Potassium (K), together with chlorine (Cl) and sodium (Na), plays an essential role in the osmotic pressure of body cells and thus the fluid balance of the body. Together, these minerals determine the cation-anion difference (also called acid-base balance) of the ration and of the body.
Potassium plays a role in the production of enzymes (important in energy transfer in cells and carbohydrate metabolism). In addition, potassium is important for the transmission of muscle impulses, including the heart. The potassium level in the blood is kept very constant and any surplus or deficit is reflected in the urine.
Potassium Requirements (CVB, 2016)
| Category | g/kg dry matter | g/animal/day |
| Young cattle from 4 months | 4.3 | 17 |
| Young cattle from 9months | 4.6 | 26 |
| Young cattle from 16 months | 4.9 | 56 |
| Dry 8–3 weeks to calving | 4.9 | 56 |
| Dry 3–0 weeks to calving | 5.0 | 55 |
| Lactating (20 kg) | 7.2 | 134 |
| Lactating (40 kg) | 8.1 | 190 |
A potassium deficiency does not cause specific deficiency symptoms but leads to a reduction in feed and water intake and lower milk production. Other symptoms may include 'licking', muscle cramps and sensitivity to all kinds of stimuli. Normally, ration contains sufficient potassium.
A potassium surplus inhibits the absorption of magnesium and calcium, making animals more susceptible to headaches and milk fever. The CVB (2005) indicates a toxicity limit of 30 g/kg (for chroni dry mattercally high levels). Eurofins Agro recommends a maximum of 25 g/kg dry matter, preferably lower.