©2007 Poultry Science Association, Inc.
Dietary Sodium and Chloride for Twenty-Nineto Forty-Two-Day-Old Broiler Chickens
at Constant Electrolyte Balance Under
Subtropical Summer Conditions
T. Mushtaq,*1 M. Aslam Mirza,* M. Athar,*2 D. M. Hooge,† T. Ahmad,*3
G. Ahmad,*4 M. M. H. Mushtaq,* and U. Noreen‡
*Institute of Animal Nutrition and Feed Technology, and ‡Department of Zoology
and Fisheries, University of Agriculture, Faisalabad, Pakistan 38040;
and †Hooge Consulting Service Inc., Eagle Mountain, UT 84043
Primary Audience: Nutritionists, Production Managers, Researchers
SUMMARY
The study was conducted to evaluate the response of broiler chicks to different dietary Na+
and Cl− concentrations with similar dietary electrolyte balance of 250 mEq/kg during 29 to 42 d
of age in a hot environment with average minimum and maximum temperatures of 32.4 and
36.6°C, respectively, and an average RH of 69.2%. Three levels of dietary Na+ (0.20, 0.25, and
0.30%) and 3 levels of dietary Cl− (0.30, 0.40, and 0.50%) were used in 3 × 3 factorial arrangement
in which BW at 28 d were used as covariate in the statistical analysis. A decreasing linear effect
of dietary Na+ was observed on breast yield and lowering of abdominal fat, whereas increasing
dietary Cl− linearly increased litter moisture and decreased dressing weights. No significant effects of
dietary Na+, Cl−, or Na+ × Cl− were observed on feed intake, BW gain, feed:gain, rectal temperature,
water:feed, or mortality. An improvement in litter condition, toe ash, blood parameters, and
lowered abdominal fat yield was observed for the diet having 0.30% dietary Na+. The results of
the present study suggest the dietary requirements of 0.20 to 0.25% Na+ and 0.30% Cl− during
the finisher phase (29 to 42 d) of broiler chicks when the ambient temperature ranged from 32
to 40°C.
Key words: sodium, chloride, broiler, hot environment, electrolyte balance
2007 J. Appl. Poult. Res. 16:161–170
DESCRIPTION OF THE PROBLEM
In countries like Pakistan, high environmental temperature is detrimental to broiler production. The problem is more pronounced when the
broiler chickens are in the growing and finishing
1
phases. The last 2 wk for broilers are very critical
in the summer season when high growth rate
leads to increased mortality and, ultimately, great
economic losses. When environmental temperature exceeds the comfort zone of the bird (above
25°C), the birds are likely to experience heat
Corresponding author: [email protected].
Present address: Hi-Tech Feeds, Lahore, Pakistan.
3
Present address: Department of Animal Sciences, University of Arid Agriculture, Rawalpindi, Pakistan.
4
Present address: Sadiq Brothers Poultry, Rawalpindi, Pakistan.
2
JAPR: Research Report
162
Table 1. Ingredient composition of the experimental diets
Treatments (Na × Cl; %)
Treatments
0.20 ×
0.30
0.20 ×
0.40
0.20 ×
0.50
0.25 ×
0.30
0.25 ×
0.40
0.25 ×
0.50
0.30 ×
0.30
0.30 ×
0.40
0.30 ×
0.50
Corn
Canola meal
Corn gluten, 60%
Soybean meal
Rice broken
Rice polishing
Wheat
Molasses
CaCl2
KCl
K2SO4
NaCl
NaHCO3
NH4Cl
L-Lys HCl
Dicalcium phosphate
DL-Met
L-Thr
Bone meal
Limestone
Vitamin and mineral premix1
38.2
5.7
3
22.1
12.8
2
7.3
4
0.13
0
0.43
0
0.05
0.25
0.25
0
0.18
0.04
2.43
0.83
0.35
38.2
5.7
3
22.1
12.8
2
7.3
4
0.66
0
0.67
0
0.05
0
0.24
0.95
0.18
0.04
0.99
0.79
0.35
38.2
5.7
3
22.1
12.8
2
7.3
4
0
0.78
0
0.04
0
0.03
0.25
0.31
0.18
0.04
1.96
1.00
0.35
38.2
5.7
3
22.1
12.8
2
7.3
4
0.04
0
0.24
0
0.23
0.32
0.24
0
0.18
0.04
2.43
0.85
0.35
38.2
5.7
3
22.1
12.8
2
7.3
4
0.45
0.05
0.43
0.12
0.06
0
0.25
0
0.18
0.04
2.43
0.57
0.35
38.2
5.7
3
22.1
12.8
2
7.3
4
0.04
0.61
0.03
0.16
0
0
0.25
0.02
0.18
0.04
2.40
0.86
0.35
38.2
5.7
3
22.1
12.8
2
7.4
4
0.19
0
0.04
0
0.42
0.20
0.24
0
0.18
0.04
2.43
0.74
0.35
38.2
5.7
3
22.1
12.8
2
7.3
4
0.46
0.09
0.18
0.07
0.31
0.01
0.24
0
0.18
0.04
2.43
0.55
0.35
38.2
5.7
3
22.1
12.8
2
7.3
4
0.14
0.35
0.13
0.29
0
0
0.25
0.04
0.18
0.04
2.38
0.79
0.35
1
Supplied the following per kilogram of diet: vitamin A (as retinyl acetate), 14,000 IU; vitamin D3 (as cholecalciferol),
3,500 IU; vitamin K (menadione sodium bisulfite), 2.8 mg; vitamin E (as D-α-tocopherol), 42 IU; biotin, 0.07 mg; folic
acid, 1.7 mg; niacin, 35 mg; calcium pantothenate, 12.32 mg; pyridoxine, 3.36 mg; riboflavin, 7 mg; thiamin, 1.7 mg; vitamin
B12, 12.1 ␮g; Fe, 98 mg; Mn, 112 mg; Cu, 9.8 mg; Se, 0.07 mg; Zn, 70 mg; choline chloride, 5.5 mg; salinomycin (as
Phibro coccidiostat; Phibro Animal Health, Fairfield, NJ), 60 mg; and zinc bacitracin (as Albac 10%, Alpharma AS, Oslo,
Norway), 50 mg.
stress. Heat stress reduces the growth rate, feed
consumption, and survivability of the broiler and
thus decreases profitability. During periods of
high temperature, the bird makes major thermoregulatory adaptations to prevent death from heat
exhaustion [1, 2]. The bird is able to control its
body temperature by behavioral and physiological responses. The physiological response to heat
stress is an increase in respiratory rate, resulting
in excessive CO2 losses causing respiratory alkalosis and high bicarbonate excretion [3, 4, 5].
Deleterious effects of high ambient temperature
may be minimized by the dietary manipulation
of electrolyte salts and by maintaining dietary
electrolyte balance (DEB) in heat-stressed birds
[6]. Electrolytes are classified as strong or weak
according to their rate of dissociation into conducting ions [7]. The optimum dietary DEB has
been reported to be 220 to 270 mEq/kg for broilers of all ages, with up to 0.40% for Na+ and
0.15 to 0.30% for Cl− [8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18].
The requirements of dietary Na+ and Cl− for
young birds have been estimated previously using
a similar DEB level in different formulas [18].
The objective of this study was to evaluate the
effect and interaction of different levels of dietary
Na+ and Cl− in growing-finishing broiler chickens
(29 to 42 d of age) with a similar DEB of 250
mEq/kg and their effect on blood biochemical
profile and carcass responses under cyclic day
and night temperature ranges of 30 to 40°C.
MATERIALS AND METHODS
Birds and Housing
The aim of the study was to evaluate the
minimum concentration of dietary Na+ and Cl−
for the optimum performance of broiler chickens
during periods of high ambient temperature and
was conducted during late June, considered an
extremely hot month in Faisalabad, Pakistan. The
room was divided into 36 pens measuring 0.92
× 1.23 m and ventilated by creating negative
MUSHTAQ ET AL.: SODIUM AND CHLORIDE FOR BROILERS
163
Table 2. Nutrient composition of experimental diets
Treatments (Na+ × Cl−; %)
Nutrients
K+ (%)
DEB1 (mEq/kg)
ME (kcal/kg)
CP (%)
EE (%)
CF (%)
Ca (%)
Available P (%)
Met (%)
Met + Cys (%)
Lys (%)
Thr (%)
Trp (%)
0.20 ×
0.30
0.20 ×
0.40
0.20 ×
0.50
0.25 ×
0.30
0.25 ×
0.40
0.25 ×
0.50
0.30 ×
0.30
0.30 ×
0.40
0.30 ×
0.50
0.97
251.0
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
1.08
251.5
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
1.19
250.7
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
0.89
252.1
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
1
252.1
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
1.11
252.1
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
0.8
250.8
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
0.91
251.1
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
1.02
251.0
2,800
20
2.45
4.35
1.05
0.5
0.53
0.91
1.15
0.79
0.24
DEB = dietary electrolyte balance.
1
pressure using exhaust fans fitted in the top on
the eastern wall of the room. Twenty-nine-dayold male Starbro broiler chicks (n = 324) were
randomly assigned to each of 36 pens, 9 chicks
per pen. There were 9 treatments with 36 chicks
each (4 replicate pens per treatment). Softwood
shavings were used as bedding material over a
concrete floor. Birds were vaccinated for infectious bursal disease on d 29. The lighting program
was 23L:1D during the experimental period.
Birds were kept up to 42 d of age, and cyclic
day and night temperatures were followed and recorded.
Ingredients and Diets
Three levels of Na+ (0.20, 0.25, and 0.30%)
were used with 3 levels of Cl− (0.30, 0.40, and
0.50%) in a 3 × 3 factorial arrangement. Before
formulation, each ingredient was analyzed in triplicate for DM, CP, EE, and CF following AOAC
[19]. The Na+ and K+ were analyzed by flame
photometry, Cl− by titration with AgNO3 [20],
total P by the aminonapthol sulfonic acid method
[21], and Ca by Versinate method [22]. Only
Na+, K+, and Cl− ions were used in the DEB
equation [8]. All feed ingredients used in the
formulation of experimental diets contributed a
part of total dietary Na+, K+, and Cl−. However,
the desired concentrations of Na+, K+, and Cl−
were achieved by incorporating NaHCO3, NaCl,
CaCl2, KCl, NH4Cl, and K2SO4. The diets were
formulated using WinFeed 2.6 [23] by stochastic
programming at the 95% level of confidence. To
isolate the effect of dietary treatments, similar
percentages of corn, wheat, broken rice, rice polishings, soybean meal, corn gluten meal (CP
60%), canola meal, molasses, L-Lys HCl, DLMet, and vitamin-mineral premix were used in
all the experimental diets (Table 1). The diets
were offered as mash.
Each experimental diet was offered to 4 replicates having 9 birds each. Dietary amino acid
contents were calculated [24] using DM and CP
contents of each feed ingredient. Available P was
calculated from total P [10].
Nutrient requirements met or exceeded those
recommended by the NRC [10] for broiler birds,
except for ME, which was lower (2,800 kcal/kg)
than recommended (Table 2). The DEB in each
case was maintained at 250 mEq/kg by the addition of K+ (Table 2). Minimum and maximum
temperatures of the house were recorded on a
daily basis. Water and diets were provided ad
libitum throughout the experimental period. No
periodic measurement was made on the water
temperature; however, it was maintained below
30°C.
Live Performance
Body weight gain, feed intake, water intake,
feed:gain ratio (corrected for mortality), water
intake:feed intake ratio, mortality (%), and litter
moisture (%) were evaluated at the end of 42 d.
Water intake was recorded twice a day, in the
JAPR: Research Report
164
Table 3. Mean ± SE of feed intake, BW gain, water consumption, and feed:gain ratio of broilers as influenced by
dietary Na and Cl levels from 29 to 42 d of age under subtropical summer conditions1
BW gain
(g)
Feed:gain
(g/g)
Rectal
temperature2
(°C)
Items
n
Feed intake
(g)
Dietary Na (%)
0.20
0.25
0.30
12
12
12
2,201.5 ± 85.5
2,019.2 ± 74.3
2,094.5 ± 79.1
937.4 ± 51.7
850.8 ± 44.9
802.8 ± 47.8
2.37 ± 0.11
2.43 ± 0.10
2.65 ± 0.10
41.44 ± 0.10
41.49 ± 0.08
41.66 ± 0.09
Dietary Cl (%)
0.30
0.40
0.50
12
12
12
2,101.4 ± 75.1
2,080.2 ± 75.2
2,133.6 ± 72.9
852.2 ± 45.4
828.6 ± 45.4
910.2 ± 44.1
2.49 ± 0.10
2.56 ± 0.10
2.39 ± 0.09
41.61 ± 0.09
41.49 ± 0.08
41.44 ± 0.09
Na × Cl
0.20 × 0.30
0.20 × 0.40
0.20 × 0.50
0.25 × 0.30
0.25 × 0.40
0.25 × 0.50
0.30 × 0.30
0.30 × 0.40
0.30 × 0.50
4
4
4
04
4
4
4
4
4
2,206.6
2,164.4
2,233.6
1,978.2
2,072.1
2,007.3
2,119.1
2,004.2
2,160.0
±
±
±
±
±
±
±
±
±
130.2
157.5
126.6
129.4
126.3
126.6
138.7
130.9
126.3
997.4
881.5
933.3
812.5
908.1
831.6
746.2
696.1
965.8
±
±
±
±
±
±
±
±
±
78.7
95.3
76.5
78.3
76.4
76.6
83.8
79.2
76.7
2.22
2.49
2.40
2.42
2.33
2.53
2.81
2.87
2.25
±
±
±
±
±
±
±
±
±
0.17
0.21
0.17
0.17
0.17
0.17
0.18
0.17
0.17
41.62
41.38
41.23
41.54
41.51
41.41
41.68
41.62
41.70
±
±
±
±
±
±
±
±
±
0.15
0.18
0.14
0.14
0.14
0.14
0.15
0.15
0.14
P-value3
ANOVA
Initial BW (covariate; 1 df)
0.048
0.274
0.518
0.090
Na
Linear
Quadratic
0.294
0.462
0.168
0.284
0.121
0.787
0.237
0.129
0.448
0.138
0.056
0.597
Cl
Linear
Quadratic
0.873
0.752
0.682
0.390
0.386
0.289
0.408
0.524
0.241
0.337
0.156
0.717
Na × Cl
0.909
0.171
0.097
0.684
Means ± SEM of 4 replicates with 9 birds in each replicate and were adjusted for 29-d BW, i.e., 1,004.1 g.
Rectal temperature was taken daily during the hottest time of the day when the birds were in panting phase by inserting a
digital probe 2 cm deep into the rectum.
3
Means within the same column and grouping judged significantly different at P ≤ 0.05 by least significant difference for
fixed effects, (i.e., Na+ at 0.20, 0.25, and 0.30% and Cl− at 0.30, 0.40, and 0.50%), whereas means were judged significantly
different by Tukey’s honestly significant difference for Na+ × Cl−).
1
2
morning and in the evening. Water consumption
was corrected for evaporated quantity of water
by placing 4 waterers containing a measured
quantity of water, and difference in quantity was
considered as evaporated. The water:feed intake
ratio was calculated by dividing water intake
(mL) by feed intake (g) during the periods. For
litter moisture, all the litter of a pen was mixed
thoroughly, and a representative sample of about
1,500 g was taken in a preweighed filtration cloth
bag especially prepared for this purpose and was
dried in a hot air oven overnight at 105°C. Rectal
temperature was recorded during 1200 to 1400
h, corresponding to the hottest hours of the day.
For this purpose, 1 bird from each replicate was
marked and always used for rectal temperature.
A digital probe was inserted 2 cm deep along
the wall of the rectum and kept until a constant
temperature was obtained. Mortality (%) was calculated as birds that died in a pen divided by
initial number of birds in the beginning multiplied
by 100.
Slaughter and Blood Data
Slaughter data and blood samples were collected at d 42. For slaughter data, 1 bird from
each replicate was selected at random (except
that marked for rectal temperature), slaughtered,
skinned, and was used for carcass yield including
giblets (% of live weight), thigh, breast, and ab-
MUSHTAQ ET AL.: SODIUM AND CHLORIDE FOR BROILERS
165
Table 4. Mean ± SE of water consumption, water:feed ratio, litter moisture, and mortality of broilers as influenced
by dietary Na and Cl levels from 29 to 42 d of age under subtropical summer conditions1
Items
n
Water
consumption
(mL)
Dietary Na (%)
0.20
0.25
0.30
12
12
12
6,211.2 ± 139.6a
5,583.3 ± 121.2b
5,669.6 ± 129.1b
2.84 ± 0.12
2.75 ± 0.10
2.74 ± 0.10
33.21 ± 0.7b
37.48 ± 0.6a
29.31 ± 0.7c
4.20 ± 2.7
6.90 ± 2.3
9.27 ± 2.5
Dietary Cl (%)
0.30
0.40
0.50
12
12
12
5,888.1 ± 122.6
5,781.4 ± 122.7
5,794.9 ± 119.0
2.90 ± 0.10
2.75 ± 0.10
2.69 ± 0.10
31.52 ± 0.7b
33.81 ± 0.7a
34.67 ± 0.7a
9.41 ± 2.4
5.03 ± 2.4
5.93 ± 2.3
Na × Cl
0.20 × 0.30
0.20 × 0.40
0.20 × 0.50
0.25 × 0.30
0.25 × 0.40
0.25 × 0.50
0.30 × 0.30
0.30 × 0.40
0.30 × 0.50
4
4
4
4
4
4
4
4
4
6,252.2
6,096.1
6,186.6
5,611.1
5,755.1
5,383.6
5,701.2
5,493.0
5,814.5
±
±
±
±
±
±
±
±
±
212.5
257.2
206.6
211.3
206.3
206.7
226.4
213.8
206.2
Water:feed
(mL/g)
Litter
moisture
(%)
Mortality
(%)
2.93
2.81
2.76
2.96
2.73
2.56
2.79
2.70
2.74
±
±
±
±
±
±
±
±
±
0.18
0.22
0.17
0.18
0.17
0.17
0.19
0.18
0.17
ANOVA
29.68
36.05
33.92
43.29
36.05
33.09
21.58
29.35
37.00
±
±
±
±
±
±
±
±
±
1.2c
1.4b
1.2bc
1.2a
1.2b
1.2bc
1.3d
1.2c
1.2b
12.95
0.31
0.03
7.59
5.29
7.81
7.69
10.11
10.00
±
±
±
±
±
±
±
±
±
4.1
5.0
4.0
4.1
4.0
4.1
4.1
4.1
4.0
P-value
Initial BW (covariate; 1 df)
0.002
0.711
<0.001
0.388
Na
Linear
Quadratic
0.007
0.018
0.023
0.766
0.532
0.714
<0.001
0.008
<0.001
0.498
0.242
0.994
Cl
Linear
Quadratic
0.785
0.587
0.670
0.335
0.156
0.704
0.022
0.006
0.793
0.384
0.305
0.353
Na × Cl
0.536
0.895
<0.001
0.258
Means within the same column lacking common superscripts differ significantly (P ≤ 0.05 by least significant difference
for fixed effects, i.e., Na+ at 0.20, 0.25, and 0.30% and Cl− at 0.30, 0.40, and 0.50%, whereas by Tukey’s honestly significant
difference for Na+ × Cl−).
1
Means ± SEM of 4 replicates with 9 birds in each replicate and were adjusted for 29-d BW, i.e., 1,004.1 g.
a–d
dominal fat yield (% of carcass). Breast yield
was taken after detaching wings from the breast.
Toe ash was estimated by burning all the toes at
550°C for 2 h. The temperature of the muffle
furnace was not set at 600°C or above, because
it was expected that this high temperature may
burn the P also.
Blood was collected from the neck by cutting
the jugular vein at slaughter during 1300 to 1500
h when the environmental temperature was 40°C.
A portion of blood from slaughtered birds was
collected in 0.01 N EDTA for blood pH. The
pH was determined immediately by a pH meter
already standardized with known buffer solutions. An aliquot of blood was used to separate
serum for Na+ and K+ determination by flame
photometry. For serum bicarbonates, samples
were taken anaerobically from live birds by puncturing the wing vein when the birds were panting.
Serum bicarbonates were determined immediately by the method described by Harold [25].
Statistical Analysis
Three levels of Na (0.20, 0.25, and 0.30%)
and 3 levels of Cl (0.30, 0.40, and 0.50%) were
analyzed as a 3 × 3 factorial design by GLM. Pen
mean was an experimental unit. It was anticipated
that variation in d-28 BW would affect the subsequent results, so the d-28 BW were used as covariate in the model [26]. In case of significance (P
JAPR: Research Report
166
Table 5. Mean ± SE of toe ash, dressing weight, breast and leg yield, and abdominal fat of broilers as influenced
by dietary Na and Cl levels from 29 to 42 d of age under subtropical summer conditions1
Items
n
Toe
ash2 (%)
Dressing
weight3
Breast
Thigh
Abdominal
fat
(% dressed weight)
Dietary Na (%)
0.20
0.25
0.30
12
12
12
12.21 ± 0.19b
12.14 ± 0.17b
13.49 ± 0.18a
64.83 ± 0.83
65.80 ± 0.72
65.78 ± 0.77
30.50 ± 0.56a
28.64 ± 0.49b
28.35 ± 0.52b
40.66 ± 0.49
40.15 ± 0.43
39.23 ± 0.45
1.76 ± 0.11a
0.80 ± 0.10b
0.94 ± 0.11b
Dietary Cl (%)
0.30
0.40
0.50
12
12
12
13.02 ± 0.17a
12.40 ± 0.17b
12.43 ± 0.16b
68.15 ± 0.73a
64.37 ± 0.73b
63.89 ± 0.70b
29.56 ± 0.49
28.54 ± 0.49
29.40 ± 0.48
39.36 ± 0.43b
41.12 ± 0.43a
39.56 ± 0.42b
1.02 ± 0.11
1.24 ± 0.10
1.24 ± 0.11
Na × Cl
0.20 × 0.30
0.20 × 0.40
0.20 × 0.50
0.25 × 0.30
0.25 × 0.40
0.25 × 0.50
0.30 × 0.30
0.30 × 0.40
0.30 × 0.50
4
4
4
4
4
4
4
4
4
11.46
12.60
12.57
13.20
12.54
10.69
14.39
12.06
14.02
±
±
±
±
±
±
±
±
±
0.29cd
0.35bc
0.28bc
0.29ab
0.28bc
0.28d
0.31a
0.29bc
0.28a
66.32
63.71
64.47
68.85
64.58
63.97
69.28
64.82
63.24
±
±
±
±
±
±
±
±
±
1.27
1.53
1.23
1.26
1.23
1.23
1.35
1.27
1.23
ANOVA
Initial BW (covariate; 1 df)
29.97
30.52
31.01
30.79
27.84
27.30
27.91
27.25
29.90
±
±
±
±
±
±
±
±
±
0.85ab
1.03a
0.83a
0.85a
0.83bc
0.83c
0.91bc
0.86c
0.83ab
40.89
42.43
38.66
39.35
40.31
40.79
37.84
40.63
39.23
±
±
±
±
±
±
±
±
±
0.74ab
0.90a
0.72cd
0.74bcd
0.72bc
0.72ab
0.79d
0.75abc
0.72bcd
2.09
1.48
1.72
0.54
0.69
1.19
0.45
1.56
0.80
±
±
±
±
±
±
±
±
±
0.18a
0.22abcd
0.18ab
0.18e
0.18de
0.18bcde
0.19e
0.18abc
0.18cde
P-value
0.794
0.573
0.217
0.032
0.173
Na
Linear
Quadratic
<0.001
<0.001
<0.002
0.969
0.937
0.814
0.029
0.017
0.207
0.407
0.217
0.447
<0.001
<0.001
<0.001
Cl
Linear
Quadratic
0.017
0.016
0.093
0.001
<0.001
0.102
0.247
0.812
0.101
0.029
0.995
0.008
0.193
0.135
0.297
<0.001
0.588
0.022
0.043
<0.001
Na × Cl
Means within the same column lacking common superscripts differ significantly (P ≤ 0.05 by least significant difference
for fixed effects, i.e., Na+ at 0.20, 0.25, and 0.30% and Cl− at 0.30, 0.40, and 0.50%, whereas by Tukey’s honestly significant
difference for Na+ × Cl−).
1
Means ± SEM of 4 replicates with 9 birds in each replicate and were adjusted for 29-d BW, i.e., 1,004.1 g.
2
All the toes were ashed at 550°C for 6 h.
3
Percentage of live weight.
4
Skinned breast and legs were taken as whole parts.
a–e
≤ 0.05), the least significant difference test was
used to compare main effects, whereas interactions were compared by Tukey’s honestly significant difference test. Linear and quadratic regression analyses were also run to estimate the
Na+ and Cl− requirements for maximum response
for each variable [27].
RESULTS AND DISCUSSION
The average minimum and maximum temperature recorded during the period was 32.4 and
36.6°C, respectively, with a maximum of 40°C
during the day and a minimum of 30°C during
the night. The average RH recorded was 69.2%.
Feed intake, BW gain, feed:gain, and rectal
temperatures are presented in Table 3. A water
sample was also analyzed for Na+, K+, and Cl−
contents. Because only traces of these ions were
detected in drinking water, they were not expected to disturb the experimental structure. No
significance differences due to Na+, Cl−, or Na+
× Cl− were observed on feed intake, feed:gain,
or rectal temperature, indicating that different
proportions of dietary Na+ and Cl− have no effects
on feed:gain and rectal temperature at DEB of
250 mEq/kg.
The results of the present study were in line
with the earlier findings [10, 28, 29] that have
MUSHTAQ ET AL.: SODIUM AND CHLORIDE FOR BROILERS
167
Table 6. Mean ± SE of blood pH, serum HCO3−, serum Na+, and serum K+ of broilers as influenced by dietary Na
and Cl levels from 29 to 42 d of age under subtropical summer conditions1
Items
n
Blood
pH
Serum
HCO3−
Serum
Na+
Serum
K+
(mmol/L)
Dietary Na (%)
0.20
0.25
0.30
12
12
12
7.22 ± 0.017b
7.16 ± 0.015c
7.31 ± 0.016a
32.32 ± 0.60b
29.31 ± 0.52c
34.29 ± 0.55a
132.3 ± 2.4a
125.4 ± 2.1b
128.9 ± 2.2ab
3.79 ± 0.16a
3.03 ± 0.14b
3.29 ± 0.15b
Dietary Cl (%)
0.30
0.40
0.50
12
12
12
7.16 ± 0.015b
7.39 ± 0.015a
7.14 ± 0.015b
31.57 ± 0.58b
33.76 ± 0.53a
30.58 ± 0.51b
134.9 ± 2.1a
125.8 ± 2.1b
126.0 ± 2.0b
3.46 ± 0.14a
3.01 ± 0.14b
3.63 ± 0.14a
Na × Cl
0.20 × 0.30
0.20 × 0.40
0.20 × 0.50
0.25 × 0.30
0.25 × 0.40
0.25 × 0.50
0.30 × 0.30
0.30 × 0.40
0.30 × 0.50
4
4
4
4
4
4
4
4
4
7.37
7.20
7.09
6.94
7.41
7.13
7.16
7.56
7.20
±
±
±
±
±
±
±
±
±
0.026b
0.032c
0.026c
0.026d
0.026b
0.026c
0.028c
0.027a
0.026c
30.37
34.12
32.47
27.61
30.52
29.79
36.73
36.64
29.50
±
±
±
±
±
±
±
±
±
0.91cde
1.11abc
0.89bcd
0.91e
0.89cde
0.89de
1.97a
0.92ab
0.89de
ANOVA
Initial BW (covariate; 1 df)
135.1
123.2
138.8
135.8
124.1
116.3
133.7
130.0
123.0
±
±
±
±
±
±
±
±
±
3.6a
4.3ab
3.5a
3.6a
3.5ab
3.5b
3.8a
3.6ab
3.5ab
3.95
2.96
4.45
3.20
3.15
2.75
3.24
2.92
3.70
±
±
±
±
±
±
±
±
±
0.25ab
0.30bc
0.24a
0.25bc
0.24bc
0.24c
0.26bc
0.25bc
0.24abc
P-value
0.159
0.993
0.645
0.642
Na
Linear
Quadratic
<0.001
<0.001
<0.001
<0.001
0.012
<0.001
0.012
0.053
0.018
0.001
0.013
0.003
Cl
Linear
Quadratic
<0.001
0.282
<0.001
<0.001
0.206
<0.001
0.017
0.018
0.010
0.019
0.280
0.009
Na × Cl
<0.001
<0.001
0.012
0.012
Means within the same column lacking common superscripts differ significantly (P ≤ 0.05 by least significant difference
for fixed effects, i.e., Na+ at 0.20, 0.25, and 0.30% and Cl− at 0.30, 0.40, and 0.50%, whereas by Tukey’s honestly significant
difference for Na+ × Cl−).
1
Means ± SEM of 4 replicates with 9 birds in each replicate and were adjusted for 29-d BW, i.e., 1,004.1 g.
a–e
reported the Na+ requirement as 0.20%. Mushtaq
et al. [18] noted a nonsignificant effect of dietary
Na+ on feed intake, feed:gain, and rectal temperature. They, however, observed a linear effect of
increasing dietary Na+ on BW gain. Results
herein were consistent with those reported by
Oviedo-Rondón et al. [14], who recommended
0.25% Na+ and 0.30% Cl− for greater feed intake
in broilers. They further noticed a quadratic effect
of Na+ levels on BW gain and determined that
0.26% Na+ gave maximum BW gain in broiler
chicks. The results of the study herein were contrary to Maiorka et al. [30], who obtained optimal
performance with 0.30% dietary Na+. Barros et
al. [31] and Murakami et al. [13] reported the
Na+ requirements as 0.25%. Borges et al. [16]
reported lower Na+ requirements in birds reared
in the thermoneutral zone than those reared under
heat stress conditions.
Findings in the study herein were in
agreement with Smith and Teeter [32], who reported that supplementing Na+ or K+ through
drinking water did not significantly affect feed
conversion ratio during cyclic day and night temperatures of 26.6 to 36.7°C in 4-wk-old broilers.
The discrepancies in Na+ and Cl− requirements
could be because these researchers did not fix
the DEB when estimating the Na+ and Cl− requirements. Mushtaq et al. [18] observed a positive correlation of 0.57 between BW gain and
feed intake, whereas no significant correlations
were observed between BW gain and any other
168
variables. No significant correlation was observed between rectal temperatures with any
other variable in their study. The results of the
trial herein were not consistent with those of
Cooper and Washburn [33], who reported a significant correlation of body temperature with
feed intake and feed:gain after 7 d of heat
stress exposure.
Water consumption, water:feed, litter moisture, and mortality are presented in Table 4.
Water consumption was significantly (P ≤ 0.007)
higher (6,211.2 mL) on 0.20% dietary Na+. It
was, however, not affected by the dietary Cl−.
Maximum water consumption (6,252.2 mL) was
noted with dietary Na+ × Cl− of 0.20 × 0.30 and
minimum water consumption (5,383.6 mL) with
dietary Na+ × Cl− of 0.25 × 0.50. The results of
the present study did not match with the findings
of Hurwitz et al. [34], Murakami et al. [12],
Oviedo-Rondón et al. [14], and Mushtaq et al.,
[18], who reported a linear effect of dietary Na+
on water consumption. However, those reported
results were not specific to the birds of 29 to 42
d of age. Birds with high initial weights significantly (P ≤ 0.001) excreted less moisture through
droppings (r = −0.30). This demonstrated the
ability of heavier birds to retain more water in
the body, which led to improved litter condition.
On dietary Na+ × Cl− of 0.25 × 0.50, minimum water consumption (5,383.6 mL), and, interestingly, minimum toe ash (P ≤ 0.001), were
observed (Tables 4 and 5). This contrasts with
Borges et al. [15] and Ahmad and Sarwar [35],
who observed the lowest rectal temperature with
maximum water consumption. The interaction
might depress mineral absorption, especially Ca,
causing lowering of toe ash.
A significant effect (P ≤ 0.001) of Na+ × Cl−
was observed on litter moisture. The lowest litter
moisture was exhibited in a 0.30% Na+ and
0.30% Cl− combination. The response might be
due to high dietary NaHCO3. The NaHCO3 has
also been reported to lower the negative effects
of heat stress in broilers more than other Na+
sources [17, 36]. The results of the study did
not correspond to the findings of Murakami et al.
[13], who observed that litter moisture increased
linearly with dietary Na+ levels up to 0.35%.
They, however, did not use high dietary Cl−, as
was used in this study. In the present trial, litter
moisture appeared to decrease as Cl− increased
JAPR: Research Report
with 0.25% Na+, but litter moisture seemed to
increase in the presence of 0.30% Na+. Possibly,
litter moisture is a function of dietary K+, because minimum litter moisture was observed in
the diet having the lowest level of dietary K+.
Moreover, the litter moisture may be the function of DEB rather than Na+, K+, or Cl− individually. Further research is needed on this issue.
Pesti et al. [37] reported a significant (P ≤
0.031) increase in litter moisture with drinking
water supplementation of K+ as KCl. The effect
of variable dietary K+ with DEB needs to be
investigated. In view of this fact, litter moisture
cannot be predicted as a function of water consumption. Mushtaq et al. [18] observed a linear
effect of dietary Na+ (P ≤ 0.09) on 37-d mortality, and diets containing 0.20% Na+ with 0.40
or 0.50% Cl− exhibited 0% mortality.
Blood pH, serum HCO3−, serum Na+, and
serum K+ are presented in Table 6. The effect
of dietary Na+ was quadratic on blood pH (P ≤
0.001), serum HCO3− (P ≤ 0.001), serum Na+
(P ≤ 0.018), and serum K+ (P ≤ 0.003). Maximum blood pH (7.39) was observed at 0.40%
Cl−. The effect of Na+ × Cl− was significant
(P ≤ 0.001) on blood pH. Birds fed the diet
containing 0.25% Na+ and 0.30% Cl− showed
minimum blood pH (acidosis). A significant (P
≤ 0.023) negative correlation (r = 0.38) was
observed between blood pH and litter moisture.
Similar response of Na+, Cl−, and Na+ × Cl− was
observed on serum HCO3−. A significant (P ≤
0.033) positive correlation of 0.39 was observed
between blood pH and HCO3−. The blood pH
increased with increased serum HCO3−, and as
a result, the birds made some physiological adjustments to keep the blood pH near optimal
(7.35). The physiological responses included increases in manure moisture and urinary excretion and significantly decreased kidney glomerular filtration rate, which is regulated by variation
in Arg-vasotocin secretion [14, 37, 38]. RuizLopez and Austic [39] also reported the depression in blood pH and blood HCO3− due to high
dietary Cl−. Dietary Na+ at 0.20% significantly
increased serum Na+ (P ≤ 0.012) and serum
K+ (P ≤ 0.001). The serum Na+ surprisingly
decreased when dietary Na+ increased from 0.20
to 0.25%, and this may have been associated
with the larger incremental increases of about
+0.10% in dietary K+ compared with +0.05%
MUSHTAQ ET AL.: SODIUM AND CHLORIDE FOR BROILERS
increases in dietary Na+ in those formulas. Increasing dietary Cl− from 0.30 to 0.40% decreased serum Na+ (P ≤ 0.001) and serum K+
(P ≤ 0.019). Serum K+ significantly (P ≤ 0.020)
increased water consumption (r = 0.39).
In the present study, a significant effect of
dietary Na+, Cl−, or Na × Cl was observed on
blood pH, serum Na+, and serum K+. Increasing
dietary Na+ increased serum HCO3− in linear
fashion. The effects of different levels of dietary
Na+ or Cl− were more pronounced on blood parameters and carcass, which supported the view
that the DEB can be used as a good criterion to
predict or adjust acid-base status of the blood
[13].
Toe ash and carcass responses are shown in
Table 5. Dietary Na+ at 0.30% significantly (P
≤ 0.001) increased toe ash, whereas dietary Cl−
above 0.30% lowered (P ≤ 0.016) the toe ash
linearly (y = 13.207 − 0.295x; R2 = 0.71). The
effect of Na+ × Cl− was significant (P ≤ 0.001) for
toe ash, which was lowest on the diet containing
0.25% Na+ and 0.50% Cl−. The results of the
present study confirmed the finding of Ahmad
et al. [17], who reported a significant decrease
in Ca2+ absorption on high dietary Cl− (as CaCl2)
in heat-stressed broilers.
Breast yield decreased linearly (P ≤ 0.017)
by increasing dietary Na+, whereas a quadratic
effect (P ≤ 0.001) was observed on abdominal
169
fat. The lowest abdominal fat was observed at
0.25% Na+. No significant effect of Na+ was
observed either on dressing weight or thigh yield
(Table 5). A quadratic (P ≤ 0.008) effect of Cl−
was observed on thighs, which had the highest
percentage at 0.40% Cl−. Abdominal fat and
breast yield were not significantly affected by
dietary Cl−. The effect of Na+ × Cl− was significant for breast (P ≤ 0.022), thigh (P ≤ 0.043),
and abdominal fat (P ≤ 0.001). Diets having
0.25% Na+ and 0.30% Cl− decreased breast and
abdominal fat but were without effect on thigh
yield. The results of the study herein agree with
the findings of Mushtaq et al. [18], who observed
maximum dressing weight and thigh with 0.40%
dietary Cl− and maximum breast yield and the
lowest abdominal fat yield with 0.30% dietary
Na+. Similarly, the nonsignificant effect of electrolytes on carcass characteristics has been reported [40] when provided by KCl and NaCl in
the drinking water of broilers grown at elevated
temperatures. Contrarily, Hooge et al. [41, 42]
tested NaHCO3 at levels of 0 to 0.4% inclusion in
broiler chicken diets in pen trials across several
seasons. Dietary NaHCO3 levels of 0.2 to 0.4%
gave significant improvements in BW, carcass
yield, breast yield, and, occasionally, abdominal
fat pad, although not all responses were found
in all studies [41, 42].
CONCLUSIONS AND APPLICATIONS
1. Dietary levels of 0.20 to 0.23% for Na+ and 0.30% for Cl−, while maintaining the DEB of 250
mEq/kg, were sufficient for optimum performance of broiler chickens reared under a hot summer
environment when the cyclic temperature ranged from 30 to 40°C.
2. Additional benefits of higher dietary Na− and Cl− observed in broiler chickens were improved
bone mineralization (greatest toe ash with 0.30% Na+ and 0.30% Cl− in the diets) and thigh
yields (highest overall with 0.40% Cl− in the diets) and lower abdominal fat (lowest with 0.30%
Na+ and 0.30% Cl− in diets).
3. Litter moisture was significantly lower when using 0.30% dietary Cl− compared with 0.40 and
0.50% levels.
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+
A quadratic (P ≤ 0.023) effect of dietary Na was observed
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