Table 4.

Effect of guanidinoacetic acid (GAA) supplementation on liver creatine metabolism, malondialdehyde (MDA) concentration, and antioxidant enzyme activities (superoxide dismutase, SOD, and glutathione peroxidase, GPx) of male broilers subjected to heat stress in the finisher phase at d 26 and 39¹ (n = 12).

Item	Dietary treatment2			SEM	P value
Supplemental GAA, g/kg	0.0	0.6	1.2		Model	Linear	Quadratic
Total creatine, mg/kg
d 26	2.3b	4.1a	4.3a	0.26	0.001	0.001	0.095
d 39	3.2	3.6	3.9	0.23	0.497	0.243	0.951
Creatinine, mg/kg
d 26	0.21b	0.25ab	0.27a	0.09	0.010	0.004	0.383
d 39	0.21b	0.24ab	0.30a	0.01	0.009	0.003	0.417
GAA, mg/kg
d 26	6.4	7.4	5.7	0.40	0.190	0.457	0.104
d 39	3.7	3.6	2.5	0.28	0.147	0.093	0.353
MDA, nmol/g
d 26	96	87	94	2.7	0.396	0.707	0.194
d 39	77	77	82	1.8	0.418	0.247	0.532
SOD, U/g
d 26	172	164	159	5.3	0.591	0.312	0.909
d 39	283	260	257	11.7	0.631	0.386	0.691
GPx, U/g
d 26	3.9	4.2	3.8	0.09	0.237	0.807	0.095
d 39	3.7	3.6	3.6	0.08	0.727	0.435	0.889

¹Broilers were fed a corn-soybean starter diet from d 0 to 10, a grower diet from d 10 to 25, and a finisher diet from d 25 to 39.

²Mean values with different superscripts (a, b) per sampling day are significantly different at P < 0.05.