Maximising summer feed utilisation

Global food production systems have experienced some unprecedented challenges during the past 18 months. Irish farmers have faced many adversities, including extremely volatile consumer markets, extraordinary climate change-related weather events, and record increases in production costs. These increases in farmgate production costs can be partly attributed to imported feed cost inflation. The vast majority of animal feed production on Irish farms is grass-based; typically, grazed grass (€0.121/kg dry matter [DM]) and silage production (€0.204/kg DM) costs on pasture-based farms comprise most total variable costs. Since these costs have increased considerably, it is imperative to fully utilise this feed source.

Major input costs to producing good-quality grazed grass and silage in Ireland include fuel, electricity, contractor charges and nitrogen (N) fertiliser. Irish farmers have demonstrated their resilience and commitment to Ireland’s climate change targets through reducing dependency on chemical N fertiliser usage. Preliminary statistics from the Department of Agriculture, Food and the Marine show a 55.9 per cent decrease in sales of N fertiliser in the period between October 2022 and April 2023, when compared with the same period for the previous year.

Even with this reduction, farmers can reduce feed costs and improve summer grass and winter silage utilisation through: appropriate grassland management; and getting the silage-making process correct.

Grassland management

Good grassland management usually forms the cornerstone of any grazing system, and it is a simple process, though it is often overthought and overcomplicated. A grazing farm should set out these targets:

• Extend the grazing season from early spring into late autumn where possible.
• Ensure that the calving/lambing pattern of your herds/flocks coincides with the onset of the growing season.
• Match your farm stocking rate with pasture growth potential.
• Maximise productivity and feed utilisation through soil fertility and reseeding.
• Ensure that good grazing infrastructure is in place.
• Use appropriate grassland management decision support software, such as PastureBase.

Table 1 sets out grassland management targets for a milk production system over a typical grazing season.

In an ideal scenario, June through August is a time when Irish farmers can operate in cruise control, maintaining a low cover/cow in line with normal-to-high growth rates. Rotation length should be maintained at 18-21 days, but this will depend on growth rate. For example, where growth rate is 60kg DM/hectare (ha)/day and target pre-grazing yield is 1,300kg DM/ha, target rotation length = target pre-grazing yield (1,300)/current growth rate (60) = 21.7 or 22 days. Target pre-grazing yield should range from 1,200 to 1,500kg DM/ha, while target graze-out height should range from 4-4.5cm. In a milk production system where cows graze, if cover/cow is above the threshold of 190kg DM and growth rates are high, surpluses should be removed almost immediately to bring this grazing land area back into the grazing rotation. Using a mixture of early-, mid- and late-heading grass cultivars in seed mixes will provide a more even spread of high-quality feed to livestock over the grazing season.

Recent University College Dublin research has highlighted the importance of grazing multispecies swards. Aside from the ability of species-diverse swards to produce herbage under restricted artificial N fertiliser scenarios, they are more drought-tolerant and more capable of sustaining high growth rates during drought periods when compared with perennial ryegrass-dominant grazing swards. Some farmers will pre-mow enough grass to feed cows for up to 24 hours, maximising utilisation of pasture during periods of high growth rates. Zero-grazing is also an option to make the best use of grass grown on land blocks that are inaccessible to the herd. However, grass should only be zero-grazed from swards that were previously topped or mechanically worked to maximise palatability and thus utilisation. Zero-grazed grass should have similar pre-grazing yields to that of grazed swards (1,200–1,500kg DM/ha). At times when seed head is being produced and pre-grazing covers are greater than 1,500kg DM/ha, cows should not be forced to graze out to 4cm, as this will reduce milk production. Cutting losses, grazing to 5-6cm (bearing in mind that 1 cm = 250kg DM/ha) and topping is advised here so that grass quality is not impacted in the following grazing rotation.

The silage-making process

Silage-making is an important process, and results will determine:

1. How well homegrown feed will be utilised in terms of winter animal performance (Table 2); and
2. What level of imported concentrates will be required.

Second and third-cut silage-making is well underway at this stage in July. Once this is completed, farmers should bring silage ground back into the grazing rotation, thus extending rotation length.

While Table 2 applies to earlier-cut silage, the principle that letting silage crops 'bulk out' will undermine animal performance still applies to second- and third-cut silage.

The success of the silage-making process can be influenced by several factors:

• Nutrient management.
• Grass varieties.
• Weed control.
• Cutting date.
• Ensiling process.

Nutrient management: For best-quality silage, apply the correct amounts of macronutrients (nitrogen, phosphorus and potassium) at least six weeks before the planned cutting date.

Grass varieties: When reseeding silage ground, it is important that tetraploid grass varieties predominate the grass seed mix. This information will be given on the seed label.

Weed control: For the herbicide to work, docks, nettles, thistles, etc., should be sprayed in the springtime, when weeds are growing rapidly with leaf cover available.

Cutting date: It is also important to bear in mind cutting date, as this can determine dry matter digestibility (DMD) of the crop. Every farmer’s silage crop will be greater than 75 per cent DMD at some stage. The DMD content will decrease by two to three percentage units per week from the second half of May, mainly due to the increasing stem proportion in the plant. The same applies for second-cut silage in late June and early July.

Ensiling process: This can have a huge effect on silage quality. Maintaining low grass nitrate and high sugar readings is key for the fermentation process to work effectively and for silage pH levels to decrease as quickly as possible. A silage additive such as Egalis will help speed up the fermentation process where all other good silage-making practices have been completed. These include:

Cutting grass when sugars are high (>3 per cent on Brix refractometer) and nitrates are low (<600 parts per million).

Keeping the crop dry (27–30 per cent DM).

Achieving adequate compaction in the pit/baler.

Ensuring that the silage wrap/plastic remains intact so that no air gets through.

Protecting plastic from birds and other vermin with nets, covers, etc.

All of the aforementioned practices will also aid in the feeding-out process.

Additional helpful tips to minimise waste include: feeding out enough silage for a maximum of 24 hours in warm weather, moving across the pit face in 48-72 hours, and regularly cleaning refusals away from the feed passage.