Grass Watch 19


Grass Watch 2019

Grass Watch is designed to demonstrate the value of grass in milk production and the impact this variable food source can have on key components such as butterfat and Protein(%).
This key information on grass quality can help shape a feeding program to achieve the results of a modern day high yielding herd. Samples are taken Weekly every Monday from the Paddocks the cows are grazing and are sent off to be analysed. Several monitor farms are used locally and are combined to achieve average. Program runs until November.
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Overview of this week results by Trouw’s Dairy Technical Support coordinator 

Grass Quality:

  • Average grass dry matter last week was 15.0%, ranging from 11.7% to 17.0% across monitor farms. Based on the average grass dry matter of 15.0% ‘maximum’ grass intakes are likely to be 15kgDM/head/day at the moment – however this maximum value relies on good grass quality and the correct allocation of grass to meet these intakes. On the other hand, the monitor farm with the lowest grass dry matter last week of 11.7%, ‘maximum’ intakes are likely to be 14kgDM/head/day, again requiring good grass quality and correct allocation of grass to meet these intakes.
  • Average grass ME last week was 11.2MJ/kgDM, but ranged significantly from 10.2 to 12.4MJ/kgDM across monitor farms. This time last year grass ME average was 11.7MJ/kgDM. Based on last week’s average grass ME, grass alone could support a maximum of 15.5litres (based on max. grass DMI 15kgDM, at an average grass DM of 15.0%) or 13.4litres (based on max. grass DMI of 14kgDM, at lowest weekly recorded grass DM of 11.7%) – These milk yield predictions allow for additional energy expenditure at grass and a predicted 1.0 litre milk loss to account for the weekly average NFEPB (see section on NFEPB below). The corresponding ‘minimum’ concentrate required to support milk production is highlighted in Table 1.

Table 1: Minimum concentrate requirements provided conditions are optimal to achieve maximum dry matter intakes

  Average Grass DM 15.0%

Assuming Max. intake 15kgDMI

Lowest Grass DM 11.7%

Assuming Max. intakes 14kgDMI

Litres/cow/day Minimum kg Concentrate required Minimum kg Concentrate required
20 2.2 3.2
22 3.2 4.2
24 4.2 5.2
26 5.2 6.2

Reflecting on 2017 and 2018 GrassWatch monitor farm average milk yields. The better feed rates due to the drought in 2018 resulted in significantly better milk yield persistency in the late summer/autumn as can be seen in the graph below. To achieve similar results to 2018 many farms will have to re-evaluate their feed rates currently. Many farms recently have been trying to support 22-26 litres milk from 2kg concentrate on poor grass dry matter intakes, as a consequence milk yields and milk proteins have suffered.

Trouw Nutrition - Claire Beckett
Trouw Nutrition – Claire Beckett

Tips for managing grazing:

  • Continue to hold at least a 30 day rotation to allow grass covers to recover
  • Walk the grazing platform at least once per week to monitor grass supply
  • Ensure residuals of 4cm are still being achieved – this may become a challenge as grass can be excessively high in nitrogen at the moment, making it less palatable to cows.
  • Continue to sow at a rate of 25-30 units of nitrogen per acre on the grazing platform. Where fertilizer application ceased on some farms over the drought period, blanket spread the entire grazing platform with 25-30 unitsN/acre.
  • Phosphorus (P) will be essential in root recovery after the drought, therefore where farm Phosphorus balances allow, application of compound fertilizer containing phosphorus should be considered. Application of potassium and Sulphur may also aid in sward recovery

The dry matter (DM) content of forage (measured as a percentage) is the proportion of total components (fibres, proteins, ash, water soluble carbohydrates, lipids, etc) remaining after water has been removed.
Knowing the dry matter percentage of forage is important. The lower the dry matter content, the higher the fresh weight of forage required to achieve a target nutrient intake, whether this is grazed grass or conserved forage.

In Ireland, due to the climate, we typically have very low grass growth rates in the spring and again in the autumn, with maximum growth rates being achieved during the month of May. Although there is little we can do about the weather in the spring and autumn periods, there are a number of measures we can take to improve grass production at the shoulders of the season.

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Weekly Dry Matter

Predicted Milk Yield From Grass Only: Based on Average Grass Energy

Compound (kg/d) based on Average Grass ME

14kg DMI

Crude Protein %

Oil Process A

ME     (MJ/kg)


Sugars – Fresh

Energy From Grass

Weekly Grass Growths (PastureBase Ireland)

Weekly Grazing Information

Butter Fat Alert (Average)

Turnout – Getting More From Grass

Short informative video on key essentials to maximizing yield from grass systems.

Energy from Grass

Grass Watch 2019