Table 5.

Amino acid composition of endogenous protein¹ (g per 100 g crude protein) at different ages of broilers.

	Age (days)							Orthogonal polynomial contrasts
Parameter	7	14	21	28	35	42	Pooled SEM	Linear	Quadratic
Indispensable amino acids
Arg	3.031	2.439	2.679	2.992	2.883	2.551	0.1069	0.415	0.922
His	1.304	1.359	1.243	1.367	1.348	1.232	0.0422	0.462	0.253
Ile	2.780	2.658	2.763	2.942	2.712	2.479	0.0401	0.004	0.001
Leu	4.335	3.971	4.178	4.622	4.367	3.910	0.1028	0.582	0.031
Lys	2.869	2.429	2.366	2.695	2.532	2.217	0.1139	0.018	0.832
Met	1.189	0.985	1.045	1.200	1.078	0.859	0.0357	0.001	0.031
Thr	5.952	6.284	6.234	5.874	6.287	6.353	0.1724	0.274	0.747
Trp	0.923	0.967	1.039	1.096	1.074	1.086	0.0343	0.001	0.115
Val	3.599	3.583	3.751	3.927	3.764	3.683	0.0569	0.035	0.008
Dispensable amino acids
Ala	3.312	3.028	3.124	3.569	3.319	3.106	0.0803	0.676	0.189
Asp	6.244	6.093	6.331	6.489	6.428	6.169	0.0861	0.297	0.049
Cys2	2.092	2.345	2.314	2.192	2.310	2.540	0.0572	0.001	0.379
Glu	7.616	6.504	6.889	7.547	7.279	6.613	0.1668	0.171	0.808
Gly2	3.443	3.269	3.497	3.697	3.571	3.527	0.0455	0.002	0.091
Pro	4.043	4.068	4.227	4.111	4.212	4.179	0.1046	0.273	0.599
Ser	4.684	4.689	4.919	4.699	4.916	4.909	0.1097	0.109	0.914

¹Each value represents the mean of six replicates (14, 12, and 10 birds per replicate for 7, 14, and 21-d old birds, respectively; eight birds per replicate for 28, 35-d old birds; and six birds per replicate for 42-d old birds).

²Semi-indispensable amino acids for poultry.

Abbreviations: IAA, total endogenous flow of indispensable amino acids; DAA, total endogenous flow of dispensable amino acids; AAA, total endogenous flow of all amino acids.