Table-8.

Effect of amino acid supplementation in a low-protein diet on the economic profitability of broiler chickens.

Itemsb	Treatmentsa				p-value
	CON	CP-1%	CP-2%	SEM	CON versus treatment	Linear	Quadratic
Total cost	34.22a	33.58b	33.05c	0.052	<0.001	<0.001	0.22
Total return	48.54b	48.65b	49.63a	0.382	0.008	0.005	0.19
Net profit	14.31b	15.07b	16.58a	0.379	<0.001	<0.001	0.25

^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.

^bTotal cost was calculated from the summation of total fixed cost and total variable cost. Total returns were the sum of litter sale and chicken sale. Chicken sale value = body weight at end of the experiment g× price. Net profit was the net income using the following equation: Net profit=Total return−Total cost