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Modelling Mortality and Reproduction Rates for Management of Sheep Flocks in Northern Australia

Pepper, P.M., Mayer, D.G., McKeon, G.M. and Moore, A.D. (1999) Modelling Mortality and Reproduction Rates for Management of Sheep Flocks in Northern Australia. In: Applied Modelling and Simulation, September 1-3, Cairns, Australia.


Organisation URL: http://www.iasted.org
Publisher URL: http://www.actapress.com


By quantifying the effects of climatic variability in the sheep grazing lands of north western and western Queensland, the key biological rates of mortality and reproduction can be predicted for sheep. These rates are essential components of a decision support package which can prove a useful management tool for producers, especially if they can easily obtain the necessary predictors.

When the sub-models of the GRAZPLAN ruminant biology process model were re-parameterised from Queensland data along with an empirical equation predicting the probability of ewes mating added, the process model predicted the probability of pregnancy well (86% variation explained). Predicting mortality from GRAZPLAN was less successful but an empirical equation based on relative condition of the animal (a measure based on liveweight), pregnancy status and age explained 78% of the variation in mortalities.

A crucial predictor in these models was liveweight which is not often recorded on producer properties. Empirical models based on climatic and pasture conditions estimated from the pasture production model GRASP, predicted marking and mortality rates for Mitchell grass (Astrebla sp.) pastures (81% and 63% of the variation explained). These prediction equations were tested against independent data from producer properties and the model successfully validated for Mitchell grass communities.

Item Type:Conference or Workshop Item (Paper)
Additional Information:Reproduced with permission from ©The International Association of Science and Technology for Development (IASTED). Access to published version may be available via Publisher’s website.
Keywords:Model; sheep; reproduction; mortality.
Subjects:Animal culture > Sheep
Science > Statistics > Simulation modelling
Live Archive:15 Mar 2005
Last Modified:03 Sep 2021 16:47

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