Table 1. Fish performance, metabolic parameters and body composition of rainbow trout fed to satiation with balanced amino acid diet and imbalanced amino acid diet at two levels of water dissolved oxygen: hypoxia vs. normoxia for 42 days.

	Normoxia			Hypoxia			P value
	Balanced diet	Imbalanced diet		Balanced diet	Imbalanced diet	Pooled SEM	Water DO level	Diet	Water DO x Diet
Fish performance
Initial body weight (g)	53.0	52.0		53.3	51.9	0.72	0.844	0.143	0.828
Final body weight (g)	144.4a	109.5b		110.8c	92.5b	2.52	<0.001	<0.001	0.011
Growth (g kg−0.8 d−1)	15.3a	10.8b		10.7b	8.2c	0.29	<0.001	<0.001	0.010
Food intake (g DM fish−1 d−1)	2.1a	1.5b		1.3c	1.1d	0.04	<0.001	<0.001	0.006
Digestible energy intake (kJ kg−0.8 d−1)	259a	213b		185c	162d	4.1	<0.001	<0.001	0.021
Digestible protein intake (g kg−0.8 d−1)	5.4a	4.4b		3.7c	3.2d	0.08	<0.001	<0.001	0.014
Glutamic acid intake (mg kg−0.8 d−1)	1400a	1399a		970b	1031b	24.9	<0.001	0.263	0.249
Lysine intake (mg kg−0.8 d−1)	287a	125b		199c	92d	2.5	<0.001	<0.001	<0.001
Methionine intake (mg kg−0.8 d−1)	131a	74b		91c	55d	1.4	<0.001	<0.001	<0.001
Metabolic parameters
Total ammonia nitrogen loss (mg N per g DPI)	50	73		49	71	6.2	0.779	0.006	0.965
Protein retention efficiency (%)*	44.9	34.3		45.2	33.9	0.48	0.998	<0.001	0.482
Final body composition **
Protein (g kg−1)	164.3a	145.1b		164.2a	140.1b	0.94	0.028	<0.001	0.033
Fat (g kg−1)	108.0	123.0		99.2	113.1	3.36	0.024	0.003	0.882

SEM, Standard error mean; DO, dissolved oxygen; DM, dry matter; DPI, digestible protein intake.

Mean values in a row with unlike superscript were significantly different and assigned only if the interaction effect was significant (p<0.05).

^*Protein retention efficiency (%)  =  (Wet protein gain/protein intake in dry weight) ×100.

^**Initial body composition (g kg wet weight⁻¹): 157, protein and 80.5, fat.