Table 8.

Effect of graded levels of guanidinoacetic acid (GAA) on energy metabolites in serum and muscle (Exp. 1)

Item	GAA, mg/kg					SEM	P-value
	0	300	600	900	1,200		ANOVA	Linear	Quadratic
Serum1
day 35
ATP, mmol/L	0.79	0.87	0.69	0.88	0.91	0.08	0.36	0.88	0.96
CK, U/mL	0.45	0.54	0.54	0.52	0.54	0.07	0.89	0.58	0.45
day 70
ATP, mmol/L	0.73	0.82	0.85	0.84	0.89	0.05	0.26	0.29	0.19
CK, U/mL	0.32	0.5	0.45	0.36	0.60	0.09	0.25	0.81	0.06
day 98
ATP, mmol/L	0.70e	0.75d	0.84c	0.87b	0.90a	0.01	<0.01	<0.01	<0.01
CK, U/mL	0.31	0.49	0.33	0.45	0.56	0.12	0.53	0.89	0.46
Muscle2
ATP, mg/g	1.80	2.77	2.49	2.32	2.51	0.30	0.21	0.29	0.05
ADP, mg/g	0.77	1.03	0.95	0.95	0.93	0.10	0.39	0.23	0.17
AMP, mg/g	0.19	0.29	0.26	0.24	0.26	0.03	0.21	0.29	0.05
IMP, mg/g	1.42	1.66	1.63	1.57	1.47	0.11	0.54	0.19	0.35
CK, U/mg	6.48	9.50	7.35	6.46	5.90	1.78	0.63	0.79	0.33

Data are the means of 6 replicates of 1 pig per pen.

^a–eMeans with different superscripts within a row differ (P ≤ 0.05).

¹U is the symbol for one enzyme unit, one U is defined as the amount of the enzyme that produces a certain amount of enzymatic activity.

²mg/g or U/mg means the content in muscle protein; CK = creatine kinase; AMP = adenosine monophosphate; IMP = inosine monophosphate.