A comparison of different techniques to assess the biological availability of feed phosphates in pig feeding.

Abstract

Piglets from about 6 weeks old were fed on basal diets with P 0, 0.6, 1.2 or 1.8 g/kg, 0, 1.2 or 2.2 g/kg, and 0 or 2.0 g/kg in experiments 1, 2 and 3, respectively. Blood factors did not show a significant response to P intake. Plasma alkaline phosphatase activity was not linearly related to P intake, while regressing the inorganic P content to the quantity of supplemented P resulted in a low fitness of the model (Rsuperscript 2 = 53%). Results from bone fat-free DM, concentration of ash in fat-free DM, amount of ash, concentration of P in ash and bone breaking strength were better (Rsuperscript 2 = 45 to 94%). There were slight differences in the results using tibia, femur or third and fourth metatarsals. However, the highest degree of fit was found using the apparent digestibility of P as the dependent variable (Rsuperscript 2 = 96 to 100%). After relating the criteria to the retention of P, again the apparent P digestibility was the most accurate factor to determine the biological availability of P. Basing the nutritional value of feed phosphates on digestibility of P, significant differences were shown between form and origin of feed phosphate. The values within a type of feed phosphate showed a high repeatability. (Abstract retrieved from CAB Abstracts by CABI’s permission)