Grasswatch 2020

 

  • Please find attached GrassWatch report for samples submitted week beginning 1st June (week 23).

    Summary:

                                                                                                                                           

    • Grass Quality
    • Grass quality last week was very good with improved digestibility compared to the week previous. Grass dry matters remain very high – 21.8%, supporting high dry matter intakes. Metabolisable energy is very good at 12.2MJ/kgDM and NDF’s low 37% – further driving high dry matter intakes. Crude proteins have slipped to 21.8% – but still providing a lot of excess rumen degradable protein.  

     

    • Risk of milk fat depression:
      • The risk of milk fat depression from RFC (quickly fermentable carbohydrates i.e. sugars), acid load and fibre index is “high”, whilst risk from RUFAL (unsaturated oils) is “moderate”.
      • Butterfats have been a challenge on some farms in recent weeks. In addition to RFC, Acid Load and Fibre Index of grass currently, other contributing factors include:
        • Selective grazing (avoiding the stemmy proportions of grass and grazing the leafy parts)
        • Sudden changes in diet (introducing buffer feed or the extreme variability in grass quality between paddocks on individual farms)
    • Heat stress
        • Variable grass intakes (due to grass availability, grass quality or heat stress)
        • Increased concentrate intakes

     

     

    • Maximum expected intakes and milk yield:

    o   Maximum grass dry matter intakes for the start of June with the current dry weather conditions and high grass dry matters are estimated at 17kgDM/head/day on full-time grazing – capable of supporting maintenance plus 22.7 litres (0.75 litres/cow/day has been deducted due to excess rumen ammonia, (NFEPB 986g/day from forage alone) and small-moderate allowances made for excess energy expenditure at grass – deduct 1-2 litres more for moderate to long distances to pasture).

     

    o   Maximum grass dry matter intakes on daytime only grazing is estimated at 8.5kgDM/head/day; this along with 5kgDM of good quality grass silage (>11ME, 30%DM) at night is expected to support maintenance plus 14.5 litres (0.28 litres/cow/day has been deducted due to excess rumen ammonia, (NFEPB 495g/day from forage alone) and small-moderate allowances made for excess energy expenditure at grass – deduct 1-2 litres more for moderate to long distances to pasture).

     

    o   Maximum grass dry matter intakes stated above are only achievable where cows are turned into target pre-grazing covers of around 1500kgDM/ha, grass quality is excellent, the correct area is allocated to allow maximum intakes and time spent away from pasture (time spent standing in collecting yard for milking) minimized.

     

    • GrassWatch monitor farm performance:
      • A number of monitor farms have included a buffer feed to stretch rotation length as grass availability remains an issue with the current dry conditions. Litres and milk quality has held well given the circumstances. Rotation length varies between 17-28 days depending on farm and particular paddocks within individual farms. Pre-grazing covers are being maintained at 1400-1500kgDM/ha. Milk ureas vary from 15-23mg/dl.

     

    Management tips for drought affected farms:

    Rain is on the cards for most of the country over the coming days, hoping to relieve some pressure on grazing platforms suffering from severe soil moisture deficits. In the meantime farms should:

    o   Hold AFC at 750kgDM/ha – this will allow the farm to get back on track quicker once rain comes

    o   Match rotation length to grass growth rate. Extending rotation length to 24-25 days should be sufficient in most cases (grazing 4% of platform each day). Extending rotation to 30 days or more is not advised as it will greatly reduce grass quality in the current conditions

     

    Growth Rate (kgDM/ha/day)

    Target Rotation Length (days)

    % of grazing platform to graze per day

    50

    28

    3.6

    60

    23

    4.3

    80

    18

    5.5

    100

    14

    7.1

    **Assuming target pre-grazing cover 1500kgDM/ha and target residual 100kgDM/ha**

     

    o   Match supply and demand, example:

    o   Growth 50kgDM/ha/day

    o   Demand 60kgDM/ha/day

    o   Deficit 10kgDM/ha

    o   Stocking rate 3.5LU/ha

    o    Deficit to replace with buffer feed =  10kgDM/ha   /   3.5LU/ha  = 2.8kgDM/cow

    o   Where buffer feed is being used, offer 2-4 hours before evening milking as to not affect grazing intakes post milking

    o   Assess the need for additional protein supplementation in the buffer feed depending on how pastures are burning up, milk ureas and how well litres are being maintained

    o   Back fence to protect any re-growths

    o   Pre-mow swards to replenish quality for next rotation. Avoid over wilting grass where pre-mowing is being practiced

    o   Where field size is sufficient for several days grazing, graze night and day in these fields as opposed having night time and day time fields. This allows the paddock to rest again as soon as possible, to get grass growing again.

    o   If drought conditions prevail avoid topping residuals. Where topping is being practiced, avoid topping too low as this will slow regrowth and top directly after grazing – maintaining a slightly higher residual will reduce soil exposure to sunlight and maintain more moisture in the soil.

    o   Continue to sow fertilizer unless:

        • Drought condition prevail for longer than 25 days
        • Paddocks that are browning
        • Soil moisture deficits are >60mm