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Supporting the Immune System in the Weanling Puppy
By Bretaigne Jones, DVM
Immunity is an intricate, complicated, and fascinating process. The immune system relies on several factors to optimize appropriate responses and productivity. In the weanling puppy, there are several challenges to the developing immune system, and nutrition can play a substantial role in the success of its development.
The science of immunity
The body’s ability to resist infection by pathogenic (disease-causing) agents is referred to as immunity. Pathogenic agents include bacteria, viruses, and parasites. The process by which a body responds to the presence of a pathogen is complicated. The disease-causing microorganism typically invades the body through the mucous membranes of the respiratory system, the gastrointestinal tract, or through the skin. A response to this invasion is inflammation when the body attempts to create an unwelcome environment and potentially wall off the pathogens. Specialized defensive blood cells get involved to neutralize or kill, and remove the microorganisms if possible. The body develops a memory system so that in future exposure events to that same pathogen, a faster, more effective response occurs.
The immune system is comprised of several protective and responsive systems that synchronize for optimal defense. The protective barriers involve the skin, mucous membranes (found at any body orifice and lining the respiratory and gastrointestinal systems), and tiny hair-like projections called cilia that line the nasal passages, trachea and bronchi of the lungs.
To counter bacterial invasion, these structures provide a barrier, secretions, plus enzymes, and create a lower pH. Collectively, these are called the external immune system.
Inflammation is a defensive immunological response. Chemicals released with inflammation attract specialized blood cells (neutrophils and macrophages, types of white blood cells), which attempt to prevent the spread of the pathogenic organisms and destroy them. This is innate immunity.
A limiting factor with the innate immune response is that it has no “memory,” so the reaction and inflammatory response will repeat full force each time it is stimulated. This is also called nonspecific immunity.
Acquired immunity results from exposure to a pathogen, which triggers a “memory” response. The body will quickly recognize that particular pathogen next time it is encountered, expediting protective actions and targeted defensive mechanisms. Vaccines help develop acquired immunity without causing the actual disease(s).
Tissues of the immune system include bone marrow, thymus gland, lymph nodes, the lymphatic system (like the intricate system of blood vessels, it circulates a colorless liquid called lymph), tonsils, spleen, and liver. A very intricate communication system coordinates all the various aspects of an animal’s immune system to maintain health.
Immunity in a weanling puppy
In a weanling puppy, the various tissues, cells, and communication systems are still developing and often not fully communicating. Because of this, the weanling pup is at great risk from infectious diseases. (Infectious means the disease is caused by a microorganism.)
During pregnancy, small amounts of the mother’s antibodies (proteins made in response to exposure to a specific antigen, such as parvovirus type II, which can recognize the pathogen and start the inactivation process) cross through the placenta to the fetal puppies. Due to the type of placenta found in dogs, only 5 to 10 percent of the passive maternal antibodies are transferred this way. The bulk of antibodies are delivered through the colostrum, the very viscous and protein-rich secretion from the mammary glands the first few days after birth. In order for the newborns to obtain some protection against environmental bacteria and viruses, the intestinal tract is very permeable for the first 16 to 20 hours after birth, allowing the mother’s antibodies to be absorbed intact from the small intestines into the bloodstream. This is called passive immunity because the antibodies come from a different animal (mother) and not as a direct reaction to the exposure to a pathogen in the newborn. Those antibodies that aren’t absorbed into the blood stream provide a local immunity inside the intestinal tract of the puppy. It is vitally important for each puppy to nurse as soon and as frequently as possible after birth to ingest as much colostrum as possible.
Some organ systems in a weanling pup, including the gastrointestinal tract and the immune system, are immature and not fully functional. It is easy for these delicate systems to be overwhelmed or damaged.
The effects of stress on the weanling puppy’s immune system
Stress is a very real threat to young pups. When the body is stressed through fatigue, disease, fear, or environmental over-stimulation, it releases higher levels of adrenaline. An effect of higher adrenaline is a suppressive action on the immune system. This can add up to a potentially life-threatening situation for the weanling pup.
Consider an 8-week-old puppy that has been stressed by separation from its mother and littermates. In a best-case scenario, this pup has gone directly from its birth home to the new owner’s home. Already compromised by an immature digestive tract and immune system, it is also being exposed to a whole new range of microorganisms. Add the additional stimulation of being handled by multiple new family members while acclimating to a new environment, a new feeding schedule, new dishes, and water that may smell and taste different from its origin kennel. There may also be other incumbent pets in the new home too. This imposes a tremendous amount of stress on several levels, including social, immunological and nutritional.
Now, consider the stressors faced by a pup that is leaving its dam and siblings to go to a broker—new environmental microbes, new social interactions both canine and human, and again a likely change in diet. This stress can last from 24 hours to several days. Plus, there’s the stress placed on the pup as it is transported. Then that pup moves to a retailer, again with new environmental microbes, more new social interactions, another change in diet, and lots of people traffic. Then the pup is purchased and introduced to yet another new environment where the previously mentioned stresses are repeated.
Again, stress prompts the release of adrenaline, which suppresses the immune system. So, take a naturally very vulnerable young animal, and impose a tremendous amount of stress and microbial exposure. Is it any wonder that these little creatures get sick so easily?
The role of nutrients in immunity
Extensive research has proven that certain nutrients can stimulate the weanling pup’s immune system allowing a faster, more effective response to pathogens. Beta-carotene and lutein are carotenoid pigments that have strong antioxidant activity and stimulate the immune system. Two special fiber sources that also enhance immune response in these very young pups are fructo-oligosaccharides (FOS) and mannan-oligosaccharides (MOS). FOS promotes the growth of “good” bacteria in the gut (bididobacteria, lactobacilli, and so on), which helps minimize the growth of “bad” bacteria (E.coli, and salmonella species). MOS stimulates the immunological activity of the cells lining the intestinal tract, increasing local antibody production. It also neutralizes those pathogenic bacteria that latch onto intestinal cells and release toxins.
Other antioxidants that have been proven to exert a supportive role in immunity include vitamins E, C, the pigment lutein, and taurine (an amino acid). These nutrients have a special synergistic effect to stimulate immune responses when exposed to pathogens.
An ingredient that has a more passive role, but increases protection in the intestinal tract, is zeolite (or sodium aluminum silicate). These are natural clay minerals that are highly porous, absorb toxins and form a soothing, protective covering on the surface of the intestinal mucosa.
Omega-3 fatty acids protect the intestinal tract with anti-inflammatory action. This reduces the risk of dehydration, while also reducing the potential for pathogens to cross from the intestinal tract into the blood stream through damaged mucosal tissue.
Puppies that have been fed diets with these supportive nutrients are able to produce higher levels of protective antibodies in response to vaccination. Diets with highly digestible ingredients also help maintain intestinal health. Puppies don’t have the ability to produce the full range or quantity of digestive enzymes as older dogs do, so superior digestibility allows the pup to process, digest and absorb all the necessary nutrients for optimal growth and health.
© 2010 ROYAL CANIN USA, Inc. All photos courtesy of Royal Canin