The objective was to determine the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and AA in 2 sources of single cell protein (SCP) and fish meal (FM) fed to growing pigs. The SCP1 (produced in Korea) contained 88.0% DM, 65.1% CP, 2.8% ether extract, and 4.2% ash; the SCP2 (produced in China) contained 90.4% DM, 75.6% CP, 1.3% ether extract, and 4.3% ash; and the FM (tuna fish meal produced in Korea) contained 85.2% DM, 54.9% CP, 8.8% ether extract, and 19.8% ash. Eight barrows (initial BW = 41.3 ± 1.2 kg) surgically fitted with a T-cannula in the distal ileum were allotted to a replicated 4 × 4 Latin square design. Three experimental diets were formulated to contain 25% SCP1, SCP2, and FM, respectively, which were the sole source of nitrogen in each experimental diet. A nitrogen-free diet was also prepared. All experimental diets contained 0.5% chromic oxide as an indigestible index. Values for the AID and SID of most indispensable AA in the SCP1 and FM were greater (P < 0.05) than those in the SCP2. There were no differences in the AID and SID of most indispensable AA between the SCP1 and FM. In conclusion, the digestibility of most indispensable AA in the SCP1 and FM were greater than those in the SCP2. Table 1. AID and SID of AA in SCP (n = 7 and 7) and FM (n = 8)

Item	AID			SEM	SID			SEM
SCP1	SCP2	FM	SCP1	SCP2	FM
Arg	41.7b	22.0c	53.0a	3.6	55.7b	38.5c	70.3a	3.6
His	41.1a	25.3b	41.2a	4.1	51.9a	36.1b	53.5a	4.1
Ile	43.0a	21.9b	45.8a	5.1	52.1a	32.7b	58.4a	5.1
Leu	46.5a	28.1b	53.5a	4.4	54.1a	36.8b	63.9a	4.4
Lys	81.5a	22.4c	48.5b	3.8	84.3a	36.6c	59.2b	3.8
Met	63.0	63.0	53.3	7.0	66.4	66.9	59.7	7.0
Phe	40.3a	25.0b	46.6a	4.4	49.9a	35.5b	57.8a	4.4
Thr	30.0a	13.7b	28.2ab	5.2	43.6ab	29.6b	48.5a	5.2
Trp	25.1ab	−11.7b	30.7a	11.2	40.7ab	10.1b	52.5a	11.2
Val	34.4a	18.2b	39.2a	4.7	45.5a	31.4b	56.2a	4.7