Title page for ETD etd-05112017-102210

Type of Document Master's Thesis
Author McGill, Tyler R
Author's Email Address tmcgil12@vt.edu
URN etd-05112017-102210
Title Improving the Efficiency of Dairy Cattle Feeding
Degree Master of Science
Department Dairy Science
Advisory Committee
Advisor Name Title
Dr. Mark Hanigan Committee Chair
Dr. Michelle Rhoads Committee Member
Dr. Mike Akers Committee Member
  • ruminant
  • nitrogen efficiency
  • model evaluation
Date of Defense 2017-04-26
Availability unrestricted
Biological functions that use amino acids (AA) are limited by AA supply. This concept was likened to staves in a barrel, where the shortest stave determines the barrel’s ability to hold water (Mitchell and Block, 1946). Inaccuracies in models that predict nutrient supply and requirements of dairy cows result in inefficient feeding, as under-prediction of requirements results in deficiency, and over-prediction results in excess. To avoid limitations in production due to AA deficiencies, protein is fed in quantities that likely exceed requirements. Overfeeding of AA results in increased expenses for producers and increased N excretion to the environment, providing economic and environmental incentives to increase N-efficiency. Work presented in the following chapters evaluated the impact of AA supplementation on milk production in dairy cattle, and evaluated the PREP10 and NRC (2001) nutrient requirement model predictions. In two feeding trials (Chapter 2 and Chapter 3), low protein diets did not result in decreased milk production, indicating that protein requirements were overestimated. Although supplementation of AA did not increase milk production, low protein diets resulted in greater N-efficiency, especially when supplemented with Histidine. Evaluation of the PREP10 and NRC (2001) models (Chapter 4) used production data from the literature to identify deficiencies in prediction equations, and found that correction of model bias would considerably reduce prediction errors. Model inaccuracies affect the inefficiency of dairy cow feeding, and must be evaluated to improve feed efficiency. Such improvements could act synergistically with AA supplementation to more closely match nutrient supply to requirements.
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