| Three experiments were conducted to validate, in vivo, the increased phosphorus availability in low phytate barley suggested by laboratory phytate analyses and to determine if lowering the phytate content in low phytate barley would compromise its nutritional value. Six low phytate barleys (1 hull-less, 5 hulled) and two iso-geneic wild type barleys (1 hull-less 1 hulled) were used in each experiment. By analysis, hull-less wild type barley (NNB) contained 0.15% nonphytate P (nP) and 0.38% total P (tP); hull-less low phytate barley (NLPB) contained 0.22% nP and 0.34% tP; hulled wild type barley (NB) contained 0.12% nP and 0.36% tP; hulled low phytate barleys (LPB-1, LPB-2, and LPB-3) contained 0.20%, 0.27%, and 0.30% nP and 0.31%, 0.35% and 0.35% tP, respectively. Experiment 1 utilized the semi-purified method of feeding, while experiments 2 and 3 utilized commercial-type diets. Response variables were body weight gain, feed intake, tibia ash, toe ash and P retention. In experiment 3, analyzed ME and total amino acid values for the barleys were used in the formulation of the diets. The results of the three experiments demonstrated that P in low phytate barleys is more available than P in wild-type barleys, and decreasing the phytate content did not compromise its nutritional value. The increased availability of P in low phytate barleys has several benefits; the reduction of supplemental inorganic P addition to diets, reduction in P excretion thereby lessening the problem of P pollution, and improved utilization of nutrients bound by phytate.; An in vitro method was developed to predict phosphorus (P) availability from inorganic phosphate sources. The in vitro procedure consisted of separate peptic and pancreatic digestion periods, designed to simulate the digestive conditions in poultry. Analysis of data was based on slope-ratio procedures. There were no statistical differences (P > 0.05) in P bioavailability or in vitro P release among the phosphate sources. Results of these studies indicated that the in vitro study may be useful in predicting relative bioavailability of inorganic phosphate sources. The in vitro method was also used to predict P availability from 15 plant-origin feed ingredients. Results of that assay indicated a significant positive correlation (R = 0.87) between in vitro P release and published in vivo P availability values for the 15 plant-origin feed ingredients and a significant positive correlation (R = 0.84) between in vitro P release and the analyzed non-phytate P values. The in vitro method presented here may be a valid alternative to conducting in vivo studies for ranking plant-origin feed ingredients with respect to P availability. |
