Table 1.

Summary of general lineal models (GLMs) showing the influence of (a) male age on plasma oxidative status, (b) plasma oxidative status on comb size, (c) age on seminal oxidative status, (d) seminal oxidative status on sperm swimming velocity, and (e) seminal antioxidant status on oxidative DNA damage in red junglefowl (Gallus gallus). Full models and the models that retained only variables that caused a significant increase in deviance (minimal adequate models) are shown. Significant values in full and minimal adequate model are shown in bold

		Full model						Variables		Minimal model
Dependent variable	Variables	Parameter estimate	F	df	P	Observed power	Effect size	Retained term	Removed term	Parameter estimate	F	df	P
(a) Plasma antioxidants	Intercept	2.606								2.289
	Age	–0.123	0.067	1, 15	0.800	0.057	0.004		Age	–0.123	0.067	1, 15	0.800
	Body condition	0.001	0.405		0.534	0.092	0.026		Body condition	0.001	0.411	1, 16	0.530
									Age × Body condition	0.003	2.616	1, 14	0.128
Plasma lipid peroxidation	Intercept	0.211								0.242
	Age	0.039	0.808	1, 15	0.383	0.134	0.051		Age	0.039	0.808	1, 15	0.383
	Body condition	–8.660e−5	0.882		0.363	0.142	0.056		Body condition	–3.141e−5	0.211	1, 16	0.652
									Age × Body condition	0.000	0.585	1, 14	0.457
(b) Comb size	Intercept	1048.984								1053.348
	Plasma antioxidants	113.139	4.265	1, 10	0.066	0.463	0.299	Plasma antioxidants		112.732	5.695	1, 12	0.034
	Plasma lipid peroxidation	–2119.030	12.036		0.006	0.877	0.546	Plasma lipid peroxidation		–2097.537	18.132	1, 12	0.001
	Age	14.334	0.021		0.889	0.052	0.002		Age	12.034	0.040	1, 11	0.845
	Body condition	–0.006	0.001		0.977	0.050	<0.001		Body condition	–0.006	0.001	1, 10	0.997
									Age × Plasma lipid peroxidation	2282.606	1.528	1, 9	0.248
									Age × Plasma antioxidants	–224.511	1.749	1, 8	0.223
									Age × Body condition	0.435	0.214	1, 7	0.657
(c) Seminal antioxidants	Intercept	–3.351								–2.762
	Age	6.686	18.144	1, 11	0.001	0.972	0.623	Age		6.573	12.283	1, 13	0.004
	Plasma antioxidants	3.373	11.069		0.007	0.422	0.253	Plasma antioxidants		3.512	20.522	1, 13	0.001
	Age × Plasma antioxidants	–4.227	43.693		<0.001	1.000	0.799	Age × Plasma antioxidants		–3.731	26.337	1, 13	<0.001
	Body condition	0.003	6.641		0.026	0.651	0.376		Body condition	0.003	4.409	1, 12	0.058
	Plasma lipid peroxidation	7.002	2.786		0.123	0.332	0.202		Plasma lipid peroxidation	7.002	2.786	1, 11	0.123
									Age × Body condition	–0.003	1.497	1, 10	0.249
									Age × Plasma lipid peroxidation	–32.233	0.417	1, 9	0.535
(d) Sperm motility	Intercept	57.759								64.401
	Seminal lipid peroxidation	–24.156	3.916	1,7	0.088	0.401	0.359		Seminal lipid peroxidation	–23.955	4.671	1, 8	0.063
	Seminal antioxidants	–0.089	0.005		0.948	0.050	0.001		Seminal antioxidants	–0.089	0.005	1, 7	0.948
(e) Sperm DNA damage	Intercept	1.116								1.041
	Age	0.115	6.273	1,14	0.025	0.645	0.309	Age		0.085	5.982	1, 16	0.026
	Body condition	–9.488e−5	0.832		0.377	0.136	0.056		Body condition	0.000	1.034	1, 15	0.325
	Seminal antioxidants	0.004	0.172		0.684	0.067	0.012		Seminal antioxidants	0.004	0.172	1, 14	0.684
									Age × Body condition	0.000	0.799	1, 13	0.388
									Age × Seminal antioxidants	–0.003	0.027	1, 12	0.871