Table 4.

Effects of different standardized ileal digestible threonine:lysine ratios (Thr:Lys) on plasma threonine, lysine and urea nitrogen concentrations (mmol/L) of weaned pigs reared under clean and unclean sanitary conditions.¹

Item	Clean sanitary condition2									Unclean sanitary condition3
	Analyzed SID Thr:Lys, %					SEM	P-value4			Analyzed SID Thr:Lys, %					SEM	P-value
	61	64	67	69	72		Thr	Lin	Quad	61	64	67	69	72		Thr	Lin	Quad
Plasma-free Thr	523	617	622	652	634	38.4	0.199	0.050	0.185	415	517	629	592	639	55.4	0.070	0.010	0.241
Plasma-free Lys	138	117	127	119	123	15.0	0.896	0.570	0.581	199	200	168	171	209	33.0	0.848	0.938	0.399
Plasma urea nitrogen	3.55	3.73	2.92	2.64	3.37	0.33	0.110	0.226	0.207	3.74	4.10	3.40	3.99	3.81	0.33	0.616	0.980	0.871

SID = standardized ileal digestible; SEM = standard error of mean.

¹Values are least square means; n = 6 per treatment.

²Clean sanitary condition: piglets were housed in cleaned and disinfected rooms and fed antibiotic-free diets.

³Unclean sanitary conditions: piglets were housed in a room where cleaning and disinfection was not done, moreover, manure from swine herd was added (5 kg per pen) to the pens on d 0 and 7 of the experiment.

⁴Probability values of linear (Lin) and quadratic (Quad) effects for dietary SID Thr:Lys (%).