Effect of dietary phytate and phytase on proteolytic digestion and growth regulation of broilers

Abstract

This study was designed to investigate the effect of dietary phytate and phytase on proteolytic digestion and growth signalling in the gastrointestinal tract of broilers. Diets containing phytate phosphorus (2.2 or 4.4 g/kg) with phytase dose rates of 0, 500, or 1,000 FTU/kg were fed to 504 female Cobb chicks for three weeks. Diets containing high phytate reduced the activity of pepsin and trypsin, whereas the inclusion of microbial phytase increased the activity of pepsin, H(+)K(+)-ATPase, trypsin and alanyl aminopeptidase. In the intestine, phytate upregulated the mRNA expression of somatostatin, and down-regulated the mRNA expressions of ghrelin and target of rapamycin (TOR). Phytase down regulated the somatostatin gene, and upregulated the genes of ghrelin, TOR, p70 S6 kinase (S6K) and methionyl aminopeptidase. Significant interactions between phytate and phytase on the mRNA expressions of ghrelin, somatostatin and S6K in the jejunum were detected. The results suggest that dietary phytate and phytase can influence the gastrointestinal endocrine and exocrine systems, as well as the peripherally regulatory network of growth in broilers.

Separate feeding of calcium improves performance and ileal nutrient digestibility in broiler chicks

“…The addition of phytase to pig and poultry diets tends to disproportionately improve the ileal recovery of threonine, serine, proline, aspartic acid, glycine and cysteine compared with the more recalcitrant amino acids methionine, arginine, glutamic acid and lysine (Cowieson and Bedford 2009). This is partly due to a reduction, with phytase addition, in ileal endogenous amino acid flow (Cowieson and Ravindran 2007) and partly due to altered absorptive function (Liu et al 2009). The separate feeding of Ca in the present study resulted in an improvement in ileal amino acid digestibility of 8% (comparing the 2.5 g/kg diet with the 10 g/kg diet).…”

Review: Anti-nutritional effects of phytic acid in diets for pigs and poultry – current knowledge and directions for future research

“…Indeed, Knuckles et al (1989) reported a 9 to 14% reduction in pepsin digestion of casein and bovine serum albumin in vitro due to addition of phytic acid to the incubation media, whereas Vaintraub and Bulmaga (1991) reported a 60 to 92% reduction in pepsin digestion of casein, hemoglobin, bovine serum albumin and soybean protein in vitro due to addition of phytic acid to the incubation media. Furthermore, Liu et al (2009) reported a 6.3% reduction in the activity of pepsin in the proventriculus of broiler chickens due to dietary phytic acid, whereas observed reduced activity of pepsin in piglets by 46% due to addition of phytic acid to a phytic acid-free diet.…”

“…Phytic acid has been reported to reduce the activity of porcine pancreatic lipase in vitro (Knuckles et al 1989) and pancreatic lipase activity in the small intestine of broilers (Liu et al 2009), implying that the reduced fat digestibility by phytic acid could partly be a result of reduced activity of lipase. Phytic acid could also reduce fat digestibility and absorption by binding bile acids via divalent cations such as calcium to form insoluble phytic acid-mineral-bile acids complexes, thereby reducing fat digestion and absorption, and bile acids re-absorption.…”

“…1). In addition to reducing pepsin activity, Liu et al (2009) have reported a 24.2% reduction in trypsin activity in the jejunum of chickens due to an increase in dietary phytic acid level from 0.78 to 1.56%. Thus, phytic acid can reduce performance partly by reducing the digestibility of dietary amino acids.…”

“…In poultry, Liu et al (2009) reported reduced serum total cholesterol and hepatic triacylglycerol content due to an increase in the level of phytic acid level in the diets for broilers from 0.7 to 1.4%. Thus, results from these studies indicate that phytic acid reduces the (re)absorption of fat, cholesterol and bile acids, leading to reduced hepatic and serum lipid levels.…”