Hulless barley (Hordeum vulgare l.) with altered starch traits: rumen degradation kinetics
The objective of this study was to determine the effect of new hulless barley lines (zero-amylose waxy, CDC Fibar; 5%-amylose waxy, CDC Rattan; normal-amylose, CDC McGwire and high-amylose, HB08302) on rumen degradation kinetics and in vitro intestinal nutrient digestion with CDC Copeland included as a hulled control. Three dry Holstein cows fitted with rumen cannula were used for measuring rumen degradation of barley varieties. The estimation of intestinal digestion was determined by a modification of the three-step in vitro procedure described by Calsamiglia and Stern with duplicate of each in situ residue. Among the hulless barley lines, CDC Rattan was greater (P<0.05) in effectively degradable starch (EDST: 461 g/kg DM) but reduced (P<0.05) in rumen undegradable protein (RUP: 55g/kg DM) while CDC Fibar was greater (P<0.05) in effectively degradable crude protein (EDCP: 90 g/kg DM) and total digestible protein (TDP: 147 g/kg DM) than other hulless barley lines. CDC McGwire showed greater (P<0.05) in total digestible bypass starch (TDST: 590 g/kg DM), effectively degradable CHO (EDCHO: 581 g/kg DM) and total digestible CHO (TDCHO: 600 g/kg DM) than other hulless barley lines but no significant difference compared to CDC Copeland (P>0.05). HB08302 was greater (P<0.05) in rumen bypass starch (BST: 218 g/kg DM vs. 146 g/kg DM and 155 g/kg DM) and effective degradable NDF (EDNDF: 74 g/kg DM vs. 49 g/kg DM and 52 g/kg DM) than CDC Fibar and CDC Rattan. HB08302 was also greater in total digestible NDF (TDNDF: 93 g/kg DM vs. 62 g/kg DM and 67 g/kg DM) and intestinal digestible rumen bypass starch (IDBST: 180 g/kg DM vs. 122 g/kg DM and 130 g/kg DM) compared to CDC Fibar and CDC McGwire. HB08302 also showed greater (P<0.05) in bypass CHO (BCHO: 179 g/kg DM) and intestinal digestible bypass CHO (IDBCHO: 31 g/kg DM) than other hulless barley lines. Amylose and amylopectin were significantly correlated (P<0.001) to EDCP (r=-0.71, r=0.64) and TDP (r=-0.85; r=0.77), while amylose, ratio of amylose and amylopectin were positively correlated (P<0.01) to EDNDF, TDNDF, BST, IDBST and TDCHO (P<0.05). BCP, IDP, TDP, BNDF were positively correlated to beta-glucan levels (P<0.001) while EDST, TDST, EDCHO and TDCHO were negatively correlated to beta-glucan levels in hulless barley lines (P<0.01). in conclusion hulless barley lines with altered carbohydrate traits have the potential to increase rumen and intestinal nutrient availability to ruminants. Altered beta-glucan levels had a greater effect on rumen carbohydrates and crude protein degradation than altered starch traits.
amylose and amylopectin ratio
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