Evaluation of the National Research Council (1996) dry matter intake prediction equations and relationships between intake and performance by feedlot cattle1

• Published in: Journal of animal science Vol. 87; no. 3; pp. 1138 - 1146
• Main Authors: McMeniman, J. P., Defoor, P. J., Galyean, M. L.
• Format: Journal Article
• Language: English
• Published: Champaign Oxford University Press 01.03.2009
• Subjects: Cattle; Diet; Digestive system; Metabolism; Predictions
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2008-1326

Intake prediction equations of NRC based on initial BW and dietary NEm concentration were evaluated with a commercial feedlot database consisting of 3,363 pen means collected from 3 feed-lots over a 4-yr period. The DM1 predicted by NRC equations had significant (P < 0.01) mean and linear biases across the range of observed DM1 in the data-base. In general, DM1 was overpredicted by the NRC 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 DM1 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 DM1 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. [PUBLICATION ABSTRACT]