Table 2.

AA profile in the incubated ruminal fluid of steers after addition of the AA supplement¹

Addition to medium	Hour	Asp	Glu	Gln	Citrulline	Arg	Ornithine	Ammonia2
None	0	15.0 ± 1.1d	46.8 ± 3.7	33.1 ± 3.4a	5.83 ± 0.75	17.5 ± 2.2	18.4 ± 2.3	0.72 ± 0.08
	0.5	19.6 ± 1.3c	49.1 ± 3.5	31.5 ± 3.7a	6.24 ± 0.89	17.1 ± 2.1	21.0 ± 2.6	0.73 ± 0.09
	2	24.2 ± 1.6b	48.7 ± 4.2	26.0 ± 3.1b	6.50 ± 0.82	17.6 ± 2.0	22.9 ± 3.0	0.72 ± 0.08
	4	30.7 ± 1.9a	53.3 ± 4.8	13.2 ± 1.7c	7.26 ± 0.91	18.8 ± 2.3	22.7 ± 3.2	0.71 ± 0.10
	P-value	<0.001	0.581	<0.001	0.473	0.812	0.306	0.842
RUAA	0	14.7 ± 1.3d	46.0 ± 1.8d	6027 ± 14a	5011 ± 6	18.3 ± 2.4	18.2 ± 2.1c	0.72 ± 0.09d
	0.5	21.5 ± 1.7c	826 ± 45c	5050 ± 39b	5008 ± 22	19.1 ± 2.5	23.9 ± 2.2b	1.46 ± 0.17c
	2	28.3 ± 2.0b	1450 ± 63b	3987 ± 171c	5014 ± 24	20.3 ± 2.5	30.5 ± 2.4a	2.13 ± 0.24b
	4	34.6 ± 2.4a	2600 ± 178a	2902 ± 233d	5007 ± 10	21.6 ± 2.7	32.8 ± 2.5a	3.20 ± 0.29a
	P-value	<0.001	<0.001	<0.001	0.997	0.748	<0.001	<0.001
RPAA	0	14.5 ± 1.2d	46.0 ± 1.8d	1468 ± 91a	1207 ± 94	18.2 ± 2.1	18.1 ± 2.0c	0.71 ± 0.08d
	0.5	20.3 ± 1.6c	475 ± 85c	984 ± 56b	1213 ± 96	19.4 ± 2.3	21.5 ± 2.2bc	1.05 ± 0.12c
	2	26.2 ± 2.0b	709 ± 101b	723 ± 39c	1210 ± 92	19.8 ± 2.0	23.2 ± 2.5ab	1.28 ± 0.14b
	4	31.9 ± 2.1a	985 ± 112a	498 ± 47d	1202 ± 95	20.7 ± 2.5	25.4 ± 2.6a	1.62 ± 0.15a
	P-value	<0.001	<0.001	<0.001	0.985	0.764	0.012	<0.001

¹Values, expressed as nmol/mL of ruminal fluid for AAs and µmol/mL of ruminal fluid for ammonia, are means ± SEM, n = 6.

²The sum of NH₃ plus NH₄⁺.

^a–dMeans within a column not sharing the same superscript letter differ (P < 0.05), as analyzed by one-way analysis of variance for repeated measures data, followed by the Student–Newman–Keuls multiple comparison test.

RPAA = rumen-protected AA product (5 mM l-citrulline plus 6 mM l-glutamine was added to the incubation medium at time 0 h); RUAA = rumen-unprotected AA product (5 mM l-citrulline plus 6 mM l-glutamine was added to the incubation medium at time hour).