ARTICLE FEED & ADDITIVE MAGAZINE February 2021 55 better knowledge on the utilisation of P will lead to reduced feed costs and reduced pollution potential. Numerous studies have looked at the evaluation of P nutritional value from raw materials and feeds beyond the total P content following different concepts and different systems of evaluation. Currently, P evaluation in poultry is based on three different principles: 1. NRC (1994) refers to non-phytate P as the difference between total P and phytate P assuming inorganic P completely available whereas organic P is not, 2. INRA (2004) approach based on a bio-assay adding graded level of dietary P of a test and a reference phosphate to a P deficient basal diet to calculate from the slopes the relative biological value (RBV) or available P, 3. CVB (1997) approach is based on the determination of P retention using P deficient diets (on a 3 days balance study following 10 days adaptation period). More recently some trials were conducted to give digestible P (ileal digestibility) values representing the part of P that may be absorbed in the digestive tract of the animals. But digestibility trials depend on a lot of factors from the diet but also on the animal physiology and gave so far non consistent results (Rodehutscord et al.,2016). When considering dietary P level, independently of the methodology chosen, it is impossible to ignore the dietary Ca as this has such a large effect on P absorption and utilization. The body maintains the serum levels of these minerals within narrow and stable limits. Absorption of Ca and P from the diet occurs mainly in the duodenum. An imbalance between Ca and P supply can interfere with their digestibility and their metabolic use. Excess Ca will impair P absorption, increase gastrointestinal pH and could have implications in gut health such as necrotic enteritis, affecting the performance of the animal and bone mineralisation. It is therefore crucial to analyse P and Ca in feed. 0,19 0,19 0,23 0,36 0,42 0,71 0,72 0,80 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 Corn (n=11,037) Barley (n=1,598) Wheat (n=16,859) Soybean - Full fat (n=718) Soybean Meal (n=12,242) Sunflower meal (n=373) Canola meal (n=6,186) Wheat bran (n=137) Cereals Protein products Cereal coproduct Phytate P, % Figure 1 – A box-plot showing the phytate-P content and variability of some common raw materials used in EMEA. Data collected from April 2017 to present. The horizontal line across the box refers to the median value, the blue horizontal line represents the mean value, and the top and bottom of the “box” represents the interquartile ranges. The vertical lines, or whiskers, highlight variation outside of the interquartile range.
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