Phosphorus is one of the most important minerals in animal nutrition. After calcium, it is the second most abundant element in the animal body; about 80% of phosphorus is found in bones and teeth, while the remainder is present in body fluids and soft tissues.
Average Total Phosphorus and Calcium Content in Adult Animals
| Animal | Weight | Calcium | Phosphorus |
|---|---|---|---|
| Laying hen | 2 kg | 22 g | 13 g |
| Sheep | 50 kg | 550 g | 280 g |
| Dairy cow | 600 kg | 7000–9600 g | 3600–5000 g |
Sources:
V.I. Georgievskii, Mineral Nutrition of Animals, Butterworths, 1982
H.J. Oslage, Zeitschrift Tierphysiologie, Tierernährung, Futtermittelkunde, 1964
Physiological Functions of Phosphorus
Phosphorus plays a fundamental role in metabolism and is involved in more physiological functions than any other mineral. These include the following key metabolic processes:
Development and maintenance of skeletal tissue:
Most phosphorus, together with calcium, precipitates in the form of hydroxyapatite to form the skeleton. The skeleton not only serves as a structural support but also as a reservoir for calcium and phosphorus. During pregnancy, lactation, or egg production, absorption and release of these minerals are continuous.
Maintenance of osmotic pressure and acid-base balance:
Phosphorus, along with other minerals, plays an important role in maintaining the body’s buffering capacity, osmotic pressure, and acid-base equilibrium.
Energy utilization and transfer:
Phosphorus is a critical component of energy metabolism. Phosphate compounds such as ATP (adenosine triphosphate) are universal carriers of stored and transferred energy. ATP is essential for converting chemical energy into mechanical energy during muscle activity.
Protein synthesis, fatty acid transport, amino acid metabolism:
Phosphorus compounds participate directly or indirectly in all major physiological processes. Phosphorylation is essential for carbohydrate absorption, glycolysis, lipid transport, and amino acid metabolism. Phosphorus is also a component of many coenzymes.
Growth and cell differentiation (DNA):
Phosphorus is present in nucleic acids, which carry genetic information and regulate protein biosynthesis and immunity.
Appetite control, feed efficiency, and productivity:
Phosphorus plays a key role in overall animal health and production performance.
Phosphorus Requirement
Adequate amounts of biologically digestible and available phosphorus are essential for optimal health and productivity. However, phosphorus requirement is closely linked to calcium and vitamin D. For instance, phosphorus deposition in bones depends on both these components.
Therefore, not only sufficient phosphorus intake but also an appropriate calcium-to-phosphorus ratio (Ca:P) and adequate vitamin D levels are critical for balanced nutrition.
Phosphorus Deficiency
Insufficient phosphorus intake leads to phosphorus deficiency, negatively affecting both animal health and economic performance. Early signs include decreased blood phosphate levels and mobilization of calcium and phosphorus from bones. As a result, appetite decreases, body weight gain slows, and feed efficiency declines.
Poor housing conditions can worsen the effects of deficiency. Symptoms vary by species:
- Laying hens: Reduced egg production, thinner eggshells, and lower hatchability. “Cage fatigue syndrome” and osteomalacia (bone softening) may occur.
- Broilers: Leg weakness, bone fractures, tibial dyschondroplasia, osteomalacia, and rickets, leading to economic losses.
- Cattle: Reduced feed intake, poor fertility, irregular ovulation, decreased milk yield, lameness, and joint deformities.
Optimum Calcium:Phosphorus Ratios
| Species | Ca:P | Ca:vP |
|---|---|---|
| Laying hens | 4.1 – 5.8 | 11.4 – 12.3 |
| Broilers, chicks, pullets | 1.2 – 1.5 | 2.2 – 2.3 |
| Dairy cow (600 kg; 35 kg milk/day) | 1.15 – 1.4 | – |
Sources:
V.I. Georgievskii, Mineral Nutrition of Animals, Butterworths, 1982
Centraal Veevoeder Bureau (CVB), Netherlands, 2004
Determining Phosphorus Requirements
Animal phosphorus needs are generally established, but the daily required amount varies according to:
- Performance level of the animal
- Breed and genetic differences
- Individual variation within herds or flocks
- Composition of feed ingredients
For farmers, the main goal is to enhance both animal welfare and productivity while maintaining economic efficiency. Furthermore, minimizing environmental impact by properly balancing phosphorus intake is becoming increasingly important.
Source:
Feed Phosphates – Phosphorus: A Vital Source of Animal Nutrition