Table 4.

Effects of different levels of taurine on antioxidant function in serum and liver of broilers.

Items	Dietary taurine concentration treatment3				SEM1	P Value
	CON	TAU1	TAU2	TAU3		Linear2	Quadratic2
Serum
T-AOC (U/mL)	12.873b	14.014a,b	14.199a	14.060a,b	0.210	0.043	0.116
SOD (U/mL)	106.365b	127.796a	123.059a	123.285a	1.825	<0.001	<0.001
GPX (U/mL)	224.016c	241.721b	256.230a	237.541b	2.861	0.006	<0.001
GSH (umol/L)	9.536b	11.513a	10.931a	11.222a	0.173	<0.001	0.001
CAT (U/mL)	8.424	8.740	8.604	8.446	0.067	0.909	0.084
MDA (nmol/mL)	10.949a	10.486a,b	10.116b	9.954b	0.116	0.001	0.452
Liver
T-AOC (U/mg prot)	0.878b	1.043a,b	1.122a	1.030a,b	0.034	0.070	0.051
SOD (U/mg prot)	312.594	332.161	324.747	330.215	3.525	0.148	0.311
GPX (U/mg prot)	42.63d	49.25a	45.03c	47.00b	0.533	0.004	0.001
GSH (mg/g prot)	3.392c	3.923b	4.609a	4.708a	0.123	<0.001	0.194
CAT (U/mg prot)	10.434	10.542	10.774	11.018	0.151	0.159	0.825
MDA (nmol/mg prot)	1.258a	1.029b	1.011b	1.026b	0.025	<0.001	0.002

^a–dMeans within the same row with no common superscript differ significantly (P < 0.05).

Abbreviations: CAT, catalase; GSH, glutathione; GPX, glutathione peroxidase; MDA, malonaldehyde; SOD, superoxide dismutase; T-AOC, total antioxidant capacity.

¹Standard error of the means (n = 8).

²Orthogonal polynomials were used to evaluate linear and quadratic responses to the levels of taurine treatment.

³CON, basal diet; TAU1, TAU2 and TAU3 group, basal diet adding 2.50, 5.00, and 7.50 g/kg TAU, respectively.