A novel formulation for small animal arthritis?

When cats and dogs are in need of long-term/‘chronic’ pain relief we try to give them NSAIDs (non-steroidal anti-inflammatory pain relief). This is because NSAIDs have the most scientific evidence supporting their analgesic (‘pain-relieving’) effect and, unlike morphine, are able to be given orally as ‘take-home’ medications. Carprofen and meloxicam are just some examples of NSAIDs used in dogs and cats.

Veterinarians are scientists and have a responsibility to make evidence-based (i.e. using results from published studies in peer-reviewed journals) decisions on how to treat our patients. This means it is somewhat unethical to use or prescribe medications with very little evidence that they actually work. One such drug is tramadol. Tramadol is often used in cats and dogs where NSAIDs are contraindicated (e.g. kidney disease or gastrointestinal problems), or in combination with NSAIDs for ‘added effect’. It is an opioid agonist, however evidence for its analgesic effect is controversial. It may not actually be relieving pain, but instead just sedating animals so that they are not able to show signs of pain. The SkeptVet does an excellent job of reviewing Tramadol for Pain in Dogs and Cats and at one point suggests “The evidence is strong enough that tramadol should not be relied on as a sole or first-line analgesic.”

If this is the case, then what can we use in those animals where we might not want to give NSAIDs? Pain is a significant animal welfare issue. There is a reason it ranks highly in animal welfare assessment scales and evaluations. We have an ethical responsibility to treat it. The old adage of ‘if they are in pain they aren’t moving and so won’t do any more damage to themselves’ is not acceptable.

A recent publication in BMC Veterinary Research may shed some light on the future of chronic pain relief – by introducing a novel composite formulation [1]. This article is open access (free) online and can be found here. The authors argue that osteoarthritis treatment should “reduce inflammation, minimise pain, and maintain joint function.” They therefore propose the use of palmitoylethanolamide (PEA) in combination with quercetin in models of osteoarthritic pain and inflammation.

PEA is an endogenous (produced normally in the body – therefore has reduced risks of side-effects) fatty acid amide produced by tissues in response to acute inflammatory and painful conditions, but decreased in chronic conditions. There is evidence already for its anti-inflammatory and analgesic effects in some other conditions, but the authors wanted to explore whether it would help with osteoarthritis. PEA is an endocannabinoid (i.e. binds to cannabinoid receptors in the body). The authors combined it with quercetin, a natural antioxidant, as PEA is rapidly oxidised in the body. They compared this combination to the NSAID meloxicam as their ‘benchmark’ drug.

They used two different rat models of inflammatory and osteoarthritic pain: by causing paw oedema; and inducing osteoarthritis. The first step of the experiment involved giving the different treatments being tested ‘pre-emptively’ (i.e. before they did anything to the rats). This way they could see if it actually worked to reduce pain and inflammation before moving onto the second step. In this second step they used it ‘therapeutically’ three times a week to see if it would work clinically on osteoarthritis.

The results show that their ‘PEA-Q’ combination decreased inflammatory and hyperalgesic (increased sensitivity to pain) responses by:

  • Reducing oedema in the rats paw
  • Decreasing an inflammatory score used in histology (microscopic structure of tissues)
  • Reduced activity of a marker of inflammatory cell infiltration
  • Decreased thermal/heat pain sensitivity

These effects were better using their novel drug combination – compared with using the NSAID.

In their osteoarthritis model they found the combination:

  • Reduced mechanical allodynia (triggering of a pain response from stimuli which do not normally provoke pain)
  • Improved locomotor function
  • Protected the cartilage from damage

These effects were equal to or better than the NSAID treatment.

These are exciting results for anyone trying to manage long-term pain in dogs and cats as the authors have now moved to translate these findings to canine and feline osteoarthritic pain. Watch this space!

{The author would like to acknowledge Adrienne French for feedback on the draft of this post.}

References

  1. Britti, D., et al., A novel composite formulation of palmitoylethanolamide and quercetin decreases inflammation and relieves pain in inflammatory and osteoarthritic pain models. BMC Vet Res, 2017. 13(1): p. 229.

 

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Poisonous to cats

Do you know what you can and cannot have around your pet cats?

This post will explore some common things that you should avoid having around your cats. I won’t try to list all the potential poisons out there, but I will deal with as many as I can, while also explaining WHY they are so bad for our pet cats.

Lilies – inside or around the house

My mum adores lilies and we always had them in the house growing up. They are stunning plants, but do you know how dangerous they are to your cat? ‘Day lilies’, in particular, are highly toxic to cats. They are ‘nephrotoxic’, meaning they can cause kidney failure! The whole plant is toxic: petals, stamen, leaves, and pollen. If your cat eats even a small amount of these they can quickly show signs such as: salivation, vomiting, loss of appetite, and depression. But if they are seen quickly by a veterinarian, fluid therapy directly into their veins can help.

What can you do? I would recommend not keeping lilies in or around (including outside) the house if you have cats. If you do have lilies, keep them away from your cats as much as possible! This includes the pollen. If the pollen drops onto the floor or other surfaces, your cat may pick it up on their coat and then ingest the toxic pollen when they groom themselves.

IMG_5840
Cats spend a lot of time grooming themselves
A hazard in the garage; antifreeze

Another common toxin that can affect a cat’s kidneys is antifreeze. Antifreeze and coolants that contain ‘ethylene glycol’ can be fatal in even the smallest amount. Cats can be exposed by drinking the toxin (it is sweet-tasting!) or by indirectly licking it from their feet if they walk through it. Dangerous areas are in and around the garage or where cars may be parked and leak antifreeze-containing coolant. The toxin causes kidney failure very quickly. Cats may be seen vomiting or acting drunk, but usually it is picked up in the later stages when they are already having urination issues. If it is caught early enough your veterinarian can treat with medical ethanol intravenously, but most times it is too late. This poisoning has a very poor prognosis.

Please keep car products away from your cats! When doing anything with your car at home hose down the area afterwards. Or better yet, do ‘car things’ somewhere your cat cannot access. If you notice your car leaking ANYTHING, get it seen to ASAP.

Human medications are not for cats

Cats lack some of the enzymes that we have to break down and use our ‘human’ medications. Non-steroidal anti-inflammatory drugs such as paracetamol and ibuprofen are examples of these. If a cat is given these medications, their liver cannot break them down in the same way that ours can. Toxic products form instead and have disastrous effects on cats’ kidneys. Please keep these products away from cats and do not be tempted to give them when you think they are in pain. See a vet instead who will prescribe a medication designed with cats in mind.

Flea & tick products designed for dogs

Cats are also sensitive to certain products used to treat fleas and ticks in dogs. If a product is recommended for dog use ONLY please do not use it on cats – even in a smaller dose. Dog products contain a different active ingredient to those used in cat products. This ingredient is toxic to cats. It can cause neurological signs such as head tremors and even death. If you have both cats and dogs in your home and you use a flea/tick product on your dog, keep them apart to prevent accidental contact until the medication has had time to dry on the dog’s body.

Rodenticides

Rat or mouse poison is potentially life-threatening if your cat ingests it. Most cats dislike the taste (unlike dogs). However, it is best to be on the safe side and keep these poisons in areas that your cat cannot access. Similarly, keep them away from mice and rats that may eat the poison. Your cat can get ‘secondary’ poisoning by eating a rodent just after they have eaten the poison.

These poisons work by causing haemorrhages. They work against products in the body needed for blood clotting and can thereby cause death from generalised bleeding.

Cleaning products

Many of these are safe to use around pets. However, please be careful. Avoid letting your cat walk on still-wet surfaces, as they may be tempted to lick their paws and ingest the product afterwards. Also store them in a secure cabinet – cats love to rub things with their face so it is best to keep the products away from this behaviour.

Foods

Some things that we eat cannot be eaten by cats. Unlike dogs, cats are a little pickier with their food and will usually turn their nose up at foods they recognise as poisonous. But some may not have this innate ability, so it is best to keep these things away from them:

  • Onions and garlic
  • Coffee grounds and tea
  • Fatty foods
  • Chocolate
  • Avocado
  • Grapes and raisins
  • Yeast dough
  • Macadamia nuts
  • Alcohol
  • Anything containing the artificial sweetener ‘xylitol’

Onions and garlic are particularly toxic to pets and fatty foods can cause pancreatitis – a very painful condition for your pets!

This is a simplified summary of some poisons you may not have realised were dangerous to your cats. Please think twice before letting your cats near things that you aren’t sure about. Ask your veterinarian or consult a reputable website, e.g. AVMA, International Cat Care, for more information.

Feline Four or Five?

In an earlier blog post, I mentioned the animal welfare science and bioethics Journal Club I am involved in. We meet fortnightly to review articles of relevance to animal welfare, behaviour, and bioethics. The intention is to broaden and disseminate knowledge within the research group and question and improve on our existing ideas and methods.

This week, it was again my turn to select and present an article – and of course I chose one involving cats! (it’s no secret that I am a crazy cat lady)

But I also chose this article because I am interested in behavioural profiling (of humans and animals) and wonder if this will be a requirement of animal-based research in the future. Will we have to declare the temperament of our test subjects in the same way as we record their sex and ages?

The article I chose to review was:

Litchfield, C. A., Quinton, G., Tindle, H., Chiera, B., Kikillus, K. H., & Roetman, P. (2017). The ‘Feline Five’: An exploration of personality in pet cats (Felis catus). Plos One, 12(8), e0183455. doi:10.1371/journal.pone.0183455

It is published in an open-access online journal here.

A few words on personality profiling in humans

One of the most widely used personality profiling devices in humans is the ‘Big Five’. It is based on ‘common language’ descriptors of personality. Each ‘factor’ consists of related traits and characteristics that fit within them. An individual’s personality is determined by where they sit on the continuum for each of the five factors.

The five factors are commonly known by the acronym ‘OCEAN’:

  • Openness to experience
  • Conscientiousness
  • Extroversion
  • Agreeableness
  • Neuroticism
Who wrote the article and why?

Human psychologists and ecologists in South Australia and New Zealand (Victoria University of Wellington) were involved in the study. It is part of a larger project (Cat Tracker Project) aimed at tracking pet cats in South Australia and New Zealand.

It is interesting that there appears to be no input from animal scientists – behaviour or welfare. A quick perusal of the reference list indicates that a large volume of feline behaviour and temperament literature appears to be overlooked – or at least not referenced. And, as the authors wrote about animal ‘personality’/expressivity, or behaviour profiling, it also seems absurd that Francoise Wemelsfelder’s Qualitative Behaviour Assessment (QBA) work was not referenced.

The Journal Club group also discussed the idea of ‘personality’ in animals. Many of us thought ‘person’-ality was the wrong terminology to use when discussing animal traits. The preferred term is ‘temperament’. It was our view that the human-centric approach taken for this study has resulted in this wording. I only wonder at why the article was not instead named ‘An exploration of ‘purr-sonality’ in pet cats…’ – at least this has an adorable human-centric approach.

The authors set-out to “analyse personality in a large sample of pet cats – using personality inventory completed by the owner”. Their research question was “how many reliable and interpretable factors depict personality in pet cats and what traits do they represent?”. They based these questions on previous research which have used: small sample sizes, wild/captive cats or those with behavioural problems – rather than ‘normal’ cats, researchers evaluating cat behaviour – rather than animal carers, and insufficient inter-rater reliability assessments.

Methods used

An online survey in South Australia and New Zealand collected information about 2,802 cats. It used 52 items based on a previous survey of Scottish Wildcats. Cat owners were asked to rate their cat on a Likert scale, according to how far they felt each trait was applicable. The authors used a type of exploratory factor analysis called ‘principle axis factoring’ (a technique similar to Wemelsfelder’s ‘principal component analysis’) to understand the relationship among these reported traits. This enabled them to group traits under common headings/factors.

What did they find? (results)

They found FIVE ‘factors’ (common headings for a group of traits) that explained ~47% of the variance in personalities:

  • Neuroticism
  • Dominance
  • Impulsiveness
  • Agreeableness
  • Extraversion

Interestingly, the authors chose to deal with items that ‘cross-loaded’, or loaded onto multiple factors, by assigning the item ONLY to the highest loading factor.

Why cat personality?

The authors drew our attention to some benefits of this type of research, namely: grouping compatible cats in multi-cat households and providing more hiding places for neurotic cats. A low/high score in an area could also improve the welfare of that cat by encouraging owners to seek advice.

The main issues we had with this article
  • The authors appear to have not considered animal (welfare or behaviour) scientists or a range of feline behaviour references in their article;
  • Reference to Francoise Wemelsfelder is sorely lacking – using 52 items from a Scottish Wildcat study also seemed unusual when the intention was to steer away from references to ‘wild/captive’ cats;
  • No consideration was given to the human-animal bond and how attached an owner was to their cat and/or how well they knew their cat – could this have contributed to a reporting bias for some owners?;
  • The labelling of 4 of the 5 personality factors were reasonably well explained, but the sudden inclusion of the fifth (‘extraversion’) appears contrived. We had to wonder if they were trying to force it to fit ‘Feline Five’ – it was too similar to the human list (see above);
  • Assigning items that cross-loaded ONLY to the highest loading factor ignores the complexities inherent in ‘personality’/temperament profiling.

Overall, this study is a great example of the importance of research collaboration. Think outside the (litter) box. 

    Exploring end-of-life management of old and chronically ill cats

    My second study towards my PhD is well under way. The recruitment phase started on social media (Facebook and Twitter) with a call for cat owners to participate. Interested cat owners who have put down their cat in the last 6 months are redirected to an online survey which takes them through a few quick questions. These are to help us interview the right people.

    We want to make sure we are interviewing cat owners who recently euthanased their pet. If it was too long ago then the vet involved may not remember enough details for their (separate) interview. The cat owners, and their vet, must also be in New Zealand. The interviews are done in person so I need to be able to visit them. We are also asking owners to tell us why the cat was put down. If it was due to a disease that lasted a long time, or because the cat was older, then we might get more information about tricky decisions that were made. On the other hand, a cat that was put down because it was involved in an accident would probably provide much less information. The owners also need to give us permission to contact their vet for interview and leave us enough information to contact them.

    We have also had a write-up about the study in VetScript – the magazine for The New Zealand Veterinary Association (NZVA). An email has also gone out to all NZVA members. Massey University has got on board with an article on their website and the study has been shared through their social media channels. These various initiatives are helping get the word out about the importance of the study and how to participate.

    Why am I doing the study?

    The research seeks to uncover how the owners of older cats or cats with chronic disease perceive the role their vets have played in the euthanasia process, before comparing this to the vet’s own understanding of their involvement. We are also looking at the decision-making process and how cat owners, and their vets, are making euthanasia decisions. This improved understanding of what drives owner behaviour would safeguard older cat welfare and further inform vets of their role in end-of-life management.

    How can you get involved?

    If you are a cat owner who meets our criteria, or you know someone that might, please take the time to visit our online recruitment page and answer a few questions. This should only take 5-10 minutes of your time.

    If you are a veterinarian and you think you might have a client that would be happy to chat to me then please direct them to our online recruitment page.

    If anyone has questions about the study they can get in touch with me at: K.Littlewood@massey.ac.nz

    Cat Friendly Veterinarians

    Following on from my previous post on environmental enrichment for New Zealand cats, this post will focus on some things veterinarians can do to improve the lives of their feline patients.

    There are many ways we can increase the number of positive experiences pet cats have. Not least is helping to ensure their experiences when visiting a veterinary clinic are less negative, and more positive [1, 2]. This is where individual veterinarians and clinics come in. If a cat is not ‘happy’ about going to the clinic, then an owner is less likely to bring their pet to the veterinarian as often as they may otherwise [3, 4]. Feline environmental enrichment is not just good for the cat; it is good business.

    How can we treat our cat patients with kindness? (and differently to dogs)

    Cat are not just mini dogs. They respond very differently towards veterinary consultations. From the cat that refuses to leave its carrier, to the one who refuses to go back in; the cat who stiffens up and tries to draw blood, to the one who just wants to rub its face all over you. We know there are many differences even between cats. However, there are a few things we can do to make life a little easier for those that are struggling with going to see a veterinarian.

    cat-friendly-vets

    Cat carrier training

    For starters, training cats to not completely hate the idea of going in their cat carrier can make life much easier for everyone. This is something that owners will need to work on at home, but as veterinary professionals we can help pick up on these problems and guide owners in the right direction. If a cat is not apparently ‘happy’ about going in a carrier, then an owner is probably going to think twice about bringing ‘Fluffy’ in to get that cough looked at. This can be bad for the cat, and bad for business.

    Dr Sarah Ellis (@sarahlhellis) has written an excellent blog post on Katzenworld about how to train cats to like their carrier. The post starts off with some tips about what makes a good cat carrier and then goes through how to counter-condition cats to their own carrier. It would be a great post for veterinary professionals to be familiar with and then make owners aware of. A veterinarian could quite easily have a chat to an owner about carrier training if they mention having troubles, or if the cat is clearly not happy about going back in at the end of a consultation. It could even just be something we casually ask, for example ‘How does fluffy like her carrier?’.

    I was in a pet store recently (acquiring more toys for my spoilt felines) and happened to be walking past a couple who were looking at cat carriers. They were complaining about their cat not liking the one they already own. They saw the cat toys I had and (guessing I had a menagerie) asked me which one I used for my cats. As a busy-body (and cat enthusiast) I could not help but ask them if they had ever heard of cat carrier training. They had not and were very interested to hear about it. I gave them the link and they (happily) trotted off to have a read.

    Cat friendly veterinary practices

    Veterinarians and clinics with cat friendly approaches can also get involved in feline environmental enrichment. Once cats arrive at the clinic, in the carrier they have now learnt to like, it is up to us to make that experience as positive as possible. Not only do we want them to come back, but we also want to tip the balance of their possible experiences towards the positive side as much as possible [1, 2] – if we are aiming to be the animal welfare advocates that the New Zealand Veterinary Council would like us to be.

    Low stress handling techniques and clinic design can have a massive impact on the experiences of our feline patients. Many clinics could be re-designed with feline patients in mind (e.g. separate dog and cat waiting areas, separate consulting rooms, and separate hospitalisation areas with each species comfort in mind), but there are also simple cost-effective ways of providing for our feline patients. Cats do not respond well to aggressive handling techniques. How many veterinarians or veterinary nurses have ‘lost’ a cat after pushing it too far? It makes it very difficult to work with them in the future – and the owners are never very impressed. The International Society of Feline Medicine (ISFM) recognise this and have written an excellent article [5] in The Journal of Feline Medicine and Surgery about feline-friendly handling guidelines.

    The ISFM are also responsible for the worldwide Cat Friendly Clinic programme, designed to increase the number of cat friendly veterinary clinics by providing free information – to enable clinics to work towards a voluntary accreditation scheme. The importance of handling cats in clinics is emphasised by this scheme. Once accredited, veterinary clinics can advertise this accreditation to cat owners and are then eligible to be listed on the ISFM website. Veterinarians and clinics can register their interest for free to receive more information about this accreditation scheme.

    In addition to all these differences in the ways we treat our feline patients, there are some things we can do for them that we are already doing for dogs. Providing yummy cat friendly treats in consult rooms can be used to reinforce any positive experiences and counter-condition pets to the veterinary clinic [6]. If it makes it easier to examine an overweight cat after a few treats are given, then this is probably going to do more good than potential harm – so long as we are clear with the owner why we are doing it in this instance. Giving cats a little more time, once out of their carrier, to acclimatise themselves to the room (as we so often allow for in dogs) is also likely to help the consult go smoothly.

    These are just a few of the ways that, as veterinarians, we can improve the lives of our feline patients – at least during the time that we have some control over their experiences. Enriching the lives of cats is not just good for them; it is also good for us.

    References

    1. Green, T.C. and D.J. Mellor, Extending ideas about animal welfare assessment to include ‘quality of life’ and related concepts. New Zealand Veterinary Journal, 2011. 59(6): p. 263-71.
    2. Yeates, J.W. and D.C.J. Main, Assessment of positive welfare: A review. Veterinary Journal, 2008. 175(3): p. 293-300.
    3. McMillan, F.D., Maximizing quality of life in ill animals. Journal of the American Animal Hospital Association, 2003. 39(3): p. 227-235.
    4. Vogt, A.H., et al., AAFP-AAHA feline life stage guidelines. Journal of feline medicine and surgery, 2010. 12(1): p. 43-54.
    5. Rodan, I., et al., AAFP and ISFM Feline-Friendly Handling Guidelines. Journal of Feline Medicine and Surgery, 2011. 13(5): p. 364-375.
    6. Westlund, K., To feed or not to feed: Counterconditioning in the veterinary clinic. Journal of Veterinary Behavior: Clinical Applications and Research, 2015. 10(15): p. 433-437.

    Environmental enrichment for New Zealand cats

    Lately there has been an exciting boom in posts, blogs, popular articles, tweets, and even a journal article [1], illuminating the benefits of environmental enrichment for pet cats. There are entire websites (e.g. food puzzles for cats) dedicated to helping cat owners find ways to positively enrich the lives of their pet(s).

    The concept of environmental enrichment is not new; zoological parks and laboratory animal facilities have been using enrichment programmes as a means of alleviating boredom and negative mental states in captive populations for some time [2-4]. The 2015 World Associations of Zoos and Aquariums (WAZA) Animal Welfare Strategy has an entire chapter dedicated to environmental enrichment [5].

    Interactive ‘food puzzles’ used for zoo animals are easily translated to our pet felines [1]. The authors of this journal article are based in North America, where the fact that a large proportion of pet cats are kept indoors means their feline populations could also be regarded as ‘captive’ animals. However, even for our largely ‘free-ranging’ New Zealand cats, there are benefits to providing them with more opportunities for positive affective engagement.

    ‘Positive affective engagement’ happens when animals are able to respond to motivations they have to behave in ways they find rewarding [6]. The animal is engaged and experiencing positive ‘affects’ or mental states (e.g. happiness, playfulness). Therefore, environmental enrichment involves providing these opportunities for animals to respond behaviourally to their environment and/or other animals.

    In addition to food puzzles, there is another enrichment activity that cat owners could take from zoos (and dog owners!); reward-based training. Yes, cats can be trained. Drs John Bradshaw (@petsandus) and Sarah Ellis (@sarahlhellis) have written a book (The Trainable Cat) to show us how to do this. I am excited to read (and use) it! There is also an excellent ‘train your cat’ series of videos, which demonstrates how you can train your cat to like its cat carrier, be good at the vet, and even come back to you. Julie Hecht (@DogSpies) would also like you to know cats are open to training and takes us through the steps she took with her cat and a new sofa. Training could be another opportunity to provide cats with opportunities for positive affective engagement. Zazie Todd (@CompAnimalPsych) summarises reward-based training in an excellent blog post ‘Reward-based training is for all our pets’. It’s not just for dogs or animals in captivity.

    The life of a domesticated cat is essentially a ‘dumbed down’ version of their wild cousins. In place of long hours spent hunting for food, they are instead provided with energy-dense cat biscuits and meat from a can. They need to expend this unused energy somehow and this can often result in negative behavioural consequences, including (but not limited to); bullying of other cats in the household (a problem in my house) or stalking and torturing wildlife. This last issue is particularly problematic given the conservation status of much of New Zealand’s native birdlife. Environmental enrichment for our cats; using toys, food puzzles, and training, could be the answer.

    My Experiences

    My husband and I are currently owned by two ‘free-range’ (during the day) cats. Our male ginger can be a bit of a bully towards our female tabby. This is much worse when he is bored. On days when we have not made efforts to entertain him, and/or the rain stops him frolicking outdoors, he is relentless with his attacks on his fluffy sister. However, when one (or both) of us has the energy to play with him his sister is free to roam without fear of sudden ginger attack. With the recent addition of a slow feeder bowl, he now has to expend more energy eating than he had to previously. The ginger attacks have again reduced.

    We long ago taught him to ‘sit’ on command – he is very amenable to food-based rewards. This was as far as we went with him. However, with all this excitement surrounding cat training I am keen to try some more tricks! My husband rolls his eyes and calls me crazy when I ask the ginger for his paw in exchange for a treat. I think the cat will have the last laugh though – he is getting more and more compliant…

    Version 2
    The ginger lies in wait

    Environmental enrichment strategies, such as food puzzles and reward-based training, can (and should) be used for outdoor cats too.

    References

    1. Dantas, L.M., et al., Food puzzles for cats: Feeding for physical and emotional wellbeing. Journal of Feline Medicine and Surgery, 2016. 18(9): p. 723-732.
    2. Mellor, D.J., Affective states and the assessment of laboratory-induced animal welfare impacts, in ALTEX. 2011.
    3. Fraser, D., Understanding animal welfare: the science in its cultural context. UFAW Animal Welfare Series, ed. J.K. Kirkwood and R.C. Hubrecht. 2008, Chichester, United Kingdom: Wiley-Blackwell.
    4. Young, R.J., Environmental enrichment for captive animals. 2003, Oxford, UK: Blackwell Science.
    5. WAZA, Chapter 3: Environmental Enrichment, in Caring for Wildlife: The World Zoo and Aquarium Animal Welfare Strategy, D.J. Mellor, Hunt, S. & Gusset, M., Editor. 2015, World Association of Zoos and Aquariums (WAZA) Executive Office: Gland, Switzerland p. 34.
    6. Mellor, D.J., Enhancing animal welfare by creating opportunities for positive affective engagement. New Zealand Veterinary Journal, 2015. 63(1): p. 3-8.