Delaying the contact of fatty acids with ruminal microorganisms was tested by treating protein capsules containing fish oil with flavoring agents and heat. Ruminal breakdown was determined by sealing a single treated capsule in a nylon bag and suspending it in ruminal contents (Daisy incubator) for 0, 6, 12, 24, and 48 h (n = 14). After each period, 4 bags were randomly selected and dried for 24 h at 105°C for determination of percentage DM, and the remaining bags were opened and capsules removed. Four of the removed capsules at each rumen exposure time were analyzed for fatty acids by GC, 3 were suspended in pepsin/HCl for 2 h in a disintegration tester at 40°C, and the remaining 3 were suspended for 2 h in a buffer solution containing pancreatin at 40°C. The completely randomized design included the main effect of incubation time with 2 orthogonal contrasts. Untreated capsules totally disintegrated with release of all fish oil in <15 min suspension in rumen buffer at 40°C. Treated porcine # 0 hard gelatin capsules suspended in ruminal contents had similar (P = 0.82) DM remaining at 0 (99.0%) vs 6, 12, and 24 h (average 98.2%), but lower (P = 0.006) DM remaining at 48 h (88.2%). Similarly, the percentage of EPA in recovered capsules was the same for 0 versus 6, 12, and 24 h (18.3%) but lower (P < 0.01) at 48 h (17.1%). Capsules removed from ruminal contents and then exposed to pepsin/HCl had similar DM remaining for 6 (97.4%) vs 12 and 24 h (97.1%), but lower (P = 0.06) DM remaining for 48 h (62.1%). Capsules removed from ruminal contents and then mixed in a pancreatin solution had similar DM remaining for all rumen exposure times (average 1.95%). Results were similar for treated small and large soft gel capsules containing fish oil. The treatment protocol developed in this study successfully slowed disintegration time of gelatin capsules in ruminal contents and minimized changes in fatty acid profile of fish oil contents. Extensive disintegration occurred when treated capsules were exposed to pancreatic proteases.