Feed Strategy - April 2018 - 19
FeedStrategy ❙ 19
phagocytosis cells, such as mast cells. Complex mechanisms will then activate adaptive immune responses
- of which inflammation is a natural reaction.
Immunity cells, like T-cells and granulocytes, are produced in the primary lymphoid organs: thymus, bone marrow and, specifically for birds, in bursa of Fabricius. Those
cells migrate to the secondary lymphoid organs, such as
gut associated lymphoid tissue (GALT): mesenteric lymph
nodes, isolated lymphoid follicles and Peyer's patches.
"Immunity actors are quite numerous in an animal's digestive tract," said Delphine Le Roux, immunity teacher at école Nationale Vétérinaire d'Alfort
(ENVA), a French veterinary medicine institution.
Because much of the immune system resides in the
digestive tract, researchers are increasingly focused on
the connection between feed and immunity to gain a
April 2018 ❙ www.WATTAgNet.com
better understanding of the ways an animal's diet may
contribute to good health maintenance.
Young animal immunity
On its first meeting with pathogens, the immune system produces antibodies: mainly IgM
(Immunoglobulin M, non-specific) and then IgG,
which is more efficient.
The first ingestion contributes to young animal's
immunity with, for mammals, colostrum consumption.
It must occur less than six hours after the birth. Very
rich in cytokines, lymphocytes and antibodies, colostrum's content depends on the species. In humans and
dogs, it is very rich in IgA; in horses, pigs and cats, it
is rich in IgG; and in ruminants, IgG1.
Young birds are also passively protected by their mother's antibodies for at least 10 days by either IgY, which had
been transferred from the hen's serum when the egg was in
the ovary, or IgA and IgM, transferred in albumin during
the passage of the fertilized egg in the oviduct.
In all species, the mother's antibodies might interfere in
vaccination efficiency. The critical period for vaccination
is the time when the young animal is not well protected by
its mother's antibodies, a point which will not inactivate the
vaccination, but not yet protected by its own immunity.
Here, a supportive feeding strategy is most beneficial. Some vitamins help the animals to fight infection. It is well known vitamin D and a combination of
selenium and vitamin E (pig, chicken, cows) protect
against stress. But, one must take care to avoid feeding them in excess as this combination will produce
Immunologists are also very interested in vitamin A. It is transformed to retinol by digestive
enzymes and then into retinoic acid, which immune
cells need. Innate lymphoid cells (ILC), a new class
of immune cells discovered in 2010, proliferate
when vitamin A concentration is increased in feed.
However, knowledge is yet to be built regarding
their precise role.
Several studies show feed can help protect against
disease. For example, carotenoid-enriched corn protects poultry against coccidiosis. Other studies show