Effects of micronization of flaxseed on nutrient disappearance in the gastrointestinal tract of steers

Two steers fitted with ruminal and duodenal cannulas were used in a randomized complete block design to determine the effects of micronization on ruminal and postruminal and total tract digestibility of protein and amino acids of flaxseed. Micronized flaxseed had lower (P<0.05) in situ soluble and higher (P<0.05) slowly degradable dry matter (DM) and crude protein (CP) fractions than unheated flaxseed. Micronization reduced (P<0.05) ruminal DM and CP degradability of flaxseed by 14 and 21%, respectively. Following 12 h of ruminal incubation, concentrations of ruminal undegraded amino acids were higher (P<0.05) for micronized than unheated flaxseed. Micronization increased (P<0.05) intestinal digestibilities of ruminal undegraded amino acids of flaxseed. Relative to the unheated flaxseed, the increase in postruminal digestibility ranged from 59% for histidine to 390% for phenylalanine. No differences in total tract amino acid digestibilities were observed between the two flaxseed treatments. It was concluded that micronization is an effective heat treatment to improve the postruminal supply of amino acids from flaxseed.