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Evaluation of a feed intake model for the grazing beef steer
J C Hyer1, J W Oltjen, M L Galyean
1Oklahoma State University, Stillwater 74078.
Journal of Animal Science
|February 1, 1991
Summary
This study evaluated a beef cattle feed intake model, finding it accurately predicts energy supplementation effects but struggles with protein-limited diets. The model needs refinement for protein supplementation to improve accuracy in grazing beef cattle nutrition.
Area of Science:
- Animal Science
- Ruminant Nutrition
- Computational Biology
Background:
- Accurate prediction of feed intake is crucial for optimizing grazing beef cattle production.
- Existing feed intake models require validation against diverse forage qualities and supplementation strategies.
- Understanding model sensitivity to various parameters is key for improving predictive capabilities.
Purpose of the Study:
- To evaluate the performance of a feed intake model for grazing beef cattle.
- To assess model responses to changes in model parameters, forage composition, and energy/protein supplementation.
- To identify limitations of the current model, particularly concerning protein supplementation.
Main Methods:
- Model simulations were conducted using varying parameters, forage types (differing in digestibility and fiber content), and supplementation with energy (corn grain) and protein (cottonseed meal).
- Model predictions of forage intake were compared against expected outcomes based on established nutritional principles and in vivo data.
- Sensitivity analyses were performed on key model parameters, including microbial growth and composition constants, and fiber content.
Main Results:
- The model systematically underpredicted intake for low-quality forages and overpredicted for high-quality diets without supplementation.
- Model predictions were highly sensitive to nondegradable fiber content and microbial carbohydrate composition.
- While the model accurately predicted substitution ratios for energy supplementation, it failed to predict increased forage intake under protein limitation.
Conclusions:
- The feed intake model adequately predicts responses to energy supplementation and forage composition but requires significant improvement for protein-limiting scenarios.
- Current model parameters may not fully capture the physiological mechanisms regulating intake in response to supplemental protein.
- Further research is needed to refine the model's ability to predict forage intake under protein supplementation for grazing beef cattle.