True amino acid availability in chinese high-oil corn varieties determined in two types of chickens

National Feed Technology Engineering Research Center, China Agricultural University, Beijing, China 100094.

True amino acid availability (TAAA) was determined in conventional corn (CC) and in 2 Chinese high-oil corn varieties (CHOC1; CHOC2). The CC, CHOC1, and CHOC2 contained 3.7, 6.6, and 7.5% oil (ether extract) on a dry matter basis, respectively. The CP content (% dry matter) of the corn increased from 8.6 to 12.2% as oil increased from 3.7 to 7.5%. Birds (Hy-Line roosters or Arbor Acres broilers) were given 1 of the 3 corn varieties as the sole dietary ingredient in a conventional (intubation method) TAAA assay. There was a significant (P < 0.05) effect of bird type on gut metabolic (endogenous) amino acid excretion values with the broilers having higher excretions. For all amino acids, there was also a significant (P < 0.05) effect of bird type on TAAA with the Hy-Line roosters having higher TAAA values. The mean value for TAAA calculated over all of the amino acids showed a 9.8% unit higher digestibility for roosters compared with the broilers. Differences in TAAA between the corn varieties were statistically significant for alanine and valine only. Overall, the present results indicate that TAAA is equal to or superior to that in CC and that the TAAA content is higher in CHOC compared with CC. Bird type has an important effect on TAAA results and should be considered when developing TAAA assays and interpreting TAAA values.