Assessing Plant-Wax Markers as a Tool to Estimate intake and diet Composition in Beef Cattle

Authors

Emily J. Hilburger, University of Nebraska-LincolnFollow

First Advisor

Ronald M. Lewis

Date of this Version

7-2017

Citation

Hilburger, E. J., H. C. Wilson, H. C. Freetly, and R. M. Lewis. 2017. Assessing plant- waxes markers as a tool to estimated intake and diet composition in beef cattle. Master Thesis University of Nebraska, Lincoln.

Comments

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 Ronald M. Lewis. Lincoln, Nebraska: July, 2017

Copyright (c) Emily J. Hilburger

Abstract

Estimating feed efficiency of ruminants in grazing environments is difficult due to challenges in measuring intake and diet composition of animals that are freely grazing. Plant-wax markers, especially n-alkanes (ALK), have been shown to be a potential tool to calculate intake and diet composition.

Two indoor experiments were conducted in successive years to assess ALK reliability to facilely estimate DMI (EDMI) and diet composition. Heifers were fed a ration of 69.8% corn silage and 30% ground alfalfa with a daily supplement containing a ALK marker (C₃₂). Using a pooled fecal sample increased the correlation between observed DMI and EDMI (in 2015, r =0.79; in 2016, r = 0.65) when compared to daily intakes methods. Furthermore, the EDMI was sensitive to diet composition estimates due to the forages having two distinctly different concentrations of C₃₁ and C₃₃.

A series of grazing studies followed each experiment. The predominant plant species in all studies (smooth bromegrass and Kentucky bluegrass) had ALK profiles that allowed 10% difference in diet compositions to be distinguished (P < 0.02). Differences in concentrations of marker C₃₃ between plants resulted in unrealistic EDMI. When EDMI based on the C31:C32 ratio were compared to observed intakes from the indoor studies, the results were highly variable (0.01 < r2 < 0.99), which could be due to many factors including animal behavior and forage availability. Despite the lack of fine demarcations, sensible intakes were obtained in a grazing setting. The plant-wax methodology therefore shows promise for commercial use.