Lactational Evaluation of Ruminally Protected Methionine in Diets Containing Extruded Soybeans and Urea

Abstract

The addition of urea to diets containing extruded soybeans may sufficiently increase ruminal lysine production so that the diet would then be limiting for methionine. Twenty-eight Holstein cows were fed a diet containing extruded soybeans and urea without or with 50 g of ruminally protected methionine product, which supplied 15 g of DL-methionine daily from wk 4 through 16 postpartum. Total mixed diets contained 16.0% CP consisting of (DM basis) 40% corn silage, 10% alfalfa hay, and 50% concentrate mix. production of milk (33.8 and 35.0 kg/d) and 4% FCM (26.8 and 28.4 kg/d) were elevated slightly with protected methionine. Percentages of fat (2.71 and 2.79), protein (3.02 and 2.98). and SNF (8.64 and 8.54), and intakes of DM (20.8 and 19.2 kg/d) were similar. Arterial concentration of methionine was increased by feeding protected methionine. Efficiency of amino acid transfer into milk protein indicated that methionine status was improved by reducing methionine from first- to second-limiting amino acid with methionine supplementation. © 1991, American Dairy Science Association. All rights reserved.