The Effect of Diet Formulations Containing Different Protein Sources on Energy and Nitrogen Utilization in Lactating Jersey Cows

Authors

Kortney Ann Harpestad, University of Nebraska-LincolnFollow

First Advisor

Paul J. Kononoff

Committee Members

Jim MacDonald, Tom Burkey

Date of this Version

8-2025

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Animal Science

Under the supervision of Professor Paul J. Kononoff

Lincoln, Nebraska, August 2025

Comments

Copyright 2025, Kortney Ann Harpestad. Used by permission

Abstract

It is well understood that lactating dairy cows require metabolizable protein (MP) for milk yield and milk protein synthesis. Diets with conventional feed sources like corn and soybean meal (SBM) may not sufficiently meet all MP and amino acid (AA) requirements so supplementation with more rumen undegradable protein (RUP) rich feeds or rumen-protected AA can be fed to support animal performance. The growth trajectory of biofuels has resulted in dramatic increases in the production of feeds like heat treated soybean meal (HTSBM). While the chemical composition of this product is understood, there is a need to better understand how HTSBM can be fed to dairy cows with other common high protein sources or with rumen-protected AA to meet the animal’s needs for MP and AA.

The objectives of this study were to; 1) determine if HTSBM and rumen-protected AA can be used to replace common RUP sources; 2) determine if HTSBM can replace all canola meal (CM) and provide more digestible N; 3) we suspect none of these changes will affect dietary methane production but may affect N excretion and that the low Histidine content of CM may negatively affect milk protein production. This experiment utilized 12 multiparous Jersey cows in a triplicated 4x4 Latin square design, randomly assigned to 4 different treatment diets; HTSBM, blood meal (BM) + SBM, HTSBM + CM and CM + BM. Results showed no significant differences in DMI, milk yield, milk fat yield, methane production or whole-animal energy utilization. Milk protein yield was affected, CM+BM diet had the highest milk protein output and HTSBM diet resulting in the lowest. Despite these differences, diets containing HTSBM, especially when paired with CM, maintained overall milk production while improving the efficiency of metabolizable energy use. Cows on HTSBM-based diets excreted less fecal N compared to those consuming CM + BM, suggesting improved N utilization. Therefore, we can conclude HTSBM can replace common high protein sources.

Advisor: Paul J. Kononoff