Abomasal Infusion of Choline and Methionine with or Without 2-Amino-2-Methyl-1-Propanol for Lactating Dairy Cows

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Abstract
Effects of abomasal infusion of choline and methionine either alone or with infused 2-amino-2-methyl-1-propanol, an inhibitor of choline synthesis, were investigated in lactating dairy cows. Four rumen-fistulated mature Holstein cows were utilized in a single reversal experiment with 5-wk periods. Cows were fed total mixed rations containing 40% corn silage and 60% concentrate on a DM basis. Cows were infused continuously with 2 L/d of water to which either 30 g/d choline or 45.6 g/d methionine were mixed and infused during wk 2 through 5. During wk 4 and 5, 40 g/d 2-amino-2-methyl-1-propanol were added in addition to choline or methionine in both treatments. Infusions of choline and methionine resulted in similar DM intakes and daily milk production of cows. However, cows infused with choline had .45 and .14 percentage units higher milk fat and milk protein compared with those of cows infused with methionine. Addition of the inhibitor to the methionine infusion depressed milk and 4% FCM yield of cows by 1.5 and 3.2 kg/d when compared with choline plus inhibitor. Milk protein was reduced by .30 percentage units. These results suggest that methionine functions as a methyl donor for choline synthesis.