Abomasal infusion of deuterium-labeled choline confirms that choline is a methyl donor in gestating and lactating Holstein dairy cattle.

Background: In cattle, dietary choline is fed in a rumen-protected form to bypass ruminal degradation while allowing intestinal absorption of choline. We require data to help us define choline utilization in the dairy cow transitioning from gestation to lactation.

Objective: The study examined choline methyl group transfer in dairy cattle transitioning from gestation to lactation.

Methods: Six multiparous, rumen-cannulated Holstein cows were enrolled in a longitudinal study design where they were abomasally infused with choline chloride (CC) for a 5-d experimental period at -3 wk from expected due date and again at 2 wk postpartum. Twenty percent of CC provided per day was replaced with the stable-isotope trimethyl-d9-CC. Plasma, milk, liver, urine, and fecal samples were analyzed for choline and choline metabolite concentrations and isotope enrichment.

Results: Plasma betaine (P < 0.01) and liver choline and betaine concentrations were lower during lactation (P < 0.01). During lactation, cows had greater circulating enrichment of d3-choline, d3-betaine, d9-betaine, and d9-phosphatidylcholine (PC; P ≤ 0.05), and greater liver enrichment of d3-glycerophosphorylcholine and d9-sphingomyelin (P ≤ 0.02). Greater urinary and fecal losses of d3- and d9-trimethylamine (TMA), and d3- and d9-TMA N-oxide (TMAO) were observed during pregnancy (P ≤ 0.05). Total choline metabolites detected in urine from infused CC were greater during pregnancy, relative to lactation (P < 0.01). Total fecal choline metabolites from infused CC were greater during lactation, relative to pregnancy (P = 0.03).

Conclusions: Our data confirm that choline is a methyl donor (e.g., detected d3-choline), and choline is used by both the cytidine diphosphate-choline and phosphatidylethanolamine N-methyl transferase pathways in the cow during gestation and lactation. We also provide evidence for endogenous recycling of absorbed choline via bile (i.e., presence of d3-TMA). Degradation of choline to TMA and TMAO must be considered when evaluating choline bioavailability.

Statement of significance: These findings are significant because this is the first study to explicitly confirm that choline is a methyl donor in the dairy cow during late gestation and early lactation.