Beat the drop: A guide to grassland management

Cows are into peak lactation at this point, so you should be seeing exactly how much body condition they have lost over the last six weeks or so.

We must now begin to match supply and demand when it comes to intake so that we are entering into a positive energy balance situation. This is especially important around breeding.

High volumes of milk at this time of year can be accompanied by low-percentage solids. One of the causes of this is that the cow is putting all her efforts into pushing out litres at the expense of body condition, or “milking off her back,” as it is often referred.

Beating the drop in milk solids while cows are coming into peak lactation, while also ensuring the cow is in the optimal body condition score (BCS) for breeding, makes April a crucial month in the calendar.

The majority of the diet going forward will be from grazed grass. With a delayed start to grazing this year and grass growth slow in many parts of the country, spring rotation planners (SRP) will have been mostly abandoned.

The number of days at grass may be reduced by 15–20 days in some cases. Where, typically, farmers would aim to begin the second rotation on April 1, this year most farms will be looking at April 15 as a more realistic target.

As discussed in previous articles, if grassland management has been good, then second-rotation grass becomes lush and leafy, making it an extremely powerful feed for cows. It is the ideal driver of milk output but can harm butterfat percentage.

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During this time of the year, the grass is high in energy and protein but lacks fibre, as well as high oil content. Cows eating 17kg of grass dry matter (DM) testing over 1 UFL have the potential to produce 22L, with enough protein, at 25% content, to support 42L.

The cows cannot absorb all this excess protein and, as a result, the majority is converted into urea (which has an energy cost) and lost in the manure.

In order to get the most out of second-rotation grass, the cow’s rumen needs to be stable, healthy and low in acidity (pH >6). Increasing the fibre content of the diet can help maintain a healthy rumen and slow down the rate of grass digestion, meaning cows will get more utilisation.

In the absence of forage/straw buffer when grass is sufficient in volume, the use of a parlour feed that has high fibre content and contains a live yeast, such as Yea-Sacc®, will help to maintain a stable rumen while grazing second-rotation grass.

A healthy rumen with adequate fibre levels will lend itself to sufficient levels of butterfat and protein. It also helps negate the effects of the oil content of grass, which can negatively impact on butterfat.

The inclusion of forage or straw-based fibre in the diet through “buffer feeding” or supplementary feeding will further promote rumen function and maintain rumen pH. Farmers may consider buffer where pre-grazing covers are low and to support intakes in higher-yielding herds.

Factors for good grassland management

1. Residuals

Difficult grazing conditions this spring mean that many farms may not have grazed out paddocks to the optimal post-grazing sward height.

First-rotation grass is generally high in DM, but also has high amounts of dead organic matter too. With this in mind, it is vital to ensure a residual of 4–5cm from now on, restoring quality to the sward for following rotations.

2. Understanding regrowth

So as not to undo the great work of the cows in achieving residuals of 4cm, it is vital to understand the important part regrowth plays in the entire system.

Regrowth can occur six to seven hours after a paddock is grazed out. If cows are in a paddock for too long and cows begin to nibble at regrowth, then this can reduce the volume in the next rotation as grass takes longer to re-establish itself post-grazing.

Power in numbers is the phrase that comes to mind when discussing grass-regrowth protection. Moving through a paddock as quickly as possible will help to protect the paddocks regrowth.

A 36-hour grazing infrastructure and having the correct paddock size for the number of cows grazing are vital here. A herd of 100 cows will need a 1.9ha (4.8ac) paddock.

Paddock shape also plays a crucial role in protecting grass regrowth. A square paddock will encourage the group to graze as a mob. Try to avoid long, narrow paddocks, as the cows will have to track back over the regrowth when entering and exiting the paddock for milking.

Back fencing is also an option to consider when strip-grazing larger paddocks.

3. Rotation length

Rotation length is, essentially, determined by growth rate. The optimum rotation length is based on the week’s daily growth rate.

The table (below) outlines target rotation lengths with growth rates. The higher the growth rate, the shorter the rotation length needs to be. By hitting the right balance, the grass should reach the three-leaf stage, which is ideal for cows to get the best out of this feed.

4. Pre-grazing cover

Targeting ideal pre-grazing covers of between 1,400 and 1,500kg DM/ha from the second rotation onwards will lead to entering grass at the three-leaf stage. A cover of 1,400–1,500kg DM/ha is the equivalent of 8–9cm of grass.

Entering covers that are too high (above 1,500kg DM/ha) should possibly be skipped in the rotation and taken out as surplus bales or used for other stock. Methods to avoid grass from going ‘too strong’ in front of cows include increasing the demand on the grazing platform.

Be careful not to push demand growth rates higher than 70kg DM/ha/day, or you may find yourself short. Introducing extra stock onto the grazing platform can increase the demand for grass and, as a result, can control the covers that the cows are going into.

Putting the above measure into practice will help you to better manage the grass in front of your cows this season. By understanding not only the quantity of grass going into cows but the quality, it is possible to get the most out of this feed without compromising on milk solids.

Meeting the cows’ nutritional demands by understanding how grass works in the animal will allow for better management of a feed that makes up to 90% of the diet this season and enable you to beat the drop.

To watch Alltech’s ‘Beat the Drop’ video, click here

For more information on solutions to help ‘Beat the Drop’, click here.

Article 1: Beat the drop: Recognise it early and protect your profits
Article 2: Beat the drop: Getting to the root of the problem
Article 3: Beat the drop: Putting farm solutions and management into practice

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