Limits on GM experimentation in New Zealand mean the next stage of research, field and animal trials, may take place off shore.
The work was led by AgResearch science team leader, plant biotechnology, Greg Bryan and principal scientist Nick Roberts.
- It is essential to improve our forage species to increase productivity.
- Advancement in forage performance through plant breeding has created productivity gains of less than 1 percent a year.
- AgResearch has developed genetically modified (GM) forages with significantly greater energy content and growth rates.
- Results from glasshouse experiments indicate these forages could dramatically improve productivity at the same time as reducing greenhouse gas (GHG) emissions.
- Field and animal nutrition trials are necessary to confirm the value of these novel forages for New Zealand’s pastoral industry.
Improving our feed supply
Have we maximised the productivity of our pastoral based system? Without new technology, the best farmers probably have. There are a number of farmers that could make increases in productivity by adopting existing technology and management practices. However, once done, they too will face limitations to further productivity gains.
So what technology could make major improvements in productivity without significantly increasing the cost of production or the environmental footprint of dairy farming?
One answer is reducing the cost of our feed supply through better performance of our forages. In 2013, the cost of our feed supply was approximately $1.50 per kg milksolids1. This is the one area with significant potential to reduce cost.
It is no surprise then, that the pastoral sector in New Zealand places a strong emphasis on improving the performance of our forages. The genetics of perennial ryegrass and white clover are complex and provide a challenge for breeders trying to make improvements in dry matter yields and forage quality. The annual improvement in forage productivity has been below 1 percent and there is little evidence that this has led to improvements in animal nutrition2.
Recently, a significant breakthrough in forage biomass and energy concentration has been achieved by AgResearch using GM. The plant biotechnology team at AgResearch has developed a technology to enhance photosynthesis3 in ryegrass plants by increasing levels of lipids (fat molecules) in leaves.
Growth rates faster
The crucial advance out of the technology named High Metabolisable Energy (HME) is significantly enhanced growth rates of these plants. Perennial ryegrass plants have been developed in the glasshouse that have 25-40 percent faster growth rates. This is due to increased CO2 assimilation, so effectively more efficient photosynthesis. In a model plant species (the equivalent of the lab rat for plant scientists) called Arabidopsis, the increase in carbon assimilation is 24 percent³. In HME perennial ryegrass lines in Figure 1 below, the increase in carbon assimilation is 20 percent.
More metabolisable energy
HME ryegrass is also likely to have more ME (about 10 percent) available for conversion by animals. This has yet to be determined from animal feeding trials, however, in a trial of ram lambs, groups of animals were drenched with additional lipid to simulate HME forage. Lambs with a lipid intake of 8 percent ate 16 percent less forage than pasture-only control lambs but achieved the same live-weight gain. The forage conversion efficiency increase in the high lipid animals was 30 percent4. This experiment used ram lambs on ideal pasture. HME forages may have greater benefits for lactating animals.
The enhanced growth rates of HME ryegrass is demonstrated in Figure 1 below. Simulated grazing has been conducted in pot trials in the glasshouse. Over a period of 30 months plants were clipped every three to four weeks and allowed to regrow. The simulated grazing has been repeated over 30 times and the enhanced growth rate was consistent.
How does HME work?
There is limited genetic variation in plants for leaf lipid levels and the normal level of lipids in forage plant leaves is about 3.5 percent. The HME technology enables the accumulation of seed like oil bodies in the green tissue of plants and increased lipid production. HME plants have 8 percent total leaf lipids and therefore more potential ME. The increased lipid production results in recycling of CO2 in the cell which leads to significantly increased CO2 assimilation. The enhanced photosynthesis results in accelerated plant growth (by up to 50 percent in some cases) and therefore more biomass and resulting dry matter.
Benefits for dairy production
It is unknown exactly how much of the enhanced growth rate and energy benefit measured in glasshouse experiments will translate to plants grown in the field. These experiments need to be performed in carefully designed replicated field trials in multiple environments over two or more seasons. It is important to determine if the plants are more or less susceptible to stress, insects, disease, have normal reproduction, and assess their response to water stress.
It will also be essential to conduct animal nutrition trials to measure animal performance, safety, metabolism, determine the fate of the additional lipids in animal products, measure greenhouse gas emissions and identify if there are any negative effects.
AgResearch has conducted modelling to explore the potential of HME forages in a dairy and beef and lamb production system. The modelling and laboratory work conducted so far includes the following potential benefits: a 12 percent increase in MS production, improvements in animal fecundity, possible increases in liveweight gains, 17 percent decrease in N2O emissions, 15-30 percent decrease in methane emissions, more options for pasture management due to greater pasture growth rates, improved drought tolerance due to enhanced root systems and improved water use efficiency. It is also possible changes in milk and meat lipid composition may provide human health benefits due to an improved ratio of unsaturated to saturated fat.
The trade-offs for adopting GM crops in New Zealand
The arguments for and against the adoption of GM crops in New Zealand are numerous. To date, GM crops grown overseas do not provide a compelling value proposition for New Zealand as the species (corn, soybean, canola, cotton, papaya) are not significant crops in New Zealand. For these reasons there has not been a significant need to debate the merits of these technologies in New Zealand.
New Zealand forage species are specialised for temperate pastoral grazing systems and do not have the massive acreages of the main arable crops corn, soybean and cotton. This has meant that forages have not been a major focus of the developers of these arable crops. It has been necessary for New Zealand to develop technology directly applicable to its pastoral grazing system. The HME technology developed by AgResearch using government funding is ‘home grown’ and free from any commercial constraints of the main GM crop producers.
AgResearch is currently investigating options to test these forages offshore with a tentative start date of 2017.
1. DairyNZ Economic Survey 2014-15 dairynz.co.nz/publications/dairy-industry/
2. Crush, J. R., S. L. Woodward, J. P. J. Eerens, and K. A. Macdonald. 2006. Growth and milk solids production in pastures of older and more recent ryegrass and whiteclover cultivars under dairy grazing. New Zealand Journal of Agricultural Research 49: 119-135.
3. Winichayakul, S., R. W. Scott, M. Roldan, J-H. B. Hatier, S. Livingston, R. Cookson, A. C. Curran, and N. J. Roberts. 2013. In Vivo Packaging of Triacylglycerols Enhances Arabidopsis Leaf Biomass and Energy Density. Plant Physiology 162: 626-639.
4. Cosgrove, G. P., C. B. Anderson, T. W. Knight, N. J. Roberts, and G. C. Waghorn. 2004. Forage lipid concentration, fatty acid profile and lamb productivity. Proceedings of the New Zealand Grassland Association 66: 251-256.
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