Changes

==Roles in the Body==

==Roles in the Body==

In terms of its structural role, the main function of phosphorus is, when combined with calcium, in the formation of hard structures such as bones and teeth. Phosphorus is also involved in many key processes such as membrane integrity and provision of so-called energy-rich compounds vital to energy metabolism.  It is also a component of enzyme cofactors. These are relatively small organic molecules, associated with larger enzyme molecules, which are necessary for the enzymes to function effectively. The cofactors often combine with and then release molecules or fragments of molecules as part of the overall enzymatic process. Dietary phosphorus absorption is controlled principally by parathyroid hormone (PTH), which regulates the renal production of 1,25-dihydroxyvitamin D. The vitamin stimulates the absorption of phosphorus from the small intestine similar to the effect on calcium [Link to WikiVet Calcium].     

In terms of its structural role, the main function of phosphorus is, when combined with calcium, in the formation of hard structures such as bones and teeth. Phosphorus is also involved in many key processes such as membrane integrity and provision of so-called energy-rich compounds vital to energy metabolism.  It is also a component of enzyme cofactors. These are relatively small organic molecules, associated with larger enzyme molecules, which are necessary for the enzymes to function effectively. The cofactors often combine with and then release molecules or fragments of molecules as part of the overall enzymatic process. Dietary phosphorus absorption is controlled principally by parathyroid hormone (PTH), which regulates the renal production of 1,25-dihydroxyvitamin D. The vitamin stimulates the absorption of phosphorus from the small intestine similar to the effect on [[Calcium - Nutrition|calcium]].     

==Consequences of Phosphorus Deficiency==

==Consequences of Phosphorus Deficiency==

===Dog:===

===Dog:===

There are surprisingly few direct studies of phosphorus deficiency in dogs. Normal phosphorus metabolism requires normal levels of calcium and the emphasis is usually on calcium requirement and the close relationship of dietary calcium and phosphorus – the Ca:P ratio. It is often difficult to produce clear signs of phosphorus deficiency without the almost inevitable involvement of calcium nutrition. Excess dietary calcium or a very high Ca:P ratio can adversely affect the absorption of phosphorus and this will inevitably result in impaired skeletal development [1]. Like calcium, this is particularly serious for young puppies, where the skeleton is still developing.

There are surprisingly few direct studies of phosphorus deficiency in dogs. Normal phosphorus metabolism requires normal levels of calcium and the emphasis is usually on calcium requirement and the close relationship of dietary calcium and phosphorus – the Ca:P ratio. It is often difficult to produce clear signs of phosphorus deficiency without the almost inevitable involvement of calcium nutrition. Excess dietary calcium or a very high Ca:P ratio can adversely affect the absorption of phosphorus and this will inevitably result in impaired skeletal development<ref>Schoenmakers, I, Hazewinkel, HAW, van den Brom WE (1999). “Excessive Ca and P intake during early maturation in dogs alters Ca and P balance without long-term effects after dietary normalization”. J Nutr. 129:1068-1074.</ref>. Like calcium, this is particularly serious for young puppies, where the skeleton is still developing.

====Recognised Syndromes related to Phosphorus Deficiency====

====Recognised Syndromes related to Phosphorus Deficiency====

#'''Skeletal malformation''': Jenkins and Phillips [2,3] described poor appetite and skeletal malformations in German shepherd puppies fed dietary phosphorus at 0.23% on a dry matter (DM) basis. These effects were largely ameliorated when the dietary content was increased to 0.33% DM. The calcium content was 0.6% DM so the Ca:P ratios were 2.6 and 1.8 respectively, higher than the ideal ratio of around 1:1.

#'''Skeletal malformation''': Jenkins and Phillips<ref>Jenkins, K, Phillips P (1960a). “The mineral requirements of the dog. 1. Phosphorus requirement and availability”. J Nutr. 70:235-240.</ref><ref>Jenkins, K, Phillips P (1960b). “The mineral requirements of the dog. 2. The relation of calcium, phosphorus and fat levels to minimal calcium and phosphorus requirements”. J Nutr. 70:241-246.</ref> described poor appetite and skeletal malformations in German shepherd puppies fed dietary phosphorus at 0.23% on a dry matter (DM) basis. These effects were largely ameliorated when the dietary content was increased to 0.33% DM. The calcium content was 0.6% DM so the Ca:P ratios were 2.6 and 1.8 respectively, higher than the ideal ratio of around 1:1.

===Cat:===   

===Cat:===   

As with the dog there are very few studies of dietary phosphorus deficiency in cats but the effects on skeletal development will be expected to be similar to those seen in dogs. In adult cats clinical signs of deficiency including haemolytic anaemia, permanent flexion of the hind legs, apathy and metabolic acidosis were observed in those animals receiving a diet containing 0.21% phosphorus and 0.83% calcium (DM basis). The diet therefore had a very high Ca:P ratio of about 4:1 [4]. The importance of the Ca:P ratio is shown by the observation from the same study that no clinical signs occurred when the dietary concentrations of calcium and phosphorus were both 0.21% DM.   

As with the dog there are very few studies of dietary phosphorus deficiency in cats but the effects on skeletal development will be expected to be similar to those seen in dogs. In adult cats clinical signs of deficiency including haemolytic anaemia, permanent flexion of the hind legs, apathy and metabolic acidosis were observed in those animals receiving a diet containing 0.21% phosphorus and 0.83% calcium (DM basis). The diet therefore had a very high Ca:P ratio of about 4:1<ref>Kienzle, E, Thielen, C, Pessinger, C (1998). “Investigations on phosphorus requirements of adult cats”. J Nutr. 128 (suppl):2598S-2600S.</ref>. The importance of the Ca:P ratio is shown by the observation from the same study that no clinical signs occurred when the dietary concentrations of calcium and phosphorus were both 0.21% DM.   

==Toxicity==

==Toxicity==

==Dietary Sources==

==Dietary Sources==

Phosphorus is more widely distributed than calcium and is found in dairy, meat, vegetable and cereal products. However in cereals and vegetables phosphorus may be combined as phytate, which is less bioavailable. Common sources in manufactured dog and cat foods include bone meal, meat and bone meal, fish meal, and inorganic phosphate salts – usually those of calcium, sodium, potassium or ammonium. Home-made diets that are mostly composed of meats typically have a very abnormal Ca:P ratio [Link to WikiVet Calcium].  

Phosphorus is more widely distributed than calcium and is found in dairy, meat, vegetable and cereal products. However in cereals and vegetables phosphorus may be combined as phytate, which is less bioavailable. Common sources in manufactured dog and cat foods include bone meal, meat and bone meal, fish meal, and inorganic phosphate salts – usually those of calcium, sodium, potassium or ammonium. Home-made diets that are mostly composed of meats typically have a very abnormal [[Calcium - Nutrition|Ca:P ratio]].  

==References==

==References==