Determination of strong ion difference and anion gap in serum biochemical markers of the lactating cow

Abstract

Acid-base abnormalities are frequently present in sick animals. Measurement of strong ion difference (SID) and anion gap (AG) is not only useful in explaining the underlying disease mechanisms of acid-base disorders but also assist in proper treatment protocols. The objectives of this study were to determine SID and AG in serum of high yielding lactating dairy cows with a history of inappetence and drop of milk production. Data on serum biochemical markers of 8 cows were collected from diagnostic reports preserved at the department of Physiology, Biochemistry and Pharmacology, Chattogram Veterinary and Animal Sciences University. The SID was calculated as SID = [strong cations] – [strong anions] = ([Na+]+ [K+]+ [Ca2+]+ [Mg2+]) – ([Cl-]+ [Lactate-]) and the AG was calculated as AG =([Na+]+[K+])-([Cl-]+[HCO3-]) with all values in mEq/L. Mean value of total plasma concentration of nonvolatile weak acids (Atot) was calculated following the equation, Atot = 0.325275*[albumin] + 2*[phosphate], and the mean value of HCO3- was calculated as [HCO3-] =SID-(Atot×Ka)/(Ka+10-pH), where Ka = 0.9 * 10-7 and pH = 7.38 . The fixed value of lactate was 0.54 mM/L. The calculated mean values of SID were SID3, 37.56 mEq/L; SID4, 37.02 mEq/L; SID6, 40.14 mEq/L, respectively. Total plasma concentration of non-volatile weak acid was 28.10 mmol/L. And the mean value of anion gap was 16.62 mEq/L. Anion gap was highly correlated with the total plasma ion concentrations of non-volatile weak acids (r=0.99) followed by phosphate (r=0.89) and total protein (r=0.47). In summary, we may conclude that high total plasma concentration of non-volatile weak acids, hyperphosphataemia and high total protein concentrations were
commonly associated with lactating cows.