Neutralizing Fibroblast Growth Factor 23 Reduces Phosphate Requirements in Growing Chicks
T.R.
1Biology
1
Jarmes ,
E.A.
2
Bobeck ,
M.E.
2
Cook
152 Fall Semester Independent Project 2Department of Animal Sciences, University of Wisconsin-Madison, Madison, WI, 53706, USA jarmes@wisc.edu
Abstract
Results
Environmental phosphate pollution may be decreased by reducing livestock’s dietary
phosphate requirement. Fibroblast growth factor 23 (FGF-23) is a hormone that aids
in phosphate regulation by promoting excretion of excess phosphate. It was
hypothesized that the neutralization of FGF-23 may minimize the phosphate
requirements in chicks. White leghorn hens were immunized with 5 FGF-23 peptides
(8 amino acids long, arbitrarily named FGF-2, FGF-3, FGF-C, W, T) or an FCA control.
Chick progeny received passively transferred maternal antibody from each injected
hen and were randomly assigned a low or normal phosphate diet on day of hatch.
Growth, plasma phosphate, and bone ash were analyzed to determine the effects of
maternal antibody on the phosphate requirements of the growing chicks. Feeding
FGF-3 chicks a low phosphate diet resulted in a significant 25.14% decrease in final
body weight vs. normal phosphate (p=0.0008). FGF-3 chicks fed low phosphate diets
did not have significantly reduced plasma phosphate as compared to FGF-3 fed
normal phosphate (p=0.1525). FGF-3, T, and W chicks fed a low phosphate diet were
not significantly different than FGF-3, T, or W fed normal phosphate (p>0.19). As
expected, chicks assigned to low phosphate diets expressed lower average bone ash
percentages than chicks on high phosphate diets (p>0.05). These data show strong
evidence that maternal antibody treatment can be used to neutralize FGF-23 and
decrease the phosphate requirements necessary for chicks to grow by reducing the
amount of phosphate an animal excretes.
Effect of Anti-FGF-23 on Growth
•Low phosphate diet FCA control chicks had a significant 16.7% decrease in body weight compared to high
phosphate FCA chicks with p=0.007 (Figure 1).
•No significant differences between low and normal phosphate diets within antibody treatment were found in
body weight gain except in the FGF-3 antibody treatment, where low phosphate-fed chicks’ average weight was
significantly reduced by 25% (Figure 2).
•Diet had an overall main effect of p<0.001.
•The main effects of antibody (p=0.1018) and diet*antibody (p=0.8616) were not significant.
Figure 1. Total gain. Chicks were weighed weekly and total gain was calculated from start and end weight. Averages are shown with standard error for
each treatment. Data were analyzed for differences between low and normal phosphate diets within antibody treatments. *Indicates significant
difference between low and normal phosphate within antibody treatment.
Introduction
•Phosphate supplements are fed in excess to enhance growth in livestock (Ward et al.,
2001).
•Rain runoff from livestock operations contributes to phosphate pollution of surface
water.
•Fibroblast growth factor 23 (FGF-23) is a hormone in vertebrates that aids in
phosphate regulation by promoting the excretion of excess phosphate (Stubbs et al.,
2007).
•Antibody treatment has shown to be successful as a safe and effective way to
enhance growth among animals (Chalgoumi et al., 2009, Cook, 2010).
•By neutralizing FGF-23 with antibody treatment received passively from the mother,
phosphate requirements of growing chicks may be decreased.
•The ability of all antibodies (except FGF-3) to overcome growth depression due to phosphate deficiency could
be the result of the increased hatch weight of these chicks receiving passive antibody to FGF-23 (data not
shown).
•The heavier a chick is at hatch, the faster the growth rate (Wilson et al., 1991; Ulmer-Franco
et al., 2010).
•FGF-3, T, and W prevented reduced bone ash in low phosphate diets when compared to normal phosphate
diest, as bone ash percent between low and normal phosphate was not significantly different (p>0.19, Figure
3).
•FGF-3, T, and W were successful at minimizing the bone mass lost from a low phosphate diet.
•Could be explained by decreased excretion of phosphate from the body due to maternal
antibody.
Hypothesis: The chicks with maternally transported FGF-23 antibodies will
present equal or higher growth, plasma phosphate levels, and bone ash
percents than untreated chicks (FCA control).
Methods
Figure 2. Average plasma phosphate. Average plasma phosphate with standard error at study completion is shown for each treatment. Data were
analyzed for differences between low and normal phosphate diets within antibody treatments. *Indicates significant difference between low and
normal phosphate within antibody treatment.
Thanks are extended to Dr. Mark Cook and Elizabeth Bobeck for the support, guidance, and knowledge supplied
while completing this study.
References
•Chalghoumi, R., Beckers, Y., Portetelle, D., & Thewis, A. (2009). Hen egg yolk antibodies (IgY), production and use for passive immunization against bacterial enteric
infections in chicken: a review. Biotechonology Agronomy Social Environment. 13(2): 295-308.
•Cook, M. E., & Trott, D. L. (2010). IgY-Immune component of eggs as a source of passive immunity for animals and humans. World's Poultry Science Journal. 215-226.
•Mahdavi, A.H., Rahmani, H.R., et al. (2010). Effects of dietary egg yolk antibody powder on growth performance, intestinal Escherichia coli colinization, and
immunocompetence of challenged broiler chicks. Poultry Science. 89: 484-494.
•Moore, P., Daniel, T., Sharpley, A., & Wood, C. (1995). Poultry manure management: Environmentally sound options. Journal of Soil and Water Conservation. 50(3). 321327.
•Stubbs, J., Liu, S., & Quarles, L. D. (2007). Role of Fibroblast Growth Factor 23 in Phosphate Homeostasis and Pathogenesis of Disordered Mineral Metabolosm in Chronic
Kidney Disease. Seminars in Dialysis. 20(4): 302-308.
•Ulmer-Franco, A., Fasenko, G., Christopher, E. (2010). Hatching egg characteristics, chick quality, and broiler performance at 2 breeder flock ages and from 3 egg weights.
•Ward, K. (2001). Phosphorus-friendly transgenics. Transgenic animals engineered to express a bacterial provide a solution to a common form of environmental pollution.
Nature Biotechnology. 415-416.
Data Analysis
•An ANOVA was conducted with a 2 X 2 factorial with dietary phosphate and antibody
type as the main effects. All possible comparisons between the groups were made.
Treatments means were deemed different if p<0.05
*Low and normal phosphate diets
contained 0.52% and 0.66% total
and 0.28 and 0.42 available
phosphate (Pi), respectively.
Conclusion
Altering the function of FGF-23 through maternally derived antibody may reduce the dietary phosphate
requirements of the chick. The poultry industry currently uses 0.4 million tons of feed phosphate at a cost of
$400 million in the USA. A vaccine could potentially be developed that would lower the animal’s requirement
for phosphate using one of the candidate antibodies identified in this study. FGF-3 may be an ideal candidate
because it not only prevented bone loss, it additionally prevented decreases in plasma phosphate when
compared to the FCA control chicks of the same diets, a result that has not been seen in past experiments.
Acknowledgments
Data Collection
•Chicks were weighed on day of hatch and weekly for the following two weeks to
determine total weight gain throughout the 14 day study.
•Blood was analyzed to determine plasma phosphate (mg/dL).
•The right tibiotarsus from each chick was ether extracted to remove fat and then
ashed at 600°F to determine dry, fat-free bone ash.
Table 1. Experimental diet.
Two diets were mixed to
accommodate low and normal
phosphate levels. The low
phosphate diet was deficient in
available inorganic phosphate but
adequate in total phosphate.
Effects of Anti-FGF-23 on Bone Ash
•Chicks fed high P diets consistently had higher bone ash percentages than low P chicks of same treatment
(main effect of diet, p<0.0001).
•Feeding T and FGF-3 chicks low phosphate diets only resulted in a non-significant 6.5% and 6.6% decrease in
bone ash as compared to T and FGF-3 chicks fed a normal phosphate diet (p=0.50).
•Main effect of antibody (p=0.64) and diet*antibody interaction (p=0.30) were not significant (Figure 3).
FCA control chicks had a significant 20.8% decrease in bone ash, as expected (p=0.03)
Discussion and Conclusion
Objective
The purpose of this experiment is to study how effective 6 different antibody
treatments (FGF-2, FGF-3, FGF-C, T, W, and FCA control) are in neutralizing FGF-23 and
therefore decreasing phosphate requirements in growing chicks.
•FGF-23 peptides (8 amino acids in length) were selected based upon location,
hydrophobicity, accessibility, antigenicity, and structure of the FGF-23 protein.
•White leghorn hens (3 per treatment) were injected with FGF-23 peptides (FGF-2,
FGF-3, FGF-C, T, W, or FCA control and inseminated.
•Chick progeny were hatched and randomly assigned to a high or low phosphate diet
(Table 1).
•ELISA was performed to verify the presence of antibody in the vaccinated hens’ egg
yolks (data not shown).
Effects of Anti-FGF-23 on Plasma Phosphate Level
•FGF-C and FGF-2 chicks fed a low phosphate diet had largest percent decreases (Figure 2), with 56.69% and
46.5% decreases, respectively (p<0.0001).
•FGF-3 chicks fed low phosphate diets showed the smallest decrease in plasma phosphate levels, with only
13.69% (p=0.1525).
•All antibodies except FGF-C and FGF-2 resulted in equal or better (less decrease in plasma phosphate levels
from chicks fed high phosphate diets to low phosphate diets) plasma phosphate levels.
•FCA control chicks showed a 42.51% decrease in plasma phosphate levels (p=0.0011), a significant decrease
compared to a majority of treated chicks (Figure 2).
Figure 3. Average bone ash %. Right tibiotarsi were ether-extracted to remove fat and then ashed in a muffle furnace at 600°F overnight. Treatment
averages are shown with standard errors. Data were analyzed for differences between low and normal phosphate diets within antibody treatments.
*Indicates significant difference between low and normal phosphate within antibody treatment.