Table 3.

Effect of guanidinoacetic acid (GAA) supplementation on heart 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 treatment 2			SEM	P value
Supplemental GAA, g/kg	0.0	0.6	1.2		Model	Linear	Quadratic
Total creatine, mg/kg
d 26	676b	795ab	953a	39.3	0.011	0.003	0.801
d 39	960	1120	1209	46.2	0.084	0.029	0.706
MDA, nmol/g
d 26	85	84	103	5.6	0.317	0.209	0.397
d 39	73	72	71	3.2	0.972	0.813	0.992
SOD, U/g
d 26	52	52	49	3.0	0.872	0.658	0.787
d 39	56	52	59	1.8	0.285	0.540	0.145
GPx, U/g
d 26	1.2	1.2	1.2	0.03	0.692	0.651	0.470
d 39	1.3	1.2	1.3	0.04	0.687	0.640	0.469

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.