Characterization and Estimation of Digestibility of Phosphorus Forms in Rendered Animal Protein Ingredients and Fish Meals

Title: Characterization and Estimation of Digestibility of Phosphorus Forms in Rendered Animal Protein Ingredients and Fish Meals

Principle Investigator: Dominique Bureau

Year: 2003

Lay Summary/Industry Summary:
The experiment results suggest that P digestibility model accurately estimated P digestibility and digestible P contents of the experimental diets formulated with a wide variety of ingredients used in practice. The P digestibility model is the first mathematical model developed to estimate digestible P content of fish feeds and it can be a useful tool in practical feed formulation.

Scientific Abstract: Phosphorus (P) is present in different chemical compounds in animal feeds, and the solubility and digestibility of these different compounds are known to differ significantly. Animal protein ingredients generally have a high P content and are major contributors to total P of feeds for fish and other domestic animals. Estimation of different P compounds in these ingredients could help to improve the accuracy of estimates of digestible P contents of feeds. Bone-P and organic P contents were quantified in 32 animal protein ingredients, including 10 fish meals, 14 meat and bone meals, and 8 poultry by-products meals, using a fractionation protocol. The total P contents of the ingredients ranged from 2.1% to 8.3% on a dry matter (DM) basis. Organic P contents varied between 0.3% and 1.3% of DM. Highly significant (p < 0.001) linear relationships were observed between total P and ash and between bone-P and ash for all ingredients combined: total P (%) = 0.185 * ash(%) (r2 = 0.88), and bone P (%) = 0.188 * ash(%) - 0.852 (r2 = 0.94). These results suggest that bone-P can be easily and reliably estimated on the basis of ash content in animal protein ingredients. A digestibility trial was conducted to validate a mathematical model that estimates the digestible phosphorus (P) content of salmonid feeds. The P digestibility model estimates digestible P contents of fish feed based on the dietary inclusion level of different P chemical compounds, which were characterized into five categories: bone-P, phytate-P, organic P, Ca monobasic /Na/ K Pi supplement, Ca dibasic Pi supplement. The model suggests that the digestibility of these P compounds differs significantly, and the digestibility of bone-P is not additive. Test diets were formulated with two types of fish meal, two types of poultry by-product meal, two types of soy protein concentrates, and one type of meat and bone meal. The digestibility trial was carried out with rainbow trout (initial body weight - 48 g/fish) using the Guelph feces collection system. Comparison between experimental observed and model predicted values suggested that the model well predicted digestible P content of diets formulated with a wide variety of ingredients used in practical feed formulation. The model can be a useful tool in practical feed formulation. Publications:
Rendered products in fish aquaculture feeds

Determination of phosphorus fractions in animal protein ingredients

Modelling digestible phosphorus content of salmonid fish feeds