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Importance of Phosphorous Supplementation in farm animals Phosphorous is the essential element involved in energy and nutrient metabolism. The deficiency of this mineral negatively affects animal performance, fertility and bone mineralization in all farm animals (Swiatkiewicz et al., 2008). Introduction The importance of phosphorous (P) supplementation for optimal animal health and production cannot be over emphasized. Most pastures and ingredients used in animal nutrition cannot supply the grazing and housed animal with enough P to sustain a high level of performance in terms of reproductive rate, milk production and growth. The supplementation of phosphorous is a costly practice, but the repercussions of not supplying P in situations where animals have either an acute or even a sub- clinical P deficiency, could be even more costly. The importance of Phosphorous Phosphorous is the second most abundant element in the animal’s body and plays a major metabolic role – it has more known physiological functions in the animal body than any other element. Eighty percent of the phosphorous in the animal’s body is found in the skeleton where it acts as a reservoir for phosphorous. By far the greatest proportion of P is devoted to maintaining and supporting the skeleton. Phosphorous, together with other minerals, also plays a major role in maintaining the osmotic pressure, buffer capacity and acid-base balance in the animal body. Phosphorous further plays a vital part in energy utilization and transfer. Phosphorous compounds are both directly and indirectly involved in all major physiological functions and are also a component of a large number of co-enzymes and the structure of nucleic acids (DNA). Lastly, phosphorous also plays an important role in appetite control, efficiency of feed utilization and the fertility of all farm animals. Phosphorous deficiency A phosphorous deficiency will develop in farm animals without an adequate supply of P, or if the P is supplied in a form which the animal cannot utilize (use of P sources with a low “digestible” or “available” P content). The consequences of a P deficiency vary between the different types of farm animal, but in all cases affect the physical well being of the animals, as well as their economic performance. Some of the deficiency symptoms include: Sows – fertility is reduced and the sows can develop posterior paralysis (Downer Syndrome) and osteomalacia. Fattening pigs – Growth rate and feed efficiency is reduced. Pigs also develop rickets, which can lead to piglet mortalities, while bone breakages during transport and processing affects meat quality and results in economic losses. Ruminants – Reduction in feed intake and lower feed utilization. Reduced fertility, irregular or suppressed ovulation and lower conception rates. Other symptoms may include reduced milk production, lameness, stiffness of gait and in severe instances, enlarged and deformed joints and bones. Phosphorous requirements The production phase of the animal will influence its requirement for phosphorous. Animals need a basic amount of P for maintenance and this will increase as the size of the animal increases. Growing animals have an additional demand for P and the amount they need is directly related to the rate of weight gain. Pregnancy also increases the demand for P, especially for the development of the fetus and placenta. Lactation imposes a heavy demand for P because of the relatively high content of P in milk (e.g. 0,95 - 1 g P/ liter of cow’s milk). Table 1 shows the P requirements of pigs, cattle and dairy. Table 1 Piglets P requirements for pigs and ruminants P requirements for pigs Digestible P in the feed (% as fed) 0.4 P Requirement for Ruminants Daily P requirement (g) Dairy cow, 600 kg, 35kg milk /day Beef stock 400 kg 1.4 kg gain/day 84.6 Fattening pigs 36.0 0.3 < 50 kg 0.24 50-100 kg Sows: 0.32 Lactating 0.25 Pregnant Sources: 1) CEFIC 2) WCF Bulletin, April 1986; Mineral Nutrition of Ruminants, F Meschy Supplementation of Phosphorous Phosphorous can be supplied to animals by sources from plant and animal origin as well as inorganic sources. The phosphorous content of plant materials typically used in animal nutrition ranges from 0.09 % to 1.09 % (CEFIC). Most of the phosphorous in plants are in phytate form and is approximately 60 % available to ruminants and 10 to 39 % available to pigs (CEFIC). Animal sources providing P includes meat, fish and bone meals. The available P from these sources varies between 59 and 74 %, depending on the source and production process. The Animal Feed Act currently bans the feeding of meat and bone meal to any ruminant. As a result of the problems with P sources of plant and animal origin, it became common practice to use inorganic feed phosphates to supply animals with P. When using inorganic feed phosphate, one must be aware that not all inorganic P sources are the same in terms of quality. It is therefore vital to have a sound knowledge of the differences between the sources in order to make a well informed choice. Differences between inorganic sources Chemical Composition – Use a product of which the chemical composition is not only according to the correct specification, but is also consistent and can be guaranteed by the manufacturer. Physical appearance – Products should be dust and lump free, free flowing and easy to handle. Undesirable elements – De-fluorinated phosphoric acid should be used in the manufacturing processes to ensure a low content of fluorine and cadmium, as well as other undesirable element. Bioavailability - describes to what extent an animal can utilise a given nutrient. Knowing the bioavailability of a P source is important, as this makes it possible to optimise feed formulation according to the animal’s requirements for digestible P, instead of formulating for total P. Conclusion Phosphorous is one of the most important minerals in animal nutrition. A deficiency of this mineral will negatively affect the health as well as economic performance of an animal. Inorganic sources are widely used to supplement P, but one must be aware of the differences between these sources. The improvement in animal performance concerning general health, growth rate, milk yield, weaning weight and rate of reproduction, will outweigh the cost of supplying a high quality phosphate.