| The experiments were conducted with growing pigs to determine the true fecal phosphorus and calcium digestibility in unconventional plant-feedstuffs and endogenous fecal phosphorus and calcium losses by the regression analysis technique.In vivo, 24 barrows, average initial body weight 25kg, were allotted to four groups randomly, fed six diets each group according to a 6×6 Latin Square design.Six cornstarch-based diets containing six levels of P or Ca based on fed status each group were formulated from barley-SBM, sorghum-SBM, peanut-SBM or rapeseed-SBM. In vitro, the dailyzability of phosphorus and calcium in unconventional plant-feedstuffs were measured by three dailytic methods established by the study, which were pepsin-trypsin digestive method, gastric juice and intestines juice digestive method, and pepsin-intestines juice digestive method.The prediction model of digestible phosphorus were be established based on the concentration of dialyzable phosphorus and total phosphorus, phytate-P, phytase.Results show that:there were significant linear relationship(P<0.05) between fecal P outputs and dietary inputs of P when both expressed as g/kg.DMI intake diet with total P level of diet, which suggests a stable amount of endogenous P lose in feces for pig and a additivity between digestible P from basal feed and assay feed. This implicated that the four assays are valid for estimating endogenous P outputs and true phosphorus digestibility for basal feed and assay feed in growing pigs. The endogenous P outputs and true fecal P digestibility values of soybean meal were 0.95g/kg.DMI and 52.31% respectively associated with soybean meal and barley grain. The endogenous P outputs and true fecal P digestibility values of sorghum grain and soybean meal were 0.29g/kg.DMI, 56.05% and 39.41% respectively associated with soybean meal and sorghum grain. The endogenous P outputs and true fecal P digestibility values of peanut meal and soybean meal were 0.53g/kg.DMI, 28.00% and 38.87 %respectively associated with soybean meal and peanut meal. The endogenous P outputs and true fecal P digestibility values of rapeseed meal and soybean meal were 0.21/kg.DMI, 10.21% and 32.94% respectively associated with soybean meal and rapeseed meal.there were significant linear relationship(P<0.05) between fecal Ca outputs and dietary inputs of Ca when both expressed as g/kg.DMI intake diet with Ca level of diet, which suggests a stable amount of endogenous Ca lose in feces for pig and a additivity between digestible Ca from basal feed and assay feed. This implicated that the two assays are valid for estimating endogenous Ca outputs in growing pigs. The endogenous Ca outputs were 0.83g/kg.DMI associated with soybean meal and barley grain. The endogenous Ca outputs were 0.29g/kg.DMI associated with soybean meal and sorghum grain.the sequence of significance for factors on sample-P dialyzablity are as follows: time of trypsin digestion(or time of intestines juice digestion)>volumes of dialyzing solution>pH of pepsin solution(or pH of gastric juice digestion) >pepsin concentration(or gastric juice concentration) > time of pepsin digestion(or time of gastric juice digestion) > temperature > trypsin concentration(or small intestines juice concentration) > pH of trypsin solution(or pH of small intestines juice solution). The sequence of significance for factors on sample-Ca dialyzablity are as follows: pH of trypsin solution(or pH of small intestines juice solution) >time of trypsin digestion(or time of intestines juice digestion) >temperature>pepsin concentration(or gastric juice concentration) >trypsin concentration(or small intestines juice concentration) >pH of pepsin solution(or pH of gastric juice digestion) >time of pepsin digestion(or time of gastric juice digestion) >volumes of dialyzing solution. The suitable condition or determining the dialyzability of sample P and Ca in vitro are as follows: weighting exactly 1g sample and transferring it into a test tube, then adding 2ml pepsin solution or 2.46ml gastric juice (in which the enzyme concentration is 2000NFU/ml, and the pH is equal to 2.5) and hydrolysising for 100min, then neutralizing pH to 6.5 with 1M sodium bicarbonate, and transferring it into a dialysis tube, adding 0.5ml trypsin solution or 0.46ml small intestines juice(in which enzyme concentration is 1625NFU/ml) and hydrolysis in 100ml buffer solution for 6hr at 35℃.The prediction models of digestible P were being established based on the concentration of dialyzable phosphorus and total phosphorus, phytate-P, phytase. Results showed that:True digestible P(g/kg)=1.1378×dialyzable P(g/kg)(R2=0.92, P<0.01) The optimal prediction model:True digestible P(g/kg)=0.9690×TP(g/kg) - 0.9786×PP(g/kg)+0.0021×Phy(FTU/kg) (R2=0.89, P<0.01)the phytase can increased the dialyzability of P and Ca in plant feedstuffs(P<0.05 ).The relationship between P release from plant feedstuffs and the concentration of phytase are as follows:Amounts of inorganic-P released from plant feedstuffs(g/kg)= 0.4054×PP(g/kg)+0.00019×phy (FTU/kg)(R2=0.97, P<0.01=.
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