| Two experiments were conducted to investigate the effects of different dietary sodium chloride(NaCl)supplemental levels or dietary sodium and chloride levels on growth performance,blood gas indices,serum physiological and biochemical indices,organ indices,jejunal morphology,tibia ash content and the sodium percentage content in the ash of broilers fed a corn-soybean meal diet from 1 to 21 days of age,and proper sensitive indices were selected to evaluate the optimal dietary NaCl supplemental level,sodium and chloride level of broilers.Experiment 1 An optimal dietary sodium chloride supplemental level of broiler chicks fed a corn-soybean meal diet from 1 to 21 days of ageThe experiment was conducted to investigate the optimal dietary NaCl supplemental level of broilers fed a corn-soybean meal diet from 1 to 21 days of age.A total of 490 commercial 1 day-old Arbor Acres(AA)male chicks were randomly allotted by body weight to 1 of 7 treatments with 7 replicate cages of 10 chicks each in a completely randomized design.The broilers of each treatment were fed a NaCl-unsupplemented corn-soybean meal basal diet(control)or the basal diet supplemented with 0.10,0.20,0.30,0.40,0.50 or 0.60%NaCl for 21 days.The results showed that:(1)Dietary supplemental NaCl level affected(P<0.0001)the average daily gain(ADG),average daily feed intake(ADFI),feed/gain ratio(F/G),mortality and average daily water consumption of broilers from 1 to 21 days of age,and the excreta moisture rate of broilers from 16 to 20 days of age.The ADG,ADFI,average daily water intake and excreta moisture rate increased linearly(P<0.0001)and quadratically(P<0.0001),while F/G and mortality decreased linearly(P<0.0001)and quadratically(P<0.0001)as dietary supplemental NaCl levels increased.The ADG reached a plateau at the supplemental NaCl level of 0.30%,and the F/G reached a plateau at the supplemental NaCl level of 0.20%.(2)Dietary supplemental NaCl level did not affect(P>0.62)pH and H+concentration in blood,but influenced(P<0.0001)the pressure of CO2(PCO2),total CO2(TCO2),base excess(BE),anion gap(Anion Gap,AG),and the concentrations of HCO3-,Na+,Cl-and K+in blood of broilers on day 21.The PCO2,TCO2,BE and AG,and the concentrations of HCO3-,Na+and Cl-in blood increased linearly(P<0.0001)and quadratically(P<0.0004),while the K+concentration in blood decreased linearly(P<0.0001)and quadratically(P<0.0001)with the increase of dietary NaCl levels.The PCO2,TCO2,BE and the concentrations of HCO3-,K+,Na+and Cl-in blood reached a plateau at supplemental NaCl levels of about 0.20-0.60%.(3)Dietary supplemental NaCl level affected(P<0.002)the osmotic pressure(OSM)and the concentrations of Na+,Cl-,K+,uric acid(UA)and glucose(GLU)in serum of broilers on day 21,the OSM and the concentrations of K+,UA and GLU in serum decreased linearly(P<0.0001)and quadratically(P<0.0001)as dietary supplemental NaCl levels increased.The UA and GLU concentration in serum reached a plateau at supplemental NaCl levels of 0.20%,and the K+concentration and OSM in serum reached the lowest point at the supplemental NaCl level of 0.20%.(4)Dietary supplemental NaCl level did not affect(P>0.06)the jejunal Villus Height/Crypt Depth ratio(VH/CD)and the relative weights of spleen and lung,but affected(P<0.001)the jejunal VH and CD,relative weights of heart,liver and kidney,tibia ash percentage and the sodium percentage content in the ash of broilers on day 21.With the levels of supplemental NaCl increased,the jejunal VH and CD,tibia ash percentage and the sodium percentage content in the ash increased quadratically(P<0.002).In addition,the heart,liver and kidney indices decreased quadratically(P<0.0001)as supplemental NaCl levels increased.Heart,liver and kidney indices,the jejunal VH and CD,tibia ash percentage and the sodium percentage content in the ash reached a plateau at the supplemental NaCl level of 0.20%.(5)The blood PCO2,TCO2,BE and AG,blood concentrations of HCO3-,Na+,K+and Cl-,serum OSM,serum concentrations of UA,GLU,Na+,K+,jejunal VH,tibia ash percentage,the sodium percentage content in the ash,the relative weights of heart,liver and kidney were new and sensitive indicators for estimate the optimal dietary NaCl supplemental level of broilers from 1 to 21 days of age.Based on the best fitted broken-line or asymptotic models of the above sensitive indicators,the optimal dietary NaCl supplemental level were 0.08-0.24%for broilers fed the corn-soybean meal diet from 1 to 21 days of age.The results from the current study indicate that the optimal dietary NaCl supplemental level would be 0.24%to meet the demand for normal growth and development and maintain the homeostasis of internal environment,which was lower than the current dietary NaCl supplemental level(0.30%)in the Chinese broiler production.Experiment 2 An optimal dietary sodium and chloride level of broiler chicks fed a corn-soybean meal diet from 1 to 21 days of ageThe experiment was conducted to estimate dietary optimal sodium and chloride level of broilers fed a corn-soybean meal diet from 1 to 21 days of age.A total of 490 commercial 1 day-old AA male chicks were randomly allotted by body weight to 1 of 7 treatments with 7 replicate cages of 10 chicks each in a completely randomized design.The control group was not supplemented with sodium and chlorine in the dietary,and the dietary sodium and chlorine levels were 0.14%,0.20%,0.26%,0.33%,0.39%and 0.14%,respectively,and the ratio of sodium to chlorine in the diet 1:1.The trial lasted for 21 days.The results showed that:(1)Dietary sodium and chloride level affected(P<0.0001)the ADG,ADFI,F/G,mortality and average daily water consumption of broilers from 1 to 21 days of age,and the excreta moisture rate of broilers from 16 to 20 of age.The ADG,ADFI,average daily water intake and excreta moisture rate increased linearly(P<0.0001)and quadratically(P<00.0001),while F/G and mortality decreased linearly(P<0.0001)and quadratically(P<0.0001)as dietary sodium and chloride levels increased.The ADG and F/G reached a plateau at the dietary sodium and chloride level of 0.14%.(2)Dietary sodium and chloride level did not affect(P>0.34)pH and H+concentration in blood,but influenced(P<0.0001)PCO2,TCO2,BE,AG,and the concentrations of HCO3-,Na+,Cl-and K+in blood of broilers on day 21.The PCO2,TCO2,BE and AG,and the concentrations of HCO3-,Na+ and Cl-in blood increased linearly(P<0.0003)and quadratically(P<0.0007),while the K+concentration in blood decreased linearly(P<0.0001)and quadratically(P<0.0001)with the increase of dietary sodium and chloride levels.The PCO2,TCO2,BE and the concentrations of HCO3-,K+,Na+and Cl-in blood reached a plateau at dietary sodium and chloride level of 0.14%.(3)Dietary sodium and chloride level did not affect(P>0.05)Cl’ and Na+ concentration in blood,but influenced(P<0.0001)the OSM and the concentrations of Na+,Cl-,K+,UA and GLU in serum of broilers on day 21.As the levels of dietary sodium and chloride increased,the OSM and the concentrations of K+,UA and GLU in serum decreased linearly(P<0.0001)and quadratically(P<0.0001).The OSM,and the concentrations of K+,UA and GLU in serum reached a plateau at dietary sodium and chloride level of 0.14%.(4)Dietary sodium and chloride level did not affect(P>0.20)the jejunal VH/CD,relative weights of spleen and lung,but affected(P<0.02)jejunal VH,CD and VH/CD,relative weights of heart,liver and kidney of broilers on day 21.As the levels of dietary sodium and chloride increased,the jejunal VH and CD,tibia ash percentage and the sodium percentage content in the ash increased quadratically(P<0.0006).In addition,the heart,liver and kidney indices decreased linearly(P<0.0003)and quadratically(P<0.0009)as dietary sodium and chloride levels increased.And they reached the lowest point at the dietary sodium and chloride level of 0.14%.(5)The ADG,ADFI,F/G,blood PCO2,TCO2,BE and AG,blood concentrations of HCO3-,Na+,K+and Cl-,serum OSM,serum concentrations of UA,GLU and K+,tibia ash percentage and the relative weights of heart,liver and kidney were sensitive indicators for estimate the optimal dietary sodium and chloride level of broilers from 1 to 21 days of age.Based on the best fitted broken-line or asymptotic models of the above sensitive indicators,the optimal dietary sodium and chloride levels were 0.07-0.16%for broilers fed the corn-soybean meal diet from 1 to 21 days of age.The results from current study indicate that the optimal dietary sodium and chloride level would be 0.16%to meet the demand for normal growth and development and maintain the homeostasis of internal environment,which was lower than the current NRC recommended sodium and chloride requirements(0.20%).In summary,these results suggested that the optimal dietary NaCl supplemental level would be 0.24%,and dietary optimal sodium and chloride level would be 0.16%for broilers fed the corn-soybean meal diet from 1 to 21 days of age.The above results have important theoretical and practical significance for scientific and rational adding NaCl and the accurately meeting the requirements of sodium and chlorine in broiler production. |
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