Mid-season grass, secret of success

There has been a lot of very early season grazing this spring, and with suitable conditions, pastures were generally well grazed to less than two inches and were in great shape facing into April. However, very cold and wet April/May weather resulted in very poor growth and grazing conditions.

A lot of supplementation and on /off grazing were necessary. Complete indoor feeding for periods was required in many areas to avoid damaging pastures.

Many farmers are unnecessarily overstocked for their type of farms and also for their quotas.

They are influenced by hype about carrying 2.9 cows per hectare, but the grass and/or land type on their farms fall short of requirements.

These farmers are particularly punished in years like this, because their winter feed is also likely to be scarce, and many have already fed most of the areas closed for next winter’s silage.

Generally farmers with 2 to 2.5 cows per hectare (1 cow/acre), with good yields per cow, are under a lot less pressure than those farming on the edge. They will have better opportunities to make up for the loss of grass in April/early May than those heavily stocked.

The most important task for every farmer now is to get all grassland back into good shape after a very difficult and costly period.

Adequate fertiliser has to be applied, and this depends on what it has received already. High N compounds containing NPK and sulphur will be required where these minerals may be low.

Extra nitrogen (within directive limits) will be required sooner rather than later to avail of good growing conditions. Preparations must also be made as soon as possible to ensure adequate winter feed.

How good is our grass?

Research and findings from Teagasc monitor farms indicate that high quality mid-season grass is one of the most important factors for profitable milk production and particularly for the milk protein percentage. As mid-season grass quality varies, so do the protein percentage and milk yields.

Most of the milk from spring calving herds is produced from mid season grass.

Based on the average lactation stage of Irish cows, milk protein should keep rising from May, but milk supply trends show the opposite is the reality. In fact, average milk protein generally drops to about 3.25% in June and to almost 3.2% in July. From July the protein rises steeply to 3.3% in August, 3.45% in September and to almost 3.6% in October when it flattens out for the remainder of the year. This is a strong indication that mid-season grass quality is not as good as it should be on a lot of farms.

Grass quality

Research in Moorepark a few years ago by Michael O’Donovan and colleagues has given excellent guidelines for mid-season grassland management. The research was carried out between mid-April and mid-October 2010 with pre-grazing grass covers of 1,000; 1,500; and 2,300 kg DM/ha. All swards were grazed down to 4.5 cm.

This research indicated that cows should not be going into low grass covers of around 1,000 kg. Apart from growing less grass, low pre-grazing covers and short rotations are difficult to manage and are prone to deficits of grass, especially in poor growing conditions.

Heavy covers over 2,000 kg are also difficult to manage and grass can easily get ahead of cows and very often a lot of bales have to be taken off to control quality. A pre-grazing cover of around 1,400 kg to 1,600 kg seems ideal from the point of view of grass growth and ease of management. At reasonable stocking rates, it also allows closing up a sufficient area in late March/early April for a good crop of first cut silage.

In order to have top quality mid season grass, preparation should start in early spring by achieving a low stubble height of less than 2 inches (4.5cm) and maintaining it right through the season. Sometimes this is difficult to achieve on heavy land. Grazing to 2 inches will maintain a low stubble height but a tight topping during the first half of the grazing season may be necessary on some farms. If tight grazing results in the under feeding of cows they should get adequate supplementary feeding. When a low stubble height is maintained all the grass above this level in subsequent rotations will be highly digestible and palatable and will facilitates high intakes.

Grass quality is measured mainly by its dry matter digestibility (DMD). Most farmers are familiar with silage DMD, but not of grass DMD even though it is more important. Good quality grass will have a DMD of over 80 while poor grass will be less than 70. Good quality grass will support yields of 6.5 gallons and increases milk protein by around 0.2%. Poor quality grass will only support yields of 4.0 gallons and depresses milk protein.

Grass quality has a major influence on cow performance as indicated in the table (see table, above).

As can be seen from this table, not only can cows eat more of the good grass but also each kilo of this grass contains a lot more energy (The same applies to high and low DMD silage).

The limitations of poor pasture are also likely to be a significant factor causing infertility in cows.

Too many farmers give priority to the quantity of mid season grass rather than quality. Poor grazing conditions such as cold/wet weather will also reduce cow intakes of grass.

Most dairy herds are capable of milking in excess of 6 gallons per cow per day during the main grazing season. Yet the majority of dairy herds fall short of 5 gallons. This indicates that either the majority of grass quality is below standard or that cows are forced to graze too tightly and are underfed.

Old pastures

Pasture species not only have a big influence on pasture production but also on digestibility.

For example, good ryegrass will have a DMD of around 80, while Yorkshire Fog and Bent grass are likely to be around 70 DMD. This emphasises the value of reseeding old pastures that are low in ryegrass. Teagasc surveys indicate that grass production can be increased by 25% to 50% on most farms.

On the Teagasc / Co-Op monitor farms, it was found that when reseeded pastures were compared to old pastures, protein content in milk consistently rose by up to 0.2%.

Of course it is essential that cows have sufficient grass available and not forced to graze too tightly or forced to graze grass that is too strong.


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