Table 4.

Concentrations of oxidative stress parameters in the blood serum of younger and older bulls in relation to different season (mean ± SD).

Season	PCC (mmol/L)		Test t	TBARS (mmol/L)		Test t
	Young	Old	Y/O	Young	Old	Y/O
Winter	16.3 ± 0.5a	20.2 ± 0.8a	**	1.1 ± 0.6a	0.4 ± 0.1b	*
Spring	17.2 ± 0.8ab	19.4 ± 0.7ab	**	1.2 ± 0.7a	0.4 ± 0.1b	*
Summer	12.3 ± 0.9b	16.3 ± 0.4b	**	0.5 ± 0.1b	1.0 ± 0.5a	ns
Autumn	16.1 ± 0.4ab	17.2 ± 0.3ab	**	0.7 ± 0.2ab	0.9 ± 0.3ab	ns
r	PCC
TBARS	0.81 **

Description: Values with different letters (a, b) differ significantly between rows at P < 0.05.

PCC protein carbonyl content, TBARS thiobarbituric acid reactive substrates.

Test T—t-Student’s test, **P ≤ 0.01; *P ≤ 0.05.