Managing high yielding cows at grass

20 May 2019

The successful management of high yielding cows (greater than 30 litres) at grass requires excellent grassland management and targeted concentrate supplementation in order to meet the nutritional requirements of the cow whilst maintaining bodyweight.

The key is to focus on maximizing the cow’s daily herbage intake.

To achieve this, high yielding cows require the consistent provision of

  • Densely tillered swards, of high digestibility and palatability
  • Pre-grazing covers of 3000-3200kgDM/ha
  • Post-grazing covers of 1700-1800kgDM/ha (6-8cm)
  • Swards at the 3 leaf stage – optimum stage for intake, sugars, leaf-to-stem ratio, minerals, regrowth and responsiveness to fertilizer
  • Fresh grass after each milking
  • The correct allocation of grazing area to support intakes – 100 cow herd requires 3 acres/day to support intakes of 15kgDM/cow/day
  • Maximise the time spent at pasture (minimizing standing time in collecting yard and walking to pasture)
  • A sufficient ‘clean’ water supply – 7m trough space/100 cows and cows should not have to walk more than 250m to a water trough

If cows do not graze paddocks out tight, corrective measures to replenish quality of post-grazing residuals may be required, such as:

  1. Topping
  2. Pre-mowing a full rotation
  3. Baling each paddock at least once during the grazing season

Setting parlour M+  in feed-to-yield systems

With good grazing management, grass dry matter intakes of 15kgDM/head/day are achievable (supporting 19-20 litres). With excellent grazing management intakes of up to 17-18kgDM/head/day can be achieved (supporting 23.5-26 litres), but this is often restricted to a few days at a time when grazing conditions are optimum. Table 1 illustrates the maximum recommended M+ setting for cows under ‘excellent’ grazing management and optimum grazing conditions. An honest assessment of grassland management and cow condition should be considered before adopting these settings. M+ setting for heifers is typically set 3-4 litres below the cows.

Table 1: Maximum recommended feed-to-yield M+ setting under ‘excellent’ grazing management and ‘optimum’ grazing conditions

  Cows M+
End April 18
Mid May 22 22
Early June 20
Early July 16
Mid July 14
Early Aug 13


However, wet weather can reduce grass intakes, which requires adjustment of M+ settings in the parlour (see Table 2).

Table 2: Effects of weather on grass dry matter intake (DMI)

  Reduction in grass DMI Reduce M+ setting in parlour by:
Continuous light rain 1kgDM/head/day 2.0 – 2.5 litres
Continuous heavy rain 2kgDM/head/day 4.0 – 4.5 litres


Excess protein and fertility

Swards that are well managed and fertilized can have crude proteins of greater than 25%. Much of the protein in grass is rumen degradable, leading to excess levels of ammonia in the rumen and consequently high blood and milk urea levels (greater than 25mg/dl), which can have negative effects on cow fertility and reduce yields by 0.5 to 2.5 litres/cow/day.

To reduce the risk of negative effects on fertility:

  1. Transition cows onto grass gradually
  2. Trouw Nutrition’s NutriOpt formulation package can help your local nutritionist formulate lower crude protein compound feed (with higher proportions of rumen-protected protein). In addition, the Greenline GrassP pack can help lower rumen ammonia.

Summary

  • Optimise sward characteristics to maximize grass intakes 
  • Set feed-to-yield M+ in line with true assessment of grazing management and cow condition (make allowances for additional energy expenditure and poor grazing conditions) 
  • Where fertility at grass is historically an issue and milk urea levels are high discuss feed options with your local nutritionist