Ruminal biohydrogenation and abomasal flow of fatty acids in lactating cows: Oilseed provides ruminal protection for fatty acids

Fat sources, besides the energy-rich content, have featured beneficial effects on dairy cow production, reproduction and health. This work aimed to study the biohydrogenation process and fatty acid abomasal flow in lactating dairy cows fed different fat sources. Eight rumen and abomasum cannulated cows (188 ± 27.3 days in milk, 18.9 ± 3.24 kg of milk yield, and 572 ± 59.6 kg of body weight) were used in a 4 × 4 Latin square design. Control (CON) diet without fat source, soybean oil (SO), raw soybean grain (SG) and calcium salts of unsaturated fatty acids (CS) were evaluated. Fat sources decreased dry matter (DM), crude protein and neutral detergent fiber (NDF) intake and increased ether extract (EE) intake and ruminal pH (P < 0.05). Acetate to propionate ratio was lower in animals fed diets with fat (P < 0.05). Diets had no effect on microbial protein synthesis, and energy and nitrogen balances. NDF digestibility and DM passage rate were lower in animals fed diets with fat sources (P < 0.05), while protected sources (SG and CS) tended to increase ruminal fiber digestibility (P = 0.092) in relation to SO diet. Intake and abomasal flow of FA were higher (P < 0.05) for animals supplemented with fat sources than those fed CON. Protected sources (SG and CS) promoted greater abomasal flow of linoleic acid (C18:2) and lower biohydrogenation rate compared to the SO diet. Fat sources increased unsaturated milk fatty acids and serum cholesterol concentration while protected sources (SG and CS) increased milk C18:2 cis concentration (P < 0.05). Fat sources improved ruminal fermentation without compromise nutrients digestion and increasing fatty acids abomasal flow and milk concentration. Raw soybean grain had higher ruminal biohydrogenation protection than calcium salts.