Table 3.

Effects of dietary tryptophan levels and diquat injection on the concentrations of tryptophan, large neutral amino acids (LNAA) and urea nitrogen in the plasma of the weaned piglets

Item	- diquat			+ diquat			SEM	P
	Trp 0.18%	Trp 0.30%	Trp 0.45%	Trp 0.18%	Trp 0.30%	Trp 0.45%		Trp	diquat	Trp × diquat
Tryptophan, nmol/mL	45b	50b	61a	29c	40b	44b	4	< 0.05	< 0.05	0.08
LNAA, nmol/mL	497b	411c	453bc	582a	447bc	421c	17	< 0.05	0.05	< 0.05
Tryptophan/LNAA	0.09b	0.13a	0.14a	0.05c	0.09b	0.11ab	0.01	< 0.05	< 0.05	0.67
Plasma urea nitrogen, mg/L	95.12c	60.02d	64.27d	212.50a	135.02b	142.17b	7.90	< 0.05	< 0.05	0.06

+diquat, intraperitoneal injection diquat; − diquat, intraperitoneal injection of sterile 0.9% NaCl solution; Trp 0.18%, dietary tryptophan level 0.18%; Trp 0.30%, dietary tryptophan level 0.30%; Trp 0.45%, dietary tryptophan level 0.45%; LNAA, large neutral amino acids (sum of valine, methionine, isoleucine, leucine, phenylalanine, tyrosine and histidine).

^{a, b, c}Mean values with unlike superscript letters were significantly different (P < 0.05).

(Mean values with their pooled standard errors, n = 6).