Feeding rumen-protected choline to prepartum Holstein cows in negative energy balance increases circulating lipoprotein phosphatidylcholine and triglyceride levels while preventing hepatic triglyceride accrual.
A. Myers1, M. G. Zenobi2, B. A. Barton3, C. R. Staples2, and J. W. McFadden1, 1Cornell University, Ithaca, NY, 2University of Florida, Gainesville, FL, 3Balchem Corp., New Hampton, NY.
Rumen-protected choline (RPC) supplementation may increase hepatic phosphatidylcholine (PC) synthesis to promote triglyceride (TG) secretion within very-low density proteins. To assess whether RPC enhances lipoprotein PC and TG levels in dairy cows, forty-one pregnant, non-lactating, multiparous Holstein cows were fed a RPC (ReaShure, Balchem Corp., New Hampton, NY) that provided 0 (control), 6.5, 12.9, 19.4, and 25.8 g/d of choline ions, respectively. Diets were fed to exceed nutrient requirements for 5 d, then cows were restricted to consume ~31% of their net energy requirements for 9 d. Plasma and liver were collected on d 9 of feed restriction. Plasma TG-rich and low-density lipoprotein fractions were isolated using liquid chromatography. Lipoprotein fraction total TG, cholesterol and phospholipid levels were measured. Lipoprotein fraction and liver lipids were processed for lipidomics. Statistical analyses was done using the Mixed procedure of SAS. Birth weight of the calves and number of days prepartum at enrollment were covariates. Normalized omic data were natural log transformed. A significant linear increase in TG-rich lipoprotein total TG levels was observed with 12.9 or 25.8 g/d of choline ion supplemented, relative to control (P < 0.01). Likewise, RPC linearly increased TG levels within LDL fractions (P = 0.02). Total phospholipid levels tended to be modified by treatment (quadratic, P = 0.09). The majority of TG-rich lipoprotein PC increased linearly with increasing RPC (37 out of 55 PC; e.g. PC 38:5; P < 0.01). A similar linear outcome was observed for TG-rich lipoprotein TG (106 out of 317 TG; P < 0.05). In LDL, RPC increased PC (0 vs rest; 25 out of 64 PC; e.g. PC 38:3; P < 0.05); however, TG was not overtly modified. In liver, RPC increased PC (0 vs. rest; 40 out of 57 PC; P < 0.05). Hepatic TG were lowered by RPC (0 vs. rest; 17.5 vs. 13.6% of tissue DM; P < 0.05). Our data support the likelihood that RPC increased hepatic PC synthesis and VLDL secretion to prevent liver TG accrual in dairy cows.
Key Words: choline, liver, phosphatidylcholine
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