Effect of Reducing Dietary Cation-Anion Difference on Acid-Base Balance, Plasma Minerals Level and Anti-Oxidative Stress of Female Goats
Reducing dietary cation-anion difference (DCAD, Na+K-Cl-S, mEq/kg DM) has been proved an effective way to prevent milk fever in dairy cows. Based on the similar physiological gastro-intestinal tract anatomy and metabolic process between female goats and dairy cows, this study was conducted to evaluate the effects of varying DCAD on fluid acid-base status, plasma mineral concentration and anti-oxidative stress capacity of female goats. Urinary pH, plasma Ca, P and Mg; and anti-oxidative stress indices of total superoxide dismutase (T-SOD), hydrogen peroxide (H2O2), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) were determined to evaluate the effect. Forty-eight Guizhou black female goats (15±1.9 month old, 22.3±3.75 kg live weight) were randomly allocated to 4 blocks of 12 goats each and fed 1 of 4 diets that differed in DCAD level. Levels of DCAD were preliminarily designed to be control (+150 mEq/kg DM, CON), high DCAD (+300 mEq/kg DM, HD), low DCAD (0 mEq/kg DM, LD) and negative DCAD (-150 mEq/kg DM, ND), respectively. A commercial anionic salts (Animate) and sodium bicarbonate (NaHCO3) were supplemented to reduce and increase DCAD level, respectively. There was no difference in dry matter intake for 4 groups of goats. Urine pH was aggressively decreased (P<0.0001) with reduced DCAD and there was a strong association between DCAD and urine pH (R2=0.793, P<0.0001). Compared with CON and HD, feeding of LD and ND resulted in greater (P<0.05) plasma Ca concentration. Plasma P level was increased (P<0.05) when anionic salts were supplemented. The DCAD alteration did not affect (P>0.05) plasma Mg level. There was no significant (P>0.05) difference in plasma GSH-Px activity and H2O2, but anionic salts supplementation in LD and ND significantly increased (P<0.05) plasma T-SOD activity and tended to reduce MDA (P<0.1) over HD and CON. Results from this study indicated that reducing DCAD could decrease urine pH and increase plasma Ca concentration of female goats. Specially, reducing DCAD was helpful to enhance oxidative stress tolerance capability of female goats.
Keywords: dietary cation-anion difference, urine pH, plasma calcium, anti-oxidative stress, female goats