Effects of ileal digesta collection time on standardized ileal digestibility of amino acids in corn, soybean meal, and distiller's dried grains with solubles fed to growing pigs

The objective of this experiment was to determine the minimum collection time needed to obtain representative samples of ileal digesta from pigs fed different types of diets. Eight barrows with an initial BW of 34.6 kg (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 per square. Three diets contained corn, soybean meal (SBM), or distiller's dried grains with solubles (DDGS) as the sole source of CP. 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. When pigs were fed the corn diet, the standardized ileal digestibility (SID) of most indispensable AA and dispensable AA increased and then decreased (quadratic, P < 0.05) during each of the six 2-h periods. The SID of most AA were less (P < 0.05) if the ileal digesta samples were collected from 1800 to 2000 h or from 1600 to 2000 h compared with the SID values from the ileal samples collected over the entire 12-h period. When pigs were fed the SBM diet, the SID of Ile, Leu, Thr, Trp, Val, Ala, and Cys increased and then decreased (quadratic, P < 0.05) but the SID of all other AA linearly decreased (P < 0.05) during the six 2-h periods. The SID of almost all AA were greater (P < 0.05) if the ileal samples were collected from 0800 to 1000 h, from 0800 to 1200 h, from 1000 to 1400 h, or from 0800 to 1400 h but less (P < 0.05) if collected from 1600 to 1800 h, from 1800 to 2000 h, from 1600 to 2000 h, or from 1400 to 2000 h compared with the SID values from the ileal samples collected over the entire 12-h period. When pigs were fed the DDGS-based diet, the SID of Ile, Leu, Lys, Phe, Trp, Val, and Tyr increased and then decreased (quadratic, P < 0.05) during the six 2-h periods. The SID of most AA were less (P < 0.05) if the ileal samples were collected from 1800 to 2000 h compared with the SID values from the ileal samples collected over the entire 12-h period. In conclusion, diurnal variations in SID of AA in pigs indicate that 6 h of ileal sample collection starting 4 or 6 h after feeding may provide representative samples of ileal digesta from pigs fed different types of diets.