Protection of polyunsaturated fatty acids against ruminal biohydrogenation: Pilot experiments for three approaches.

Three methods for protection of PUFA against biohydrogenation by ruminal microorganisms were evaluated. In method 1 a blend of ground flaxseed, calcium oxide, and molasses was processed through a dry extruder. In method 2, a blend of ground flaxseed, soybean meal, molasses, and baker's yeast was moistened and prewarmed, allowing enzymes from yeast to produce reducing sugars, and the mixture was subsequently processed through a dry extruder like in method 1. In method 3, ground flaxseed was embedded within a matrix of dolomitic lime hydrate (L-Flaxseed) as a protective barrier against biohydrogenation. Dolomitic lime was mixed with ground flaxseed, water was added, the mixture was blended in a high-speed turbulizer, and the resulting material was then dried to form a granular matrix. Methods 1 and 2 were tested in 1 study (study 1), and method 3 was tested in 2 studies (studies 2 and 3). In study 1, 60 crossbred yearling steers (BW = 475 ± 55 kg) were used in a randomized complete block design experiment. Steers were fed for 12 d with a diet consisting of 48.73% steam-flaked corn, 35% wet corn gluten feed, 12% corn silage, and 4.27% vitamins and minerals (Control). For the other 4 treatments, a portion of wet corn gluten feed was replaced with 5% of unprocessed or extruded mixtures as described for methods 1 and 2. Steers were weighed, and jugular blood samples were taken for analysis of long-chain fatty acids (LCFA) on d 0 and 12 of the study. Both methods failed to improve resistance of PUFA against biohydrogenation (P > 0.1). In study 2, in situ fatty acid disappearance was evaluated for ground flaxseed (Flaxseed) or L-Flaxseed using 6 ruminally fistulated Holstein steers. The proportion of α-linolenic acid (ALA) that was resistant to ruminal biohydrogenation was approximately 2-fold greater for L-Flaxseed than for Flaxseed (P < 0.05). In study 3, 45 steers (269 ± 19.5 kg initial BW) were used in a randomized complete block design. Steers were fed diets containing 0% Flaxseed (No Flaxseed), and in treatments 2 and 3, a portion of flaked corn was replaced with Flaxseed or L-Flaxseed. Animals were weighed and blood samples were taken on d 0, 7, and 14 of the study, and LCFA were analyzed. The use of L-Flaxseed in study 3 increased plasma concentrations of ALA to more than 4 times the level observed in cattle fed unprotected flaxseed, suggesting the dolomitic lime hydrate was effective as a protective barrier against biohydrogenation.