To Grow More Grass – Keep to a 20 Day Rotation

The results from over 1,400 grass silage samples sent to the Dairygold laboratory for analysis are in, and there is very little difference in the average DMD (feeding value) of silage made in 2014 versus 2013 (69.4 versus 69.1) or in the crude protein level (11.7 versus 11.8). Averages from the last five years are shown in the graphics below.   
Dairygold Silage Analysis Average DMD by Year (2010-2014)
Dairygold Silage Analysis Average Crude Protein by Year (2010-2014)
Averages can hide a multitude however; and there are large variances between and within farms as can be seen in the pie charts below.
Range of Silage DMD levels in 2014
Range of Silage Crude Protein % in 2014
It’s a powerful reminder that nobody should rely on guess-work for determining silage Quality. Recommended concentrate supplementation rates for milking cow will vary by up to 3Kg per head per day for <60 DMD silages versus >70 DMD silages. 
Key point: We recommend testing all silage, each pit / cut of bales to accurately determine supplementation rates

Most dairy farmers actually know this but may not put it into practice.  However, it is no harm to remind ourselves as to why it is necessary.  As can be seen from the picture the grass plant produces new leaf.  These come every 7 days.  The grass plant is right for grazing when it is at the 3 leaf stage.  The performance of plant and performance of the cow grazing this plant are both in the ideal phase.  If a “fourth” leaf begins to appear, the 1st leaf begins to decay or die off.  This results in 4 negative consequences for the cow and the grass plant.  

1. Less grass will be grown – a leaf has been lost

2. This decaying leaf will be eaten by a cow and is poorer quality forage

3. The stem of the plant will begin to appear more and harden and thereby reducing forage quality

4. Stem grows slower than leaf – lower grass production results


Key Point: LONGER ROTATIONS RESULTS IN: Less grass grown/ha – poorer cow performance - less grass utilised per ha – less of the additional €160/ha per tonne of additional grass eaten – LESS PROFIT.  


Of course if grass starts growing the “fourth” leaf – the rotation is getting too long – then this field/paddock should be removed as surplus silage.  Try to keep to a 20 day rotation and graze the magic 1,400 kgDM/ha. (A GROWTH RATE OF 70 kg DM/ha/DAY FOR 20 DAYS = 1400 kgDM/HA


For those who measure grass, the average farm cover should be at 160-180 kgDM/cow. This is the average farm cover divide by the stocking rate on the milking platform. Once the cover/cow is established, the key thing is to make a decision and act upon it.


Grass supply can change fast during May.  It is difficult to predict the weather – therefore predicting grass growth is also not easy.  How you respond to grass growth is the key.  You have to be aware as to what is happening on the farm in terms of grass growth. Walking the farm would be a good start!!

Some farmers will try to graze strong grass for fear of running short of grass.   It is better from a grass plant point of view and cow performance point of view to be chasing grass rather than having too much grass.  The temptation is to go topping grass when the grass gets too strong.  This is wasting feed.  Most farmers are going to carry more cows.  It makes more sense that this “wasted” feed is in a bale than let it rot after topping


Every 4% reduction in Grass Digestibility will reduce milk yield by 1kg/cow/day.

Every 4% reduction in Grass Digestibility will reduce milk solids yield by 5%


Key Point: When grass gets ‘too strong’, bale it-don’t graze (resulting in reduced animal performance) or top it (wasting feed).   



60% of the soils in Munster are deficient in lime.  Most farmers try to spread ground lime at the end or start of the grazing season.  The ground conditions are critical for this operation to happen.  Some of the farmers I work with on the heavy soils programme (see Advert) cannot spread lime during late autumn/winter/early spring period because the land is too wet to carry machinery.  So many of these farmers spread ground lime when they cut about 10 acres of land for bales or silage and apply 2 tonnes of lime per acre directly after cutting.  Many contractors will carry out this operation in those parts of the country where heavy land prevails.  This is an option of those whose soil is short of lime.  Lime is vital to raise the pH of the soil so that:

Quality Silage

May should be the month for making silage.  Overtime silage harvesting has been “slipping” into June.  However, now that quotas are gone, there is going to be a greater role for quality silage. This can come in the form of bales or good quality pit silage.  It is more likely that cows will be milked longer and have a shorter dry period to put on condition.  Most farmers will carry more cows so the demand for grass will be higher both at the front end and backend of the grazing season.  We all want to maximise the amount of grass in the diet and minimise the amount of silage.  If silage has to be in the diet of the milking cows, it needs to be good quality.  Therefore, having good quality silage must be a focus.

As the grass plant matures the sugar content rises (which helps preservation) but the digestibility declines.  However, if the dry matter content of the grass harvested is increased by wilting then the sugar content will rise and preservation will be better.  So putting 25-30ft of silage into 1 swarth and left for 12-24 hours will do very little wilting.  Keep this in mind if you are trying to make high quality (cut in May) well preserved grass silage.  The contractor may need to be reminded of this too. 


Key point: Silage is likely to make up a greater proportion of your milking cow diets post quotas. Therefore your focus needs to be more on quality than bulk. Cutting silage earlier and wilting properly are significant steps towards better quality silage.



It is important to keep applying Nitrogen fertiliser (30-40 units N/acre). CAN is the choice type of nitrogen fertiliser to apply as its “safer” than Urea. However many dairy farms are deficient in P & K, so nitrogen compounds (N, P & K products such as 18-6-12) should be applied. Many dairy farms will respond to a sulphur application during May and June. Applying ASN (26%N & 14%S per 50kg bag) now at 1.5 bags/acre will meet both your Sulphur requirement for the year and nitrogen requirement for the month.

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