There has been a big push in recent years to cut grass for silage at shorter intervals (typically 28 days), to maximise energy and protein yield. The principal definitely leads to better silage quality, reducing bought in feed costs per litre of milk produced. This system has been made much easier with the availability of high capacity harvesting equipment to cover vast areas in a short space of time, making the most of available weather windows. That said, this system does not always lead to consistent silage at feed out and if not well managed, actually creates more problems than it solves. Inconsistent silages can be more of a headache than consistently mediocre silages, as ration changes and instability causes many hidden problems. Rumen adaptation, ration formulation changes and accuracy at feed out all reduce milk production the very thing that multi cut is trying to increase
There is an assumption that if you cut grass at 28 – 35 day intervals, it will always be the same, but there are more influential factors dictating the quality of silage than just the cutting interval. The most obvious one being the weather. If the crop has only seen rain and cold, like the June we had a couple of years ago, the sugar levels may well be lower and growth may be faster. Similarly, a drought stressed plant will throw a seed head up after maybe only 3 weeks and become far more lignified, reducing its quality.
The more cutting dates you need the more good weather windows you need too, so the chances of getting all 6 cuts in good conditions are slim. Wet harvests will lead to wetter, more butyric silages that feed poorly, however good the standing grass was.
Weather can vary and it is a matter of risk, but one thing that will never vary and always leads to variation in quality is season. As the season goes on, total NDF increases and, more importantly, NDF digestibility decreases. This significantly affects the fibre pools in the rumen and, therefore, rumen balance and milk yield. The reasons behind it becomes more obvious when you think of the role of grass in nature. It captures sunlight that varies significantly with the time of year, so there will be more energy available to grow around the summer equinox. It is also a survival technique. If that plant does not flower, the species will die out. By being cut earlier, it cannot do this, so, by being more lignified next time, there is less chance of it being grazed and more of developing a seed head.
Another big issue on dairy farms is nutrient management. A shorter growing window means less time for any slurry or nitrogen to be applied and taken up. Residue in the silage will affect fermentation, leading to spoil and waste.
All of this aside, we are still better off using a multi cut system and it’s a matter of management to reduce inconsistencies to make the most of it. Here are some tips to help:
- Thin layers in silage pits. The ‘Lasagne’ pitting technique leads to more rolling, better fermentation and a cross section of cuts, reducing the disadvantages of poorer cuts. This ultimately leads to more consistency for the cow and helps to reduce slipping (common place with high quality silages).
- Look at the crop not just the calendar. This may lead to cutting in 3 weeks if the plant is bolting, or 5 if it is still very lush.
- Don’t apply slurry to aftermaths. Almost impossible, but if you do, use a dribble bar or injector, apply lightly (10,000L/ha) especially after summer equinox. This significantly reduces the risk of contamination, which is even more of a problem on sand bedding.
- Cut and pick up in a day. Grass does most of its wilting in the first 6 hrs, so leaving it overnight invariably creates more rotting and less wilting of the crop. Cut from 7am to 3pm, ted from 10am to 6pm. Harvest from 2pm onwards. With lighter cuts there will be enough wilt.
- Use an inoculant. Especially if you think it is a bit tight on nitrate uptake or there is less sugar in the grass.
- Consider companion clamping. Mix in a straight such as wheat feed or a formulated clamp compound as the silage is clamped. This is a very cheap way to buy feed and will aid fermentation and increase dry matter of silage. Highly recommended with late cut silage that is lower in sugar and can often be wetter
By following these points on a multi cut system, the best of both worlds will be achievable. High quality silage with high yields per hectare and consistency at feed out.
Dairy Technical Specialist (Midlands)
m: 07876 824314