The Value of Grass after a late Spring

By Dr Jane Sayers, CAFRE Dairying Development Adviser, Omagh

Offer milking cows fresh grass twice daily.

In dairy production where margins are incredibly tight, high-quality grass can be the key to profitability so keeping a constant supply in front of the dairy herd makes sound financial sense.  Essential to the production of milk, grass is a cost-effective feed that can be utilised all year round, in spring and summer by grazing (or zero grazing) dairy cows and in winter as silage.  However grazed grass is cheaper by factors of between 2.5 and 4.0 when compared to grass silage and concentrates respectively.  

Jane Sayers says that “The Spring grazing season has got off to a very slow and wet start with cows late to go to grass on many farms. Successful management of high yielding cows (producing greater than 30litres) at grass requires excellent grassland management and targeted concentrate supplementation to allow the cow to meet her nutritional requirements in terms of milk production, compositional milk quality, going back in calf and maintaining body weight.  The key is to focus on maximizing the cow’s daily grass intake”.

With good grazing management, grass dry matter intakes of 15 kg DM/head/day are achievable (supporting 19 to 20litres).  With excellent grazing management intakes of up to 17 – 18 kg DM/head/day can be achieved (supporting 23-25litres), however this is often restricted to a few days in the year at a time when grazing conditions are ideal.  Table 1 illustrates the maximum recommended M+ setting for cows grazing high quality swards under optimum conditions (grazing/weather).  It cannot be emphasized enough that an honest assessment of grassland management and cow condition should be considered before adopting these settings.  M+ settings for heifers is typically set for three to four litres below the cows. 

Table 1: Potential daily milk yields per cow produced from high quality swards which are well managed (litres)

                    April              22

                    May              25

                    June             23

                    July              19     

                    August          17

                    September    15

To achieve these levels of milk production, cows need to be offered a dense, leafy, high digestibility sward with a pre-grazing cover 3000 to 3200 kg DM/ha (12-14 cm), grazing the sward down to a post grazing cover of 1700 – 1800 kg DM/ha (residual height 6 – 8 cm).  Ideally the swards should be at the three-leaf stage – which is the optimum for intake, sugars, leaf to stem ratio, minerals, regrowth and responsiveness to fertilizer.  Jane advises that “It is critical cows are allocated the correct grazing area to support intakes – a 100 cow herd requires 1.0 ha/day (2.5 acres/day) to support intakes of 15 kg grass DM/cow/day”.   Furthermore, fresh grass should be offered after each milking and cows should be allowed to maximise the time spent grazing at pasture (that is minimize the time in collecting yard and walking to the field) to support high grass intakes.

The M+ figures quoted are only achievable under ideal grazing conditions and will be reduced due to wet weather.  Wet weather will reduce grass intakes.  Similarly driving wind and rain will cause cows to seek shelter, reducing grazing times and consequently grass intakes.    In these circumstances M+ settings in the parlour require adjustment as noted in Table 2.  Flexibility is key. 

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

Concentrates

Where cows are yielding above the M+ production figures for grass, supplementation with concentrate is necessary, cows should be fed at a rate of 0.45 kg concentrate for each additional litre milk produced. 

Failure to feed cows for their level of production will result in reduced milk yield, poor quality milk composition, low body condition score and poor fertility throughout the season, which in the long term will have a financial impact on the dairy business cashflow.  It’s a case of being aware of what to feed and why. 

Protein

Cows should be fed a low protein concentrate at grass (less than 18% CP freshweight), preferably 16%.  Swards that are well managed and fertilized can have crude protein greater than 21%.  The grass crude protein content increases as the grazing season progresses (from 18 to 25% or more).  Much of this protein in grass is rumen degradable, leading to excess levels of ammonia in the rumen and consequently high blood and milk urea levels, which can have negative effects on cow fertility and reduce milk yields.  Reducing crude protein content results in a better balance of energy and protein in grazing rations.

Energy

Energy, not protein or minerals, is the greatest limiting nutrient in the dairy cow diet.  Cows should be fed a good quality nut.  Milk yield should only drop on average by 2.5%/week (10%/ month) from peak yield. 

Concentrate Type

Jane advises that “Spring grass is leafy, highly digestible and contains a higher proportion of sugars, while fibre content increases and sugar declines as the grazing season progresses.  This suggests that higher fibre concentrates may be more appropriate in the early season, while higher starch supplements would best balance late-season grass”. 

In early grazing season, the use of quality digestible fibre and sugar sources (i.e. sugarbeet pulp, soyahulls, citrus pulp) is to be encouraged to reduce the risk of digestive upsets, particularly if high levels of concentrate are being fed to cows (10 kg conc/day).  In certain situations, it may be necessary to include an acid-buff in the diet to reduce the risk of rumen upsets.  Also, the use of some “protected” fat may be of benefit to the higher yielding cows, especially where grass energy content is less than favorable.

Buffer Feeding

The limitation on grazing availability, and hence the cow’s grass dry matter intake, is the main influence on the nutritional productivity of cows throughout the grazing season.  Where grass availability may be limited due to restricted grazing ground, poor grass growth, mixed weather or management consider either buffer feeding or partially housing cows at night.  The aim is to balance the estimated grass availability with silage and concentrates to help maintain the cow’s level of milk production, health and fertility status.   

During periods of grass shortage, offer cows 2 to 4 kg DM (10 – 20 kg freshweight) of high-quality silage at milking time, this will allow a buildup of grass and extend the grazing rotation.  Alternatively, some farmers may graze cows during the day and house at night.  In this instance, intake of silage is greater and dependance on grazing reduced, however it allows high yielding cows to achieve their milk yield potential, while optimising health and reproductive status.         

Summary

Jane concludes that “After a difficult Spring, try to offer cows high quality grass to maximise grass intakes, which in turn is capable of supporting milk yield, cow health and ensure good fertility.  Set ‘feed to yield’ M+ depending on grazing management, the weather and cow body condition”. 

Consider discussing your feed options with your own nutritionist or local CAFRE dairying adviser.

Notes to editors: 

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