Temporal changes in plasma choline and choline metabolite concentrations in response to an esophageal bolus of rumen-protected fish oil in early lactation cows fed rumen-protected choline

Fish oil (FO) is a rich source of omega-3 fatty acids (FA), which may be preferable FA for hepatic phosphatidylcholine (PC) synthesis via the actions of phosphatidylethanolamine N-methyltransferase. Our objective was to determine whether rumen-protected choline (RPC) feeding increased concentrations of circulating PC enriched with omega-3 FA in cows fed a bolus of rumen-protected FO. Eighteen Holstein cows (3.6 ± 2 [mean ± SD] lactations) were randomly assigned to 2 groups (n = 9/group) at −21 ± 3 d prepartum: unsupplemented (CON) or supplemented (RPC) with rumen-protected choline (0 or 60 g/d, respectively; 25% choline chloride; Rupro col®; Vetagro S.p.A., Reggio Emilia, Italy) until d 35 postpartum. At d 27 ± 4 postpartum, all cows were provided with a gelatin capsule containing 100 g of lipid-microencapsulated FO as an esophageal bolus (36% FO; 10.2 g of omega-3 FA; Prototype 6; Vetagro S.p.A.). Cows were fed a total mixed ration and milked twice daily. Blood was sampled at 0, 10, and 24 h, relative to bolus delivery. Plasma was analyzed for choline and choline metabolites using LC/MS. Data were analyzed under a mixed model with the random effect of cow, and the fixed effects of treatment, hour, and their interaction. At h 0, plasma betaine concentrations were greater in RPC, relative to CON; however, plasma choline concentrations were not modified by treatment. Following FO bolus administration, circulating trimethylamine N-oxide and dimethylglycine (DMG) were increased by h 10. Cows supplemented with RPC tended to have greater plasma DMG and methionine, relative to CON. Although no changes were detected for plasma LPC-22:5, LPC-22:6, total LPC, PC -16: 0/ 22: 5 or PC -18: 0/ 22: 5, RPC group increased plasma LPC-20:5, PC -16: 0/ 22: 6, and PC -18: 0/ 22: 6, compared with CON. Plasma PC -18: 0/ 20: 5 and total PC concentrations were greater in RPC cows by h 24, relative to CON. We conclude that RPC feeding augmented the ability of dietary FO to increase plasma PC concentrations in early lactation cows.