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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Kenneth Kalscheur


Rumen protected amino acid, lysine, canola meal, forage level


Amino acid supply and metabolism by the lactating dairy cow has received considerable focus because of the potential for improving milk production responses by supplying the ideal amino acid profile to the cow. Lysine is often considered the first limiting amino acid for milk and milk protein synthesis. Several studies have examined the effects of improving the lysine content of metabolizable protein and its subsequent effects on milk production. Variable responses have been observed when examining production responses to altering the supply of amino acids to the small intestine. These inconsistencies are likely due to differences in the amino acid composition of a feedstuff, variability in the digestibility of the amino acids (AA) within a feedstuff, and challenges associated with the modeling of amino acid flows to the small intestine. Rumen-protected lysine has been used to improve the lysine content of metabolizable protein (MP) and production responses to rumen-protected lysine have reported variable responses for milk and milk protein. The lysine supply to the small intestine may also be improved by utilizing feeds that contain an optimal profile of amino acids in rumen undegradable protein (RUP) and maximize microbial protein synthesis. Compared to other protein meals such as dried distillers grains with solubles (DDGS) and soybean meal (SBM), canola meal (CM) has a high quality amino acid profile. Canola meal has been shown to effectively replace protein supplements such as SBM, DDGS, and cottonseed meal in lactating dairy cow rations. The objectives of this research were to examine the effects of using rumen protected lysine in a conventional corn silage based ration, as well as, the effects of using canola meal across a variety of forage levels in order to evaluate the amino acid supply and utilization of lactating dairy cows and their subsequent effect on lactation performance. The arterio-venous technique was used to assess the utilization of amino acid (AA) and both the NRC (2001) and AMTS ration modeling programs were used to estimate MP lysine supply. In the first experiment rumen protected (RP) lysine (Lys) was used to linearly increase MP Lys supply. In the second experiment, we varied the level of forage in the diet while maintaining CM as the primary protein source at 11% of the diet (DM basis) and all diets were formulated to be similar in protein content and MP Lys supply. The results from experiment one allowed demonstrated that balancing diets for increasing MP Lys supply using RP Lys effectively improved the amino acid balance of the cow (lysine was not first limiting) and helped to improve milk protein percent and yield. The results from experiment two demonstrated that canola meal provides a high quality AA profile to the small intestine and that cows fed canola meal in diets containing as much as 66% forage can not only maintain milk production, but also improve feed efficiency compared to cows fed lower forage levels.

Library of Congress Subject Headings

Dairy cattle -- Feeding and feeds
Amino acids in animal nutrition
Proteins in animal nutrition
Canola meal as feed
Lysine in animal nutrition


Includes bibliographical references (pages 91-100)



Number of Pages



South Dakota State University


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