Effects of collection time on flow of chromium and dry matter and on basal ileal endogenous losses of amino acids in growing pigs

The objectives of this experiment were to examine the diurnal patterns of chromium and DM flow at the distal ileum of pigs and to determine the effect of collection time on basal ileal endogenous losses (BEL) of CP and AA. Eight barrows with an initial BW of 34.6kg (SD = 2.1) were individually fitted with a T-cannula in the distal ileum and randomly allotted to a replicated 4× 4 Latin square design with 4 diets and 4 periods in each square. Three diets contained either corn, soybean meal, or distillers dried grains with solubles as the sole source of CP and AA. An N-free diet was also prepared. All diets contained 0.5% chromic oxide as an indigestible marker. Equal meals were provided at 0800 and 2000 h. Ileal digesta samples were collected in 2-h intervals from 0800 to 2000 h during the last 3 d of each 7-d period. The concentration of Cr in ileal digesta samples collected in each of the six 2-h periods exhibited a quadratic effect ( < 0.01) that increased and then decreased in pigs fed the CP containing diets. However, the concentration of Cr in ileal digesta collected in each of the six 2-h periods from pigs fed the N-free diet increased (linear, < 0.01). These differences were possibly related to differences in DM flow, because DM flow to the distal ileum had a pattern that was opposite of that observed for the concentration of Cr in the ileal digesta samples. The BEL of all indispensable AA and the sum of indispensable AA from pigs fed the N-free diet decreased (linear, < 0.05) in each of the six 2-h periods, with the exception that the BEL of Arg increased and then decreased (quadratic, < 0.05). The BEL of Asp, Cys, Glu, Ser, and Tyr also decreased (linear, < 0.05) during each of the six 2-h periods, whereas the BEL of Pro and the sum of dispensable AA increased and then decreased (quadratic, < 0.05) over the 12 h. Collection time did not affect BEL of CP. No differences were observed in the concentration of Cr, flow of DM, or basal endogenous loss of all AA if ileal digesta samples were collected over 6-, 8-, or 10-h periods, compared with collection over a 12-h period. In conclusion, diurnal variation of Cr concentration, DM flow, and the BEL of all AA were observed, but 4 to 6 h of ileal sample collection starting 4 or 6 h after feeding may provide representative samples that allow for calculation of accurate values for CP and AA digestibility.