No abstract

The kinetics, mineral dependency, and pH dependency of phytate hydrolysis by preparations of chicken small intestinal brush border membrane vesicles were determined. Substantial phytate hydrolysis occurred over the pH range from 5 to 6.5 with a maximum hydrolysis at pH of 6. Inclusion of 25 mM MgCl2 in the media doubled the rate of phytate hydrolysis. The brush border was shown to have no nonspecific acid phosphatase activity and excess phytate had no effect on alkaline phosphatase activity at pH 11. Under optimal conditions of pH 6 plus 25 mM MgCl2, a kinetic model of a single Michaelis-Menten type of enzymatic activity with a Km of 0.160 +/- 0.008 mM and a Vmax of 42.5 +/- 1.0 nmol/mg vesicle protein per min plus a small unsaturable component converged to the data (P < 0.05). The specific and total activities of intestinal brush border phytase were highest in the duodenum (P < 0.05) and decreased progressively down the length of the gut. Intestinal brush border vesicles prepared from broiler chicks and mature laying hens had comparable specific phytase activity. However, the total activity of brush border phytase was 35% higher in the small intestine of laying hens (P < 0.05). Intestinal brush border phytase could contribute to phytate-phosphorus digestibility and may be subject to regulation in response to the dietary phosphorus and vitamin D status of the chicken.

This review provides a general overview of the subject along with a specific focus on factors that affect the efficacy of phytate hydrolysis and methods to reduce further or eliminate indigestible phytate in plant-based diets fed to livestock.

A dephytinized protein concentrate prepared from canola seed (CPC) was assessed for nutrient digestibility and performance in rainbow trout (Oncorhynchus mykiss). The apparent digestibility coefficients of CPC were: dry matter, 817 g kg−1; crude protein, 899 g kg−1; gross energy, 861 g kg−1; arginine, 945 g kg−1; lysine, 935 g kg−1; methionine, 954 g kg−1; threonine, 893 g kg−1. A 9‐week performance trial assessed 7 diets. Fishmeal provided 940 g kg−1 of the protein in the control diet. Test diets consisted of CPC or water‐washed CPC replacing 500 and 750 g kg−1 of fishmeal protein; and CPC plus an attractant replacing 500 and 750 g kg−1 of fishmeal protein. No significant differences in performance were observed (P > 0.05). A subsequent 9‐week performance trial evaluated the effect of adding CPC into compound diets containing fishmeal/soybean meal/corn gluten meal. Five diets were prepared: fishmeal provided 670 g kg−1 of the protein in the control diet, in the remaining diets CPC was incorporated into commercial‐like trout diets at 100, 200 and 300 g kg−1 replacement of fishmeal protein, the fifth diet included an attractant in the 300 g kg−1 replacement diet. No significant differences in performance were obtained (P > 0.05). These studies show that dephytinized canola protein concentrate has potential to replace substantial levels of fishmeal in diets for carnivorous fish without compromising performance.