Why is phosphorus so important for your dairy cattle?
Phosphorus is an essential mineral that cows need for good general condition, optimal claw health and fertility. Creating a good understanding of the level of phosphorus intake from the ration and the excretion of phosphorus in the milk produced is therefore very important. In this article, we will tell you more about it.
A cow needs phosphorus for her resistance, physical growth, for fetal development and for optimal milk production. Most phosphorus is needed in milk production. In addition, phosphorus is important for rumen function, microbial protein formation and enzyme production.
Optimal phosphorus levels lead to improved fertility, better feed intake, increased milk production and healthy bones. In growing animals, sufficient phosphorus can prevent skeletal deformation and ensures optimal feed efficiency. This is particularly essential for heifers and second-calf cows: after all, they produce a lot of milk while also having to grow and have limited feed intake capacity. To maintain animal health and therefore milk production and growth, it is important to consider phosphorus levels.

When and how much phosphorus does a cow need?
Research by the GD (2020) shows that phosphorus content in milk varies widely between individual cows and dairy farms. For optimal herd health, the amount of phosphorus excreted through the milk determines the amount of phosphorus needed in the ration.
Advice on phosphate varies considerably. Jan Dijkstra, associate professor of cattle nutrition at Wageningen University reports that the current standardization has a wide safety margin. On average, A ration with an average of 3.5 grams of phosphorus per kilo of dry matter is sufficient for a lactating cow with 10,000 kg (about 22046.2 Lb) of milk. Previously, the standards were kept too low, resulting in unconscious shortages. The following standards of phosphorus can be adhered to, according to him:
- Small calves 3.4 g/kg ds
- Older calves and heifers 2.3 g/kg ds
- Dry cows 2.0 g/kg ds
- Dairy animals need more: at 20 kg milk 2.5 g/kg ds, at 40 kg milk 3.3 g/kg ds and for animals with >40 kg milk the norm is 3.5 g/kg ds
After calving, phosphorus is most important
Due to high milk production at the beginning of lactation, phosphorus requirement is highest here. At the end of the lactation, the cow can replenish its phosphorus reserves. An optimal dry matter intake, including good rumination activity, is important. The better the rumination activity, the more favorable this is for phosphorus recycling in the body. Saliva contains a lot of phosphorus and ensures that it flows back into the rumen. Optimal rumen activity means more phosphorus recycling in the body. This has positive consequences for the P requirement.
A cow uses about 1/3 of the phosphorus needed for maintenance. The rest is excreted through milk production. When a cow excretes more phosphorus through milk than it takes in, it draws on its limited bone reserves to compensate for deficiencies. It is therefore always good to pay attention to phosphorus levels.
Proactive approach to optimal phosphorus levels
To maintain phosphorus levels, it is important to take measures around calving. Around calving, the cow’s body is already asking for extra energy, and this will only increase at the beginning of lactation because of the milk yield peak (see graph 1).

Dairy farmer de Boer: time savings and improved animal health
According to the testimonial of the dairy farmer Siem de Boer (Netherlands):” Despite good feed management, my high-producing cows had calcium, magnesium, and phosphorus deficiencies. This always costs me a lot of time and therefore money. With the AHV Milk Start Paste, these deficiencies are now ideally supplemented, in one go. Calcium absorption is fast due to the added vitamin D3. They also get an energy boost and become active quickly, leading to improved feed intake. Now I am ready quickly and pulling my cows well through the start-up phase.”
What is the advice from the AHV Specialist?
The advice from the AHV Specialists is to administer the AHV Milk Start Tablet as fast as possible after calving. This way you ensure that the cow gets through the next 24hours better. After all, she receives the necessary substances that ensure that her energy needs can be met. Something that is important for both cow and calf.
If you also have challenges with placenta expelled, this is often due to a lack of calcium and phosphorus. This is because cows with an abnormal energy balance have often already taken not enough feed in the dry period, creating challenges. To prevent this challenge, it is best to administer AHV Metri Tablet and AHV Milk Start immediately after calving. The AHV Metri Tablet ensures that the afterbirth comes off faster and the uterus is cleaned up. With the AHV Milk Start Paste, you quickly provide the cow with sufficient magnesium, calcium, and phosphorus again. In addition, the paste gives the cow an energy boost, making it feed faster and more often and getting the process going again.
By deploying these solutions, you significantly reduce the risk of challenges, and with just 50 liters (approx. 100 Lb) of extra milk delivered (AHV, 2022), you will already have earned back the investment. Not to mention the consequences for further lactation, start-up of the calves, fertility, and costs you would otherwise have incurred for buying restorative products.
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