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NWF Weekly Grass Watch – 22nd April 2022

Grass Growth

Grass growth this week has seen a considerable increase to an average 56kg DM/ha/day. For the same period last year 30.5kg DM/ha/day was seen while the 6-year average is 43kg DM/ha/day. The Southwest and East see the highest grass growth rates figures at 60kg DM/ha/day. As grass growth increases so too does the risk of grass staggers. It is vitally important magnesium supplementation levels are sufficient and monitored closely throughout periods of rapid grass growth to prevent issues.

Milk Yield from Grazing (MYFG)

  • Increases in potential grass DMI means MYFG has once again risen this week to an average of M+5.6 litres/day, although considerable variation is seen across regions. Wales and West see’s the highest average MYFG at M+8.4 litres/day, while the Northwest sees the lowest average at M+1.7 litres/day.
  • It is worth noting that individual farms analyse grass for MYFG to enable management adjustments where expected levels are not met. To enable the report to be as accurate as possible, MYFG sample submissions must be adequate enough to allow accurate reporting (approx. 10 handfuls). Where ‘N/A’ is shown on the report, this indicates insufficient sample size for that region which is typical early in the season.

Grass quality

  • Crude protein (CP) has been higher through the start of the season versus 2021 averages. This week sees a rise in CP to 23% DM (last week 22.7% DM) and a drop in sugars averaging 9% DM (last week 11.2% DM). As a result, the ratio CP to sugars is away from the optimised 2:1 and compromises nitrogen use efficiency in the rumen. This is also established in the increased NFEPB average of 98.3g/kg DM which is further reflected in the NFEPB potential milk loss increasing to an average of 0.7 litres/day.
  • Control strategies to help minimise production losses may include feeding a fermentable source of energy best suited to individual farms. This will work to help optimise the balance between effective rumen degradable protein and fermentable metabolisable energy, helping offset negative impacts on health and performance in cattle.
  • Average sugar levels for the week have increased slightly to 10.75% DM, although a range can still be seen from 4.6% to 14.5% DM. Sugar levels below 10% DM are at risk of poor fermentation making unstable forages. This week’s nitrate levels have decreased averaging 179.8mg/kg (fresh weight.) It is important to monitor nitrate levels to ensure they remain below the 2500mg/kg maximum target. With most of the UK experiencing a period of dry, warm weather followed by some rain showers, predictions make for a risk period for high nitrate levels as a result of increased uptake in such conditions.

Pre-cut NDF tracker

  • This week the average UK NDF content has decreased slightly to 43.44%DM, which is still above the target of 38-40% DM. As grass is continuing to grow and mature, many fields, on an NDF basis, may be ready for cutting. The recent hot spell has caused heat stress in some grass crops meaning grass has gone to seed which will compromise energy content of silages. Farmers should begin to consider starting their first cut before grass becomes too mature and lignified, which will compromise silage quality. As expected, there is a range in NDF levels from 35-54%DM meaning individual farms should analyse their grass to understand when to cut for optimal silage quality.

Source:  Trouw Nutrition

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