INTRODUCTION:
Broiler chickens are known fast growing
species reaching market weights of about 3 kg of body weight within 8 weeks of
age. However, one of the environmental stressors that impede the fast growing
process of the birds is nutrition. Specifically, when the diet of the birds is
deficient in nutrients or under-supplied the birds become runts leading to huge
losses on the part of the broiler farmer (NRC, 1993). In the past, antibiotics
were used in poultry diets at sub-therapeutic levels to overcome this as their
uses were seen to improve growth and even reproductive performance. Currently,
there are bans on the use of certain antibiotics in poultry diets because of
the development of strains of pathogenic organisms that are resistant to some
antibiotics (NRC, 2012; Bekenev et al., 2015). To this extent, animals’ producers, including
poultry producers and nutritionists are in search for alternatives to the use
of antibiotics. One of the means of achieving this is via the fortification of
poultry diets with micro-nutrients, particularly vitamins which have been touted
to improving growth rates of livestock, including poultry primarily as a result
of their protective effects (Bekenev et al., 2015).
Based on the above stated implications of
vitamins in enhancing animal growth rates, Herbert et al. (2005) and Stahly et al. (2007), respectively demonstrated
that fortifying animal diet with vitamins is a dependable nutritional means of enhancing
animal growth and performance characteristics as they act as antioxidants
thereby protecting animals from oxidative stress. Some of the vitamins are
vitamins A, B, C and E. These vitamins have also been shown to synergistically
work together in improving growth rate and meat quality (Stahly
et al., 2007; Johnson et al., 2019).
With reference to vitamin C, it is required
as an essential nutrient for various biochemical and physiological functions in
the animal’s body. It is a well-known fact that the animal cannot synthesize
enough of vitamin C to meet all its biochemical and physiological requirements,
hence the need for vitamin C supplementation (NRC, 2012). Supplementation
levels needed in respect to broiler requirements regarding reduction of lipid
depositions, particularly the ‘bad’ cholesterol as well as up-regulating
antibodies in maintaining sound health of broiler chickens is not well
established. The paucity of information on these data therefore warranted this
current study. Therefore, the objectives of this study are: to investigate the
effects of feeding graded levels of vitamin C on total cholesterol (TC),
triglycerides (TG), low density lipoprotein (LDL), high density lipoprotein (HDL)
and very low density lipoprotein (VLDL) in broiler chickens as well as to
investigate broiler chickens’ antibodies responses to graded levels of vitamin
C: namely, immunoglobulin (Ig) G, immunoglobulin (Ig) A and immunoglobulin (Ig) M.
MATERIALS AND METHODS
Experimental site: This study was
carried out at the poultry unit of the Teaching and Research Farm, Rivers State
University, Nkpolu-Oroworukwo, Port Harcourt. The
farm is situated at latitude 40 48’N and longitude 60 48’E
at the Rivers State University campus.
Animals: One hundred and twenty (120) Agrited day-old chicks were acquired from a
reputable commercial poultry dealer in Port-Harcourt, Rivers State. The animals
on arrival at the Rivers State University Teaching and Research Farm were
brooded to proper pre-condition them to their new environment. The animals by
the fourth week were observed to have properly adapted to their environment and
thus were randomly assigned to four dietary treatment groups of 30
birds/treatment group with 3 replications of 10
birds/replicate. The pens were properly cleaned and disinfected before
the birds’ arrival. Feeders and drinkers were also properly cleaned to also
ensure that the animals’ environment were “pathogen-free”. During the brooding
period all protocols, including the necessary medications were provided.
Animals were fed similar diets from day one through the end of the 4th
week. Water was provided ad libitum.
The experiment lasted for 8 weeks and thus animals received their respective
experimental diets for 4 weeks.
Experimental Diets: Hybrid feedTM
grower mash were used in the study. In other
words, the diets fed to the animals during the last four weeks of the
experimental period were similar in all dietary nutrients except their dietary
vitamin C levels as: negative control or treatment 1 (T1, contained
only basal level of vitamin C of 30mg/kg of diet); whereas the positive
treatments, viz: treatment 2 (T2, contained
200mg of vitamin C), treatment 3 (T3, contained 300mg of vitamin C)
and treatment 4 (T4, contained 400mg of vitamin C)/kg of diet,
respectively. The animals were fed these graded levels of vitamin C-based diets
for 4 weeks.
Experimental Procedure and Data Collection: At the end of the
study period, birds were killed for blood collection. Three birds were randomly
collected from each replicate of the four treatment groups. The blood was collected from each bird into non-treated ethylene diamine tetra-acetic acid (EDTA) tubes and immediately snap
frozen in ice for later lipids and antibody analyses. Lipids were analyzed
according to the method of Nauck et al. (2002) and antibodies were analyzed according to the method
of Rey et al. (2017).
Experimental Design and Statistical Analysis: The study was
carried out as a completely randomized design (CRD). Data were subjected to
analysis of variance (ANOVA) using general linear model (GLM) procedure of SAS.
Treatment means were compared using Tukey’s test. The
model was: Yij=
µ + Xi + Eij, where Yij= individual
observation of the treatment, µ =
population mean, Xi =
effect of the ith dietary treatment (ith diet = 1, 2, 3, 4) and Eij=
the error term. An α-level
of 0.05 was used for all statistical
comparisons to represent significance.
RESULTS
Animals
in all the four dietary treatment groups readily consumed their respective
diets and grew throughout the experimental period as evidenced by their sizes
and weights at the end of the study period. Vitamin C ingestion was observed to
have profound effects on the lipid profiles of the birds in a dietary vitamin C
ingestion levels dependent fashions as depicted in Table 1.
As
shown in Table 2, there were no significant (P > 0.05) differences amongst all treatment groups in terms of the
serum levels of IgG and IgM
immunoglobulins. However, there were tendencies for
higher levels of IgG and IgM
in the sera of animals on diets 2, 3 and 4. Serum levels of IgA were very low
for all treatment groups, hence could not be statistically analyzed.
DISCUSSION
Fast
growing animal species, such as broiler chickens required their diets to be
well-fortified with dietary nutrients, especially micro-nutrients such as minerals
and antioxidant vitamins to elicit properties that better support their fast
growth rates without incidence of sudden deaths (NRC, 2012; Johnson et al., 2019). This is more so now that
the use of antibiotics had been banned in non-ruminant diets, including poultry
(Bekenev et
al., 2015).Environmental stressors, such as unbalanced nutrition of the animals
can lead to imbalance between oxygen reactive substances production and the animals’
anti-oxidant defense system resulting in cellular damage and incidence of
diseases in the presence of lowered immune response. This condition also results
in high economic losses on the part of the farmer (NRC, 2012).
Many dietary additives have been studied in
order to mitigate against stress, including oxidative
stress. Antioxidant vitamins, such as vitamin C acts as a catalyst in
oxide-reduction reactions and as a reducing agent that neutralizes free
radicals in aqueous compartments (Frei et al. 1989).Therefore, supplementing
broiler diets with vitamin C may be to the rescue by increasing antibody
concentration, lower LDL and thus improve performance in addition to good
quality meat (Holmannova et al., 2012).In this study, one of the major objectives was to
investigate the effect of feeding graded levels of vitamin C on the lipid
profiles of broiler chickens. As shown in Table 1, the ingestion of dietary
vitamin C reduced the total amount of cholesterol in the animals that were fed
the vitamin C-enriched diets. Furthermore, dietary ingestion of vitamin C
reduced body triglycerides. More importantly dietary vitamin C reduced LDL levels,
the “bad cholesterol” and increased the HDL levels, the “good cholesterol.” These
findings are in agreement with the findings of Das et al. (1997) and Frikke-Schmidt et al. (2011). From nutrition
standpoint, these findings in this current study point to the fact that vitamin
C could be used for value capture of broiler chickens as consumers prefer to pay
higher premiums for broiler meats of good quality in respect to reduced fat
contents of the broiler meat. This finding in this current study again is in agreement
with the data of Holmannova et al. (2012).
It is common knowledge that LDL is one of the
common causes of sudden deaths syndrome in fast growing animal species, such as
broilers and the pig, including humans. LDL normally forms plaques such that when
the plaques accumulate usually lead to the blockage or narrowing of blood vessels,
such as the arteries thereby impeding the normal process of blood circulation. These characteristics of LDL when not well managed is very
fundamental to cardiac arrest or heart attack of the animal resulting in atherosclerosis
(Das et al., 1997). Therefore, it is
not a gainsaying that cardiovascular disease is highly correlated with the
amount of lipids, particularly LDL in the blood. Since dietary vitamin C
reduced the levels of circulating LDL as found in this study, it can be
inferred that vitamin C can be used to protect the animal against
cardiovascular disease. This is more so as vitamin C reduced the LDL and
concomitantly increased the “good cholesterol.” These findings are in tandem
with those of Marc and McRae (2008) and Shariat et al. (2013).
The second object of this current study was
also to investigate the effects of feeding graded levels of vitamin C on the
antibodies status in broiler chickens. Many dietary additives have been
investigated as it relates to mitigation of stress in the animal. To this
point, many vitamins have been considered for this role. One of such vitamins
is vitamin C as it acts as a catalyst in oxide-reduction reactions and as a
reducing agent that neutralizes free radicals in aqueous compartments as
evidenced by the findings of Hamilton et
al. (2000). Vitamin C supplementation has been shown to up-regulate
immunoglobulin concentrations and thus improve performance characteristics in
piglets (Bekenev et
al., 2015). As also shown in Table 2,
dietary ingestion of the vitamin C-enriched diets had no remarkable effects on
the status of immunoglobulins compared to the control
in this study. However, there were trends of improved IgG
and IgM immunoglobulins by
the vitamin C enriched diets. This suggests that vitamin C could be used to
improve immunoglobulin status of broiler chickens to reduce stress in the chicken
and thus improve performance parameters. Furthermore, vitamin C enriched diets had
no effects on IgA immunoglobulin in this study.
Conclusions: Vitamin C can be used
to reduce the total cholesterol, triglycerides and low density lipoprotein
contents of the broiler chicken. On the other hand, vitamin C can be used to
increase the high density lipoprotein contents in the broiler chicken. The
overall benefits of these are that vitamin C can be employed in the production
of broiler chickens with less fat contents for better value capture as vitamin
C can improve the HDL contents of the chicken that consumers cherish.
REFERENCES
Bekenev,
V.; Garcia, A. and Hasnulin, V. (2015). Adaptation
of piglets using different methods of stress prevention. Animals,
5:349-360.
Das, S.; Snehlata, B. L and Srivastava, L. K. (1997). Effect of
ascorbic acid on lipid profile and peroxidation in hyper-cholesterolemic
rabbits. Nutr. Res. 17(2):231- 241.
Frei,
B. England, L. and Ames, B. N. (1989). Ascorbate
is an outstanding antioxidant in human blood plasma. Proc. Natl. Acad. Sci.
USA. 86:6377-6381.
Frikke-Schmidt,
H. Tveden-Nyborg, P.; Muusfeldt,
M. and Lykkesfeldt, J. (2011). High dietary fat and
cholesterol exacerbates chronic vitamin C deficiency in guinea pigs. Brit. J. Nutr. 105:54-61.
Hamilton, I. M. J.; Gilmore, W. S.;
Benzie, I. F. F.; Mulholland, C. W.; and Strain, J. J. (2000). Interactions
between vitamins C and E in human subjects. Br. J. Nutr.
84:261- 267.
Herbert, K.; House, J. D. and Guenter, W. (2005). Effect of dietary
folic acid supplementation on egg folate content and
the performance and folate status of two strains of
laying hens. Poult. Sci. 84:1533-1538.
Holmannova,
D.; Kolackova, M. and Krejsek,
J. (2012).
Vitamin C and its physiological role with respect to the
components of the immune system. V nitr.
Lek.
58(10): 742-749.
Johnson, N. C.; Popoola,
S. O. and Owen, O. J. (2019). Effects of single and
combined antioxidant vitamins on growing pig performance and pork quality.
International Journal of Advance Research and Publication.
3(8):86-89.
Marc, P. and McRae, D. (2008). Vitamin C
supplementation lowers serum low-density lipoprotein cholesterol and
triglycerides: a meta-analysis of 13 randomized controlled trials. JCM. 7(2):548-581.
Nauck,
M.; Warnick, G.R. and Rafai,
N. (2002).
Methods for measurement of LDL- cholesterol: A critical assessment of direct
measurement by homogeneous assays versus calculation. Clinical
Chemistry. 48(2):236-254.
NRC (1993). Nutrient
Requirements of Poultry, 9th Ed. Nalt.
Acad. Press, Washington, D. C.
NRC, (2012). Nutrient
Requirements of Swine, 11th Ed. Nalt.
Acad. Press, Washington, D. C.
Rey, A. I.; Lopez-Bote,
C. J. and Litta, G. (2017). Effects
of dietary vitamin E (DL-α- tocopheryl acetate) and
vitamin C combination on piglets’ oxidative status and immune responses at weaning.
Journal of Animal Feed Science. 26:226- 236
Shariat,
S. Mostafavi, S. A. and Khakpour,
F. (2013).
Antioxidant effects of vitamin C and E on the low-density lipoprotein oxidation
mediated by myeloperoxidase. Iran Biomedical Journal.
17(1):22-28.
Stahly, T. S.; Williams, N.
H.; Lutz, T. R.; Ewan, R. C.; Swenson, S. G. (2007). Dietary vitamin B needs of
strains of pigs with high and moderate lean growth. Journal
of Animal Science. 85(1):188-195.
