Table 8.

Effects of antibiotics and low-crude protein diets on pig humoral immune status, creatinine, and serum urea nitrogen¹

Item2	ATB−3		ATB+4		SEM	P-value
	18.5% CP5	13.0% CP6	18.5% CP5	13.0% CP6		ATB	CP	CP × ATB
66 d of age
SUN, mg/dL	22.7	13.8	23.2	13.2	1.01	1.000	<0.001	0.585
Creatinine, mg/dL	0.97	0.94	0.92	0.93	0.024	0.267	0.731	0.480
IgG, mg/dL	290	306	204	225	34.5	0.021	0.593	0.948
IgA, mg/dL	11.0	10.6	10.9	10.3	0.81	0.799	0.537	0.965
87 d of age
SUN, mg/dL	21.9	13.4	20.3	13.8	1.05	0.564	<0.001	0.374
Creatinine, mg/dL	1.03	0.95	0.99	0.89	0.020	0.022	<0.001	0.647
IgG, mg/dL	419	417	410	386	17.9	0.272	0.477	0.552
IgA, mg/dL	17.7	12.2	11.6	11.5	2.05	0.098	0.173	0.187

¹Experimental medicated diets (ATB +) were fed from 59 to 73 d old. In the post-medicated period, all pigs were fed their respective crude protein (CP) control diets from 73 to 87 d of age.

²IgG, immunoglobulin G; IgA, immunoglobulin A; SUN, serum urea nitrogen.

³ATB -, diet without antibiotics.

⁴ATB +, diet with 100 mg/kg tiamulin and 506 mg/kg oxytetracycline.

⁵18.5% CP, diet with 18.5% of CP.

⁶13.0% CP, diet with 13.0% of CP.