Cattle herd dynamics: An integer and stochastic model for evaluating production alternatives

Table of Contents

ILCA Research Report No. 2
June 1982

Panos A. Konandreas and Frank M. Anderson

INTERNATIONAL LIVESTOCK CENTRE FOR AFRICA
ADDIS ABABA, ETHIOPIA

ILCA PUBLICATIONS The International Livestock Centre for Africa (ILCA) is an autonomous, non-profit making research and information centre with a mandate to improve livestock production throughout sub-Saharan Africa. The activities and publications of the centre are financed by the Consultative Group on International Agricultural Research (CGIAR). The CGIAR members which have funded ILCA to date are the International Development Research Centre, the International Fund for Agricultural Development, the United Nations Development Programme, the World Bank, and the governments of Australia, Belgium, Denmark, the Federal Republic of Germany, France, Iran, Ireland, Italy, the Netherlands, Nigeria, Norway, Saudi Arabia, Sweden, Switzerland, the United Kingdom and the United States of America. Responsibility for ILCA publications rests solely with the centre and with such other parties as may be cited as joint authors. Until 1982, the centre's two main series of scientific publications were Systems Studies and Monographs. These two series have now been superceded by the present series of Research Reports.

This electronic document has been scanned using optical character recognition (OCR) software and careful manual recorrection. Even if the quality of digitalisation is high, the FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.

Table of Contents

Preface

1. Introduction

2. Analytical background

2.1 Forage intake

2.1.1 Ad libitum forage intake
2.1.2 Forage intake in real systems

2.2 Energy utilization

2.2.1 Maintenance
2.2.2 Lactation
2.2.3 Pregnancy
2.2.4 Liveweight gain
2.2.5 Energy released from mobilization of body reserves
2.2.6 Energy available to calves from milk consumed

2.3 Animal reproduction

3. The simulation model

3.1 Overview of the computer simulation model
3.2 Specification of forage on offer and animal activity
3.3 Algorithms simulating biological processes

3.3.1 Feed intake
3.3.2 Growth and milk production
3.3.3 Reproduction
3.3.4 Mortality

3.4 Herd management policy options

3.4.1 Supplementary feeding
3.4.2 Milk offtake
3.4.3 Weaning
3.4.4 Breeding
3.4.5 Purchases
3.4.6 Sales
3.4.7 Drought policy

4. The simulation process

Appendix A: A procedure to estimate liveweight growth curves

Appendix B: A procedure to estimate the age effect on potential milk yield

Appendix C: A procedure to estimate the lactation curve

Appendix D: A procedure to estimate the age effect on fertility

Appendix E: A procedure to estimate the age effect on mortality

Appendix F: Example input data set

Literature cited

The consultative group on international agricultural research

ILCA research publications