Cation-anion balance

The term cation-anion balance (CAB), sometimes also referred to as dietary cation-anion balance (DCAB), describes the balance between cations and anions in a feed or a ration. The CAB is calculated using a formula that takes into account the cation and anion contents of a ration. The unit in which the CAB is expressed is mEq (milliequivalent) per kg feed. The CAB can be used to estimate the influence of a feed on the acid-base balance in the body.

Cations are positively charged ions, such as Ca2+, K+, Na+, Mg2+, NH4+. In the body, they have an alkalising or basic effect.

Anions are negatively charged ions, such as S2-, PO4 3-, Cl-. They have an acidifying effect.

A mineral salt, such as ammonium chloride (NH4Cl), “breaks down” into its ions in the body, releasing 4 Cl- ions, which have a mildly acidifying effect.

The CAB is important for the targeted shifting or stabilisation of the acid-base balance or the pH value. In horses, this is important, for example, in performance sport, to counteract muscle over-acidification or tying-up with alkalising rations. In other animal species, such as cats, the pH value in the urine can be deliberately acidified through the feeding of mineral salts in order to dissolve urinary stones.

In horses, studies suggest that the chlorophyll from green feed such as grass or hay helps to significantly buffer blood pH. Mineral salts therefore cannot achieve a targeted acidifying effect in rations rich in green feed. Urinary stones in horses must therefore be prevented in a different way (e.g. through a low-calcium diet). Horses with over-acidification (e.g. sport horses), on the other hand, should be given an alkalising ration rich in grass or hay. Rations rich in concentrate feed and lower in hay increase over-acidification.