Dogs in pain – what is it and how to look for it?
Whether you describe your dog as a drama queen or not, most dogs are incredibly good at hiding pain. This mechanism makes complete evolutionary sense. Showing pain, showed a weakness of which predators could take advantage of. Here at my Pet Nutritionist, when you book for a consultation, we ask certain questions to determine if undetected pain could be present, amongst other things. Whilst you may immediately consider the dog limping or struggling to get out of their bed, chances are by this point, the pain has moved past a threshold that they are unable to hide. Our best chance as owners is to notice the subtleties of pain in the canine and know when to seek further help. So let’s explore the mechanism of pain in a little more detail, signs to watch out for what we can do for our four-legged friends. What is pain? We’ve all stubbed our toe in the middle of the night or stood on a piece of lego. This is acute pain, the event, despite being painful, is in fact short lived. This can occur for our dogs too, when they run into a plant pot in the garden for example. But pain can become chronic and this is often what they hide. Chronic pain is more commonly associated with musculoskeletal issues in our dogs, in cases of dysplasia or arthritis. But it can also be associated with gut dysfunction and many other diseases in the body. The origin of all pain is inflammation. Irrespective of the type of pain whether it is acute or chronic pain, peripheral or central pain, nociceptive or neuropathic pain, the underlying origin is inflammation and the inflammatory response. So what is the inflammatory response? Inflammation is a normal response of the body to protect tissues from infection, injury or disease. The inflammatory response begins with the production and release of chemical agents by cells in the infected, injured or diseased tissue. These agents cause redness, swelling, pain, heat and loss of function. Inflamed tissues generate additional signals that recruit leukocytes to the site of inflammation. Leukocytes destroy any infective or injurious agent and remove cellular debris from damaged tissue. This inflammatory response usually promotes healing but, if uncontrolled, may become harmful. Acute inflammation typically lasts only a few days. If a wound gets hot, turns red, hurts, and swells, we recognise that inflammation is at work. In this instance, inflammation is a beneficial process, serving to immobilise the area of injury as the rest of the immune system mobilises to heal. The treatment of acute inflammation, the administration of non-steroidal anti-inflammatory agents, provides relief of pain and fever. In contrast, chronic inflammation lasts weeks, months or even indefinitely and causes tissue damage. In chronic inflammation, the inflammation becomes the problem rather than the solution to infection, injury or disease. Chronically inflamed tissues continue to generate signals that request help from leukocytes in the bloodstream. When leukocytes reach the tissue, they bring inflammation to the party. This chronic inflammatory response can break down healthy tissue in a misdirected attempt at repair and healing. As mentioned, perhaps the most understood cause of pain is joint inflammation. Repeated trauma or stress to the joint, incurred during everyday use, training, or performance, is often the cause of joint inflammation. You will notice the familiar symptoms like lameness, swelling and heat. The initial inflammation usually involves only the soft tissue structures of the joint, and cartilage damage is often not present at this stage. This inflammation allows leukocytes, or white blood cells, which are normally filtered out of the joint, to invade the joint space. The inflamed synovial membrane and the leukocytes release destructive enzymes such as free radicals, cytokines, and prostaglandins, all of which are potentially damaging to the cartilage. This is primarily what anti-inflammatory medications work on, they generally inhibit the production of prostaglandins. Joint degradation is an unfortunate side effect of ageing, but this can occur a lot sooner in those working or particularly active dogs. Degradation can also occur as aside effect in cases of dysplasia; as the bones are not sitting in the joint correctly, friction results in excessive degradation and subsequent inflammation and pain. In these cases, treatment is more relating to pain management and making your dog more comfortable. There are a number of practitioners that specialise in musculoskeletal concerns in the canine. Specialist Vets Chiropractors Vets Qualified in Acupuncture Canine Massage Therapists Hydrotherapists Physiotherapist Whilst there are breeds that are genetically predisposed to conditions like hip or elbow dysplasia, being mindful of appropriate nutrition during development along with appropriate exercise during growth is essential. Large breeds undergo a rapid stage of development and so essential nutrients to bone mineralization should be included in the diet; namely whole food sources of calcium and phosphorus along with vitamin D. Weight should also be monitored in the growing puppy. The bottom line? Count the nutrient dense, fresh food additions to your puppy’s diet, not the calories. As an aside, there is a lot of attention paid to the calcium: phosphorus ratio in the growing large breed. The note to make is that organic sources of both minerals are slowly and less efficiently absorbed; so, in fresh fed dogs this is less of a concern in terms of excess. Phosphorus found in meat products however is more efficiently absorbed than that found in plants. Findings here Gut Pain As humans, we are familiar with tummy aches, well, this can also biochemically occur in the dog as well. They just can’t tell us about it. As we have noted, pain is inflammation, and there are certainly plenty of things that can result in inflammation. Inflammation in the gut can be a result of things getting to places they shouldn’t really be, and so the immune response is summoned. Potentially harmful substances can find their way into the gut, but anything that is identified as non-self, kicks up the immune system. This can simply be a poorly digested protein. If
Fresh Food to Add to Your Dog’s Bowl
Whether you are a seasoned raw feeder, rather new to the journey, the Gordon Ramsey of the home-cooked dog food world, or simply want in to add some fresh food to your commercial pet food, here at My Pet Nutritionist, we have a few favourite fresh food additions. Try saying that on a Friday night! Anyway, they all pack a fair punch in terms of nutritional value, so we’ve decided to let you in on our secrets. 1) Green Leafy Vegetables! Top of the list for a reason. Green leafy vegetables include spinach, kale, watercress and broccoli. In green leafy vegetables you will find vitamins A, C, E and K along with many of the B-vitamins. These vegetables also contain carotenoids. Carotenoids act as an antioxidant, deactivating free-radicals and limiting the damage they can cause. There are two broad classifications of carotenoids: carotenes and xanthophylls. The latter containing oxygen, whilst the former do not. Xanthophylls include lutein and zeaxanthin, which are both primarily associated with eye health. They are often indicated in cases of macular degeneration. Beta-carotene one of the carotenes is turned into Vitamin A and is found in those green leafy veg like spinach and kale. Vitamin A is important in maintaining healthy skin, mucous membranes and supporting a functioning immune system. Vitamin A is regularly implicated in abnormal hair cycling, both deficiencies and toxicities can cause issues. For that reason, it is generally deemed that a whole food diet is more than capable of providing healthy levels. Green leafy vegetables also contain a rich source of folate, this is after all, where the name came from. Folate comes from the Latin folium, because it was first found in leaves! Folate functions as a coenzyme in many processes in the body. It is needed to make DNA and other genetic material and is essential in cell division. In short, it helps tissues grow and makes cells work. Folate is also involved in neurotransmitter synthesis, so it is implicated in mood and subsequently behaviour. And, one particular study showed a reduced rate of bladder cancer when leafy veg was added to the dog’s diet! Findings here So, lightly steam your kale or spinach, or blitz it up in a blender, pop it in a freezer mould and add them to your dog’s bowl! 2) Mushrooms! There are literally thousands of species of mushrooms on the planet, so it can be a challenge to know where to start. But they are incredible in terms of the benefits they can provide. Mushrooms can be involved in the prevention of certain disease, the regeneration of damaged cells, the protection of tissues and cells and used during treatment of existing conditions. The bioactive compounds of mushrooms include polysaccharides, proteins, fats, ash, glycosides, alkaloids, volatile oils, tocopherols, phenolics, flavonoids, carotenoids, folates, ascorbic acid enzymes, and organic acids. Reishi mushrooms are adored for their immunomodulating benefits. In short,they have regularly been used successfully in chronic autoimmunity and allergy cases. Maiitike mushrooms have been used for their antibacterial function and cordyceps have been seen to inhibit inflammatory responses throughout the body. Findings here Certain species have been seen to stimulate natural killer cell function, supporting the innate immune system in the body. Mushrooms are widely accepted a having anti-cancer properties. The bottom line? Mushrooms have been seen to be: Anti-inflammatory Anti-microbial Antioxidant Prebiotic Anti-diabetic If you are looking to add mushrooms to the bowl, cook them fully, lightly sauteed is fine. If you are looking to use them therapeutically, then please feel free to get in touch for advice and guidance. 3) Eggs! There’s a reason eggs are the protein reference. They contain the full essential amino acid profile. Eggs contain essential lipids, proteins, vitamins, minerals and trace elements including vitamin A, iron, vitamin B12, riboflavin, choline, zinc and calcium. Egg proteins are distributed equally between egg white and egg yolk, whilst lipids, vitamins and minerals are essentially concentrated in the egg yolk. The yolk is a rich source of linoleic acid and as we know, LA is abundant in the epidermis of the skin, so eggs are a great source of food to support skin health. The one thing that eggs are rarely associated with is being anti-microbial. But there are a range of proteins found in the egg that exhibit antibacterial, antiviral, anti-fungal and anti-parasitic activity. Avidin is seen to target bacteria, lysozymeis seen to target bacteria, virus and fungi, and cystatin targets the above with parasites included! Chicken eggs also contain a range of antioxidant compounds that include vitamins, carotenoids, minerals and trace elements. They have demonstrated reductions in pro-inflammatory cytokines in vitro. Conclusions suggest the supplementation of egg yolk proteins to reduce intestinal oxidative stress. Findings here Lysozyme, an enzyme found in eggs has been indicated in the treatment of inflammatory bowel disease; it has been seen to protect in cases of colitis. Largely from its anti-inflammatory properties. Findings here Where you source your eggs from is essential, free-range birds produce more nutrient dense eggs than caged. Free-rearing results in much higher levels of tocopherol, alpha-tocopherol and lutein content. The anti-microbial function of the egg white is also modulated when hens are exposed to environmental microbes. Findings here So, if you want to add egg to the bowl,source free-range and organic. You can feed raw or cooked, and the egg shell is perfectly safe to feed too! 4) Berries! If you’re in the middle of a yeast or gut healing protocol, then berries may not be the first thing to add to your bowl, but for the typical dog, they are a beautiful addition. Berries contain many vitamins but that also have an impressive antioxidant profile. Anthocyanins (Greek anthos =flower and kyáneos = blue) belong to the flavonoid group of polyphenols, which are responsible for the red and blue colour of plant organs such as fruits, flowers, and leaves. Many studies have linked these compounds with antioxidant, anti‐inflammatory and anti-carcinogenic properties, protection against both heart disease and cancer, as well as a
How Much Sleep Should My Dog Get?
Here at My Pet Nutritionist, we often see rest and recovery as a forgotten need of dogs. With the advent of daycare centres and dog walkers, most of us relish the idea that our dog can be kept occupied whilst we are in work. When owners research potential breeds to bring home, their exercise quota is usually discussed along with the need for mental stimulation. Exercise is important for canine health – we’ll come back to that later. So is mental stimulation, especially for those smart, working breeds. But there needs to be a balance so lets discuss, why we let sleeping dogs lie. Pop into any social media group discussing dogs being left alone and destruction inevitably comes up. Well-meaning owners often suggest that the dog is bored and by providing things for the dog to do, they will cease the destructive behaviour. It’s clear that destruction when left alone is a symptom of anxiety; not boredom. Toys and food are only ever used in a separation anxiety protocol to help the dog make positive associations with a confinement area. Part of this protocol is to assess how the dog behaves immediately after finishing the puzzle to establish whether in fact it was a distraction or actually taught the dog to relax. Boredom in dogs often isn’t the big deal that social media groups make it out to be. Those behaviours associated with boredom are often symptomatic of frustration or anxiety. So, how much interaction does your dog need on a daily basis? This is a difficult question to answer. As with humans, dogs have different personalities and purposes. However, we can’t argue with the science. Dogs are diurnal. Like us, they are active during daylight hours. Rest occurs during the dark. But activity increases in the last two dark hours. A rest period is common at noon and then reduced activity continues during the afternoon. Findings here Sleep is widely studied, for its evolutionary benefits. It is crucial for most daily functions. It is clear in humans, that when suffering sleep restriction, they have attention lapses, slowed working memory, reduced cognition and depressed thought. Studies have shown a significant reduction inactivity in dogs experiencing sleep restriction. Findings here One of the main purposes of sleep is to consolidate memories or learning. This has also been found true in dogs. Learning affects sleep structure which ultimately decides whether you retain the information or not. Interestingly, in studies, those dogs allowed to sleep after learning anew command were more likely to retain the command at a later date than dogs allowed to walk or play. Findings here So, if you want to train your dog, they need their sleep. Under laboratory conditions, dogs will sleep around 13 hours per day. But this is very generic. Older dogs will sleep more as they tend to experience periods of broken sleep. Puppies too will sleep a lot more – generally 18-20 hours. The rule of thumb is to let sleeping puppies sleep! For the puppy, consider how much socialisation and training you are undertaking. When you think you’ve only got around 4-6 hours per day of awake time; take some mealtimes out of that, and your safe play in the garden… it’s easy to see how you can quickly overwhelm a puppy. What’s really interesting is, like in humans, negative or positive interactions, affect sleep length and quality. Following a negative interaction with a human, dogs tend to fall asleep quicker. This goes against what we’ve found in humans; the idea that stress impedes sleep. It is termed stress-induced quiescence (protective sleep in response to stress). Findings here This throws a bit of a curve ball when we are considering the overall health of our dog. We usually understand that they are content when they fall asleep – but now we must consider that it could be a potential stress-response. It’s worth looking out for these patterns and seeing how your dog sleeps. This has never been more relevant when considering daycare. More and more are popping up and I often hear owners say that their dog does nothing but sleep when they get home. It is generally understood that the dog has had such a busy day, they are just exhausted. But, what if, in these daycares with upwards of 50 dogs on site, the dog is just over-aroused? How realistic is it for your dog to get his rest in such a busy site? When his normal rhythm tells him to rest around noon and then have a quiet afternoon, and he’s actually running, chasing and playing for 8-10 hours of the day? This is sadly where non-aggressive dogs get labelled as aggressive, simply because they have reached their peak of “activity” for that day and some annoying puppy continues to hang off their ear! Also a consideration to be made when a new puppy is introduced into an adult dog home. Any daycare worth their salt should value rest and recovery as much as play and interaction. Sleep is not the only way that your dog can rest and recover. Simply having quiet, settled time can be of benefit. All too often, owners consider that their dog always needs to be doing something. Here it must be questioned, does your dog need to be kept occupied simply to keep them out of trouble? Some dogs just don’t learn how they need to behave because they aren’t given the opportunity. This is a whole new issue which is too big to tackle in this article. Maybe at a later date. If your dog has their own space, whether it’s their bed, a crate, a den or a corner in the home, they soon learn that it is their safe place. They can learn to settle and rest there. But they need to know that no one will hassle them, so children need to keep their distance. You can use lickimats or stuffed kongs to help them associate the space with calm and quiet,
Is Your Dog A Yeasty Beast?
Another particularly common issue we see here at My Pet Nutritionist is yeast! More technically known as candida, it is actually harmless when kept in check. The issue is when our dog’s system goes a little awry and can’t keep those little blighters from colonising. Whilst it sounds like a military operation, the dog’s system functions very much like that. Let’s take a look at yeast in a little more detail and how we can armour dog’s defences for a fighting chance! What is Yeast? Candida is an opportunistic fungal pathogen. It is a normal part of the gastrointestinal flora and genital tracts. Healthy systems are more than capable of keeping it in check with their beneficial bacteria. The issue arises when there aren’t enough good guys to keep the bad guys in check. The good bugs we find in our dog’s gastrointestinal tract will compete with the bad bugs for food sources and attachment sites. As we know there are a number of factors that can skew the microbial community found in our dog’s system. Antibiotics Broad spectrum antibiotics target all bugs,so whilst they get rid of the ones running amok, they also wipe out the beneficial ones too. Whilst the microbiome can recover to some extent, eventually; this takes time and there’s evidence which suggests key species are never fully repopulated. Findings here Stress There are clear links that stress, whether physical or emotional, affects the composition of the gut. On many occasions, stressor infliction significantly reduces the good guys. This has been associated with increased inflammation in the gut, which then continues the cycle. Findings here The Environment There is a huge amount of data which shows exposure to environmental pollutants significantly alters the gut microbiome. This includes bisphenols, phthalates, organic pollutants, heavy metals and pesticides. Bisphenol is an industrial chemical used to make hard, clear plastic. It is also found in epoxy resins which is often used as a protective later in some metal food and beverage cans/tins. Bisphenol has been linked to reduced microbiome diversity, and a significant decrease in protective bacteria. Phthalates are plasticisers and stabilisers found in vinyl flooring, clothing, detergents, personal care products, toys, medical equipment, and plastic packaging. Because they are non covalently bound to materials, they can leach into the environment. Phthalate exposure induces microbiota changes and has been known to inhibit the synthesis of certain short-chain-fatty acids. Heavy metals are associated with reduced microbiota diversity along with the altered metabolism of vitamin E and bile acid. Findings here Pesticides are renowned for altering the gut microbiome. This not only includes the pesticides administered to pets (flea and tick treatments), but also those found in the environment, particularly those sprayed on public footpaths. What is also worth considering is that antibiotic use has been seen to increase bioavailability of pesticides within the body. Findings here You are what eat! Of course, nutrition also plays a part in modulating the gut microbiome. But we always knew that. We are all pretty selfish in evolutionary terms, and this includes the bugs we find throughout our body. Our ultimate aim, and theirs, is to survive. So, we just need to modify how many of them actually do. This means keeping the colonies of good bacteria strong, so offering our dogs a diet full of pre and probiotic foods! Prebiotics are like the fertilisers in the garden, they help to feed and grow the beneficial bacteria in our garden. Probiotics however contain live organisms which can contribute to the population of the garden. Findings here There are a number of prebiotic foods suitable for dogs and they include mushrooms, chicory root, garlic and dandelion greens. Probiotics include fermented food, but supplements are available; soil-based are a good call for your canine friend (hold off on the fermented food until later, if your dog has already developed an overgrowth). Yeasts seem to like sugar as fuel, so diets high in grains, starches and other carbohydrates seem to contribute to an overgrowth. Generally, certain beneficial bacteria will metabolise these sugars, keeping candida in check by disrupting its food supply, but in the absence of good bacteria, candida is partying it down at the all-you-can-eat buffet! Immunity A weakened immune system is also a huge risk factor for developing a candida overgrowth. Whether this has been a natural progression over a period of time for a range of factors, or even due to medications like steroids. Immune function has natural peaks and troughs, young dogs and ageing dogs naturally have a lower function, but pre-existing conditions along with a range of medications can affect it too. The immune system is like a nosey neighbour. It keeps tabs on everything going on in the body and knows when something isn’t quite right. When it identifies something as non-self, it sends the army to fight the foreign invader and, all being well, wins, before sitting back down with its cup of tea. The issue arises when it can’t get up from its chair and so the foreign bodies are left to invade. There are a number of factors which can compromise immune function from sleep, to stress and nutritional status; there are several key nutrients essential to its performance. So, supporting this is essential in the prevention and treatment of any bacterial overgrowth. Top Tips: Adequate rest Reduced exposure to stress Nutrient dense diet withVitamins A, C, D and B’s, along with Zinc, Selenium, and Iron Address any pre-existing issues like inflammation in the digestive system or poor pancreas function which can contribute to poor nutritional status Findings here Careful use of medications like antibiotics, NSAIDs and steroids Findings here on Vitamin D Findings here on Zinc What if your dog has already got an overgrowth? If indeed your dog has developed a candida overgrowth, you will notice symptoms like: Ear infections Greasy coat Sores Odour (yes, that cheesy type of smell) Green/yellow discharge Crusty/flaky skin Hair loss Itching/scratching Incessant licking/grooming of an area due to irritation Rust
Mood Food for Dogs
In humans, the definition of anxiety is a feeling of unease, a worry or fear. It can be mild or severe. It’s quite easy to label these feelings ourselves, but as our four-legged friends haven’t yet figured out how to talk, what makes them anxious can be difficult to pin down. What we do know is they demonstrate stress behaviours alongside triggers, so we can intimate they feel anxious. What is clear, is that these behaviours aren’t great for our four-legged friends, so whilst we can also tackle the triggers, there are certain nutrients that can help modulate anxiety too. We have collated 5 of our top Fido-friendly-foods that can be safely added to their diets. Fatty Fish In dogs, the body has a requirement for two distinct Essential Fatty Acid families. The Omega-6 and Omega-3 series. Omega-6 Linoleic Acid (LA) Arachidonic Acid (AA) Omega-3 Alpha-Linolenic Acid (ALA) Eicosapentaenoic Acid (EPA) Docosahexaenoic Acid (DHA) Fatty fish contain Omega-3 fatty acids which have a number of biological effects in the body. To start us off, studies have shown that aggressive dogs are characterised by low Omega-3 fatty acid status. This does not indicate causation, but there is certainly a correlation. Findings here Omega-3’s, in particular DHA, play critical neuroprotective and anti-inflammatory roles in the brain. Supplementation of omega-3 has been seen to: – Improve cognitive function Findings here – Reduce anxious symptoms Findings here – Reduce aggressive behaviours Findings here – Reduced stress-related hormone production Findings here Omega-3s are classed as polyunsaturated fatty acids. Fatty acids can be saturated, monounsaturated, or polyunsaturated. The difference is in their structure. Saturated fatty acids contain no double bonds between the carbon atoms and are therefore saturated with hydrogen. Monounsaturated fatty acids have one double bond (mono=one). Polyunsaturated fatty acids have two or more double bonds (poly=many). The more double bonds a fatty acid has, the less stable the molecule, which means it is more susceptible to oxidation, resulting in rancidity. This is why fish oils should be stored in a dark, glass bottle and why PUFA rich oils aren’t the best to fry your eggs with. Fats also act as carriers for fat soluble vitamins A, D, E and K which means that low-fat diets can affect the metabolism of these crucial vitamins. Much data has highlighted that low vitamin D status is associated with anxiety and depression, so fatty fish helps modulate the metabolism of vitamin D too (if it is present in the diet of course). Findings here Sources to include: – Mackerel – Salmon – Sardines Oysters Whilst you may struggle to get your hands on oysters, what we’re really interested in is their zinc content. In the human literature, zinc is a trait marker of a mood disorder. Zinc deficiency is regularly associated with depression and anxiety, and supplementation often improves mood and cognitive function. Zinc plays a role in many metabolic processes, including enzyme catalysis, cell signalling and DNA replication and transcription. What this essentially means, this mineral is involved in neural development, learning, memory and mood. We know zinc plays a role in mood because we find zinc enriched neurons in parts of the brain associated with emotions. Before we knew better, in rat studies, we found that increasing zinc levels reduced rat-fighting behaviour and when supplemented alongside anti-depressant medication, rats developed improved resilience. The issue we have is that zinc also plays a role in the inflammatory response and likewise the down regulating of the same response. So, when we are in a state of chronic inflammation, when zinc should be in the nervous system, modulating, its instead crusading with the inflammatory (or anti-inflammatory) team and the brain is left with neurotransmitters where they shouldn’t be, or not even where they should be! Whilst it stands to reason that low dietary intake results in low levels of zinc, phytates found in cereals, corn and rice also inhibit zinc absorption. There are also some breeds who are predisposed to zinc deficiency, for example, certain sled dogs. Foods high in zinc: Oysters, beef, chicken, pork, hemp seeds, shiitake mushrooms and red meat. Whilst brazil nuts, tuna and oysters are also high in selenium, red meat is an easy addition in your dog’s diet. Another mineral, low levels of selenium are regularly reported in cases of anxiety, depression and fatigue. Findings here Selenium’s prime function is as an antioxidant. It works as a component of glutathione peroxidase, an enzyme which protects cell membranes and red blood cells from damage by free radicals. However, it is thought to modulate mood through its involvement in the synthesis and metabolism of thyroid hormones. Selenium deficiency is thought to dysregulate thyroid function and therefore play a role in mood disorders. Not only that but selenium has been found to exhibit modulatory effects on the dopaminergic, serotonergic and noradrenergic systems which are all involved in the regulation of mood and behaviour. One of the mechanisms is to inhibit the degradation of serotonin, resulting in an overall increase in levels. Selenoproteins also demonstrate antioxidant properties on dopaminergic neurons vulnerable to oxidative stress. Findings here Food Sources of Selenium: Pork, beef, turkey, chicken, fish, oysters, eggs, shiitake mushrooms and white meat. The word protein comes from the Greek word proteios which means of prime importance. Amino acids are the basic units of proteins and are held together by peptide linkages to form long protein chains. For the dog there are certain amino acids that are essential; they cannot be synthesised by the body, so they must be supplied by the diet. These include: Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine For the cat, this also includes taurine. These amino acids found in certain foods,are precursors to certain neurotransmitters. Tryptophan, which is found in chicken and turkey, is the precursor to serotonin. Manipulation of serotonin through supplementation or depletion of tryptophan has established a role in higher order brain functions, memory, and mood. Low dietary tryptophan is associated with anxiety-like behaviour and increased defensive aggression. Tryptophan