Browsing by Author "Farrell, Lydia"

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    Bio-economic system-dynamics modelling to investigate strategic management options in New Zealand sheep farming enterprises : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Farm Management, School of Agriculture and Environment, Massey University, Manawatu, New Zealand
    (Massey University, 2020) Farrell, Lydia
    The average and range of production and profit levels achieved in New Zealand sheep farming enterprises indicate potential for improvement across many farms. Ewe wastage, use of terminal sires, and breed transition to produce higher value wool are issues currently pertinent to the profitability of farms on New Zealand North Island Hill Country with dual-purpose breeding ewe flocks. A bio-economic system-dynamics sheep farm model was identified as appropriate to model these profitability scenarios where changes in ewe flock structure were integral. The objectives of the current research were: to develop the model; validate output through examining ewe flock wastage (premature ewe losses) rates; and use the model to investigate use of terminal (meat breed) sires to increase income from lamb sales, and a gradual flock breed transition from purebred Romney to ¾ Merino ¼ Romney to increase income from wool sales. Component modules were flock dynamics (including sheep sales), sheep feed demand, feed supply from pasture, feed balance, wool production, and economics. Model output aligned with previously published industry data and was therefore considered a realistic representation of New Zealand North Island Hill Country sheep farming systems. Flock wastage rates ranging from 5% to 21% were studied, sheep enterprise cash operating surplus (COS) reduced by $1,069 per 1% increase in ewe wastage rate due to reductions in numbers of lambs for sale. The scope for terminal sire use in self-replacing flocks was limited by requirements for purebred ewe lambs. The maximum proportion of the breeding flock able to be bred with terminal sires ranged from 18% to 65% and was greater with higher lambing rate and lower replacement rate. Maximising terminal sire use increased COS by up to $101/ha compared with no use of terminal sires, due to higher survival and growth rates in crossbred lambs sold earlier for higher prices. Flock breed transition through crossbreeding a Romney flock with Merino sires demonstrated reductions in COS during the breed transition period and greater COS post-breed change. Net present value analysis showed whole farm COS with breed transition to be up to 26% greater than maintaining the purebred Romney flock. Breed transition scenarios with higher Merino-Romney crossbred ewe lamb selection intensity achieved lower average wool fibre diameter, with a longer breed transition period (i.e. ten years of transition) and greater economic benefit. Overall, the model was effective in investigating the selected scenarios and the results can be used to inform decision making of New Zealand farmers.