Effect of dietary cation-anion difference on ruminal metabolism, total apparent digestibility, blood and renal acid-base regulation in lactating dairy cows.
The present study aimed to evaluate the effect of dietary cation-anion difference (DCAD) on ruminal fermentation, total apparent digestibility, blood and renal metabolism of lactating dairy cows. Sixteen Holstein cows were distributed in four contemporary 4×4 Latin Square designs, which consisted of four periods of 21 days and four treatments according to DCAD: +290; +192; +98 and -71 milliequivalent (mEq)/kg dry matter (DM). Ruminal pH and concentrations of acetic and butyric acid increased linearly according to the increase of DCAD. Similarly, NDF total apparent digestibility linearly increased by 6.38% when DCAD increased from -71 to 290 mEq/kg DM [Y=65.90 (SE=2.37)+0.0167 (SE=0.0068)×DCAD (mEq/kg DM)]. Blood pH was also increased according to DCAD, which resulted in reduction of serum concentrations of Na, K and ionic calcium (iCa). To maintain the blood acid-base homeostasis, renal metabolism played an important role in controlling serum concentrations of Na and K, since the Na and K urinary excretion increased linearly by 89.69% and 46.06%, respectively, from -71 to 290 mEq/kg DM. Changes in acid-base balance of biological fluids may directly affect the mineral composition of milk, as milk concentrations of Na, K, iCa and chlorides were reduced according to blood pH increased. Thus, it can be concluded that the increase of DCAD raises the pH of ruminal fluid, NDF total apparent digestibility, and blood pH, and decreases the milk concentration of cationic minerals, as well as the efficiency of Na utilization to milk production.
1Department of Nutrition and Animal Production,School of Veterinary Medicine and Animal Sciences,University of São Paulo,Av. Duque de Caxias Norte,225-Campus USP,13635-900,Pirassununga,São Paulo,Brazil.
C M M R
CM
Martins
1Department of Nutrition and Animal Production,School of Veterinary Medicine and Animal Sciences,University of São Paulo,Av. Duque de Caxias Norte,225-Campus USP,13635-900,Pirassununga,São Paulo,Brazil.
M A
MA
Arcari
2Department of Animal Science,School of Food Engineering and Animal Science,University of São Paulo,Brazil,Av. Duque de Caxias Norte,225-Campus USP,13635-900,Pirassununga,São Paulo,Brazil.
K C
KC
Welter
1Department of Nutrition and Animal Production,School of Veterinary Medicine and Animal Sciences,University of São Paulo,Av. Duque de Caxias Norte,225-Campus USP,13635-900,Pirassununga,São Paulo,Brazil.
J L
JL
Gonçalves
1Department of Nutrition and Animal Production,School of Veterinary Medicine and Animal Sciences,University of São Paulo,Av. Duque de Caxias Norte,225-Campus USP,13635-900,Pirassununga,São Paulo,Brazil.
M V
MV
Santos
D000136:Acid-Base Equilibrium; D000818:Animals; D000838:Anions / Q000008:administration & dosage / Q000737:chemistry*; D002412:Cations / Q000008:administration & dosage / Q000737:chemistry*; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000592:standards / Q000662:veterinary*; D004063:Digestion; D005260:Female; D005285:Fermentation; D007668:Kidney / Q000378:metabolism; D007774:Lactation; D008892:Milk / Q000737:chemistry*; D008903:Minerals / Q000032:analysis
D000838:Anions; D002412:Cations; D008903:Minerals
calcium metabolism; dairy cows; metabolic acidosis; mineral balance; renal control