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

This Article Full Text (PDF) All Versions of this Article: jas.2008-1326v1 87/3/1138    most recent 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 McMeniman, J. P. Articles by Galyean, M. L. Search for Related Content PubMed PubMed Citation Articles by McMeniman, J. P. Articles by Galyean, M. L.

Evaluation of the NRC (1996) dry matter intake prediction equations and relationships between intake and performance by feedlot cattle

Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409-2141

jmcmeniman{at}nsaaust.com.au

Abstract

Intake prediction equations of NRC (1996) based on initial BW and dietary NEm concentration were evaluated with a commercial feedlot database consisting of 3,363 pen means collected from 3 feedlots over a 4-yr period. The DMI predicted by NRC (1996) equations had significant (P < 0.01) mean and linear biases across the range of observed DMI in the database. In general, DMI was over predicted by the NRC (1996) equations. Adjustment of the NEm-based prediction by use of a 12% increase in NEm concentration and a 4% decrease in predicted DMI associated with the feeding of monensin decreased bias. Dry matter intake predicted by the NEm-based monensin-adjusted, NEm-based, and initial BW equations explained 67, 66, and 64% of the variation in observed DMI, respectively. Relationships between ADG and G:F with DMI as a percentage of BW and NEg intake also were examined in the same data set. Across the wide range of average shrunk BW in the database (334.4 to 548.0 kg), ADG was positively related to DMI as a percentage of BW (P < 0.01); however, this relationship was not strong (r² = 0.17). Likewise, G:F showed little relationship with DMI as a percentage of BW (P < 0.01; r² = 0.05). By accounting for differences in maintenance energy requirements of pens with varying average BW, NEg intake was strongly and positively related to ADG (linear and quadratic, P < 0.01; R² = 0.70); however, G:F showed little relationship with NEg intake (P = 0.02; r² = 0.01). Our evaluations with measurements of DMI by cattle in commercial feedlots indicated the shortcomings of current published equations for predicting DMI and suggest the need for development of new equations with improved accuracy and precision. Furthermore, our data indicate that increasing NEg intake increased ADG in a quadratic manner, but did not affect G:F by pens of cattle in feedlots. These findings suggest a diminishing returns effect of energy intake on energy retention.

Key Words: dry matter intake • feedlot cattle • feedlot performance • intake prediction equations