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Nutritional and Chemical Evaluation of Urea and of Biuret in Complete Ensiled Finishing Diets by Lambs^{1, 2,}

University of Illinois, Urbana³

Abstract

A series of metabolism experiments, a feeding experiment and a fermentation study were conducted to compare urea and biuret as nitrogen sources in an ensiled diet and to determine the relative nutritive value of concentrate mixtures added to chopped corn plant at times of ensiling or to silage at feeding time.

Addition of biuret to the basal silage significantly increased nitrogen retention in two of the three experiments, while the addition of urea resulted in consistently lower nitrogen retention. Dry matter digestibility coefficients were higher when either urea or biuret was added to the basal, but the difference was significant (P<.05) in only one of the three experiments.

Addition of the NPN sources to the basal increased (P<.01) gains by 26% and reduced feed required per pound of gain by 1.35 lb. Source of nonprotein nitrogen had no significant effect on rate of gain.

The concentrate mixtures added at ensiling time compared with their addition to silage at feeding time improved (P<.01) dry matter and nitrogen digestibilities, nitrogen retention and percent apparently digested nitrogen retained. Rate of gain was not significantly affected, but 13% less feed was required per pound of gain.

Biuret was fairly stable during ensiling and the ensuing fermentation process, and it appeared to reduce or alter fermentation compared with the basal. Approximately 28 to 57% of the added urea was hydrolyzed, providing a possibility of losing nitrogen from the silage mixture.

DES implants increased (P<.01) nitrogen retention, percent apparently digested nitrogen retained and gains, but had no significant effect on percent of dry matter or nitrogen digested.

¹ Supported in part by a grant-in-aid from Grace Chemical Corrroany, Memphis, Tennessee.

² Part of a thesis submitted to the Graduate College of the University of Illinois by the senior author in partial fulfillment of the requirements for the Ph.D. degree.

³ Department of Animal Science, University of Illinois, Urbana.