P.PSH.1044 - Improving the use of forage brassicas in mixed farming

Summary

his project aimed to validate the potential of forage brassicas to fill feed gaps in livestock systems across the mixed farming regions of Australia. Multi-site evaluation of a diverse range of forage brassica types showed that several genotypes produced similar or higher yields of metabolizable energy than forage cereals. This was further confirmed with long-term simulations of productivity under a wide range of climatic conditions and environments.

Incorporation of forage brassicas into pasture-dominant forage systems was predicted to reduce the frequency and magnitude of feed deficits by 20-45% or allow stocking rates to be increased by 10-20% without increasing risk. Despite the opportunities, forage brassicas can accumulate secondary compounds that present some animal health risks and grazing management challenges for producers.

Glucosinolate concentrations, which influence animal palatability and intake can vary dramatically amongst genotypes, production environments and in response to management. Similarly, nitrate concentrations at concerning levels were common, but may be mitigated by high soluble carbohydrates in forage brassicas.

The project has sparked growing interest and adoption of forage brassicas through communicating emerging information and recommendations widely and via 22 on-farm demonstrations where forage brassicas were tested in diverse livestock systems.

Objectives

• Explore the potential of new forage brassica options to provide alternative options to fill feed gaps in mixed farming regions. Multi-environment evaluation of diverse genotypes, coupled with development and application of simulation modelling enabled predictions of the productivity and relative performance of forage brassicas compared to current forage options across Australia’s mixed farming regions.
• Understand factors influencing variable livestock performance and animal health risks when grazing forage brassicas. Experiments focused on the influence of brassica genotype and growing environment on animal behaviour and performance, and relationships with the presence of anti-nutritional secondary compounds.

Key findings

• Forage rapes and raphnobrassica cv. Pallaton were found to perform well across many mixed farming regions, particularly under drier conditions, where they either matched or exceeded the yield of metabolizable energy provided by forage cereals.
• Simulation modelling showed that brassicas offer largest advantages over forage cereals in later sowing windows in medium rainfall regions, and where feed shortages during late winter and spring occur frequently.
• Incorporating 15% of the grazing area to forage brassicas across many different production systems has the potential to reduce the frequency of feed gaps by 25-40% or increase stocking rates by 10-30%.
• The accumulation of secondary compounds such as nitrates and glucosinolates are a widespread occurrence in many forage brassicas, posing animal health risks and reducing forage acceptability and hence animal growth. Crop nutrition, growing environment and genotype all seem to influence their expression, but these are difficult to predict.

Benefits to industry

This project has demonstrated the wider potential and benefits of using forage brassicas in mixed farming systems to diversify both forage and cropping systems and reduce the frequency and magnitude of feed gaps. Forage brassicas can often provide higher quality forage than forage cereals and produce more metabolizable energy per hectare thereby improving animal production.

Our analysis and on-farm demonstrations suggest there is potential to safely increase farm stocking rates by 10-20% or reducing supplementary feed requirements by 20-45% by integrating forage brassicas into the current farm feedbase in many regions. Forage brassica seed sales have increased by 25% over the life of this project, indicating that already there is significant uptake by industry.

MLA action

In collaboration with CSIRO a factsheet is being developed for including forage brassicas in mixed farming systems. Preliminary discussions have commenced regarding further MDC partnership with CSIRO and DLF Seeds to implement recommendations arising from this project.

Future research

There is a significant case for the wider application of forage brassicas in new regions. An ongoing program of supported on-farm testing and evaluation, coupled with advisor training, would further assist wider adoption, and avoid potential pitfalls associated with implementing forage brassicas into livestock systems. Our engagement with industry and results from this work has highlighted three key research and development needs to support better management and avoid risks for producers adopting forage brassicas, including:

• Deeper understanding of the mechanisms and management options for reducing risks of high nitrate and glucosinolates, and their subsequent impacts on animal health and performance.
• Regional research to optimise the agronomy (e.g., sowing rates) and nutrition of forage brassicas, as the existing recommendations were developed under higher productivity environments.
• Examine forage mixtures that include forage brassicas for their potential to mitigate animal health risks, provide more balanced diets, and lengthen the grazing season compared to currently used monocultures.