Keep on top of grass quality

June is one of the most important months in the grazing season. Grass growth will usually reach its peak and trying to manage grass quality is a difficult challenge. Even the best grassland managers will not prevent grass from heading out in June. Grass is a plant and will turn to a reproductive phase, whereby it produces a seed head, at some point this month.

How well grazing swards are managed from now until autumn will have a big impact on cattle performance for the remainder of the grazing season.

As grass turns to stem and produces a seed head, the feed value of the sward quickly declines. The main reason being there is less leaf present and more stem, which is less digestible.

Good grazing management means you should be removing this stemmy grass from swards now, otherwise this grass will die off. This can be carried out by:

Leaving the sward with a high percentage of white, dead grass will reduce grass growth for the remainder of the year.

In contrast, where swards have been topped to remove stemmy grass, lush after-grass will have a much higher feed value, as leafy swards are more digestible, thereby increasing grazing intakes.

The more high-quality readily digestible grass you can get cattle to eat, then the higher their daily liveweight gain or milk production.

Table 1 outlines the feed value of five grass swards. Grass samples were taken last week to compare these swards for dry matter, energy (UFL), protein, fibre and DMD. The swards are also shown by the photographs included on these pages.

Picture 1 – Sward one

This sward has a high average cover of around 3,500kg DM/ha. Grass quality is still good, with an energy value of 0.92 UFL and 73 DMD. The sward is well tillered and dense, with a good level of clover present.

The sward has been grazed twice this year and on both occasions it was cleaned out fully, which has helped to keep quality so good. It was last grazed in late May and no fertiliser was applied as growth was ahead of cattle demand.

The lack of nitrogen applied will also have led to a lower than expected crude protein level. The amount of stem was increasing in the sward, with some seed heads fully developed, while more seed heads were beginning to emerge.

Grazing this sward is still possible, but it would be better off baled for silage. If cattle are to graze this sward, use an electric fence to strip graze in small, daily allocations to avoid waste and to ensure that cattle are grazing down tight to the sward base. But in doing so, cattle will be eating more and more fibre. This means intakes will be reduced.

The other consequences of grazing this sward are that as the grass continues to head out, feed value will decline. The grass quality in subsequent grazing paddocks will also start to get out of control the longer cattle are left to graze this sward. Therefore, be brave and take this sward out for silage. Given the feed value, it would make a high-quality winter feed.

Best action: Close paddock and remove as baled silage.

Picture 2 – Sward two

This sward is at an ideal stage for grazing after an 18-day rest. The sward height is around 10cm. It will be easier to graze this sward out fully and to keep to a three-day grazing period before moving on to the next paddock. Therefore, you will get a faster regrowth from sward two compared with sward one.

Grass quality is excellent. Energy is high at 1.0 UFL, which is similar to dried barley. Protein is high at 17.7%, which will help to drive growth in store cattle. There is also a lower fibre level in sward two compared with sward one. Therefore, grazing intakes will be higher.

This sward is ideal for grazing growing cattle or spring-calving cows to help increase milk production. Grazing such a sward with spring-calving cows will also help to improve cow fertility, as dry matter energy intake will be high.

Best action: Target this paddock to be grazed within the coming days with growing cattle or spring-calving cows.

Picture 3 – Sward three

Sward three is an older sward with a high percentage of less productive grasses present. The sward is more or less fully headed out. Feed quality is much lower than sward two. It is also lower than sward one in terms of energy and DMD.

The sward is growing in a wetter paddock, which makes it harder to manage during wet conditions. Over the years, it has been poached, which allows weed grasses to become established. It also receives less nitrogen than swards one and two, which allows older grasses to remain competitive.

The problem with this sward is that with so much grass turned to stem and seed, there will be a high level of rejected grass after grazing. If this sward is not topped after the next grazing, this sward will quickly die back and drop further in terms of feed value.

Grass growth will be low for the remainder of the year, which reduces the productivity of the paddock. This is a paddock that should be marked for reseeding.

Best action: Strip graze with dry autumn-calving cows and top afterwards.

Pictures 4 and 5 – Sward four

Sward four is similar to sward one, but it shows what can happen from trying to graze very heavy grass covers with cattle. The sward has become very mature and there is a high level of trampled grass, as well as rejected grass. Cattle have selectively grazed any younger, leafy grass plants present and left behind the grass that has turned to stem.

This sward was too strong to be grazed and should have been closed for silage. But it was felt by the farmer that it could still be grazed effectively. Cattle were still present in the paddock when the sample was taken.

Picture 5 shows a sample of the sward and how much stem is present. The feed quality is poor in sward four. Energy and protein are low, as is DMD. Fibre is very high at 37%. You should target grazing swards to have below 30% fibre.

Despite the best efforts, cattle will not graze this sward clean no matter how long they are left in the paddock. Instead, animals will most likely become unsettled on this sward. Cattle performance will suffer while they are left in this paddock. Liveweight gain will be low and cows will produce less milk on this sward.

Best action: Move cattle on to a more suitable grazing sward. Then top the sward to the base and apply nitrogen to kick-start growth.

Pictures 6 and 7 - Sward five

Sward five had the highest feed value of the five samples. The sward pictured shows a 16-day regrowth and, as picture six shows, the sward consists mainly of short, highly digestible grass leaf.

The energy level of the sward is 1.02 UFL, crude protein level of 21.5% and 84 DMD. The protein level will sustain high levels of growth and probably reflects some residual nitrogen in the sward.

The results show just how a well managed grazing sward can provide a high-quality feed. Trying to maintain swards so that cattle are grazing grass like in sward five or sward two will deliver heavier cattle at the end of the grazing season.

This means heavier weanlings and store cattle to sell in the marts. It also means heavier finishing cattle that will have a shorter intensive indoor feeding period. Less concentrates fed to cattle will improve the profit margin generated.

Best action: Target sward for grazing within the next week with growing cattle or spring-calving cows.

Summary

The management of grass over the next fortnight will influence how heavy cattle are in autumn and how much meal will be required for finishing animals.

For growing cattle to gain 1kg of liveweight/day from a grass diet from now onwards, they need to be grazing grass with a high leaf content, like in sward five (pictures 6 and 7). Grass swards that have headed out need to be topped or grazed out using a group of lower priority stock to clean off – eg dry cows or ewes.

Do not force growing cattle to graze off swards with a high percentage of stem.