http:// www.jstage.jst.go.jp / browse / jpsa
doi:10.2141/ jpsa.0120135
Copyright Ⓒ 2013, Japan Poultry Science Association.
Estimation of Dietary Sodium Bicarbonate Dose Limit in Broiler
under High Ambient Temperatures
Yunzhi Peng*, Yongwei Wang*, Dong Ning and Yuming Guo
College of Animal Science and Technology, China Agricultural University, Beijing 100193, PR China
A six-week trial was conducted to estimate the dose limit of sodium bicarbonate (SB) in the diet of broiler
chickens exposed to high ambient temperature. The estimation of SB dose limit was based on the growth performance, blood biochemical parameters and histological observation of the renal tissues of chickens. A total of 450 dayold male broilers were randomly distributed to five groups with SB supplemented at levels of 0 (control), 0.5%, 1.0%,
2.0% and 4.0%. The minimum and maximum average ambient temperatures were 26.4℃ and 32.5℃, respectively,
with relative humidity ranging from 57.2% to 83.8%. Results showed that (1) A linear effect of increasing dietary SB
level was observed on body weight gain (BWG) (P＜0.05), feed intake (FI) (P＜0.05) and feed to gain ratio (F:G) (P
＜0.05) from day 1 to 21 and day 1 to 42. Supplementation of 4.0% SB decreased BWG (P＜0.001) and FI (P＜
0.001), but increased F: G (P＜0.001) from day 1 to 21, and decreased FI (P＜0.001) from day 1 to 42. (2) Compared
with the control treatment, an SB of 4.0% gave higher incidences of diarrhea (P＜0.001), mortality (P＜0.001) and
ascites related mortality (P＜0.001). (3) Rectal temperatures were linearly decreased (P＜0.05) with rising SB levels.
(4) Blood biochemical analysis indicated that SB higher than 1.0% decreased blood hemoglobin (HGB) (P＜0.001),
and increased hematocrit (HCT) (P＜0.001) and serum malondialdehyde (MDA) concentration (P＜0.001) on day 21.
(5) Microscopic examination revealed that significant renal haemorrhage appeared when SB exceeded 1.0% and
tubular dilation was observed in 4.0% SB treatment. In summary, dietary supplementation of 4.0% SB resulted in
poor growth performance and higher mortality. In addition, SB higher than 1.0% affected blood biochemical parameters and caused renal lesions. The current results suggest that the dose limit of dietary SB is less than 1.0% for
broilers under high ambient temperatures.
Key words: broiler, dose limit, high ambient temperatures, sodium bicarbonate
J. Poult. Sci., 50: 346-353, 2013
Introduction
Extreme thermal condition can decrease growth performance and reproductive efficiency in broilers and other domestic animals (Fuquay, 1981). Poultry production in many
regions of the world is adversely affected by heat stress (HS).
HS causes an economic loss of $128 million in poultry
industries every year (St-Pierre et al., 2003). Broilers are
more susceptible to HS because of their body feathers and
high metabolic rate (Lin et al., 2006a). Under high ambient
temperature, birds increase panting rate for evaporative
cooling, which results in carbon dioxide loss and acid-base
imbalance (Bottje and Harrison, 1985; Teeter et al., 1985;
Teeter and Belay, 1996). Moreover, HS can induce oxidaReceived: September 1, 2012, Accepted: April 2, 2013
Released Online Advance Publication: May 25, 2013
Correspondence: Y. Guo, College of Animal Science and Technology,
China Agricultural University, Beijing 100193, PR China.
(E-mail: [email protected])
* Authors contribute equally to this work
tive stress by increasing serum MDA production (Lin et al.,
2006b) and activity of anti-oxidative enzymes such as
superoxide dismutase (SOD) and glutathione peroxidase
(GSH-Px) (Altan et al., 2003).
Sodium bicarbonate (SB) was widely used as a regulatory
agent for chickens to alleviate the deleterious effect of HS by
maintaining acid-base balance (Hayat et al., 1999; Borges et
al., 2003; Borges et al., 2007). Dietary supplementation of
0.5-1.0% SB has been shown to improve growth performance under high ambient temperatures (Teeter et al., 1985;
Abou-El-Ella and Ismail, 1999; Borges et al., 2003; Naseem
et al., 2005; Tanveer et al., 2005; Ahmad et al., 2006;
Ghorbani and Fayazi, 2009). However, overdose of SB had
detrimental impacts on birds and may cause poor growth
performance (Hayat et al., 1999), a decrease in blood red
blood cell (RBC), hemoglobin (HGB) and hematocrit (HCT)
(Mirsalimi and Julian, 1993) and renal lesion (Mubarak and
Sharkawy, 1999). Scrivner (1946) reported a heavy mortality in 2 to 3-week-old chickens receiving 0.6% SB in their
drinking water. Clinical signs of the dead chickens included
Peng et al.: Dietary NaHCO3 and High Ambient Temperatures
subcutaneous oedema and ascites.
Previous research on overdose of SB mainly focused on
laying pullets (Davison and Wideman, 1992; Mubarak and
Sharkawy, 1999), or broilers supplemented with SB in their
drinking water (Davison and Wideman, 1992; Mirsalimi and
Julian, 1993). However, little information is available on the
dose limit of SB in broiler chicken’s diets. Since chickens
with apparently normal growth may not be in a normal
physiological state (Hayat et al., 1999), parameters such as
blood metabolites, redox status and renal histopathological
examination would be more appropriate than only the
analysis of growth performance to determine the dose limit
of SB. Thus, a dose limit of 2.0% SB in the diet, analyzed by
Hayat et al. (1999), calculated entirely from growth performance, might be overestimated. Therefore, it is indispensable
to reevaluate the dose limit of SB in broiler diet based on
more comprehensive results. Here, does limit of dietary SB
in broilers under high ambient temperatures was assessed in
terms of growth performance, mortality, blood chemical
parameters, redox status and histological examination.
Table 1.
Ingredient
Corn
Soybean meal
Soybean oil
Corn gulten meal
Dicalcium phosphate
Limestone
DL-Met
Lys．HCl
Aureomycin
Antioxidants
Choline chloride (50%)
Vitamin premix2
Trace mineral premix3
NaCl
NaHCO34
Calculated analysis
AME, MCal/kg
Crude protein
Calcium
Available phosphorus
Methionine
Lysine
Sodium
Chloride
Potassium
DEB, mEq/kg
1
347
Materials and Methods
Bird Management and Diet
The design and conduct of this study were approved by the
Institutional Animal Care and Use Committee of China
Agricultural University. A total of 450 day-old male broiler
chicks (Ross 308) were randomly allocated to five treatments
with six pens (2.4 m×0.6 m×0.6 m) of 15 chickens each.
Levels of SB in diet were 0 (control), 0.5%, 1.0%, 2.0% and
4.0%, respectively.
Diets were formulated based on NY/T33-2004 of China.
Feed composition was listed in Table 1. Ingredients of the
diet were analyzed for crude protein (CP) (Kjeldahl method),
phosphorus (P) (AOAC, 1984), calcium (Ca), and monovalent mineral (Na, K, and Cl) to validate that analyzed and
calculated values were similar. Ca, Na and K in feed were
determined by a flame atomic-absorption spectrometer (GBC
Sens AA Dual, GBC Scientific Equipment, Braeside, Australia); and Cl was analyzed by titration with AgNO3
(Lacroix et al., 1970). The SB was pre-mixed with NaCl and
then fully mixed with other feedstuffs of the diet step by step.
At the onset of experiment, diet was provided as crumbles
Composition of experimental diets (%)1
Grower diets (day 22 to 42)
Starter diets (day 1 to 21)
58 . 90
31 . 38
1 . 22
4 . 00
2 . 10
1 . 16
0 . 18
0 . 11
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
0 . 00
57 . 90
31 . 56
1 . 54
4 . 00
2 . 10
1 . 16
0 . 18
0 . 11
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
0 . 50
56 . 91
31 . 74
1 . 85
4 . 00
2 . 11
1 . 15
0 . 18
0 . 11
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
1 . 00
54 . 93
32 . 10
2 . 48
4 . 00
2 . 12
1 . 15
0 . 18
0 . 10
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
2 . 00
50 . 96
32 . 82
3 . 74
4 . 00
2 . 14
1 . 13
0 . 18
0 . 09
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
4 . 00
62 . 90
26 . 27
2 . 85
4 . 00
1 . 52
1 . 26
0 . 10
0 . 15
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
0 . 00
61 . 91
26 . 45
3 . 16
4 . 00
1 . 52
1 . 26
0 . 10
0 . 15
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
0 . 50
60 . 92
26 . 63
3 . 48
4 . 00
1 . 53
1 . 25
0 . 10
0 . 14
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
1 . 00
59 . 19
26 . 42
4 . 00
4 . 40
1 . 54
1 . 25
0 . 10
0 . 15
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
2 . 00
58 . 33
20 . 37
4 . 00
9 . 12
1 . 56
1 . 28
0 . 08
0 . 31
0 . 10
0 . 02
0 . 30
0 . 03
0 . 20
0 . 30
4 . 00
2 . 90
21 . 0
1 . 00
0 . 48
0 . 50
0 . 83
0 . 15
0 . 28
0 . 73
182
2 . 90
21 . 0
1 . 00
0 . 48
0 . 50
0 . 83
0 . 28
0 . 28
0 . 73
241
2 . 90
21 . 0
1 . 00
0 . 48
0 . 50
0 . 83
0 . 41
0 . 28
0 . 73
300
2 . 90
21 . 0
1 . 00
0 . 48
0 . 50
0 . 83
0 . 68
0 . 28
0 . 73
418
2 . 90
21 . 0
1 . 00
0 . 48
0 . 50
0 . 82
1 . 22
0 . 27
0 . 73
654
3 . 05
19 . 0
0 . 90
0 . 38
0 . 40
0 . 70
0 . 14
0 . 28
0 . 66
160
3 . 05
19 . 0
0 . 90
0 . 38
0 . 40
0 . 70
0 . 28
0 . 28
0 . 66
219
3 . 05
19 . 0
0 . 90
0 . 38
0 . 40
0 . 70
0 . 41
0 . 28
0 . 66
278
3 . 05
19 . 0
0 . 90
0 . 38
0 . 40
0 . 70
0 . 68
0 . 28
0 . 65
393
3 . 05
19 . 0
0 . 90
0 . 38
0 . 40
0 . 70
1 . 22
0 . 31
0 . 56
596
Diet was calculated to contain the following (g/kg): starter: AME, 2.9 Mcal/kg; CP, 210; Ca, 10; available P, 4.8; Met, 5.0; Met＋Cys, 11;
finisher: AME, 3.05 Mcal/kg; CP, 190; Ca, 9.0; available P, 3.8; Met, 4.0; Met＋Cys, 10;
Supplied per kilogram of diet: vitamin A 12500 IU; vitamin D3 2500 IU; vitamin E 30 IU; vitamin K3 2.65 mg; thiamine 2 mg; riboflavin 6 mg;
vitamin B12 0.025 mg; biotin, 0.0325 mg; folic acid 1.25 mg; pantothenate acid 12 mg; niacin 50 mg.
3
Supplied per kilogram of diet: Cu, 8 mg; Zn, 75 mg; Fe, 80 mg; Mn, 100 mg; Se, 0.15 mg; I, 0.35 mg.
4
NaHCO3: feed-grade purity (99%).
2
348
Journal of Poultry Science, 50 (4)
and subsequently substituted by whole pellets.
Experiment was started in late June. The room temperature was maintained at 33℃ and 31℃ from day 1 to 7 and
day 8 to 14, respectively. The heating apparatus was removed on day 15 and evaporative cooling pad was shut down
throughout the experiment. The maximum and minimum
ambient temperatures and relative humility were measured
daily with an electronic thermometer. The light cycle was 24
h light from day 1 to 13 and 23 h light: 1 h dark from the age
of day 14. During the experimental period, broilers were
given ad libitum access to feed and water. Chickens were
vaccinated for Newcastle disease and infectious bronchitis
(ND-IB) on day 7 and 21, and infectious bursal disease (IBD)
on day 14 and 28.
Growth Performance
On day 21 and 42, body weight gain (BWG), feed intake
(FI) and feed to gain ratio (F:G) were calculated and corrected for mortality, if any. Diarrhea and deaths were documented to determine diarrhea incidence and mortality. All
dead chickens were subjected to postmortem examinations to
determine cause of death. Chickens with ascitic fluid or
hydropericardium were diagnosed as AS related death
(Druyan et al., 2007).
Rectal temperature was monitored weekly from day 14.
Three birds identified per pen for temperature measurement
by using electronic thermometer probe in the morning (A.M.
6:00 to 7:00) and afternoon (P.M. 1:00 to 2:00), corresponding to the coolest and warmest times of the day, respectively
(Borges et al., 2003).
Organ Indices and Histological Examination
On day 21 and 42, birds were randomly selected and killed
by jugular bleeding after 6 h of feed deprivation. Heart,
liver, spleen and bursa were collected and weighed for calculating the organ indices. Kidney tissues from each treatment were fixed in 10% neutral-buffered formalin, embedded
by paraffin technique and stained with haematoxylin-eosin
(HE) for histological examination under a light microscope.
Blood Collection and Analysis
At the age of day 21 and 42, venous blood samples were
collected by brachial vein puncture using two tubes containing anticoagulant EDTA-K3 or no anticoagulation. Red
blood cell count (RBC), blood hemoglobin (HGB), hematocrit (HCT) and mean corpuscular volume (MCV) were determined by using an automatic blood analyzer (Sysmex KX21N, Japan). Blood pO2, pCO2, pH and HCO3- were immediately determined by a blood gas analyzer (ABL-800;
Radiometer Analytical, Denmark). Serum were immediately
harvested by centrifugation of blood samples at 3000 rpm for
15 min. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total protein (TP) were measured
using an automatic biochemistry analyzer (Beckman Coulter
Unicel DXC 800, USA). Levels of serum malondialdehyde
(MDA), glutathione peroxidase (GSH-Px), total antioxidant
capacity (T-AOC), blood urea nitrogen (BUN) and uric acid
(UA) were determined by employing the colorimetric assay
kits (Nanjing Jiancheng Bioengineering Institute, Jiangsu,
China).
Statistical Analysis
The data of rectal temperature were analyzed by two-way
ANOVA using GLM (Univariate) procedure of SPSS 17.0
for the interactive effects of SB levels and sampling times.
Duncan’s multiple-range test was used to separate means that
significantly differ at P＜0.05. The other data were analyzed
by one-way ANOVA of SPSS 17.0. The significance of differences among treatment means was evaluated by Least
Significant Difference (LSD) post-hoc multiple comparisons
test. Linear and quadratic regression analyses were conducted.
Significance was P＜0.05 unless otherwise stated.
Results
Ambient Temperature and Relative Humidity
The minimum and maximum average ambient temperatures (Max T, Min T) and relative humidities (RH) were
26.4℃ and 32.5℃ and 57.2% and 83.8%, respectively, with
a peak of 34.8℃, which indicated the exposure of the birds to
high ambient temperatures (Figure 1).
Growth Performance
As shown in Table 2, both linear and quadratic of increasing SB level were found for FI (P＜0.01), and only
linear effect for BWG (P＜0.01) and F:G (P＜0.01) during
day 1 to 21; Supplementation of 4.0% SB decreased BWG (P
＜0.001) and FI (P＜0.001), but increased F:G (P＜0.001)
comparing with the control treatment. From day 22 to 42,
linear and quadratic response were described for BWG (P＜
0.01), and linear effect for F:G (P＜0.001) with the rising of
SB level; broilers fed with SB had greater BWG (P＜0.001)
and lower F:G (P＜0.001) than the control group. From day
1 to 42, both linear and quadratic trend were revealed for
BWG (P＜0.05) and linear tendency for F:G (P＜0.001)
with the increasing of SB level; comparing with control treatment, SB supplementation improved BWG (P＜0.001) and
FI (P＜0.01), and F:G (P＜0.001) were lower in birds receiving 4.0% SB.
Diarrhea, Mortality and Ascites Related Mortality
There were both linear and quadratic effects of increasing
SB for diarrhea incidence, mortality and AS related mortality
(Table 3). Broilers fed with 4.0% SB showed the highest
diarrhea (P＜0.001), mortality (P＜0.001) and AS mortality
(P＜0.001). Moreover, all died chickens in the 4.0% SB
treatment exhibited AS syndrome, such as drooping, expiratory dyspnea, comb cyanosis, hypertrophy and dilation of the
heart, and fluid accumulation in pericardium and peritoneal
cavity (pictures were not shown).
Rectal Temperature
Irrespective of the SB treatment, rectal temperature was
higher (P＜0.001) in the afternoon than in the morning.
Rectal temperature was linearly reduced (P＜0.001) with the
increasing SB level both in the morning and afternoon
(Figure 3)
Organ Indices
A linear effect was seen for heart (P＜0.001) and bursa
indices (P＜0.05) on day 21 (Table 4); SB higher than 1.0%
significantly increased heart index (P＜0.001), and addition
of 4.0% SB gave a higher bursa index (P＜0.05) compared
Peng et al.: Dietary NaHCO3 and High Ambient Temperatures
349
Ambient maximum and minimum temperature and relative
humidity from day 14 to 42
Fig. 1.
Table 2.
SB, %
0
0.5
1.0
2.0
4.0
SEM
P-value
Trt
Linear
Quadratic
a-c
Effect of dietary SB on the performance in broilers*
Day 1 to 21
Day 1 to 42
Day 22 to 42
BWG(g)
FI(g)
F:G
BWG(g)
FI(g)
F:G
BWG(g)
FI(g)
F:G
602a
597a
572a
568a
471b
10
928a
913ab
875b
892ab
730c
15
1 . 54b
1 . 53b
1 . 53b
1 . 57b
1 . 63a
0 . 01
1203b
1388a
1405a
1438a
1474a
21
2696
2785
2771
2814
2559
30
2 . 25a
2 . 01b
1 . 98b
1 . 96b
1 . 73c
0 . 03
1805b
1986a
1977a
2006a
1945a
18
3624a
3698a
3646a
3706a
3287b
38
2 . 01a
1 . 86ab
1 . 85ab
1 . 85ab
1 . 69b
0 . 02
＜0 . 001
＜0 . 001
NS
＜0 . 001
＜0 . 001
＜0 . 05
＜0 . 001
＜0 . 001
NS
＜0 . 001
＜0 . 001
＜0 . 01
NS
NS
＜0 . 05
＜0 . 001
＜0 . 001
NS
＜0 . 001
＜0 . 05
＜0 . 001
＜0 . 01
＜0 . 01
＜0 . 01
＜0 . 001
＜0 . 001
NS
Means within column and having superscripts but lacking a common superscript differ (P＜0.05).
Effect of dietary SB on diarrhea, mortality
and ascites mortality in broilers*
Table 3.
SB, %
Diarrhea1
Mortality2
Ascites mortality3
0
0.5
1.0
2.0
4.0
SEM
P-value
Trt
Linear
Quadratic
0b
1 . 11b
2 . 22b
1 . 11b
15 . 56a
1 . 34
3 . 29b
4 . 39b
4 . 39b
4 . 40b
19 . 78a
1 . 48
0b
0b
0b
0b
19 . 78a
0 . 97
＜0 . 001
＜0 . 001
＜0 . 05
＜0 . 001
＜0 . 01
＜0 . 05
＜0 . 001
＜0 . 001
＜0 . 001
a-b
Means within column and having superscripts but lacking a
common superscript differ (P＜0.05). Data was transformed to
DEGREES ASIN SQRT (n＋1) for analysis.
1
Diarrhea chicks were recorded on day 14;
2-3
Mortality and ascites related mortality were noted during the
whole trail.
with the control treatment. On day 42, there was a linear
tendency of SB on spleen (P＜0.01) and bursa indices (P＜
0.05), and a quadratic trend on heart (P＜0.001) and liver (P
＜0.001) indices with the increasing SB level. Heart and
liver indices were the lowest in broilers fed with diet supplemented 0.5% SB.
Blood Test
On day 21, a linear response was revealed for HGB (P＜
0.001), HCT (P＜0.001) and MCV (P＜0.001) with a rising
level of SB (Table 5); chickens consumed 2.0% and 4.0% SB
showed lower HGB (P＜0.001), and higher HCT (P＜0.01)
and MCV (P＜0.01). On day 42, levels of blood RBC,
HGB, HCT, MCV were not significant different among
treatments.
Blood Biochemical Parameters
There were no significant differences in levels of serum
ALT, AST, TP, BUN and UA among the treatments (data not
shown). On day 21, both linear and quadratic trends were
exhibited in serum MDA concentration (P＜0.01) and linear
effect was showed in serum GSH-Px activity (P＜0.05) with
Journal of Poultry Science, 50 (4)
350
Renal histological changes with birds exposed to SB. (1)
heamorrhage among renal tubular (large arrow, 1A, 2A, 1B, 2B); (2)
tubular dilation (small arrow, 1B, 2B), H.E. Bar＝50 μm. Picture 1A
and 1B represented 1.0% and 4.0% SB treatment on day 21; picture 2A
and 2B represented 1.0% and 4.0%SB treatment on day 42.
Fig. 2.
Rectal temperature in the Morning and afternoon of chickens
exposed to dietary SB from day 14 to 42 of age. A, B Significant differences between AM and PM (P＜0.001); a-e significant differences
between treatments (P＜0.05).
Fig. 3.
the increasing SB level. Comparing with control treatment,
serum MDA content (P＜0.001) was improved in birds fed
with SB higher than 0.5%. GSH-Px activity (P＜0.05) was
lower with supplementation of 2.0% and 4.0% SB than that
of 0.5% SB (Table 6). However, blood redox status was not
affected by dietary SB at the age of day 42.
Blood Gas Parameters
There was a tendency of increased blood HCO3- (P＝
Peng et al.: Dietary NaHCO3 and High Ambient Temperatures
Table 4.
Heart
Liver
b
0
0.5
1.0
2.0
4.0
SEM
P-value
Trt
Linear
Quadratic
a-c
Effect of dietary SB on heart, liver, spleen and bursa indices in broilers *(%)
Day 42
Day 21
SB, %
351
Spleen
Bursa
Heart
b
a
Liver
Spleen
a
a
Bursa
0 . 480
0 . 485b
0 . 488b
0 . 587a
0 . 620a
0 . 015
2 . 853
2 . 938
2 . 957
2 . 978
3 . 077
0 . 054
0 . 085
0 . 090
0 . 093
0 . 090
0 . 093
0 . 004
0 . 168
0 . 208b
0 . 218ab
0 . 238ab
0 . 283a
0 . 012
0 . 367
0 . 277b
0 . 278b
0 . 313b
0 . 355a
0 . 009
1 . 931
1 . 533b
1 . 618b
1 . 560b
1 . 940a
0 . 043
0 . 135
0 . 068b
0 . 097ab
0 . 072b
0 . 120a
0 . 008
0 . 0898ab
0 . 0542c
0 . 0687bc
0 . 0698bc
0 . 1003a
0 . 005
＜0 . 001
＜0 . 001
NS
NS
NS
NS
NS
NS
NS
＜0 . 05
＜0 . 01
NS
＜0 . 001
NS
＜0 . 001
＜0 . 001
NS
＜0 . 001
＜0 . 05
＜0 . 01
NS
＜0 . 01
＜0 . 05
＜0 . 05
Means within column and having superscripts but lacking a common superscript differ (P＜0.05).
Effect of dietary SB on RBC, HGB, HCT and MCV in whole blood of broilers *
Table 5.
Day 42
Day 21
SB, %
RBC
(10^12/L)
HGB
(g/L)
HCT
(%)
MCV
(fL)
RBC
(10^12/L)
HGB
(g/L)
HCT
(%)
MCV
(fL)
0
0.5
1.0
2.0
4.0
SEM
P-value
Linear
Quadratic
2 . 18
2 . 32
2 . 33
2 . 40
2 . 37
0 . 03
NS
0 . 035
0 . 050
94 . 8a
100 . 7a
95 . 0a
86 . 5b
85 . 2b
1 . 52
＜0 . 001
＜0 . 001
NS
30 . 1c
31 . 9abc
31 . 7bc
33 . 8ab
34 . 1a
0 . 41
＜0 . 01
＜0 . 01
NS
138 . 6bc
137 . 8bc
136 . 4c
141 . 0ab
145 . 0a
0 . 81
＜0 . 01
＜0 . 001
NS
2 . 31
2 . 38
2 . 31
2 . 51
2 . 47
0 . 04
NS
NS
NS
94 . 5
97 . 2
95 . 2
103 . 2
105 . 8
1 . 67
NS
NS
NS
31 . 3
31 . 9
30 . 8
32 . 7
33 . 2
0 . 47
NS
NS
NS
135 . 3
133 . 9
133 . 4
130 . 9
134 . 1
0 . 75
NS
NS
NS
a-c
Means within column and having superscripts but lacking a common superscript differ (P＜0.05).
Table 6.
broilers*
Effect of dietary SB on serum MDA, GSH-Px and T-AOC in
Day 21
Day 42
SB, %
MDA
(nmol/L)
GSH-Px
(U/ml)
T-AOC
(U/ml)
MDA
(nmol/L)
GSH-Px
(U/ml)
T-AOC
(U/ml)
0
0.5
1.0
2.0
4.0
SEM
P-value
Trt
Linear
Quadratic
2 . 68c
2 . 98bc
3 . 35ab
3 . 45a
3 . 51a
0 . 08
1270ab
1655a
1330ab
963b
1096b
71
19 . 30
22 . 32
23 . 52
22 . 22
25 . 70
1 . 07
3 . 13
3 . 08
3 . 19
3 . 36
3 . 79
0 . 11
1451
1442
1446
1620
1862
78
12 . 60
14 . 08
12 . 81
9 . 89
12 . 33
0 . 58
＜0 . 001
＜0 . 01
＜0 . 01
＜0 . 05
＜0 . 05
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
a-c
Means within column and having superscripts but lacking a common superscript differ
(P＜0.05).
0.081) in broilers exposed to 1.0% SB. Blood pH, pCO2 and
pO2 of birds did not differ (P＞0.05) in all treatments (data
not shown).
Renal Histological Changes
Renal histological examination was presented in Figure 2.
Chickens fed with SB higher than 1.0% showed a haem-
Journal of Poultry Science, 50 (4)
352
orrhage between renal tubules which was determined by the
presence of erythrocytes at the age of day 21 and 42. Furthermore, tubular dilation appeared as level of SB reached
2.0% on day 42, indicating that renal lesion was intensified.
All the renal histological changes were most obvious in 4.0%
SB treatment.
Discussion
HS is a common event that can hamper the growth performance of domestic animals (Fuquay, 1981). According
to previous research, dietary supplementation of SB alleviated the detrimental effect of HS by enhancing the assimilation efficiency of nutrients, promoting organ development and maintaining blood acid-base balance (Teeter et al.,
1985; Abou-El-Ella and Ismail, 1999; Borges et al., 2003;
Naseem et al., 2005; Tanveer et al., 2005; Ahmad et al.,
2006; Ghorbani and Fayazi, 2009). However, excessive SB
has been shown to decrease growth performance. Our results
indicated that indicated 4.0% SB significantly reduced
growth performance from day 1 to 21, and resulted in extremely high diarrhea incidence, mortality and AS related
mortality. First, we suggest that excessive SB in the diet
may decrease feed palatability and feed intake. Second, the
higher SB probably quenched the thirst by increasing Na+
intake, because blood osmotic pressure in birds is a thirstregulating factor (Borges et al., 2003). Chickens would
drink excess water because of thirst, which presumably
increased feed passage rate and dilution of digestive enzymes
that could cause reduced nutrient digestibility and absorption
(Ravindran et al., 2008; Ahmad et al., 2009). From day 22
to 42 and day 1 to 42, supplementation of SB in the diet
increased BWG in chickens, whereas 4.0% SB showed the
highest mortality among all the treatments. To minimize
error in measuring BWG, it was corrected for mortality by
excluding the dead chickens from each treatment. However,
body weight of the chickens that died from ascites was lower
than the live ones. Therefore, the BWG in 4.0% SB supplemented group would be over-estimated for its high mortality. This might explain the discrepancy of BWG in broilers between day 1-21 and day 22-42.
SB higher than 1.0% significantly increased the heart and
bursa indices on day 21, and supplementation of 0.5-2.0%
SB decreased heart and liver indices on day 42. The BWG
loss under heat stress probably contributed to the discrepant
effects of SB on the heart and bursa indices between day
1-21 and day 22-42 (Bartlett and Smith, 2003). Spleen and
bursa indices showed irregular variations, which may be due
to organ specificity might be another reason, but no relevant
reference was available.
It has been shown that the levels of blood RBC, HCT and
HGB were increased in birds exposed to overdose of SB or
NaCl (Mubarak and Sharkawy, 1999; Ekanayake et al.,
2004). This hematological change was the sub-clinical
symptom of pulmonary hypertension or ascites in SB-treated
broiler chickens (Ekanayake et al., 2004). Here, we indicated that supplementation of SB higher than 1.0% decreased
HGB, and increased HCT and MCV levels on day 21. The
decreasing HGB level seemed inconsistent with previous
studies. This change in HGB level indicated a compromised
oxygen-carrying capacity in blood, which might induce red
cells proliferation for higher oxygen-carrying capacity in
broilers. Moreover, the physiological alterations of erythrocytes would increase blood viscosity (Burton et al., 1968;
Hakim, 1988; Mirsalimi and Julian, 1993), and blood pressure that may stimulate lung vascular remodeling (Yang et
al., 2010), and eventually cause AS syndrome.
Heat stress can lead to oxidative stress which is described
as the imbalance between oxidative and anti-oxidative status
in favor of the oxidation, potentially leading to per-oxidation
damage (Sies, 1997). MDA, the product of lipids oxidation,
was elevated in chickens supplemented with SB higher than
1.0%, indicating the broilers may be subjected to oxidative
injury. SOD, GSH-Px, and CAT were the most important
enzymes for preventing oxidative damage (Finkel and Holbrook, 2000). A decrement of serum GSH-Px activity might
aggravate the oxidative lesion in chickens supplemented with
2.0% and 4.0% SB compared with that of 0.5% SB. It seems
that supplementation of SB higher than 1.0% would disturb
redox balance in broilers.
As the most important organ for water and electrolyte
equilibrium, the kidney might be more susceptible to dietary
SB than other organs. The results of renal histological examination demonstrated that SB higher than 1.0% resulted in
renal heamorrhage. This histological lesion of the kidney
was more severe as dietary SB dose increased. SB higher
than 2.0% even caused tubular swelling in birds on day 42.
Considering the highest mortality was seen in the 4.0% SB
group, death of those birds might be attributed to renal
failure. However, it can be inferred that SB higher than 1.0%
probably aggravated kidney burden and led to pathological
lesions.
In summary, dietary supplementation of 4% SB decreased
growth performance, and dramatically increased diarrhea
incidence, mortality and AS related mortality. Nevertheless,
SB higher than 1.0% decreased blood HGB, increased HCT
and serum MDA, and resulted in renal morphological damage. Although dietary addition of 1.0% SB had no negative
impact on growth performance of broilers, the biochemical
blood parameters as well as renal histological examination
were significantly affected. Therefore, we suggest that dose
limit of dietary SB is less than 1.0% in broilers under high
ambient temperatures.
Acknowledgments
The research was supported by an authorized item from
Ministry of Agriculture of the People’s Republic of China.
References
Abou-El-Ella MA and Ismail A M. Ascorbic acid, sodium bicarbonate and ammonium chloride supplementation in broiler
diets at high environmental temperatures. Egyptian Journal of
Nutrition and Feeds, 2: 581-591. 1999.
Ahmad T, Mushtaq T, Khan MA, Babar ME, Yousaf M, Hasan ZU
and Kamran Z. Influence of varying dietary electrolyte balance
Peng et al.: Dietary NaHCO3 and High Ambient Temperatures
on broiler performance under tropical summer conditions.
Journal of Animal Physiology and Animal Nutrition, 93:
613-621. 2009.
Ahmad T, Mushtaq T, Mahr-Un-Nisa, Sarwar M, Hooge DM and
Mirza MA. Effect of different non-chloride sodium sources on
the performance of heat-stressed broiler chickens. British
Poultry Science, 47: 249-256. 2006.
Altan O, Pabuccuoglu A, Altan A, Konyalioglu S and Bayraktar H.
Effect of heat stress on oxidative stress, lipid peroxidation and
some stress parameters in broilers. British Poultry Science, 44:
545-550. 2003.
AOAC Official Methods of Analysis, 14th ed., Section 2.057;
Association of Official Analytical Chemists: Arlington, VA,
1984.
Bartlett JR and Smith MO. Effects of different levels of zinc on the
performance and immunocompetence of broilers under heat
stress. Poultry Science, 82: 1580-1588. 2003.
Borges SA, Fischer AV, Silva D and Maiorka A. Acid-base balance
in broilers. World’s Poultry Science Journal, 63: 73-81. 2007.
Borges SA, Fischer DSA, Ariki J, Hooge DM and Cummings KR.
Dietary electrolyte balance for broiler chickens under moderately high ambient temperatures and relative humidities.
Poultry Science, 82: 301-308. 2003.
Bottje WG and Harrison PC. The effect of tap water, carbonated
water, sodium bicarbonate, and calcium chloride on blood acidbase balance in cockerels subjected to heat stress. Poultry
Science, 64: 107-113. 1985.
Burton RR, Besch EL and Smith AH. Effect of chronic hypoxia on
the pulmonary arterial blood pressure of the chicken. The
American Journal of Physiology, 214: 1438-1442. 1968.
Cawthon D, Beers K and Bottje WG. Electron transport chain defect
and inefficient respiration may underlie pulmonary hypertension syndrome (ascites)-associated mitochondrial dysfunction
in broilers. Poultry Science, 80: 474-484. 2001.
Davison S and Wideman R F. Excess sodium bicarbonate in the diet
and its effect on Leghorn chickens. British Poultry Science, 33:
859-870. 1992.
Druyan S, Shlosberg A and Cahaner A. Evaluation of growth rate,
body weight, heart rate, and blood parameters as potential
indicators for selection against susceptibility to the ascites
syndrome in young broilers. Poultry Science, 86: 621-629.
2007.
Ekanayake S, Silva SS, Priyankarage N, Herath UT, Jayasekara MU,
Horadagoda NU, Abeynayake P and Gunaratne SP. Effect of
excess sodium in feed on haematological parameters and
plasma sodium level in broiler chickens. British Poultry
Science, 45 Suppl 1: S53-S54. 2004.
Finkel T and Holbrook NJ. Oxidants, oxidative stress and the
biology of ageing. Nature, 408: 239-247. 2000.
Fuquay JW. Heat-stress as it affects animal production. Journal of
Animal Science, 52: 164-174. 1981.
Ghorbani MR and Fayazi J. Effects of dietary sodium bicarbonate
and rearing system on laying hens performance, egg quality and
plasma cations reared under chronic heat stress (42 degrees C).
Research Journal of Biological Sciences, 4: 562-565. 2009.
Hakim TS. Erythrocyte deformability and segmental pulmonary
vascular resistance: osmolarity and heat treatment. Journal of
Applied Physiology, 65: 1634-1641. 1988.
Hayat J, Balnave D and Brake J. Sodium bicarbonate and potassium
bicarbonate supplements for broilers can cause poor perform-
353
ance at high temperatures. British Poultry Science, 40: 411418. 1999.
Herget J, Wilhelm J, Novotna J, Eckhardt A, Vytasek R, Mrazkova
L and Ostadal M. A possible role of the oxidant tissue injury in
the development of hypoxic pulmonary hypertension. Physiological Research, 49: 493-501. 2000.
Iqbal M, Cawthon D, Beers K, Wideman RJ and Bottje WG.
Antioxidant enzyme activities and mitochondrial fatty acids in
pulmonary hypertension syndrome (PHS) in broilers. Poultry
Science, 81: 252-260. 2002.
LaCroix RL, Keeney DR and Walsh LM. Potentiometric titration of
chloride in plant tissue extracts using the chloride ion electrode
1. Communications in Soil Science and Plant Analysis, 1: 1-6.
1970.
Lin H, Decuypere E and Buyse J. Acute heat stress induces oxidative stress in broiler chickens. Comparative Biochemistry
and Physiology A-Molecular & Integrative Physiology, 144:
11-17. 2006b.
Lin H, Jiao HC, Buyse J and Decuypere E. Strategies for preventing
heat stress in poultry. World’s Poultry Science Journal, 62:
71-86. 2006a.
Mirsalimi SM and Julian RJ. Effect of excess sodium bicarbonate on
the blood volume and erythrocyte deformability of broiler
chickens. Avian Pathology, 22: 495-507. 1993.
Mubarak M and Sharkawy AA. Toxopathology of gout induced in
laying pullets by sodium bicarbonate toxicity. Environmental
Toxicology and Pharmacology, 7: 227-236. 1999.
Naseem MT, Shamoon N, Younus M, Iqbal ZC, Aamir G, Asim A
and Akhter S. Effect of potassium chloride and sodium bicarbonate supplementation on thermotolerance of broilers exposed
to heat stress. International Journal of Poultry Science, 4: 891895. 2005.
Ravindran V, Cowieson AJ and Selle PH. Influence of dietary
electrolyte balance and microbial phytase on growth performance, nutrient utilization, and excreta quality of broiler chickens.
Poultry Science, 87: 677-688. 2008.
Scrivner, LH. Experimental edema and ascites in poults. Journal of
the American Veterinary Medical Association, 108: 27-32.
1946.
Sies H. Oxidative stress: oxidants and antioxidants. Experimental
Physiology, 82: 291-295. 1997.
St-Pierre N R, Cobanov B and Schnitkey G. Economic Losses from
Heat Stress by US Livestock Industries. Journal of Dairy
Science, 86, Supplement: E52-E77. 2003.
Tanveer A, Sarwar M, Mahr-un-Nisa Ahsan-ul-Haq and Zia-ulHasan. Influence of varying sources of dietary electrolytes on
the performance of broilers reared in a high temperature environment. Animal Feed Science and Technology, 120: 277298. 2005.
Teeter RG, Smith MO, Owens FN, Arp SC, Sangiah S and Breazile,
JE. Chronic heat stress and respiratory alkalosis: occurrence
and treatment in broiler chicks. Poultry Science, 64: 10601064. 1985.
Teeter RG and Belay T. Broiler management during acute heat
stress. Animal Feed Science and Technology, 58: 127-142.
1996.
Yang Y, Gao M, Wu Z and Guo Y. Genistein attenuates low temperature induced pulmonary hypertension in broiler chicks by
modulating endothelial function. European Journal of Pharmacology, 649: 242-248. 2010.