Grasswatch 2020

  • Average grass dry matters are fairly typical for this time of year at 19.7%, which will favour grass intakes. However there is a huge range in grass dry matters from 15.9% to 30.0%. Grass dry matters above 20% can lead to an under estimation of grass covers and hence intakes so be careful when judging grass dry matters.
  • Grass quality is excellent at an average ME of 12.2MJ/kgDM – very similar to this time last year. Half of the GrassWatch monitor farms were on their 2nd rotation during week 15, with better quality grass on these farms (12.6MJ/kgDM) compared to those still on their first rotation (12.1MJ/kgDM).
  • Grass intakes are expected to be around 15-16kgDMI/head/day. GrassWatch monitor farms averaged 15.5kgDMI/head/day during week 15. Based on average grass quality for week 15, grass intakes of 15.5kgDM/head/day is suffice to support maintenance plus 18.8 litres (allowances made for additional energy expenditure at pasture and excess rumen ammonia – please note these allowances are not taken into consideration in the milk yield predictions in the GrassWatch report).
  • Grass crude proteins are high at 26.9% (as high as 32.3% on one farm), leading to a lot of excess rumen ammonia. With grass intakes of 15.5kgDMI/head/day, milk losses due to excess rumen ammonia are expected to be 1.43 litres/head/day.
  • Grass NDF levels are considerably high for this time of year at 45% – but with a huge range from 29% to 54%. Grass NDF levels are typically 38-40% at this time of year.
  • Sugar levels are relatively low for this time of year, averaging 7.5% –  this may be due to lack of sunlight or grass still actively growing (depleting sugar levels) with fertilizer only sown 10-14 days ago on many of the monitor farms. Low sugar levels have resulted in a low to moderate risk of milk fat depression from RFC (rapidly fermentable carbohydrate) and Acid Load. Risk of milk fat depression due to high RFC and Acid Load is typically highest from the start of 2nd rotation to the end of June.
  • Grass oil levels are high at 6.2% (fairly typical for this time of year), which poses a risk for milk fat drop. Minimise the risk by grazing at the 3 leaf stage, avoid sowing excessive levels of nitrogen and sow directly after grazing to maximize the days between sowing and grazing. Additionally if rumen pH is maintained at optimal levels (via rumen buffers, yeast, buffer feed etc), it is believed that cows are more able to manage the higher oil intakes.