Relative plasma bioavailability of omega-3 fatty acids derived from rumen-protected fish oil in lactating Holstein dairy cows.

Fish oil is a rich source of very-long-chain omega-3 (VLCn-3) fatty acids (FA). Feeding VLCn-3 FA may have beneficial effects on health, fertility, and milk production in the dairy cow. Rumen-protected (RP) technologies aim to prevent the ruminal biohydrogenation of VLCn-3 FA. The objective of this study was to determine the bioavailability of 2 RP fish oil products. Six mid-lactation, multiparous, pregnant Holstein dairy cows (155 ± 19 d in milk; 3.0 ± 0.5 body condition score; 3.2 ± 1.1 parity; 644 ± 23 kg body weight) were randomly assigned to treat- ments in a replicated 3 × 3 Latin Square design study. Treatments were provided as a single esophageal bolus in a gelatin capsule and included (1) fish oil microencapsulated with palm oil triglycerides, (2) fish oil encapsulated with modified starch, or (3) an empty gelatin capsule (i.e., control). The provision of either fish oil product provided a 10 g equivalent of VLCn-3 FA including C20:5n-3 and C22:6n-3. Cows were fed a conventional total mixed ration to meet or exceed nutrient requirements, and were milked thrice daily. Blood was sampled at 0, 2, 4, 6, 8, 10, 12, 16, 18, 20, 24, 36 h, relative to bolus administration. A 7-d washout period was utilized between each bolus delivery. Extracted plasma was analyzed for FA and phospholipid concentrations using chromatography and mass spectrometry. Data were analyzed under a mixed model with the random effect of cow and the fixed effects of treat- ment, hour and period. Plasma concentrations of C22:3n-3 (P = 0.05) and C22:5n-3 (P < 0.01) were increased by both fish oil supplements, relative to control. Both RP fish oil treatments increased plasma concen- trations of lysophophatidylcholine-20:5, −22:5 and −22:6, and increased phosphatidylcholine (PC)-38:5 and −38:6, by h 10 (P < 0.01). Plasma PC-40:5 and −40:6 concentrations were greater in starch encapsulated fish oil by h 10, relative to triglyceride encapsulated fish oil (P < 0.05). We conclude that triglyceride or starch encapsulated fish oil increases the plasma concentrations of VLCn-3 FA and phospholipids containing these acyl chains in lactating cows.