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)

Effect of low doses of Aspergillus niger phytase on growth performance, bone strength, and nutrient absorption and excretion by growing and finishing swine fed corn-soybean meal diets deficient in available phosphorus and calcium1

“…However, these experiments have also demonstrated that concentrations of AN phytase below 500 U/kg will not support adequate bone strength or P absorption (g/d) compared with pigs fed a PC diet containing supplemental inorganic P that meets the minimum aP requirements for swine (NRC, 1998). The differences in the sensitivity ranking of the response criteria in the current experiments and the experiments of Harper et al (1997) are in general agreement with other experiments that showed apparent total-tract absorption of P and bone measurements were more sensitive criteria than blood measurements or growth performance for estimating the bioavailability of P in swine diets (Koch et al, 1984;Dellaert et al, 1990;. Adequate bone strength is essential for market hogs that must be ambulatory when slaughtered, and for structural soundness of replacement gilts that enter the breeding herd.…”

Effect of phytase on apparent total tract digestibility of phosphorus in corn-soybean meal diets fed to finishing pigs1

“…Last, we chose to focus on apparent P digestibility because we know of no data indicating that P is not digested in forms that are not fully available for utilization. This is supported by Ketaren et al (1993), who reported that percentages of apparent P digestibility and retention were similar for soybean meal when dietary P levels were below estimated requirements, and by Dellaert et al (1990), who reported that apparent P digestibility is one of the best measures to determine the nutritional value of feed phosphates. Additional discussion on P digestibility and phytase activity sites within the gastrointestinal tract have been described elsewhere (Jongbloed et al, 1992;Augspurger et al, 2003;Selle and Ravindran, 2008) and are beyond the scope of the current experiments.…”

“…Plasma iP increases with an increase in dietary P (Vipperman et al, 1974;Dellaert et al, 1990;Eeckhout et al, 1995) and, in general, with supplementation of dietary phytase (Lei et al, 1993a,b,c; Adeola et al, 1). The quadratic response is represented by the following equation: apparent P digestibility (%) = 15.80 + 0.0639 FTU − 0.0000335 FTU 2 (R 2 = 0.62).…”

Phytase, High‐Available‐Phosphorus Corn, and Storage Effects on Phosphorus Levels in Pig Excreta

“…Pigs generally absorb more P than is utilized in metabolism (Finco, 1989), with excess P being excreted via urine or as endogenous P in feces. High levels of urinary P excretion are most often a result of excess dietary P (Poulsen, 2000), and urine P levels may be used as an indicator of adequate dietary P (Dellaert et al, 1990). Spencer et al (2000) showed elevated urine P with diets higher in available P due to formulation with HAP corn and supplemental inorganic P. Because the diets used in this experiment were considerably lower in available P than diets formulated to meet National Research Council P requirements, urine P values were considerably lower than would be expected for pigs under typical production conditions.…”