by Bretaigne Jones, DVM

One of the last organ systems to fully develop and become functional in the newborn and nursing kitten is the immune system. To help protect young kittens, maternal antibodies are transferred to the newborn through the colostrum. Colostrum is the viscous, protein rich first milk produced at the time of birth and for a few days after.

Kittens are born with the ability to absorb these antibodies intact from the digestive tract and put them into their general blood circulation. However, it is a short-lived window of opportunity, closing the absorptive pathways before 24 hours of age. This passive immunity (meaning the protection comes from another source and not in direct response to a microbial organism) provides a limited defense to whatever pathogens the mother has been vaccinated against and those she has been exposed to naturally. Those antibodies that aren’t absorbed and shifted into to the blood stream protect the intestinal tract locally.

Maternal antibodies will eventually fade away, leaving the kitten vulnerable to bacteria, viruses and parasites. The term “immunity gap” refers to the time during which the maternal antibodies are no longer protective and before which the kitten can mount a defensive immune response itself; therefore, the period of risk. It is not possible to determine when this period begins or ends in any individual without extensive testing. This is the reason kittens are vaccinated around the time of weaning and boostered every three to four weeks - to build a sustainable protective titer. A complicating factor with the maternal antibodies is that while they may not provide enough action for true protection between weeks 4 and 12, the level may well be such that it inhibits the kitten’s response to vaccines. The maternal antibodies effectively block an immune response from the kitten.

In order for the kitten to have optimal defensive response, the immune system must mature correctly. Appropriate nutrition for the queen during pregnancy, and for the kittens as neonates is essential for the proper development of the kittens’ immune system.

Tissues of the immune system include bone marrow, thymus gland, lymph nodes, the lymphatic system (similar to the intricate network of blood vessels, it circulates a colorless liquid called lymph), tonsils, spleen and liver. All these tissues communicate to coordinate all the various aspects of the animal’s immune system. In the weanling kitten, the various tissues, cells and communication systems are developing, and often not fully interacting. As a result, the weanling-age kitten is at great risk from infectious diseases (caused by microorganisms such as bacteria, viruses and parasites).

Like the immune system, the kitten’s gastrointestinal tract is not fully functional until several months old. The intestinal tract is a vulnerable exposure point for potential pathogens. It doesn’t require a strong challenge for the delicate intestinal tissues or immune system to be damaged or overwhelmed in the young kitten.

Stress exerts an influence on the immune system. Fatigue, disease, fear, or environmental over-stimulation can cause stress. This can cause a suppressive action on an immature immune system further compromising the kitten’s health. Of course, this is an age when environmental stresses increase if kittens are changing homes from the breeder to the new owners. In the event the kittens are sold through a broker, additional levels of stress result.

Many breeders will wait to sell kittens until they are older in order to allow for the immune system to be more fully developed and responsive, better able to react to the stress.

In addition to wise management, the breeder and owner can support optimal immune maturity through selective nutrition. Extensive research has proven that certain nutrients can stimulate the weanling kitten’s immune system, allowing a faster, more effective, response to pathogens. Lutein and beta-carotene are both carotenoid pigments that are potent antioxidants. While both nutrients are easily absorbed in the intestinal tract, lutein is more active in stimulating the immune system in cats. Additionally, vitamins C and E exert antioxidant activity, though typically at different sites of activity. An amino acid, taurine, is another strong antioxidant. The combination of multiple antioxidants provides a synergistic effect. Other ingredients that positively impact the immune system include fructo-oligosaccharide (FOS) and mannan-oligosaccharide (MOS) fibers, and omega-3 fatty acids, EPA and DHA. FOS provides fuel for local intestinal cells and lowers the gut pH which supports the growth of beneficial bacterial species such as lactobacilli and bifidobacteria. Supported growth of “good” bacteria helps limit detrimental bacteria such as E.coli, or salmonella species. MOS actively interferes with the ability of pathogenic bacteria to attach to intestinal cells thereby causing damage and releasing toxins. As a result of this blocked action, the “bad” bacteria are carried through the intestinal tract to be eliminated. MOS also directly stimulates local antibody production within the intestinal tract. All of these fibers, along with beet pulp, are prebiotics. EPA and DHA, both omega-3 fatty acids, have definite anti-inflammatory action in the gastrointestinal tract. This helps control loss of dietary nutrients and water, which can exacerbate dehydration and nutrient deficiencies if unchecked. A neutral ingredient, zeolite, protects the lining of the gut through a thin, soothing layer of inorganic mineral salts, which are highly porous, absorbing excess moisture and any toxins present.

The benefits of these ingredients and nutrients have been demonstrated in weanling and older kittens through higher antibody levels when vaccinated. Compared to antibody titers in kittens not fed these nutrients in combination, the immunological responses are much greater in those kittens receiving these specific factors.

The combination of good animal husbandry, optimal nutrition through pregnancy, lactation and weaning, and education of new owners can provide the correct environment and opportunity for newly weaned and placed kittens to enjoy health and security as they grow.