Metabolic characteristics in ruminants of the proteins in newly developed hull-less barley varieties with altered starch traits

Abstract

Recently, new varieties of hull-less barley have been developed with altered carbohydrate traits. To our knowledge, there is no study on metabolic characteristics in ruminants of the proteins in the newly developed hull-less barley varieties. The objectives of this study were to: compare metabolic characteristics of the proteins of zero-amylose waxy (CDC Fibar), low-amylose waxy (CDC Rattan), high-amylose (HB08302), and normal starch (CDC McGwire) hull-less barley. In situ animal trials were carried out to generate the original rumen fermentation data for modeling nutrient supply to dairy cattle by using two dairy nutrition models – Dutch DVE/OEB system and NRC 2001. The major comparisons were made in terms of i) truly absorbed protein in the small intestine (DVE or MP, and ii) degraded protein balance (DPB). The study revealed that zero-amylose waxy hull-less barley was superior (P<0.05) in both DVE (123 vs. 117, 114, 103gkg−1 DM) and MP (112 vs. 93, 96, and 87gkg−1 DM) when hull-less barley was evaluated as a single feed for dairy cattle. All of four hull-less barley varieties had negative DPB (DPBOEB; −37.4, −17.1, −30.2, and −28.2gkg−1 DM for normal starch, zero-amylose waxy, waxy, and high-amylose cultivar, respectively), indicating the potential N shortage. In conclusion, the alteration of starch structure in granule provided a relatively balanced energy and protein for microbial synthesis in the rumen. The DVE and DPB predicted by using the DVE/OEB system can be explained (r2>0.76) by the equivalent parameters, predicted by using the NRC 2001 model. The alteration of starch structure in granule affects metabolic characteristics of the proteins of hull-less barley in ruminants.