HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Coleman, S. W. Articles by Barth, K. M. Search for Related Content PubMed PubMed Citation Articles by Coleman, S. W. Articles by Barth, K. M.

Nutrient Digestibility and N-Metabolism by Cattle Fed Rations Based on Urea and Corn Silage¹

University of Tennessee,³ Knoxville 37916

Abstract

Data from six total collection digestion and N-metabolism trials with steers were compiled to examine factors affecting ration digestibility and N-utilization of rations based on urea and corn silage. F-max test indicated homogeneity of variances among the trials. Multiple regression analyses were conducted to determine the effect of various ration constituents and intake parameters on nutrient digestibility .and efficiency of N-metabolism. Percentage of total N supplied by concentrates, N intake and crude fiber intake together accounted for 42,31 and 65% of the total variability in the apparent digestibility of dry matter, crude protein and crude fiber, respectively. Increasing the gross energy from concentrates resulted in an increase of apparent digestibilities of dry matter and crude fiber, and a decrease in digestibility of nitrogen. Increases in nitrogen intake resulted in decreased digestibility of dry matter and crude fiber. Increasing crude fiber intake increased digestibility of crude fiber and decreased digestibility of crude protein. However, only crude fiber digestibility was affected significantly (P< .05). Percentage of total N supplied by urea had no significant (P> .05) effect on digestibility.

When percent absorbed N retained, percent intake N retained and net protein utilization were the dependent variables, their regression on: 1) percentage of ration N supplied by urea; 2) energy supplied by concentrates; 3) N intake; and 4) fiber intake accounted for 46,22 and 26%, respectively, of the total variability in the three dependent variables. An increase in the percentage of N supplied by urea resulted in significant (P< .05) decreases in all measures of N utilization. When percent N supplied by urea increased from 5.4 to 45.4, retention of absorbed N, retention of intake N and net protein utilization decreased 17.9, 14.7 and 12.2 percentage units, respectively. Increases in N intake were accompanied by significant (P< .05) decreases in percentage retention of absorbed N and net protein utilization.

¹ Published with the permission of the Dean of the University of Tennessee Agricultural Experiment Station.

² Present address: University of Florida, Agricultural Research and Education Center, Belle Glade, Florida, 33430.

³ Department of Animal Science.