School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemAssessing the value of novel perennial ryegrasses (Lolium perenne L.) for the Australian dairy industry( 2014)The value of increasing the metabolizable energy (ME) concentration of grass using a genetically modified high-fructan perennial ryegrass (Lolium perenne L.)(‘GM ryegrass’), was assessed in this thesis. This included: an assessment of the expression of the fructan trait and effects on rumen fluid chemistry (in vitro), simulating potential profitability and greenhouse gas (GHG) emission effects on-farm, and the scale and distribution of benefits from changing the ME concentration of perennial ryegrass to the Australian dairy supply chain. The GM ryegrass was associated with an increase in herbage dry matter (DM) energy concentration between 0.8 megajoules (MJ) and 1.74 MJ of ME per kilogram (kg) of DM. In vitro experiment results indicate increasing the concentration of fructan in the GM ryegrass did not adversely affect rumen pH or methane production. Two representative dairy farms (in Terang in south-west Victoria and in Elliott in Tasmania) were used to provide context for the assessment of the value of increasing the ME concentration of perennial ryegrass herbage. Deterministic economic values, in Australian dollars (AUD) of AUD237/hectare(ha).year and AUD592/ha.year for a 1MJ/kg DM increase in pasture energy concentration were calculated using the replacement cost method for Terang and Elliott dairy farms respectively. Further economic modelling using a mechanistic pasture growth model was used to assess how farm operating profits (OP) changed when additional energy from the GM ryegrass was utilized through various management practices. Results indicate even greater changes in OP could be achieved compared to the replacement cost method if energy was utilized with greater milk production per cow. When energy was utilized through greater milk production per cow a 1MJ/kg DM increase in energy concentration was associated with an AUD482/ha.year mean increase in OP in Terang and a AUD783/ha.year increase for Elliott. Dilution of GHG emissions across the additional milk produced from cows consuming the GM ryegrass was estimated to reduce GHG emissions intensity (EI) of milk by 10% in Terang and 13% in Elliott compared to the Base Scenario. Mean total benefits to the Australian dairy supply chain from adoption of the GM ryegrass based on a 1MJ increase in energy concentration were estimated between AUD205 million and AUD300 million (as a net present value) over a 15 year period. This study also provides sensitivity analysis of the results to changes in key assumptions such as the rates of adoption and elasticities. Estimations of benefit at the Australian dairy supply chain level were calculated using an equilibrium displacement model assuming a 10% discount rate and farmers who adopted the GM ryegrass (‘adopter’ farmers) renovated 10% of their farm area into the GM ryegrass. Australian consumers were estimated to receive most (70%) benefit from farmer adoption of the GM ryegrass, followed by farmers and suppliers of the seed technology (26%). Benefits suppliers of the seed technology receive will depend on how the GM ryegrass is licensed, competition amongst seed companies, and how rapidly farmers adopt the GM ryegrass. Results from this thesis therefore supports the hypothesis that increasing expression of fructan concentration in perennial ryegrass could increase the energy concentration of herbage DM to provide significant increases in OP and reductions in GHG EI for farmers who adopt the technology. Results also provide valuable information for decision-makers for allocating appropriate resources toward deregulation of this GM ryegrass.