Table 1.

The University of Illinois patterns of amino acid compositions in ideal proteins for chicks during the first three wk post-hatching ¹

Amino acid	Amino acid content in the carcass Ref.[29](% of crude protein)2	Dean & Scott standard (1965) Ref.[33]		Huston & Scott standard (1968) Ref.[34]		Sasse & Baker standard (1973) Ref.[35]		Baker & Han standard (1994) Ref.[36]
		Amount in diet3	% of lysine	Amount in diet3	% of lysine	Amount in diet3	% of lysine	Amount in diet3	% of lysine
Arginine	6.65	1.10	98.2	1.00	105	0.95	104	0.95	106
Cystine	---	0.35	31.3	0.35	36.8	0.35	38.5	0.325	36.1
Glycine	---	1.60	143	1.20	126	0.60	65.9	0.60	66.7
Isoleucine	4.35	0.80	71.4	0.60	63.2	0.60	65.9	0.60	66.7
Histidine	1.80	0.30	26.8	0.30	31.6	0.33	36.3	0.32	35.6
Leucine	7.2	1.20	107	1.20	126	1.00	110	0.98	109
Lysine	6.6	1.12	100	0.95	100	0.91	100	0.90	100
Methionine	1.98†	0.55	49.1	0.35	36.8	0.35	38.5	0.325	36.1
Phenylalanine	4.25	0.68	60.7	0.50	52.6	0.50	55.0	0.50	55.6
Proline	---	1.00	89.3	0.20	21.1	0.40	44.0	0.40	44.4
Threonine	4.4	0.65	58.0	0.65	68.4	0.65	71.4	0.60	66.7
Tryptophan	0.98	0.23	20.5	0.15	15.8	0.15	16.5	0.145	16.1
Tyrosine	---	0.63	56.3	0.45	47.4	0.45	49.5	0.45	50.0
Valine	5.0	0.82	73.2	0.82	86.3	0.69	75.8	0.69	76.7
Glutamic acid4	---	12.0	1071	10.0	1053	12.0	1319	12.0	1333
Total amino acids		23.0		18.7		19.9		19.8
Total nitrogen		2.83		2.33		2.37		2.35

¹These ideal protein models were developed for 0- to 21-d-old broilers using crystalline amino acids. It was assumed that all of these amino acids were 100% available for absorption into enterocytes in chicks. Except for glycine and methionine, all amino acids are L-isomers. DL-methionine is used herein.

²Average values for 1-wk-old and 4- to 5-wk-old chicks.

³% of diet (as-fed basis; 90% dry matter).

⁴Provided as the nitrogenous source for synthesis of NEAA in chicks.

^†This value refers to L-methionine.