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Caini Liu

Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

D. J. Schingoethe


In a replicated 4x4 Latin square design with 4 wk per period, 12 multiparous Holstein cows averaging 83 d postpartum were used to compare com distillers grains (CDG) versus a blend (BLEND) of other protein sources (fish meal and soybean meal) with CDG, and to determine the effectiveness of ruminally protected lysine and methionine (RPLM) in improving the utilization of CDG as a protein supplement for lactating cows. The 2x2 factorial treatment arrangement was as follows: CDG diet, CDG diet plus RPLM, BLEND diet, and BLEND diet plus RPLM. All diets contained 30% com silage, 20% alfalfa hay, and 50% of the respective concentrate mixture. Array of amino acids (AA) available for absorption when fed the BLEND diet was more desirable than for CDG diet according to Milk Protein Score and Cornell Net Carbohydrate and Protein Systems. Dry matter intakes were similar (P > 0.40) among all diets. Milk yields (32.6, 31. 7, 32.8, and 32.8 kg/d) were similar for cows fed all diets. Milk fat yields and percentages (3.72, 3.76, 3.67, and 3.63) were unaffected (P > 0.21) by diet but milk protein percentages (3.23, 3.26, 3.25, and 3.-26) tended (P < 0.14) to be higher when fed RPLM. Concentrations of various proteins in milk were similar for all diets although various caseins and whey proteins synthesized in the mammary gland tended (P < 0. 04 to 0.13) to be affected by dietary protein source. Lysine, Met and Phe were indicated as the most limiting amino acids (AA) for all diets according to extraction efficiency and transfer efficiency of AA from blood by the mammary gland. Methionine status was apparently improved by RPLM supplementation; Lys status was improved by the BLEND diets. Milk yield and composition when fed CDG were not further increased by feeding blends of protein sources or RPLM; however, such dietary changes improved Lys and Met status of the cows.

Library of Congress Subject Headings

Dairy cattle -- Feeding and feeds
Distillers feeds
Proteins in animal nutrition
Amino acids in animal nutrition


Includes bibliographical references (pages 40-48)



Number of Pages



South Dakota State University


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