J. Anim Sci.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J. Anim Sci. 2007. 85:332-340. doi:10.2527/jas.2005-709
© 2007 American Society of Animal Science
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
jas.2005-709v1
85/2/332    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Shafer, W. R.
Right arrow Articles by Enns, R. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Shafer, W. R.
Right arrow Articles by Enns, R. M.

ANIMAL GENETICS

Simulation of cow-calf production with and without realistic levels of variability

W. R. Shafer*,1, R. M. Bourdon{dagger} and R. M. Enns{dagger}

* American Simmental Association, Bozeman, MT 59715; and and {dagger} Department of Animal Sciences, Colorado State University, Fort Collins 80523

1 Corresponding author: wshafer{at}simmgene.com

The Colorado beef cattle production model, a whole-herd, individual-animal, life-cycle simulation model, was used to determine if level of simulated variability affects simulation results. Beyond variability created by deterministic equations describing known biological relationships and direct input, the Colorado beef cattle production model can produce additional variation in a number of traits through its capacity to generate multinormal deviates for each animal. Runs simulating cow-calf production under ample and sparse levels of nutrition were performed with less than realistic and realistic levels of variability for mature weight, milk production, gestation length, maintenance requirements, appetite, and combinations thereof. Under poor nutrition, simulation with less than realistic variability altered means for pregnancy rate, postpartum interval, milk production, weaning weight, and mature weight by up to 14%, 8.6 d, 0.8 kg/d, 9.6 kg, and 19.1 kg, respectively, in addition to changing the output for numerous other variables. The level of simulated variability affected the means of output variables through 2 mechanisms: (1) change in potentials due to differential culling, which can only take place if potentials are allowed to vary; and (2) further interaction with the model’s nonlinear, deterministic equations. Our findings indicate that by not simulating realistic levels of variability, models with nonlinear functions may yield misleading results.

Key Words: beef cattle • interaction • nonlinear equation • simulation • variability






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2007 by the American Society of Animal Science.