Animal Science, Department of


First Advisor

Dr. Paul Kononoff

Date of this Version

Summer 7-28-2020


Buse, K. K. 2020. Characterization of protein and fat in dairy feeds and implications on digestibility and milk composition.


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, 2020

Copyright 2020 Kassidy Kate Buse


A variety of feedstuffs are used to comprise dairy rations, each with their own nutritional contributions. In order to best utilize these feedstuffs to maximize production, characterization of their chemical composition is needed. Through the use of both in vitro and in situ methods, not only can the composition of the feed be determined, but also its digestibility. Also, because of the important role they play in human health, omega 3 fatty acids have received increasing attention. Most individuals consuming Western diets do not meet the recommended requirement for omega 3 fatty acids, and one way to improve that is through the enrichment of dairy products by selective feeding high fatty acid feedstuffs to dairy cows. In the first experiment, three assays were used to determine RUP digestibility, the Mobile Bag (MOB), Modified Three Step (MTS), and Ross (ROS) assays, were compared. Also with this experiment, 10 samples of feather meal from different plants across the United States, five with blood (FMB) and five without blood (FM), were evaluated. Each of the ten samples were subjected to all three assays. The results indicate that while the average initial compositions were different between FM and FMB samples, very little difference was observed in the ruminal or intestinal digestibility of the protein. However, there was differences in values among assays. Assay had a significant effect on rumen dry matter digestibility, RDP, RUP, total tract dry matter digestibility, and total tract crude protein digestibility with MOB and MTS being the most similar in values. Nonetheless, RUP digestibility did not differ among assay or blood inclusion. Overall, even though values between samples and assays varied, there was no difference in RUP digestibility among blood inclusion and assay. The second study’s goal was to evaluate the effect of the novel fatty acid supplement, Perfect Omega 3 (PO3), on the milk fatty acid profile and energy utilization. Diets ranging in 0 to 20% PO3 inclusion were fed to four multiparous Jersey cows in a 4 × 4 Latin square, and headbox-style indirect calorimeters were used to determine the effect of increasing inclusion on energy utilization. Results show that increasing inclusion of PO3 not only increased the milk fat concentration but also increased the concentration of α-linolenic acid in the milk while decreasing linoleic acid with no difference in milk yield. Gross energy increased with increasing inclusion, but DE and ME did not differ among treatments. Increasing inclusion also had no effect on NDF and energy digestibility. Through this study, increasing inclusion of PO3 not only maintained milk production, but also increased milk fat concentration with favor towards omega 3 fatty acids.

Advisor: Paul J. Kononoff