Evaluation Of Standardized Total Tract Digestibility Of Calcium And Phosphorus In Protein Ingredients Fed To Growing Pigs And Effects Of Phytase

Five experiments were conducted to determine the effects of microbial phytase on apparent and standardized total tract digestibility(ATTD and STTD)of calcium(Ca)and phosphorus(P)in animal and plant sources protein feed ingredients fed to growing pigs.In Exp.1,the effects of microbial phytase on the ATTD of Ca and P,and STTD of P in milk co-products fed to growing pigs were determined.Sixty-four growing barrows with an average initial body weight(BW)of 16.0 ±3.1 kg were allotted to a randomized complete block design with 8 diets and 8 pigs per treatment.A basal diet containing corn,potato protein isolate,soybean oil,calcium carbonate,monosodium phosphate,salt,vitamins,and minerals was formulated.Three additional diets were formulated by adding whey powder,whey permeate,or skim milk powder to the basal diet.All diets were formulated without and with 1,000 units per kilogram of microbial phytase for a total of 8 diets.Total fecal collection was conducted to determine the ATTD of Ca and P and the STTD of P in milk co-products fed to growing pigs.Results indicated that inclusion of 1,000 FTU/kg microbial phytase increased(P<0.05)the ATTD and STTD of Ca,and ATTD of P in all diets,but that was not the case for the ingredients.However,the ATTD and STTD of Ca in whey powder and skim milk powder were greater(P<0.05)than in whey permeate,but no differences were observed between whey powder and skim milk powder.In Exp.2,one hundred and twenty pigs were used to determine effects of graded levels of microbial phytase on the ATTD of P and Ca and the STTD of P in 4 sources of canola meal(CM)and in one source of soybean meal(SBM)fed to growing pigs.Pigs(initial BW:16.2 ± 5.3 kg)were individually housed in metabolism crates and were randomly allotted to 20 diets in a 5 x 4 factorial arrangement of treatments and 6 replicate pigs per diet.Five basal diets based on high-protein canola meal(CM-HP),high-temperature processed canola meal(CM-HT),low-temperature processed canola meal(CM-LT),conventional canola meal(CM-CV),or SBM were formulated.The basal diets contained no phytase.Fifteen additional diets were formulated by adding 500,1,500,or 2,500 FTU/kg to each of the 5 basal diets.Feces were collected quantitatively for 5 d after a 7-d adaptation period.Results indicated that supplementation of microbial phytase increased(linear,P<0.01)the ATTD of Ca in diets containing CM-HP,CM-HT,CM-CV,and SBM,but not in diets containing CM-LT.Microbial phytase also increased(linear and quadratic,P<0.01)the ATTD and STTD of P in all 5 ingredients.Compared with CM-CV diets,CM-HP diets had greater(P<0.01)ATTD of Ca.The ATTD of Ca in CM-LT diet was greater(P<0.05)than in CM-HT diet,but no differences were observed in ATTD or STTD of P between CM-HT and CM-LT.The ATTD and the STTD of P were less(P<0.05)in CM-HP and CM-CV than in SBM.Regression equations were developed to calculate the response to microbial phytase on the STTD of P in CM-HP,CM-HT,CM-LT,CM-CV,and SBM.In Exp.3,the effects of microbial phytase on dialyzability of P in 20 SBM samples were determined.The pepsin and trypsin two-step hydrolysis procedure was used.Results indicated there were no difference in dialyzability of P among 20 SBM samples,but inclusion of 500 FTU/kg microbial phytase increased(P<0.05)the dialyzability of P.In Exp.4,the effects of inclusion of increasing concentrations of microbial phytase on the digestibility of DM,GE,CP,NDF,ADF,macrominerals,microminerals,and AA by growing pigs fed corn-SBM based diets were determined.Twenty four growing barrows(initial BW:37.0 ± 1.4 kg)were equipped with a T-cannula in the distal ileum and allotted to 6 diets with 8 replicate pigs per diet.The positive control diet contained 0.31%standardized total tract digestible P and 0.70%Ca,and the negative control diet contained 0.16%standardized total tract digestible P and 0.43%Ca.Four additional diets were formulated by adding 500,1,000,2,000,or 4,000 units of FTU to the negative control diet.Fecal and urine samples were collected to determine the ATTD and retention.Ileal digesta were collected using titanium oxide to determine the AID of AA.Results indicated that addition of the microbial phytase to the negative control diet tended to quadratically improve the apparent ileal digestibility(AID)of Phe(P = 0.09)and Asp(P = 0.05),and linearly increased(P<0.05)the ATTD of ADF,K,and Fe.Microbial phytase also quadratically increased(P<0.05)the ATTD of NDF and Mg,and linearly and quadratically increased(P<0.05)the ATTD and retention(%)of Ca and P.But no effects of the phytase on ATTD of GE or concentration of DE was observed.In Exp.5,the ATTD and STTD of P in corn,SBM,and CM,and additivity of values for ATTD and STTD of P in corn,SBM,and CM in diets fed to growing pigs were determined.Thirty-six growing barrows(initial BW:21.6 ±1.7 kg)were allotted to a completely randomized design with 6 diets and 6 pigs per diet.Three diets were formulated using corn,SBM,or CM as the sole source of P in each diet,respectively.Three additional diets were formulated using corn and SBM,or corn and CM,or corn,SBM and CM as the P source in each diet,respectively.Results indicated that values for respective ATTD of P in corn,SBM,and CM in growing pigs were 33.12%,50.19%,and 35.49%.Values for STTD of P in corn,SBM,and CM in growing pigs were 37.76%,56.62%,and 40.02%,respectively.The ATTD and STTD of P in SBM was greater(P<0.05)than that in corn and CM.Values for STTD of P in corn,SBM,and CM are additive in their mixture fed to growing pigs.In conclusion,in vivo and in vitro experiments of this study demonstrate microbial phytase can improve the STTD of Ca and P in protein ingredients fed to growing pigs,and has extra-phosphoric effect.