An in vitro procedure for studying enzymic dephosphorylation of phytate in maize-soyabean feeds for turkey poults

Publisher Website
Google Scholar
Abstract
Anin vitromethod was developed to predict inorganic P release from maize-soyabean poultry feeds containing supplemental phytase (EC31·3·8), and to quantify the effect of acid phosphatase (EC3·1·3·2), fungal protease (EC3·4·23·6) andAspergillus nigercellulase (EC3·2·1·4) on phytate dephosphorylation. Pepsin (EC3·4·23·1) and pancreatin digestion periods were preceded by a 30 min pre-incubation at pH 5·25 to simulate digestion in the crop of poultry. Pancreatin digestion was carried out in dialysis tubing, with a ratio of about 1:25 (v/v) between the digesta and dialysing medium, to simulate gradient absorption from the duodenum. The feed:water ratio was kept within physiological limits and a constant proportion of feed weight to digestive enzymes was maintained. There was a linear response to increasing dosages of phytase up to 1000 phytase units (FTU)/kg feed, and to increasing phosphate concentration in feeds.In vivovalidation was performed with growing turkeys (1–3 weeks) fed on diets containing 12 g Ca/kg and 0, 500 or 1000 FTU phytase/kg in a factorial arrangement with 0, 1, 2 or 3 g supplemental phosphate/kg (from KH2PO4). After a simple transformation (variable/in vitroP =f(in vitroP)), amounts of P hydrolysed from feed samples byin vitrodigestions correlated with 3-week body-weight gain (R0·986,P< 0·0001), toe ash (R0·952,P< 0·0001), feed intake (R0·994,P< 0·0001) and feed efficiency (R0·992,P< 0·0001). The dephosphorylating ability of phytasein vitrowas significantly enhanced (P< 0·05) by the addition of acid phosphatase. Fungal acid protease andAspergillus nigercellulase also enhanced the dephosphorylation processin vitro.