Why Give Dietary Fat to Chicken?
By Dr Sanjib PRATIHAR, GM technical, Rnk Agro & Chemicals P. Ltd.
All researchers from time
to time through various experiments have proved beyond any doubt the importance
and necessity of fat inclusion in the poultry diet. Some of the reasons are
enumerated here below:-
Essential Fatty Acids
Birds are not able to synthesize
all fatty acids and only some essential fatty acids such as Linoleic (18:2,
n-6), Linolenic (18:3, n-3) and Arachidonic acid (C20:4) fatty acids are easily
absorbed from the feed (Dvorin, et al.,
1998). They are termed essential because
the birds are unable to synthesize or convert one fatty acid to another fatty
acid within the same series.
A deficiency of essential
fatty acids may result in impairment of growth and immune system. Symptoms of
deficient essential fatty acids are retarded growth, increased water
consumption and reduced resistance of diseases (Balnave, 1970).Deficiency in male
birds leads to, lower testes weight and
delayed development of secondary sexual characteristics. Deficiency in Layers,
leads to decreased egg size (Watkins, 1991)
Fatty acids high on these
essential fatty acids are easily available in several crude vegetable oils
except Palm oil.
Any deficiency in Linoleic
acid adversely affects egg production, and it has been proven that
supplementation of Linoleic acid, present in vegetable oils, increase egg
weight (Shutze and Jensen, 1963, Balnave,
1971), Zero hatchability also represents
the most acute deficiency of Linoleic acid. It led to increased susceptibility
respiratory infections, poor egg production, small egg size and low fertility (Miller et.al.1963, Menge et.al.1965).
Further it was reported
that conjugated isomers of Linoleic acid have been effective in minimizing
reduced growth rates and preventing the catabolic effects of immune
stimulations (Cook et.al 1993)
Improved Carcass Quality
The addition of Fats also
influence Carcass characteristics (Crespo
and Esteve-Garcia 2001, Azman et.al
2004, Nayebpor et al.2007, Febel et al. 2008 ).In particular, the supplementation of fats and oils in
diets has an impact on the fatty acid composition of the broiler carcass.
The
observed changes in fatty acids in broiler tissue can be ascribed to the direct
incorporation of dietary fatty acids into adipose tissues. Even in Arbor Acres
–broiler Nutrition supplement it is specifically mentioned that Carcass quality
improves provided balanced unsaturated: saturated fat is included in diet,
highly unsaturated fat diet would have detrimental effect on carcass greasiness
and storage quality.
Modulators of immune
responses:
A marked improvement in the
immunity, were attributed to the presence of PUFA. Some medium chain fatty
acids are also found to be very effective in controlling Campylobacter counts
in broiler caeca (Thomas et. al.2006)
Vitamin A- Vegetable oils are a rich sources of
carotenoids which are originators for the synthesis of Vit A. Functions of
Vitamin A are namely, regulates cell growth, especially epithelial cell which
are necessary for bone metabolism through involvement with osteoblasts
(bone forming cells) and osteoclasts (cells involved on bone resorption)
Surai, et.al.2001., influences antibody production thus deficient reduces
immune response mechanism. In fact, most formulators add additional Vitamin A
in growing birds which may not be necessary if the right vegetable oil or its
blend is selected.
Vitamin-D-Its required for normal calcium absorption and its
deficiency induces less calcium absorption leading to decreased egg production (Fritts and Waldroup, 2003, Jacob et.al.2011). Vitamin D also plays vital role in cellular immune
responses (Aslam et.al.1998). Above all Vitamin D improves bone health substantially
(Edward Jr, 1990). Most recently Schmidt
et.al 2010 has reported that Vitamin A and
D regulate bile acid synthesis that helps control fat absorption along with
their own (A &D) absorption.
Vitamin E- It has been proven by Lauridesen et.al. , 1997 that
addition of Vitamin E in the diet has substantially increased the tocopherol
content of muscle membranes in many animals which helps to improve shelf life
of the chicken meat. It along with Vit A helps alleviate heat stress in
chickens (Sahin et.al. 2001. Good vegetable oil carries adequate amount of Vit E and
also helps better absorption.
Thus dietary fat plays
significant role in the absorption of fat soluble Vita A, D, E and K) by acting
as their “carrier” apart from being a major source of these vitamins (Iqbal and Hussain, 2009). These fat soluble vitamins are incorporated into
portomicrons for transportation after absorption into Liver deposited as body
lipid stores (Devon, 1991)
Hence impairment of the
absorption of fat soluble vitamins is the most serious consequence of a dietary
deficiency of fat (Jacob.et.al. 2011)
Aids in Digestion of
Amino Acids: Dr Cowieson, A.J., Scotland, recently spoke-Knowledge Day November 24th
Hyderabad- on Extra caloric gains by adding dietary fat due to better
digestion/absorption of amino acids
Lecithin
Lecithin is a phospho Lipid (phosphatidylcholine) that is extracted from Soybeans. It acts as an emulsifier assisting fatty acids into micelles that facilitates fat absorption (Cho, et al., 2008); transports triglycerides out of intestinal mucosa. Lecithin also alters the serum hormone levels; Increases the ME of added fat; Improves the tenderness of meat and increases yolk percentage as well as improves albumen density and yolk color.
Milling Benefits: When we add dietary fat as a binder, it helps improve pellet quality. It provides optimal durability, and reduced dustiness and wastage of feed during the milling process besides acting as lubricants. It also helps reduce particle separation thus improving production and transportation and packing efficiency.
Diet-Induced Thermo genesis: Conversion of carbohydrates and protein to fatty acids is a heat-producing process; the presence of an adequate level of dietary fat prevents this process. Since, high percentage of dietary Fatty acids is used in the synthesis of triglycerides which in other words means faster FAT GAIN by the bird.
Conversely, Fatty acids derived from Carbohydrates or indirect sources must pass through a series of heat producing metabolic transformation. In other words, animal utilizes its own energy in metabolism of fat extraction from carbohydrates which in turn leads to one step forward and half backwards. Net gain is lesser and slower FAT GAIN hence more cost and heat stress to the bird which may also mean mortality, due to poor resistance under hot weather conditions or leads to high energy cost in temperature maintenance of the cages and the birds.
The beneficial effects of
vegetable oil on the efficiency of energy utilization were due to a reduced
heat increment rather than to a reduction in the basal component of the heat
production concluded Shannon and Brown,
1969.
Improved Palatability:-
Due to presence of
vegetable oils the diet was found to be more palatable and liked by the birds. Chickens
have very little taste buds, but in any case they do have some indeed. These
buds in chickens are in different locations than other animals. Chickens taste
buds are distributed primarily on the back part of the roof of the bird’s mouth
with 2-4% on the birds tongue.
These buds are so far back by the time the bird tastes it it’s already too late
to toss out. Yet the sense of taste is more than just how it feels in the mouth
of a bird it’s also the sensation a bird experiences after consumption. Most of
all birds don't have a sense of smell.
It's thus, assumed then
that fat cooked pellet/mesh diet gives better feel to the bird which leads to
better pickings than a dry no fat added diet.
What has researchers to
Say in Favor of Fat inclusion in the Diet? Fat is an essential additive
Broilers
It was found by Scott et.al. that,
net amount of energy obtained by chicks from diets,
1.
is 60% of the
metabolizable energy of proteins, whereas it could draw up to 75% metabolizable
energy from the carbohydrates and,
2.
90% of
metabolizable energy of the fat was utilized by the chicks. (Scott et.al.1982)
Unlike most, it was found
out that (Baiao and Lara 2005) inclusion of oil in starter diet increased the fat
digestibility that resulted into better performance of the broiler from
starting first week to 21 days of age, than chicks fed without ration without
oils.
Also, chicks fed diets
devoid of supplemental fat had higher levels of lipogenesis (metabolic
deposition of fat) and increased adipose fat deposition (Dvorin, et al., 1998).
3.
Chicks utilized ME
more efficiently for growth if part of the carbohydrate portion of the diet was
replaced with vegetable oil and adequate ME: Protein ratio (ME/P) is maintained
at about 13.2 kcal/gm. of balanced protein.
Conclusion:
1.
Fat digestibility
-not a limiting factor in the growth of young broilers.
2.
Broiler chicks
could absorb VEG oil from 84% during the first week of age to 95% during the
second,
3.
SAFA absorption
increased from 40 to 79%.
4.
The ME of a diet
was maximized due to inclusion of fat.
5.
Day-old broiler
chicks had increased fat digestibility.
Laying hens
a.
Laying Hens when fed
with dietary fatty acids increased egg weight due to oviductal protein synthesis
a mechanism different from age related egg weight gain (Whitehead,et.al.,1993, Whitehead, 1995)
b.
Usually egg weight
gain due to age increases egg yolk rather than albumen.
c.
Differently, the
egg weight gain due to supplemental fat caused increase in albumen leading to
the weight gain.
d.
The effect on
egg weight gain is found to be more from 24 to 38 weeks of age (Grobas,et.al.,1999)
Conclusion: The Supplemental Fat exerts Favorable effects on egg
weight and egg production and lipogenesis
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