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Influence of method of surfactant supplementation on characteristics of digestion and feeding value of fat in Holstein steers fed a high-energy finishing diet

Four Holstein steers (271 ± 11 kg) with cannulae in the rumen and proximal duodenum were used to study the influence of method of surfactant (Tween 80) supplementation on characteristics of digestion and feeding value of fat. Treatments consisted of a steam-flaked corn-based finishing diet supplemented with: (1) no supplemental fat, no surfactant; (2) 6% supplemental fat (yellow grease, no surfactant; (3) 5.75% supplemental fat plus 0.25% Tween 80 (TW) added to the diet as part of the premix (TW was mixed with premix before incorporation with grain in the mixer, as second step in diet preparation) and (4) 5.75% supplemental fat plus 0.25% TW combined directly with the supplemental fat (TW was mixed with supplemental fat before incorporation into the feed mix as penultimate step in diet preparation). There was no surfactant by supplemental fat interactions (p > 0.05). Surfactant did not affect (p > 0.05) site and extent of organic matter (OM), starch, N, acid detergent fiber (ADF) and fatty acid (FA) digestion, or digestible energy (DE) value of diet. Supplemental fat decreased (p < 0.05) ruminal and total tract digestion of OM and ADF and increased (p <0.05) the DE value of diet. The decrease in postruminal FA digestion was mainly due to decreased (p <0.05) digestion of C18:0. Digestible energy of supplemental fat averaged 6.87 Mcal/kg. It is concluded, that independent of method of addition, supplementing high-fat diets with 0.22% of Tween 80 does not influence site and extent of digestion or the feeding value of supplemental fat.