0985 Effects of casein on digestibility of amino acids in distillers dried grains with solubles fed to pigs.

The objective of this experiment was to determine the true ileal digestibility (TID) of CP and AA in casein and to determine the effects of inclusion of casein in experimental diet on apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and AA in corn distillers dried grains with solubles (DDGS) fed to pigs. Eighteen barrows with an initial BW of 50.5 ± 4.5 kg were surgically fitted with T-cannula at the distal ileum and individually housed in metabolism crates. Pigs were allotted to triplicate 6 × 3 incomplete Latin square design with 6 dietary treatments and 3 periods. The 6 dietary treatments consisted of 3 diets formulated to contain 6, 10, or 14% casein; 2 diets prepared to contain 48% DDGS or 30.8% DDGS and 6% casein; and one nitrogen-free diet to determine the basal ileal endogenous losses of CP and AA. Each period lasted 7 d consisted of 5 d of adaptation period and 2 d of ileal digesta collection period. The AID of CP and all AA in casein were linearly increased (P < 0.01) with increasing dietary casein. The estimated TID of CP, Lys, Met, Thr, and Trp were 101% (SE = 3.2), 99.9% (SE = 2.12), 99.2% (SE = 1.17), 97.0% (SE = 3.23), and 98.8% (SE = 3.30), respectively. The AID and SID of Arg, Lys, Phe, and Trp in diet containing DDGS were less (P < 0.01) than those in diet containing DDGS and casein. There were no differences between the AID of CP, His, Ile, Thr, and Val in diet containing DDGS and those in diet containing DDGS and casein. However, the SID of CP, His, and Ile in DDGS diet were less (P < 0.05) than those in DDGS and casein diet. In conclusion, improving protein quality in experimental diets by inclusion of highly digestible protein sources such as casein may affect the SID of CP and AA in test ingredients of lower protein quality.