Figure 1.
Metabolism of choline and its metabolites.
The compounds shown in boxes were assayed in milk and plasma in the current study. Phosphocholine and phosphatidylcholine are formed from choline via the cytidine diphosphate (CDP) choline pathway. The formation of betaine from choline is irreversible. Betaine when oxidized will provide a methyl group to homocysteine to form methionine. Methionine is converted to S-adenosylmethionine, which is an important methyl donor. Phosphatidylcholine can be formed endogenously by methylating phosphatidylethanolamine in a three step process involving S-adenosylmethionine via the phosphatidylethanolamine N-methyltransferase (PEMT) pathway.
Table 1.
Ingredient and chemical composition of total mixed ration.
Table 2.
Choline and choline metabolite concentration in individual feed ingredients used to make the total mixed ration.
Table 3.
Milk yield and composition of dairy cows during lactation.
Figure 2.
Relationship between total choline concentration in plasma and week of lactation.
The standard errors for the intercept, linear and quadratic term were 564, 97.0, and 2.42, respectively.
Table 4.
Choline and choline metabolites concentration in plasma (µmol/L) of dairy cows during lactation.
Table 5.
Concentration of lysophophatidylcholine (LPC) and phosphatidylcholine (PC) with a particular fatty acyl chain in plasma of dairy cows during lactation.
Figure 3.
Relationship between week of lactation and milk yields of phosphatidylcholine (A), phosphocholine (B).
The standard errors for the intercept and linear terms in (A) were 0.46 and 0.02, respectively. The equation was y = a+b exp−cx with the standards errors for the fitted parameters in (B) were 0.106, 0.190, and 0.022 for a, b and c, respectively.
Table 6.
Concentration and yield of choline and choline metabolites in milk of dairy cows during lactation.
Table 7.
Concentration of lysophophatidylcholine (LPC) and phosphatidylcholine (PC) with a particular fatty acyl chain in milk of dairy cows during lactation.
Figure 4.
Relationship between plasma phosphatidylcholine concentration and either yield of phosphatidylcholine (A) or phosphocholine (B).
Each symbol represents either early ( ♦), mid (▪) and late (▴) lactation. The standards errors for the intercept and linear terms in (A) were 0.58 and 0.00007. The equation was y = a+b exp−cx with the standard errors for the fitted parameters in (B) were 0.133, 0.230, and 0.000046 for a, b and c, respectively.