Absorption and Utilization of Choline and Vitamin B12 in Lactating Dairy Cows using Different Delivery Methods

Choline and vitamin B12 are essential nutrients for growth and performances of production animals. However, both nutrients are extensively degraded during digestion in the rumen. This thesis comprised three experiments. First, four cows equipped with a rumen cannula and catheters in the portal vein and a mesenteric artery received a post-ruminal bolus of: 1) cyanocobalamin (CN-CBL) alone (0.1 g) [gram], 2) CN-CBL (0.1 g) + casein (10 g) or 3) CN-CBL (0.1 g) + whey proteins (10 g). After the bolus, blood samples were taken until 24 h [hour] post-bolus. The intestinal absorption of CN-CBL was greater when the vitamin was given in solution with casein (4 μg [micro-gram]/h) compared with CN-CBL given alone or with whey protein (-25 μg/h and -19 μg/h, respectively). Second, a LC-MS/MS methodology was established for differentiation of choline metabolites in blood and milk, from different physiological states of the lactating cow. Total choline concentration in plasma, which was almost entirely phosphatidylcholine, increased 10-fold from early to late lactation (1,305 to 13,535 μmol/L [micro-mol per liter]). In milk, phosphocholine was the main metabolite in early lactation (492 μmol/L), but decreased exponentially through lactation to 43 μmol/L in late lactation. In contrast, phosphatidylcholine in milk was the main metabolite in mid and late lactation (188 μmol/L and 659 μmol/L, respectively). Third, the choline metabolites were measured in milk and blood after post-ruminal infusion (ABO) of choline chloride or dietary supplemented with rumen protected choline (RPC) in a low dose 12.5 g (L) and high dose 25 g (H) choline/d, respectively. Although lipid soluble metabolites or total choline in plasma were not affected by treatments, total choline was transfer into milk at a low level, 2% RPC-H and 5% ABO-H. For practical application of our findings, first, dietary formulation of CN-CBL with addition of casein may improve CN-CBL absorption in dairy cows; second, milk from dairy cows at early lactation is higher in phosphocholine and thus might be used for infant formula to better match breast milk; third, prediction of choline supply may be possible based on betaine and phosphocholine yields in milk