The objective of this study was to investigate the curve-linear relationship between altered carbohydrate (CHO) traits (different levels of amylose, amylopectin and β-glucan) and rumen and intestinal digestion in dairy cattle in CDC developed hull-less barley cultivars. Four hull-less barley cultivars (zero-amylose waxy, Fibar; 5%-amylose waxy, Rattan; normal amylose, McGwire and high-amylose, HB08302) were developed at the Crop Development Centre, University of Saskatchewan, with differences in carbohydrates traits on the basis of amylose (1–40% DM) and b-glucan (5–10% DM) content. All cultivars were planted and grown in Saskatoon (Canada) and then harvested in 3 consecutive years for experimental purposes. The digestion in the rumen and intestine was determined used in situ dairy cows with RCBD design with samples year as a random effect. The rumen degradation was carried out with in situ nylon bag technique. The intestinal digestibility was carried out with 3-step in vitro technique with 16 h pre-incubation. The data were analyzed with Proc mixed model. Results showed that: 1) intestinal (IDP: 38 to 69 g/kg DM) and total digestible protein (TDP: 106 to 154 g/kg DM) had cubical (P < 0.05) relation and truly digestible neutral detergent fiber (TDNDF: 53 to 105 g/kg DM) had quadratic (P < 0.05) relation with the β-glucan level. TDP and TDNDF showed a cubical effect and IDP showed a quadratic effect (P < 0.05) with the ratio of amylose to amylopectin (A:AP). There were cubical (P < 0.05) relation between intestinal digestible rumen undegraded starch (IDBST: 78–184 g/kg DM) and A:AP, quadratic (P < 0.05) relationship between IDBST and β-glucan level. Total digestible starch (TDST) had a quadratic effect with the A:AP and a cubical effect with the β-glucan level (P < 0.05). Intestinal digestible rumen undegraded CHO (IDBCHO: 15 to 33 g/kg DM) was cubically related to the A:AP (P < 0.05). In conclusion, the alternation of carbohydrate traits in hull-less barley through modern breeding tool results in curve-linear relationship with rumen and intestinal digestion in dairy cows.