Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

David J. Schingoethe


The effectiveness of a rumen-protected methionine preparation was studied as an amino acid source for high-producing dairy cows during wk 4 through 16 postpartum. Twenty-four Holstein cows (14 primiparous and 10 multiparous) were fed concentrate containing heat-treated· soybean meal without or with 50 g/cow/day of added ruminally protected methionine product which provided 15 g of added DL-methionine daily. Cows were fed 16% crude protein mixed diets containing 30% of dry matter as corn silage, 15% as alfalfa hay, and 55% as concentrate. Milk production and composition were adjusted for pretreatment values (3 wk postpartum) by analysis of covariance. Adjusted milk yields (34.6 and 33.1 kg/day) were higher for cows fed heated soybean meal, but this difference was accounted for by higher pretreatment production (32.6 and 36.9 kg/day) of multiparous cows fed supplemental methionine. Production of 4% fat-corrected milk (28.5 and 27.6 kg/day) and solids-corrected milk (29.0 and 28.5 kg/day) was similar for cows fed both diets. Percentages of fat (2.81 and 2.92) and protein (2.88 and 2.92) were similar, while total solids (11.49 and 12.69) and solids-not-fat (8.68 and 8.77) were higher when cows were fed supplemental methionine. Milk protein percent (2.89 and 2.99) and milk protein production (.97 and 1.00 kg/day) were increased for primiparous cows fed supplemental methionine. Fatty acid composition in milk was similar. Dry matter intakes (20.2 and 21.0 kg/day) were higher especially in multiparous cows (21.5 and 23.8 kg/day) when fed supplemental methionine. Body weights (602 and 598 kg) and body weight changes were similar for the two treatments. Ruminal pH, volatile fatty acids, and ammonia, as well as blood serum urea and glucose were generally unaffected by methionine supplementation. Concentrations of methionine in arterial and venous plasma were elevated slightly when fed additional methionine, but the first in arterial and venous plasma were elevated fed additional methionine, but the first limiting amino acid for milk production, as calculated by several methods, was not changed by feeding supplemental ruminally protected methionine.

Library of Congress Subject Headings

Dairy Cattle -- Feeding and feeds
Soybean meal
Milk yield


Includes bibliographical references (pages 69-79)



Number of Pages



South Dakota State University


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Dairy Science Commons