dogs. “We don’t actually know much dogs can learn, but recent published work from the emergent field of cognitive studies in non-laboratory canines should give us pause. We now know that dogs can take their cues from dogs or humans about hidden objects and communicate this information to other dogs.

Making deductions

“Dogs appear to have the ability to ‘fast map’ – to make deductions about object class and name without having learned them directly – and to communicate this ability to humans. ‘Fast mapping’ is the first stage of language acquisition in humans. Recent work shows that dogs make the same classes of cognitive errors in learning as do young children.

“For decades we have used dogs to help those who cannot see and those who require help opening doors, turning on lights, picking up objects and getting dressed or out of bed. Dogs scan the post, luggage, planes, cars, and people for explosives and contraband. Dogs jump from helicopters to rescue the drowning and search disaster sites for both the living and the dead.

“All of these tasks are deeply cognitive, and while the dogs learn the required responses that we teach them, they also seem to learn and communicate about what they learn as much as we permit them to do so.

“The key to understanding all learning and cognitive changes – whether they are beneficial or pathological – is to understand how such processes are effected at the molecular level. Once we understand the role that various regions of the brain and learning in those play, it’s a simple step to think of helpful interventions for enhancing learning and, perhaps, cognitive abilities. “Meanwhile,” Dr Overall concluded, “we probably owe all our dogs an apology. They are clearly smarter than we thought and have likely been telling us that for a long time.”

In a second presentation, Dr Overall said that impaired glucose metabolism could contribute to Alzheimer’s disease and other tauopathies. The brain has a high energy need but a low storage capability and glucose insufficiency could be an issue in a number of pathological conditions in which cognition is impaired.

It had been postulated that if we could enhance glucose uptake and improve energy metabolism in neurons we would have neuroprotection. “Diet and supplements may be able to play a huge role in how we prevent and treat neuronal assaults,” she said.

Diagnosing CCD

“Canine dementia is a medical condition but in most cases there is a lack of recognisable clinical symptoms and the signs that lead to accurate diagnosis are almost entirely behavioural,” said Sarah Heath, who runs the Behaviour Referrals Veterinary Practice in Chester.

“It requires prompt and appropriate veterinary attention,” she said. “The most effective way of increasing the detection rate is to include a behavioural questionnaire in routine geriatric clinics.”

Quoting a US study which found that 48% of dogs eight years of age or older showed some signs of CCD (known more commonly in the States as CDS – cognitive dusfunction syndrome), she listed the four main categories of presenting signs as: disorientation, changes in social and environmental interaction, changes in the sleep/wake cycle, and breakdown in house-training.

“As the ageing process takes its toll on a dog’s heart and brain, some changes in behaviour and personality are almost inevitable and it is important to be able to differentiate between cases where the animal is simply slowing down out of necessity and those where the animal is finding it increasingly hard to function at a social level.

“In some cases behavioural changes in old dogs will noticeably resemble the symptoms of Alzheimer’s disease in people. Lack of connection between behaviour and context is a classic sign of dementia and many owners have reported that their dog seems like a stranger in its own home.

“In cases of canine cognitive dysfunction, post mortems have shown similar neuropathological lesions to those seen in people with Alzheimer’s disease and dementia and there is no doubt that this condition is part of mainstream medicine.”

Ms Heath concluded: “Detecting the symptoms of this condition at the earliest opportunity will enable these dogs to receive appropriate veterinary care and maximise the benefits of therapy in terms of increased quality and duration of life.

“Practices can vastly improve their service to geriatrics by incorporating a programme for the early detection of canine dementia into their geriatric clinics.”

  • Purina reports that it will have products containing MCTs available for sale through veterinary practices in the very near future.