The role of higher protein forages and home grown protein sources within Northern Ireland dairy systems.
In order to sustain milk production, dairy cows must have an adequate intake of dietary protein. Within higher output systems cows must be offered additional protein in the form of concentrate supplements. However, these protein supplements are expensive, and are subject to price volatility. In addition, the long term supply of non-genetically modified protein into Europe cannot be guaranteed, while the import of these ingredients has a negative effect on the carbon footprint of local dairy systems. These factors have an adverse effect on the performance of the local dairy sector within the global market place.
For these reasons there is increasing interest in the potential of locally grown ‘protein crops’ within dairy systems. However, there is little evidence that these crops really offer potential to replace imported protein in the diets of dairy cows. In addition, while protein crops have many advantages in that they can be high yielding, have a high nutritive value and fix atmospheric nitrogen (thus reducing the reliance on imported fertiliser nitrogen), these crops can be difficult to establish and grow in Northern Ireland (NI). For example, previous experience at AFBI suggests that the performance of crops such as lucerne and lupins can be unreliable under NI conditions. Nevertheless, a small number of farmers are successfully growing other protein crops. This project will provide the Northern Ireland dairy sector with information on the potential of home grown protein crops to improve performance in the market place.
1. Examine the role of red clover as a ‘high protein’ forage.
This part of the project will establish and monitor the performance of mixed red clover/ryegrass swards and pure grass swards over two years to identify dry matter yields, dry matter losses at ensiling, persistency and ensilage characteristics.
Red clover based forages will be offered to lactating dairy cows as part of their diet and the subsequent impact on animal performance and nitrogen utilisation will be assessed. An assessment of the economics of systems involving red clover will be made.
2. Examine the role of crops which provide high protein ‘grains.’
This part of the project will examine the role of locally grown field beans in dairy cow diets. Locally grown bean crops will be sourced, and issues such as maximum inclusion level, potential to replace conventional protein sources (soya, rape meal), and optimum treatment strategies (crimping, heath treatment, milling), will be examined.
This project has a primary focus on the milk production benefits and nutrient use efficiency associated with offering protein crops. Whilst the integration of ‘plant breeding’ and detailed agronomy into this proposal has been considered, it would not be possible to make any significant progress in these areas within the project time frame and budget.
Assessing the potential of red clover/ryegrass swards:
The majority of previous studies (including those at AFBI Hillsborough) have examined the potential of red clover when grown as a monoculture. However, due to difficulties which arise when ensiling these monoculture crops, there has been limited uptake of this practise on local farms. In addition, most previous feeding studies have involved the use of monocultures, with these sometimes mixed with grass in various proportions at the time of feeding. The current project moves away from the use of red clover monocultures, by growing the crop in combination with ryegrass. This approach will allow the following knowledge gaps to be addressed:
- The impact of mixed red clover/grass swards on yield of herbage produced, chemical composition of the herbage produced, and persistency of the two species within the sward. Impact of fertiliser/manure applications, especially on harvest 1 yields, and the impact of vehicle traffic on crop survival.
- Ensilability of mixed red clover/grass swards, including fermentation processes, losses and aerobic stability.
- Nutritive value of silage produced from mixed red clover/grass swards when offered to dairy cattle, including their concentrate protein saving effect and the long term effects of their inclusion on cow performance.
- Effect of offering these mixed red clover/grass swards on the digestibility of the diet offered, and on nitrogen and energy utilisation efficiency, including methane losses.
- Economics of growing and feeding red clover/grass mixtures within Northern Ireland.