Availability of amino acids in high-oil corn

Abstract

True digestibility of amino acids, bioavailability of Lys, and TMEn in three types of high-oil corn (HOC) and one conventional corn (CC) were determined. The CC, HOC1, HOC2, and HOC3 contained 4.3, 5.9, 6.6, and 9.5% ether extract, respectively, on a DM basis. True digestibility of amino acids was determined using the precision-fed cecectomized rooster assay in which each corn sample was tube-fed (30 g) to nine roosters and excreta were collected for 48 h. True digestibility of most amino acids in HOC2 and HOC3 were significantly higher (P < or = 0.05) than those in CC and HOC1. Mean digestibility of 15 amino acids in HOC2 and HOC3 was 91% compared to 80% for CC and HOC1. The TMEn values (kilocalories per gram DM) of CC, HOC1, HOC2, and HOC3 were 3.883, 4.024, 4.038, and 4.140, respectively. Lysine bioavailability was assessed using a slope-ratio chick growth assay in which a Lys-deficient crystalline amino acid diet was supplemented with 0, 0.1, or 0.2% L-Lys from L-Lys x HC1 to provide a standard curve. Six additional dietary treatments consisted of supplementing the basal diet with 28 or 56% of CC, HOC2, or HOC3. The nine diets were fed to four replicate groups of six chicks from 8 to 18 d posthatching. Lysine bioavailability was calculated using multiple regression slope-ratio methodology where Y was weight gain and X was intake of Lys from the L-Lys x HC1 or a corn. Supplementation of the basal diet with L-Lys x HC1, CC, HOC2, or HOC3 yielded linear (P < or = 0.001) growth responses. Bioavailability values (percentage) for the Lys in CC, HOC2, and HOC3 relative to the Lys in L-Lys x HC1 were 65 +/- 10, 72 +/- 10, and 91 +/- 8, respectively. The results of this study indicated that digestibility of amino acids and bioavailability of Lys in HOC are equal to or greater than those in CC.