Doctoral Dissertations

Date of Award

5-2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

John C. Waller

Committee Members

Christopher J. Richards, Kelly R. Robbins, Arnold M. Saxon, Joan R. Mount

Abstract

A series of laboratory experiments were conducted to test modifications of protocols used for evaluating nutritional value of feedstuffs for ruminants. The in situ ruminal degradation procedure was used to measure rumen disappearance of total feedstuff dry matter (DM) and a variety of feedstuff components as measured by the Cornell Net Carbohydrate Protein System (CNCPS). The in situ ruminal degradation procedure calls for the use of Dacron bags. We tested an alternate bag (F57) with and without post incubation washing with neutral detergent fiber (NDF) solution. Use of F57 bags permits sample analysis without removing feed residue from the bag as _required when Dacron bags are used. Results of a series of analyses with seven common feedstuffs known to vary widely in both digestibility and composition (alfalfa, bermudagrass hay, tall fescue hay, com, soybean meal, soybean hulls, and wheat straw) indicated that disappearance of total DM and a variety of CNCPS-measured components were similar for Dacron and F57 bags only after the F57 bags were washed with NDF solution following incubation. These same procedures were then employed to determine the nutritional value of hand clipped stockpiled forage. Three varieties of tall fescue were tested. It was determined that sample preparation (i.e. freeze-drying vs. oven-drying) significantly affected in situ rumen disappearance and values of CNCPS-measured feedstuff fractions. Regardless of the forage sample preparation method, differences in rate of dry matter disappearance were found among the tall fescue varieties tested, i.e. variety KY31E+ had lower DM disappearance rates than either Jessup E- or Jessup AR452. We applied these same methods to determine if there were any detectible differences in in situ rumen digestibility among masticate samples of forage from pastures composed of either pure stands ofKY31E+ or KY31E-, or a mixed stand ofKY31E+ and clover. The samples from the K Y31 E + pasture were found to have lower dry matter disappearance percentage than the other two forage samples, perhaps explaining, in part, the previously reported better performance of animals grazing clover containing pastures vs. K Y31 E + pasture.

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