Effects Of Dietary Phosphorus Sources,Concentration And Growth Stage On Postileal Phosphorus Digestion In Pigs

The present study was conducted to investigate the effects of dietary phosphorus(P)source,P levels and growth stage of pigs on P digestion in the hindgut.Experiment 1: Twenty-four growing pigs with T-cannulas at the distal ileum(average initial BW 57.3 kg)were divided into duplicate 12 × 4 incomplete Latin square design with 12 diets and 4 periods.Nine cornstarch-based semipurified diets containing 3 assay P sources which are soybean meal(SBM),canola meal(CM),and corn distiller's dried grains with solubles(DDGS),while the other 3 corn-SBM-based practical diets with dicalcium phosphate(DCP)which as assay P source.The 4 assay P sources were all set three levels.The results indicated that the interaction of dietary P sources and levels significantly affected the apparent total tract digestibility(ATTD)and apparent ileal digestibility(AID)of P(P <0.01).When the assay P sources was SBM or DCP,the ATTD and AID of P increased linearly with the increase of dietary P level(P <0.01).The dietary P source significantly affected postileal digested P,the proportion of postileal digested P to total tract digested P,hindgut disappearance of P,and apparent postileal digestibility(APID)of P(P < 0.01).When the assay P sources was corn DDGS or DCP,the AID of P were significantly less than ATTD(P <0.05).Experiment 2: Forty-eight growing pigs with T-cannulas at the distal ileum(average initial BW 27.8 kg)were allotted to 6 dietary treatment groups,there were 8 replicates in each treatment group with 1 pig per replicate.The basal diet was a corn-SBM based diet without DCP supplementation,and dietary total P concentration was calculated to be 3.3 g/kg.Five additional diets were formulated by the inclusion of DCP to the basal diet and thereby creating experimental diets that were calculate to contain 4.3,5.3,6.3,7.3,and 8.3 g/kg total P,respectively.The results indicated that the AID and ATTD of P,the digestible P in the ileal and total tract,ileal P output,and fecal P output increased linearly with increasing dietary total P level(P < 0.01).Experiment 3: Sixteen growing pigs with average initial BW of 25.9 kg,sixteen growingfinishing pigs with average initial BW of 61.3 kg and sixteen finishing pigs with average initial BW of 98.3 kg were fitted with T-cannulas.Each growth stage group of pigs were randomly assigned to two treatment groups,there were 8 replicates in each treatment group with 1 pig per replicate.The two diets were moderate-P corn-SBM diet without DCP and adequate-P corn-SBM diet with DCP.The results indicated that the interaction between growth stage and diet significantly affected ATTD of P,the digestible P in the ileal,and ileal P output(P < 0.05).Compared with growing pigs,the APID of P,hindgut disappearance of P,postileal digested P,and the proportion of postileal digested P to total tract digested P of growing-finishing and finishing pigs were significantly greater(P < 0.05).Whether moderate-P diet or adequate-P diet,the values of ATTD of P were greater than the estimates of AID of P for growing-finishing pigs and finishing pigs.