PoultryUSA - August 2018 - 39
Antioxidant protection for
broilers under heat stress
Heat stress causes a multi-system failure due to work overload,
leading to excessive production of free radicals that can cause
irreparable oxidative stress.
Broiler heat stress is what concerns nutritionists the
most every summer, not only because birds grow
slower and less efficiently, but also because their welfare and health can be severely impaired, leading to
increased morbidity and mortality. Neutralizing the
negative effects of heat stress is still a field that we
know very little about, and most nutritionists work
around this problem using several additives after having adjusted their formulas for the known nutrient-heat
Common heat stress additives include sodium bicarbonate, vitamin C, citric acid, common sodium and potassium
sources, and even betaine. Such additives work at different
combinations for different conditions and formulation designs, not always as effectively as one would like,
but at least they seem to alleviate the problem.
The issue of heat stress and oxidation has
not been sufficiently addressed. This is perhaps
because oxidative stress is an ill-defined term
or because we lack the practical tools to evaluate it under field conditions. We cannot easily
measure and associate the effects of a problem so
generic as oxidative stress because it does not affect only
one organ, but the organism as a whole. Oxidative stress
is equal to whole-system stress that can lead to local problems or general shutdown. Luckily, antioxidant nutrition is
becoming a recognized field of science for animals raised
under intensive conditions, and it appears nutritionists are
now considering heat stress as one more causative factor to
this generic problem.
What is oxidative stress?
Oxidation is a normal physiological process within the
animal organism. As such, there are counter processes to
neutralize damaging free radicals so as not to cause excessive or irreparable damage. However, oxidative stress
- a condition where normal antioxidant mechanisms are
overwhelmed - occurs under two situations:
First, when animals outright consume free radicals,
like oxidized feed, something that can be easily prevented with quality control and antioxidant feed protection.
Second, when stressful conditions appear in the life
of an animal, including disease, even in sub-clinical
forms, crowding, relocation, over-handling and, of
course, heat stress.
MOST PLANTS FOUND THRIVING
under extreme climatic conditions
are now recognized as sources of
phenolic antioxidant compounds.
August 2018 ❙ www.WATTAgNet.com
Although there is some innate capacity for internal
handling of oxidative stress, these mechanisms are
deemed insufficient for animals raised under modern intensive production systems. This is clearly a case
where the high genetic capacity for production of modern animals has not been followed by a concomitant
increase in antioxidant capacity. Thus, oxidative stress
prevails, and first it consumes internal and external