Phosphorus (P) - cattle
Role in the animal body
About 80% of phosphorus (P) in the body is found in the bones. This phosphorus, as well as phosphorus in milk, occurs in the form of calcium phosphate (Ca₃(PO₄)₂. Thus, both phosphorus and calcium (Ca) are required for bone formation and milk production, with the ratio of the two minerals being important.
High-producing dairy cows require large amounts of phosphorus for milk production. A shortage can therefore occur easily. The usual rule of thumb is that 1kg of milk contains one gram of phosphorus, upon which additional requirements can be estimated. With the help of hormones, vitamin D regulates the absorption and resorption of calcium and phosphorus to and from the bones. The older the animal gets, the more difficult it becomes to mobilize calcium and phosphorus from the bones, thus increasing the risk of milk fever.
Phosphorus requirements
Phosphorus Requirements (CVB, 2016)
| Category | g/kg dry matter | g/animal/day |
| Young cattle from 4 months | 3.4 | 13 |
| Young cattle from 9 months | 2.3 | 13 |
| Young cattle from 16 months | 1.8 | 13 |
| Dry cows (8–3 weeks before calving) | 1.9 | 21 |
| Dry cows (3–0 weeks before calving) | 2.0 | 22 |
| Lactating cows (20 kg milk) | 2.5 | 47 |
| Lactating cows (40 kg milk) | 3.3 | 79 |
