ABSTRACT
The objectives of this study were to evaluate milk choline as an indicator of choline absorption and to use milk choline to evaluate the efficacy of a rumen-protected choline supplement. In a preliminary 4-wk experiment, two Holstein cows in early lactation were abomasally infused with either 0 or 60 g/d of choline chloride in 2 L of water, which was used as a carrier. Choline infusion increased milk choline secretion from 1.95 to 3.95 g/d during the 2-wk choline infusion period. In Experiment 2, four Holstein cows in early lactation were abomasally infused with 0, 25, 50, and 75 g/d of choline chloride in 2 L of water using a 4 x 4 Latin square design with 1-wk experimental periods. Milk choline secretion was 2.56, 3.62, 3.72, and 3.82 g/d for the respective choline treatments. In Experiment 3, 10 Holstein cows in midlactation were fed either 0 or 50 g/d of choline using an experimental rumen-protected choline supplement during a 2-wk experiment. Milk choline secretion was increased from 2.12 to 2.99 g/d with the supplemental choline. Results of these experiments demonstrated that milk choline is responsive to postruminal choline supply and can be used as a qualitative indicator of choline absorption.
