A later start to the grazing season this year has highlighted some recurring issues regarding the lack of high-quality silage on farms, writes Luke Clogher, Teagasc Walsh Fellowship Masters student, Teagasc Castlerea.
However, it is too often the case that silage quality is not mentioned until October. The harvesting date of silage is the most important factor affecting its quality (DMD%), so it must be planned in advance.
The optimum time for harvesting high-quality silage (>70% DMD) is in late May or early June, prior to the grass getting stemmy and heading out. After grass heading out, silage quality falls by 0.5% DMD per day.
A silage crop will take 6-7 weeks to grow, so fields in the region should be closed from mid-April, for cutting in early June. Ensure silage fields have been cleared of debris (hedge cuttings etc.) and have been grazed to remove the dead butt in the grass prior to closing.
Organising a future herbicide application for weed control is an option too, if necessary. If high covers are present on silage ground, graze quickly with a large group of stock (if ground conditions are suitable) prior to closing.
In a two-cut system, apply fertiliser, close at your target date and cut prior to heading out. This gives time for a second higher quality crop to grow. Applying appropriate rates of fertiliser are essential for getting a good yield (10t/acre) of high-quality silage.
Nitrogen demand depends on sward quality. Newer reseeds with high levels of perennial ryegrass require 125kg/ha (100 units/acre). For older pastures, reduce nitrogen by 25%.
Approximately 2-3 units of nitrogen get used up each day. So if 100 units of N were applied, 50 days should be left prior to harvest to allow full utilisation from the grass crop.
Ideally, a soil test should determine P & K requirements, but a general rule of thumb is that applying slurry at 3000 gallons/acre for index 3 soils is adequate. Slurry should only be applied on low grass covers as it can cake and affect silage quality if applied to leafy swards.
High vs. Low quality
Plan to harvest high-quality silage (>70% DMD) for weanlings, finishers, stores and calved cows especially. To put it into context, cattle fed 75% DMD silage will have a live weight gain 0.52kg/day more than cattle fed 60% DMD silage.
Over a 5-month winter, it’s a live weight difference of roughly 78kg/head. Tighter margins combined with increasing silage costs demonstrate the need to make the highest quality silage possible, as poor-quality silage is very expensive in terms of feed value.
Having high-quality silage gives you options, poor quality quite simply results in reduced performance and increased meal supplementation. Decisions made in the upcoming weeks will determine the cost of production next winter.