Table-6.

Effect of amino acid supplementation in a low-protein diet on carcass traits and lymphoid organ weights (% of live body weight) of broiler chickens at the end of the experiment (35 days of age).

Item, %	Treatmentsa				p-value
	CON	CP-1%	CP-2%	SEM	CON versus treatment	Linear	Quadratic
Dressing	74.52c	76.07b	77.21a	0.461	<0.001	<0.001	0.61
Liver	2.52b	2.64ab	2.66a	0.051	0.019	0.01	0.23
Gizzard	2.38	2.44	2.40	0.049	0.43	0.60	0.24
Heart	0.55	0.58	0.59	0.206	0.29	0.25	0.27
Breast	20.78b	21.57a	22.41a	0.417	<0.001	<0.001	0.38
Spleen	0.083b	0.091a	0.093a	0.002	<0.001	<0.001	0.07
Tdymus	0.372b	0.459a	0.479a	0.014	<0.001	<0.001	0.007
Bursa of Fabricius	0.115b	0.128a	0.136a	0.004	<0.001	<0.001	0.40
Breast meat proximate analysis
Moisture	72.73a	71.64b	71.29b	0.409	0.004	0.001	0.30
DM	27.27b	28.34a	28.59a	0.397	0.005	0.002	0.24
CP	22.01b	22.33b	22.89a	0.208	0.001	<0.001	0.52
EE	2.80	2.78	2.77	0.031	0.62	0.33	0.98
Ash	2.46	3.22	2.93	0.456	0.25	0.31	0.19

^a,bMeans within rows with different letters are different at p<0.05; Tukey’s tests were applied to compare means; SEM=Standard error of the mean.

^aThe experimental diets were formulated to contain 22, 21, and 20% CP for the starting period, 20, 19, and 18% CP for the growing period, and 18, 17, and 16% CP for the finishing period in CON, CP-1%, and CP-2%, respectively. The CP-1% and CP-2% groups were supplemented with threonine, valine, and tryptophan to meet or exceed the respective levels of the control diet