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Accueil du site → Doctorat → Afrique du Sud → < 2000 → The bioeconomic implications of various stocking strategies in the semi- arid savanna of Natal.

University of KwaZulu-Natal (1994)

The bioeconomic implications of various stocking strategies in the semi- arid savanna of Natal.

Hatch, Grant Peter

Titre : The bioeconomic implications of various stocking strategies in the semi- arid savanna of Natal.

Auteur : Hatch, Grant Peter

Université de soutenance : University of KwaZulu-Natal

Grade : Doctor of Philosophy 1994

Résumé partiel
Climatic and market uncertainty present major challenges to livestock producers in arid and semi-arid environments. Range managers require detailed information on biological and economic components of the system in order to formulate stocking strategies which maximise short-term financial risk and minimise long-term ecological risk. Computer-based simulation models may provide useful tools to assist in this decision process. This thesis outlines the development of a bioeconomic stocking model for the semi-arid savanna of Natal. Grazing trials were established at two sites (Llanwarne and Dordrecht) on Llanwarne Estates in the Magudu area of the semi-arid savanna or Lowveld of Natal. The Lowveld comprises a herbaceous layer dominated by Themeda triandra, Panicum maximum and P. coloratum and a woody layer characterised by Acacia species. The sites differed initially in range composition. Llanwarne was dominated by Themeda triandra, Panicum maximum and P. coloratum, while Dordrecht with a history of heavy stocking was dominated by Urochloa mosambicensis, Sporobolus nitens and S. iocladus. Three treatments were stocked with Brahman-cross cattle at each site to initially represent ’light’(0.17 LSU ha-’), ’intermediate’ (0.23 LSU ha-’) and ’heavy’ (0.30 LSU ha-’) stocking. Data collected at three-week intervals over seven seasons (November 1986 to June 1993 or 120 measuring periods) provided the basis for the development of a stocking model LOWBEEF - OWveid BioEconomic Efficiency Forecasting) which comprised two biological sub-models (GRASS and BEEF), based on step-wise multiple linear regression models, and an integrated economic component (ECON). The GRASS model predicted the amount of residual herbage at the end of summer (kg ha-’) and the forage deficit period (days) over which forage supplementation would be required to maintain animal mass. Residual herbage mass at the end of summer (kg ha-’) was significantly related (P < 0.01) to cumulative summer grazing days (LSU gd ha-’), rainfall (mm) (measured 1 July to 30 June) and range condition (indexed as the sum of the proportions of T. triandra, P. maximum and P. coloratum).

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