Protein molecular spectral features in hull-less barley varieties and their relation to protein and energy values
The objectives of this study were to investigate the relationship between the protein molecular spectral features and protein and energy values in dairy cows of four hull-less barley (HB) varieties (normal starch conventional - CDC McGwire; zero-amylose waxy- CDC Fibar, waxy – CDC Rattan, and high-amylose – HB08302) using diffuse reflectance infrared fourier transform spectroscopy. The items included IR absorbed intensity (IR intensity unit, KM) peak area attributed to protein amide I (ca. 1715-1575 cm-1), amide II (ca. 1575-1490 cm-1), and ratio of amide I to II. The results show that (1) zero-amylose waxy was the greatest in protein amide I and II infrared reflectance peak areas; (2) α-helix to β-sheet ratio differed among HB: highamylose was the greatest, zero-amylose waxy and waxy were the intermediate, and normal starch was the lowest; (3) altered starch (CDC Fibar, CDC Rattan, and HB08302) HB varieties were similar to each other, but were different from normal starch variety in protein structural makeup; and (4) the rate and extent of rumen degradation of starch and protein were highly related to the molecular structural makeup of HB. In conclusion, this study indicated that (1) protein molecular structure affects metabolic characteristics of the proteins of HB, and (2) the altered starch HB seem to be more favorable to ruminants in terms of protein and energy values.
protein molecular structure
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