Feeding micronized and extruded flaxseed to dairy cows: Effects on digestion and ruminal biohydrogenation of long-chain fatty acids

Abstract

Four lactating Holstein cows fitted with ruminal and duodenal cannulae were used in a 4 × 4 Latin square study to determine the effects of feeding micronized and extruded flaxseed on ruminal biohydrogenation (BH) and digestibility of fatty acids (FA) in the gastrointestinal tract. Four diets were formulated: a control diet with no flaxseed (C); a raw flaxseed diet (RF); a micronized flaxseed diet (MF); and an extruded flaxseed diet (EF). Flaxseed diets contained 126 g kg-1 flaxseed (dry matter basis). Experimental periods (n = 4) consisted of 21 d of diet adaptation and 7 d of data collection. Flaxseed supplementation increased (P < 0.05) intake of individual long-chain FA, reduced (P < 0.05) ruminal BH of total unsaturated C18, and increased (P < 0.05) duodenal flow of individual long-chain FA except for C18:2. Feeding flaxseed increased (P < 0.05) post-ruminal digestibility of C18:1, C18:2, and C18:3 and total tract digestibility of C16:0, C18:2, C18:3, and of total long-chain FA. Heat treatment had no effect on ruminal BH, duodenal flow and digestibility of unsaturated FA. Ruminal BH of C18:3 was higher (P < 0.05), while the duodenal flow of C18:3 was lower (P < 0.05) for cows fed EF than for those fed MF. Intake and duodenal flow of C16:0 were higher (P < 0.05) for cows fed MF relative to those fed EF. It was concluded that inclusion of flaxseed in dairy cow diets increased duodenal flow of polyunsaturated FA. However, heat treatments were not effective in protecting unsaturated FA from ruminal BH. Key words: Flaxseed, ruminal biohydrogenation, fatty acid, heat treatment