HOW TO MANAGE HEAT STRESS IN COMMERCIAL POULTRY THROUGH FEED NUTRITION FORMULATION
Dr.Surinder Khana,poultry Poultry consultant
Temperature is one of the important
environmental factors, affecting
poultry production. The proportion
of feed energy that is deposited or
converted to product is a small
fraction of ingested energy. The
remaining portion used for
maintenance and heat increment, is
released as heat into the environment. At high temperatures (above 32 C and relative humidity
50%), the heat loss through
evaporation exceeds the sensible
heat loss (conduction, convection
and radiation). At heat stress index
of 170, high mortality may be
noticed.
Heat stress has to be managed by a combination of management
methods including House and Nutrition management.
Protein and amino acid nutrition in
heat stress is not clear. Feed
formulation may be based on the
digestible amino acid basis,
following ideal amino acid profile
(reducing the imbalances,
minimizing the excesses),
considering high energy and high
protein ingredients with more
digestibility and the amino acids
available commercially (lysine,
methionine and threonine).
Supplemental fungistats to feed
ingredients and feeds to minimize
fungal contamination and toxin
binders to bind the toxins present in
the feeds are important in heat stress.
Supplemental dietary ascorbic acid
(250-400 mg/kg), vitamin E (250
mg/kg), folic acid (1 mg/kg),
vitamin D3 (3500 IU/kg), vitamin A
(15000 IU/kg), organic zinc and
selenium are beneficial in heat
stress.
Addition of various salts (potassium
chloride (0.2-0.5%), ammonium
chloride (0.2%), sodium bicarbonate
(0.2%) and a combination of these
alters the bird’s osmotic balance, maintains acid base balance and increases water consumption
influencing water balance beneficially during heat stress.
On pelleted feed, less energy is required
for feed intake (about 67% reduction in
the energy required for taking feed).
The advantage of pellets would be lost
if pellet quality is poor (Fines more
than 10%). Survivability of the birds
can be increased by reducing chances
of heat increment in hot periods
(feeding the bird during cooler parts of
the day and withdrawing the feed from
about 4-6 hours before the initiation of
heat stress). Nicarbazin, an
anticoccidial, may be avoided in hot
weather.
Antioxidants, gut acidifiers,
emulsifiers, organic trace minerals,
liver protectives, enzymes, pre and
probiotics, ammonia binders,
nucleosides, phytobiotics and flavor
enhancers may reduce microbial
contamination, improve the resistance
of the birds to infections, improves feed
intake and increases performance.
Drinking water may be treated with sanitizer and acidifiers to minimize microorganisms in the gut.
Heat stress has to be managed by a combination of management methods.———
- Housing Management
- Nutritional Management
- Drinking Water
- Energy and Protein in Feed
- Vitamins in Feed and Water
- Electrolytes in Feed and
Water - Form of Feed
- Time of Feeding
- Feed Additives to improve
Health and Immunity - Anticoccidials
- Housing Management
Maintaining coolness in the poultry
house is an important management
option. It starts with the planning of
house design and also the
management of the house and the
birds after the house construction.
Only a mention is being made on the
methods to maintain the poultry
house cool. Broiler or layer houses,
in our country, are mostly open
sided houses.
- Nutritional Management
- DrinkingWater
- Availability of cool drinking water:
Water is the important media for
heat loss. About 70-80% of the
bird’s heat production during
heat stress is dissipated via
panting (evaporative cooling).
Adequate water provision is a
must as water restriction even
for a short period is disastrous
for poultry in hot weather.
Reduction of water temperature
and addition of salts are helpful in improving water intake.
- R e d u c t i o n o f w a t e r temperature:
Overhead water tanks are exposed to constant heat in
summer months. Location of
water tanks in shaded area or
provision of shade over water
tanks keeps water cool.
Insulation of water tanks and
provision of sprinkling water on
to the water tanks with water
retaining material (layers of
Gunny etc) reduces the water
temperature further. Water pipes
must run under ground and any
exposed pipes have to be
covered to prevent heating of the
pipes. When the water temperature is less than 28 C at bird level, an improved performance of birds is observed.
- Water Treatment:
Water may contain micro-organisms and hence may be treated with sanitiser and acidifiers to minimize microorganisms in the gut.
- Energy and Protein in Feed
Stimulation of feed intake in heat stress
improves weight gain but mortality also
increases. Increasing the ME content of
feed also improves energy intake. The
increased energy intake results in
improved growth but also in increased
fat in the carcass and also the mortality
The research conducted on
protein and amino acid nutrition in
strategies to minimize the effects of
heat stress is inconsistent and also
controversial. It appears that there is no
interaction between environmental
temperature and dietary nutrient
concentration. Increased protein in diet
cannot increase protein deposition, and
proves harmful. The heat increment
with protein (amino acid) catabolism is
more than that of carbohydrates and fat.
Reduction in protein in diet to reduce
heat increment increases feed intake,
due to the deficiency of amino acids.
Less protein in diet also reduces water
intake, a disadvantage in strategies to
minimize the effects of heat stress. The
influence on the effect of heat stress on
absorption of amino acids is not clear
and so the ideal amino acid pattern
needs to be followed in practical diets.
In diets with a fixed ME:protein ratio,
higher energy diets under supply
Under thermoneutral zone of
temperatures, reducing dietary
protein did not bring any beneficial
effects. Under heat stress
conditions, feed formulation based
on the digestible amino acids and
not by protein minimizes the
catabolism of amino acids for
elimination and reduces heat
production associated with the
elimination of excess amino acids.
High energy and high protein
ingredients with more digestibility
and the commercially available
amino acids (lysine, methionine and
threonine) may be considered in diet
formulation to meet the amino acid
requirements rather than the protein
requirements. This reduces protein
content of the diet from the values
practiced in other seasons by about
5-10% of the original value.
Supplemental fat (prohibitive cost
for layer) may also be considered at
least for shorter periods as a high-
energy ingredient
- Vitamins in Feed and Water
Vitamin A, D, E, C and folic acid are
known to reduce the effects of heat
stress. It is well known that vitamin
C enhances antioxidant activity of
vitamin E.
Supplemental dietary ascorbic acid
(vitamin C) limits and alleviates the
metabolic signs of stress and
improves the performance,
immunological competence and
behavior of birds. Optimum
responses in growth, feed efficiency
and/or livability in broilers under
heat stress seem to occur with
supplements of about 250 mg
vitamin C/kg feed. Laying hens
have also shown responses to
supplemental ascorbic acid
(250-400 mg/kg) in terms of
improvements in livability, feed intake, egg production and egg
quality with dietary ascorbic acid
(Whitehead and Keller, 2003).
Supplemental vitamin C influences
energy stores, that are used during
Vitamin E can be supplemented to
broiler diets (250 mg/kg) as a
protective management practice to
reduce the negative effects of stress
and to result in optimal performance
(Sahin et al., 2002).
Vitamin C (250 mg/kg) and folic
acid (1mg/kg) supplementation
arrests decline in performance and
antioxidant status caused by heat
stress. Supplemental dietary vitamin
C (200 mg) and vitamin E (250-500
mg) offers a good management
practice to reduce heat stress related
decreases in performance of
Japanese quails (Sahin et al., 2002).
Higher levels of vitamin D 3 (3500
IU/kg) and vitamin C (200 or 400
mg/kg) can improve eggshell
quality (Faria et al., 2001).
Supplemental vitamin C, vitamin E,
organic zinc and selenium improved
the performance of broilers due to
lower feed intake resulting in better-
feed conversion, independently on
the environment (Lagana et al., 2007).
Supplemental vitamin A (15000
IU/kg) and zinc (30 mg/kg)
improves the performance and
carcass traits in broilers, and
decreases abdominal fat pad. A
combination of vitamin A (15000
IU/kg) and zinc (30mg/kg) offer a
potential protective management
practice in preventing heat-stress-
related depression in performance of
broiler chickens (Kucuk et al., 2003).
Elimination of vitamin fortification
from the diets of broilers from 22d
age exposed to heat stress results in
significant reductions in live bird
and carcass performance. The data
(Table 11) suggest that trace mineral
supplementation may be
responsible for a further reduction in
bird performance via oxidation of
the vitamins already present. Body
weight, F/G and survivability were
adversely affected by the absence of vitamin supplementation. Carcass fat, as estimated by specific gravity and fat pad were significantly increased by the lack of vitamin supplementation.
- Electrolytes in Feed and Water
Addition of various salts to water alters
the bird’s osmotic balance, resulting in
increased water consumption,
influencing water balance during heat
stress. No growth response has been
observed by adding salts to drinking
water for non-heat stressed birds.
Increased water consumption benefits
the bird by acting as a heat receptor as
well as increasing the amount of heat
dissipated per breath. Such
thermobalance effects are principally
observed when water temperature falls
below 28°C. Birds in positive water
balance are better off in maintaining
normal body temperature. This has
special significance for the commercial
broiler as heat stress increases urine
production, independent of water
intake, thus forcing birds to sustain
higher water consumption levels than
required to simply replace water loss
due to evaporative cooling (See
Summers, 2006).
There are significant interactions
between adding salt to drinking water
and water temperature. If the
temperature of the drinking water is
below that of the bird’s body, then only,
adding potassium chloride will
increase consumption. Lowering the
temperature of the water, with no salt
addition, also improves water intake.
Indeed water temperature and
potassium chloride effects appear to be
additive. Such responses are given in
Table 12 (See Summers, 2006).
Potassium chloride even at 0.2% gives
beneficial results in increasing water
intake of laying hens (Table 13, Dai and
Bessei, 2007). During heat stress
mineral excretion via the urine and
feces is increased. Whether specific
benefits with mineral supplementation
exist, independent of their effect on
water intake, is not known. It would
appear that potassium based salt
mixtures are superior to sodium
when added to drinking water.
Acid-Base Balance:
Electrolytes maintain ionic and
water balance in the body. Broiler
growth is affected when blood pH is
below 7.2 and above 7.3. During
heat stress electrolytes are lost from
the body. The loss of electrolytes
can be prevented by intake of
electrolytes in feed and water
Increased respiration rate during
heat stress also results in carbon
dioxide loss and acid-base
alterations (Bottje and Harrison,
1985; Teeter et al., 1985). The
various drinking water supplements
may act through increased water
intake of birds (Wiernusz, 1998).
Favorable broiler responses were
observed through the
supplementation of various salts to
the drinking water
Acid base balance is influenced by
the degree and duration of thermal
stress and acclimatization. During
panting (increased number of
respirations) excessive loss of
carbon dioxide (CO ) occurs, 2
resulting in reduced partial pressure
of carbon dioxide (CO ) in blood 2
plasma. The bicarbonate buffer
system lowers the concentration of
hydrogen ion, increases plasma pH
and plasma bicarbonate levels
(Table 15). This is known as
respiratory alkalosis. More
bicarbonate is excreted through
+
kidney while retaining H . A consequence of respiratory alkalosis
is reduced feed intake. The respiratory alkalosis may start at 35 C and becomes severe with rise
in temperature. However, these
effects of altered acid-base balance
are, at present, little understood
Supplemental broiler grower diet (4-
6 weeks age) with 1.0% KCl or 1.0%
NaHCO or 0.5% NH Cl + 0.5%
3 4
KCl + 0.5% NaHCO had beneficial
3
effects on the growth performance
under high environmental
temperature during summer season
in uncontrolled broiler houses
(30.19-32.90°C and 48.08-51.03%
RH) (Osman, 2000). Supplemental
nonchloride sodium salts (sodium
bicarbonate, sodium carbonate and
sodium sulphate) to broiler diets in
heat stress conditions (29.3 to 38 C)
inceased water intake, reduced
mortality, improved body weight
and yield of carcass and parts.
Sodium bicarbonate was better than
the other sodium salts (Ahmad et al.,
2006).Dietary electrolyte balance (DEB), under practical considerations, is considered with sodium (Na ), potassium (K ) and chloride (Cl )
+
Weight gain has been enhanced with water carbonation or supplementation with acids such as NH cl or Hcl, 4
suggesting that acid-base balance is
critical for maximizing weight gain.
While a number of additives have been
used to try and alter acid/base balance
all seem to act by increasing water
intake. Thus, while water intake is an
important consideration there is also an
acid-base balance effect, which must be considered. High DEB had a direct relationship on water intake, which in turn on survivability.
Commercial electrolyte mixtures are
available and used with many
encouraging results by poultry farmers
to reduce heat stress and to increase
water intake. Some of the commercial
preparations contain vitamins, citrates
and phosphates in addition to chlorides,
bicarbonates and other salts. The effect
of electrolytes may be based on blood
pH, water intake, respiratory rate and
productive parameters.
- Form of Feed———–
- Crumbles and Pellets
Most feed used in commercial
broiler production is in the form of
crumbles or pellets. Some
integrators use mash feed in starter
and or finisher period to reduce the
feed cost. On pelleted feed, less
energy is required for feed intake
(Table 17; Jensen et al., 1962)
(about 67% reduction in the energy
required for taking feed; See Gous and Morris., 2005). Pelleting has no
effect on ME content of feed. The
energy sparing effect of pellets, due
to reduced activity for feeding is
about 6% (McKinney and Teeter,
2003). The advantage of pellets
would be lost when pellet quality is
poor (Fines more than 10%) (Jensen,
- Wet Mash
Wet mash feeding results in
increased feed intake and improved
performance, mediated by more
water intake. However,
applicability for commercial practices on large scale is not
feasible. If the feeders are not cleaned properly, fungal infestation and toxin production are the major problems
- Time of Feeding
Heat increment is associated from the time of feeding up to about 4-6 hours after feeding. Survivability of the bird will increase by feeding the birds during night and withdrawing the feed from about 4-6 hours before the initiation of heat stress.
- Feed Additives to Improve Heath and Immunity
Poultry feeds are supplemented
with trace minerals, vitamins and
coccidiostats. In heat stress, the
resistance of the bird to infections is
reduced. Several feed additives are
available to improve the resistance
of the birds to infections. Besides
vitamin E and vitamin C mentioned
earlier, the following feed additives
may be considered to improve
immunity and resist the infections
(Table 18).
At high environmental
temperatures fungal infestations are
common, particularly when relative
humidity is high. Storage of feed
ingredients to reduce fungal
infestation, supplemental fungistats
to feed ingredients and feeds to
minimize fungal contamination and
toxin binders to bind the toxins
present in the feeds are important in
heat stress
- Anticoccidials-
The toxicity of Nicarbazin (an effective anticoccidial), in hot weather, appears to be related to increased heat production Wiernusz and Teeter, 1995). It may be avoided in hot weather, even in combination with other
anticoccidials.
