Human research has taught us much about microbial functioning in the gut. Within hours of birth, numerous species of gastrointestinal microflora (GM) begin colonizing the gastrointestinal tract aiding digestion and defending the body against pathogens (Randal and Buddington, 2003). It is estimated that each adult digestive tract is inhabited by hundreds of different species of bacteria whose populations number well into the billions (Isolauri and Salminen, 2005). Normal gastrointestinal microflora in animals consists of a similar number and diversity of species to those of humans. These microflora provide benefits to the host either by promoting an action that maintains health or by preventing actions that negatively affect health. The most abundant strains of GM in dogs are Bifidobacterium spp. Lactobacilli spp. and Enterococcus spp. with cats having a similar population but lacking Bifidobacterium spp (Table 1) (Rastall, 2004).
Table 1. Some common strains of beneficial gastrointestinal microflora in dogs
| Lactobacilli spp. | Improves digestion and absorption of nutrients Prevents colonization of pathogenic bacteria |
| Bifidobacterium spp. | Stimulates immune function |
| Enterococcus spp. | Inhibits growth of pathogenic bacteria |
| Bacteroides spp. | Vitamin synthesis |
| Streptococci spp. | Stimulates immune function |
| Fusobacteria spp. | Improves digestion and absorption of nutrients |
| Eubacterium spp. | Inhibits growth of pathogenic bacteria |
| Saccharomyces boulardii | Improve the intestinal barrier, suppress inflammation |
Intestinal microbes serve various beneficial roles in digestion by promoting absorption of lipids through the deconjugation of bile acids. They also act to synthesize a number of B vitamins and assist with absorption of those vitamins within the intestinal tract. One of the most important roles of GM is to protect the body from pathogenic infection. They do this partly by stimulating immune response and partly by directly preventing the binding of pathogens to the intestinal lining. Predominant species of lactic acid producing bacteria, such as Lactobacilli spp., also act to inhibit growth of pathogens through immune stimulation, production of targeted antimicrobials, competition for nutrients, competitive inhibition of binding sites, enhancing intestinal transit time and improving the production of protective intestinal mucus (Wynn, 2009). Intestinal microflora also can act to stimulate the immune system in a number of ways (Bauer et al, 2006; Collado, 2006). Not only is this beneficial in protecting the body from infection, but it can also potentially help prevent allergies (Table 2).
Table 2. Action of beneficial gastrointestinal microflora in the body
| Synthesis of B vitamins | |
| Synthesis of digestive enzymes which enhance digestion | |
| Improving weight gain and lipid metabolism by making bile acids usable | |
| Promoting overall healthy immune response | |
| Improving the epithelial barrier against pathogens | |
| Supporting production of protective intestinal mucus | |
| Preventing loss of excess electrolytes during infection | |
| Preventing reoccurring bladder infections | |
| Preventing atopic dermatitis |
Population densities of microflora vary considerably depending on where the species reside within the gastrointestinal tract. The acidic conditions of the stomach prevent large populations of beneficial microbes from establishing but the more hospitable small intestine and colon host a diverse range of beneficial GM with Lactobacilli spp. and Bifidobacterium spp. predominating in large numbers.
Clinical significance of gastrointestinal microflora
Gastrointestinal complaints are are a common presentation in veterinary practice. Physiologic states such as infection and chronic inflammation can decrease levels of beneficial bacteria (Rastall, 2004;Dotan, 2005; Czarnecki-Maulden, 2006) within the intestines and lead to negative health effects such as malabsorption, dehydration, electrolyte imbalance and impaired healing as a result of stress, gastrointestinal discomfort, diarrhoea, constipation and vomiting. Ingestion of antimicrobials, or other pharmaceuticals that affect gastrointestinal functioning, can also have a negative effect on healthy populations of GM (Rastall, 2004; Beaugerie and Petit, 2004; Aktas, 2007;Stringer et al, 2007) as can vomiting or diarrhoea from gastroenteritis resulting from dietary indiscretion, compromised organ function, shock, stress, allergies or toxicity. Chronic digestive upsets can lead to loss of appetite, weight loss and reduced energy and this potentially can be distressing to clients who may percieve their pets to be experiencing a reduced quality of life. Gastroenteritis typically results in vomiting or diarrhoea, which can pose a zoonotic health risk to clients with young children, the elderly or the immunocompromised. It is therefore important to help prevent digestive upsets wherever possible. One way to do that is with probiotic supplementation. Depending on the particular case, probiotics may provide benefit when given anytime there is a possibility of gastrointestinal upset. Similarly, they may be given during some cases of gastrointestinal upset to encourage recovery (Wynn, 2009).
Probiotics are nutritional supplements that include strains of bacteria, which are known to provide protective health benefits and that can survive transit through the acidic conditions of the stomach. These supplements are primarily effective when they are able to colonize the intestines in such numbers that they provide health benefits. The duration of time that populations remain stable within the intestines varies depending on the strain of bacteria and whether the environment is supportive to microbial proliferation. Current research is focusing on ways to enhance viability and colonization of these species within the intestines (Willard, 2000;Baillon et al, 2004; Weese and Rousseau, 2005; Marcinakova et al, 2006; Marshall-Jones et al, 2006;McCoy, 2007; Marsella, 2009.
Providing a suitable environment for bacterial colonization within the intestines is of critical importance to ensuring the maintenance of healthy levels of GM. Studies have shown that diet can influence the rate of proliferation in specific GM species (Rastall, 2004; Wynn, 2009). For example, a diet high in carbohydrates can lead to increased numbers of Bifidobacterium spp., Lactobacilli spp. and Eubacterium spp., whereas a diet high in proteins and fats can lead to higher numbers of Bacteroides spp. With this in mind, it is easy to see how low numbers of GM can result in a bout of intestinal distress from a dietary indiscretion; for example, if an animal eats an unusually high amount of fat, the microbes responsible for digestion of fats may not be in high enough numbers to digest the fats effectively and that can potentially result in digestive upset.
Addressing bouts of intestinal distress can be a challenge, especially when the cause is unknown, but one way that overall intestinal health can be promoted is by the administration of prebiotics. Prebiotics are indigestible carbohydrates (typically oligosaccharides) that help provide a supportive environment for bacterial growth through the provision of nutrients that enable microbial fermentation by GM (Wynn, 2009). There are relatively few studies that specifically target prebiotic use in animals, but early evidence shows that prebiotics can significantly improve populations of indigenous bacteria while also minimizing toxins and faecal odour (Tarada et al, 1992).
In humans, probiotics and prebiotics have been used for many years where they are routinely added to yogurt and other dairy foods. In the last decade, probiotics and prebiotics have been added to feed for production animals as a way to improve digestion of feedstuff and encourage weight gain. In companion animals, prebiotics are added to pet foods as a way to support intestinal health. Probiotics have recently gained favour in companion animal practice likely due to the public awareness of these products as human health supplements. Clients are beginning to see the value of dietary supplements in their own lives and can see that similar supplements may potentially improve the lives of their pets.
Clinical indications
Probiotics and prebiotics are useful for preventing digestive upsets, but they are also useful for treatment of disease. Current research shows that probiotics may have clinical benefit as an aid in the management of medical conditions such as reducing the severity of inflammatory bowel disease (Wynn, 2009); reducing the incidence of chronic dietary-related diarrhoea (Czarnecki-Maulden et al, 2006); promoting good systemic immune function (Bauer et al, 2006); reducing severity of uraemia in chronic renal disease (Palmquist, 2006; Raganathan et al, 2006) and reducing inflammation and improving survival rates from acute pancreatitis (Xu and Lu, 2006).
Since probiotics are composed of indigenous strains of bacteria they are generally well tolerated, but human studies have shown that there is potential risk of bacteraemia in immunocompromised individuals, the critically ill or those with significantly impaired intestinal mucosa. It would stand to reason that following directions for administration of species-specific probiotics is key to ensuring safety for the patient.
Availability of probiotic and prebiotic supplements
There has been a lot of research into probiotic strains that will not only survive passage through the stomach and into the intestine but will also have a good shelf life (Willard, 2000; Baillon et al, 2004; Weese and Rousseau, 2005; Marcinakova et al, 2006; Marshall-Jones et al, 2006; McCoy, 2007; Marsella, 2009). However, the production of these probiotics in a commercial sense is not well supported by stringent regulations, so numerous problems exist with quality. Studies show that many products on the market lack clear identification of the strains that they contain and often there is no clear information about the number of live organisms guaranteed in each dose (Wynn, 2009). Some consumer studies have shown that numbers of viable bacteria present in the product are much lower than expected (Weese, 2002). It goes without saying that when choosing a good probiotic supplement for therapeutic use, it is helpful to approach probiotic selection with the same care as that used when choosing pharmaceuticals. Ensure that the bacterial strain is accurately identified and that the number of guaranteed live organisms is listed in the product information.
Case 1. Case study of an 18-week-old kitten.An 18-week-old female kitten was brought into the clinic with very runny faeces containing blood and mucous. The owner had adopted the kitten just a few days before and she had been bright and active until the day before when she had suddenly gone very quiet. On examination the kitten was quiet with pink, moist mucous membranes. Her heart and chest sounded clear with no abnormalities detected. The kitten's abdomei was very distended and her body temperature was 39°C (102.4o°F).The veterinarian requested administration of long-acting antibiotic (Betamox LA) and an anthelmintic (Milbemax). The kitten was sent homeThree days later, the kitten was brought back in to the clinic. The diarrhoea had not improved and in the previous 2 hours the kitten's owner stated the diarrhoea was now pouring out of her so that she could not get to the litter tray in time. On examination, the kitten was still bright and eating fine and appeared well hydrated. Her abdomen was still distended, and her temperature was now normal.The kitten was sent home with a course of antibiotics, Synulox palatable drops, Lectade and a prebiotic/probiotic paste to help encourage recovery of intestinal function. A revisit was scheduled for the next day.One day later the kitten returned for a revisit and seemed to be improving so was sent home again and the owners were to continue with the treatment. A revisit was scheduled for 1 week.A week later the owners returned the kitten to the clinic reporting that the kitten once again had blood in her faeces. On examination, she was bright and responsive, hydration and temperature were normal and the abdomen was only slightly distended. She was sent home with treatment for giardia (Panacur Granules) and more prebiotic/probiotic paste. A revisit was scheduled for 1 week.When the kitten returned to the clinic the following week, she was completely normal. The owner was very happy with the prebiotic/probiotic paste and said that the syringe applicator was easy to use. Best of all, the kitten liked the taste which made treatment much easier.Emma Hallam RVN is Veterinary Nurse at Knox and Devlin, Whaley Bridge High Peak Derbyshire, UK
Most of the major pet food companies now offer extruded diets that are enhanced with prebiotics and some even offer foods and chews with added probiotic cultures. For increased dietary flexibility, it may be useful to feed a supplement that can be added to any type of food or fed directly to the animal. Palatability and ease of administration are a key concern when considering whether to offer these supplements to clients to give at home.
Examples of some common products that contain Enterococcus spp. probiotics include FortiFloraTM by Purina® and Canikur® Pro by Boehringer Ingelheim. A product that contains Bifidobacterium spp. is ProStoraTM by Iams® and Mitomax® by Imagilin TechnologyTM contains Saccharomyces spp. Canikur® Pro is synbiotic (contains both prebiotic and probiotic action) to promote the healthy colonization of beneficial microflora in the intestines. The prebiotic in Canikur® Pro, BioMosC®, is unique to this product. It actively inhibits attachment of pathogenic bacteria. Canikur® Pro also contains the mineral montmorillonite, which is 20 times more effective than kaolin at adsorbing viruses and toxins (Lipson and Stotzky, 1983; Helmy et al, 1999; Polati et al, 2006). Canikur® Pro is extremely easy to use and animals generally find it palatable so it is ideal for dispensing to clients.
Case 2. Case study for cross bred dog: 8-year-old, male entire.Ralph is an entire male cross bred dog who is 8 years old. He was brought into the surgery with a 1-week duration of vomiting and diarrhoea. The owner reported that Ralph had a long history of gastrointestinal upset but that it usually resolved with a controlled home cooked diet. Ralph had recently been staying with some friends and the owner suspected that he may have eaten some food that didn't agree with him.Since getting Ralph back home, the owners had tried feeding him chicken, green vegetables and gravy and his diarrhoea and vomiting had briefly improved but had then become worse again with evidence of blood, mucous and undigested food. The owners reported that Ralph seemed happy and was eating and drinking normally, but seemed abnormally quiet at home.On examination, Ralph was bright and responsive, his mucous membranes were pink and moist, his heart and chest sounded clear with no abnormalities detected.Palpation of the abdomen revealed no abnormalities and his temperature was normal. The veterinarian diagnosed gastrointestinal inflammation related to the change in diet. Ralph was sent home with a course of antibiotics, Canikur®Pro paste, and instructions to feed him chicken and rice with no gravy or vegetables.Initially Ralph was not keen to receive the Canikur®Pro, however, the dosing syringe made administration quick and easy and Ralph soon grew to enjoy the taste. After a few days, Ralph's diarrhoea had cleared up and he was back to his usual bouncy self. His owners now keep Canikur®Pro paste on hand and administer a dose whenever they see that Ralph is beginning to get loose stools.Emma Hallam RVN is Veterinary Nurse at Knox and Devlin, Whaley Bridge High Peak Derbyshire, UK
Figures: Ralph receiving Canikur®Pro from the special syringe device
Conclusion
The incidence of digestive upset in companion animal practice is quite high and treatment can present many challenges. Causes of intestinal disorders range from systemic disease to infection or stress but in most cases the balance of normal intestinal microflora will be affected. Beneficial bacteria in the intestines promote health in numerous ways including stimulation of the immune system, production of essential vitamins and defence against pathogenic organisms so when these bacterial populations decrease the animal is at risk for intestinal distress. Much of this microbial imbalance can be corrected or prevented using probiotics and prebiotics.
Probiotics and prebiotics have been used for years as nutritional supplements in humans and production animals to aid in digestion and promote good intestinal health but it has only been in the last few years that their value is being recognized in the treatment of companion animals. As with human nutritional supplements, there is a wide range of quality and presentation of probiotic products on the market and care should be used in choosing a supplement that is well tolerated for patients and easy to administer for clients. Of particular interest is a new presentation of products called synbiotics, which targets gut support in two ways with the addition of probiotics, to replenish bacterial populations, as well as prebiotics, to feed and support proliferation of bacterial populations; between the two, they facilitate growth of beneficial bacteria within the intestines at levels that will promote health benefits.
Key Points
- Gastrointestinal microflora play an important role in physiological functioning.
- Digestive upsets in dogs can be a significant concern for pet owners.
- Imbalances in gastrointestinal microflora can cause digestive upsets.
- Probiotics can help prevent mild digestive upsets.
- Probiotics help treat many intestinal conditions.
- Synbiotics are a multi-pronged approach to improving gastronitestinal microflora.