Weight gain in grazing sheep: A detailed comparison between models

Wallach, Daniel; Charpenteau, J.L.; Elsen, Jean Michel J. M.

doi:10.1016/0308-521x(86)90053-3

Cited by 5 publications

(2 citation statements)

References 29 publications

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“…Webster (1980) reported heat lost in fermentation was 6 -8%) of digestible energy. Wallach et al (1984Wallach et al ( , 1986 reviewed the manner m which sheep grazing models calculate maintenance energy requirements and weight gain.…”

Section: B15 Energy Metabolismmentioning

confidence: 99%

“…It has long been recognised that the efficiency of utilisafion of ME for gain dechnes with increasing forage maturity, or conversely, efficiency of utilisation of ME for gain increases with increasing diet quality (Armstrong 1982, Wallach et al 1986, SCA 1990. SCA (1990) hst the ARC (1980) equafion for the efficiency of utilisation of ME for gain of fust growth forages in terms of ME content of the diet:…”

Section: Bl58 Efficiency Of Energy Utilisation For Gain (Kg)mentioning

confidence: 99%

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Near-real time financial assessment of the Queensland wool industry on a regional basis

Hall

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TJiis thesis describes a systems analysis of the Queensland wool industry at a farm-enterprise level, and development of a computer simulation model designed to provide near real-time physical and financial information to policy makers at a regional level as an aid to decision making.Extensive reviews of the main biological factors affecting the wool enterprise were completed: diet selection and feed intake, protein digestion and metabolism, energy digestion and metabolism, wool growth, reproduction and mortalit}\ A sensitivity analysis of three separate bio-economic models was carried out to identify system components having the greatest impact on the financial performance of wool enterprises. Fleece production, wool price and total variable costs were found to be the most important determinants in each model. Grazfeed, a commercially available software package based on the Australian feeding standards for ruminants, was tested for its ability to simulate animal production as observed in Queensland sheep grazing experiments. A FORTRAN version of the required code for sheep and cattle was written and used in the subsequent analysis. These experiments varied greatly, both temporally and spatially. A number of problems in trial management and methodology were identified, these often required adjustment of recorded data. The collation of trial data was done in a manner that allowed ease of use in computer models. Optimisation software was used to modify parameters and equations within the model in an attempt to improve the agreement between predicted and observed values. Grazfeed was found to be unsuitable using the available test data.Regression analysis techniques were then used to identify climate, soil water, pasture and dietary variables which were able to explain the observed grazing trial variation in annual fleece production and liveweight change. The dietary variables were estimated using a theoretical diet selection subroutine, and a feed intake subroutine based on

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Section: B15 Energy Metabolismmentioning

confidence: 99%

Section: Bl58 Efficiency Of Energy Utilisation For Gain (Kg)mentioning

confidence: 99%