Effects Of Dietary Cation-anion Balance On Heated-stressed Dairy Cows And Ruminant Digestion And Metabolism

Effects of Dietary Cation-anion Balance on Heat-stressed dairy cows and ruminant digestion and metabolism was studied in this paper. The first experiment was conduced with 32 cows in early cows and 32 cows in midlactation to study the effect of dietary cation-anion balance (DCAB) on production performance ,the physiological and biochemical parameters in blood of Chinese Holstein heat-stressed lactating cows in different lactating period as to determine the best level of DCAB in different lactating period and explain the mechanism of its effects .32 cows in early cows and 32 cows in midlactation were selected respectively ,which have resemble body weight ,age, lactation period and milk yield .32 cows in early cows was divided four groups :Control Group A1 (DCAB with 185mEq/kgDM ), Exp.GroupBl(basaldiet:DCABof243mEq/kgDM),Exp.GroupCl(DCABof317mEq/kgD M),Exp.GroupDl(DCABof442mEq/kgDM ); 32 cows in midlactation was divided four groups :Control Group A2 (basal diet :DCAB of 83mEq/kgDM ), Exp.GroupB2 (DCAB of 172mEq/kgDM ), Exp.GroupC2 (DCAB of 215mEq/kgDM )and Exp.GroupD2 (DCAB of 357mEq/kgDM ) .The duration of experiment was 60 days .The result indicated as follow :(1) DCAB influenced the blood gas parameters, but the influences of DCAB were not significant difference from the control group. The increased DCAB increased the pH value, PO₂, and HCO₃ of blood. The increased DCAB reduced partial pressure pf carbon dioxide (PCO₂)in blood (p>0.05) . Total CO₂ of group B1 and C1 were increased respectively with 9.04% 1.08% , which contrasted with group A1 group D1 was reduced by DCAB with 26.14%. Total CO₂ of B₂, C₂ and D₂ were increased with 6.11%, 8.77% and 4.11% (p>0.05) . (2) DCAB had some influence upon the activity of enzyme in blood serum, but not significant. .The increased DCAB increased ALP of serum. CK of every experiment group was lower than that of control group (p>0.05) . ALTof Experiment group B1, B2 were higher than that of control group, but others were lower than control group. (3 )Na, K of group C1 were the highest in early lactating cows with 142.04mmol/Land 5.12 mmol/L. The effect of DCAB on Na in blood serum was significant . K, C1 ionsin blood serum of midlactating cows were affectedsignificantly by DCAB. K ion of group B2 was the highestin four groups. Cl in bloodserum was decreased by the increased DCAB.Ca in blood serum was not affected byDCAB. (4) DCAB had no influence upon level of hormones in blood serum of dairycows .The increased DCAB increased T3, but T4, COR decreased in blood serum o PRLof group B2 and C2 were higher than control group for 10.53%n 8.50%,but group D2decreased withl3.64% (p>0.05 ) . ( 5 ) GLU and BUN in blood serum of early lactatingcows were affected significantly by DCAB.GLU of group Bl , andCl were significantlyhigher than group Al with 4.01%, 6.57% (p<0.05) . GLU of group Dl was lowersignificantly than that of control group. The trend of GLU of midlactating cows was thesame as prophase. BUN of group Bland Cl were higher than group Al significantly for17.46% and 2.72% BUN of group B2, C2 and D2 were higher than that of controlgroup for 14.73%, 14.51%and 5.49%c (6) The increased DCAB affected productionperformance significantly. The protein of milk of group Al, Bl and Cl were morethanthat of control group for 3.07%, 1.62% and 0.61%, but it has no significant effecton fat of milk .The milk yield of group Bl and Cl increased significantly with 10.2%and 4.72% (p<0.05) . But that of group Dl was lower than control group. Theproduction performance was the best when DCAB is 243mEq/kgDM in prophase.The production performance was the best when DCAB is 215mEq/kgDM inmidlactating cows .The increased DCAB increased the protein of milk. That ofgroup B2, C2 and D2 were higher than that of control group for 3.22%, 2.25% and4.18%o The milk yield of group B2 , C2 and D2 increased 1.99%, 21.1% and 9.56%respectively.The second experiment was carried out with 3 twelve-month old healthy non-concept Huang Huai goats with permanent rumen fistula ,which were feeding with three different DCAB levels respectively .A 3 x 3 complete Latin square design was applied. DCAB levels were : Group A (332mEq/kgDM), Group B (418mEq/kgDM), Group C (496mEq/kgDM) . Experimental period and formal period were seven days respectively each time. The duration of experiment was forty two days .The result indicated that the Increased DCAB increased pH value of rumen fluid. The pH value of the rumen fluid had a lineal increase with the increase of DCAB level in the same period of different experiments; while it was a curve variety in the same experimental group. The degradability of green hay DM, CF in rumen increased with the time . Degradability of DM and CF of group B was the highest and group A was the lowest in the same period and there was obvious difference (p<0.05) in the three groups at the...