Grasses are most nutritious during the growing season. At this time there is usually sufficient energy and protein in the diet and phosphorus becomes the most limiting nutrient. The greatest benefit of feeding phosphorus will be realised during the growing season where increased growth rates of up to 40kg can be achieved.
Why feed phosphorus?
Phosphorus is important for a range of metabolic processes including:
- formation of bones and teeth and a structural component of skeletal tissues
- absorption of carbohydrates such as glucose through intestinal tissues
- transport of fatty acids throughout the body
- metabolism of energy
- facilitation of fat, carbohydrate and protein utilisation
- improving efficiency of feed utilisation
- energy transfer reactions
- normal milk secretion
- buffering of body fluids.
Phosphorus deficient cattle have the ability to mobilise phosphorus from their skeleton. This is particularly important for lactating breeders as phosphorus plays a critical role in milk production. As phosphorus content in the skeleton is depleted, cattle are left vulnerable to injuries such as broken bones.
How do I know I should be feeding phosphorus?
Obvious signs of phosphorus deficiency include:
- bone chewing
- depraved appetite
- stiff gait
- bone fragility leading to breakages.
Less obvious signs include:
- reduced feed intake
- reduced milk production
- reduced fertility.
A blood phosphorus analysis will provide the best indication of phosphorus status in growing cattle, however this is not recommended for lactating cows. If cattle are not already being fed phosphorus a faecal near infrared reflectance spectroscopy (NIRS) in conjunction with a faecal phosphorus analysis can be used.