Table 4.

Effects of dietary addition of Echinacea purpurea polysaccharides (EP) on serum immune function of broilers.

Items	Age, d	Groups1				SEM	P-value
		CON	EPL	EPM	EPH		ANOVA	Linear	Quadratic	EPs × age
IgA, μg/mL	21	223.4b	248.5ab	276.4aA	285.3aA	7.804	0.015	0.001	0.004	0.410
	42	191.1	241.3	231.0B	233.1B	7.688	0.092	0.147	0.109
IgG, μg/mL	21	172.1A	165.2A	170.9A	163.8	3.358	0.042	0.025	0.036	0.004
	42	131.1abB	123.6bB	148.6aB	147.3a	3.487	0.013	0.010	0.041
IgM, μg/mL	21	265.7	226.0	256.8	255.2B	10.477	0.595	0.918	0.774	0.001
	42	232.3b	201.9b	227.1b	351.6aA	13.094	<0.001	<0.001	<0.001
IL-6, pg/mL	21	15.4aA	12.9bA	13.1bA	10.1c	0.513	<0.001	<0.001	<0.001	<0.001
	42	11.2B	10.6B	11.3B	10.8	0.164	0.414	0.768	0.929
IL-10, pg/mL	21	20.5	20.0	21.6	19.5B	0.330	0.135	0.584	0.315	0.049
	42	20.5b	21.8ab	23.0ab	23.2aA	0.395	0.041	0.006	0.014

Ig = immunoglobulin; IL = interleukin; CON = control; SEM = standard error of the mean.

Different lowercase letter superscripts in the same row indicate significant differences among EP addition levels (0.0, 0.3%, 0.6%, and 0.9%) (P < 0.05). Different uppercase letter superscripts within the same column indicate significant differences between age stages (21 and 42 d) (P < 0.05); EPs × age denotes the interaction between EP addition levels and ages.

¹CON, EPL, EPM, and EPH, represent EP addition levels of 0.0, 0.3%, 0.6%, and 0.9% in the diet, respectively (n = 6).