Practical Aspects of Feeding Grass to Dairy Cows

Research that has been carried out by Teagasc at Moorepark Farm, Ireland have shown that fresh grass is one of most productive and viable feeds. Complete grass systems are operated in New Zealand and Australia - should other countries be adapting these grass management techniques to increase milk yields. From the 43rd University of Nottingham Feed Conference, TheCattleSite junior editor Charlotte Johnston.
calendar icon 22 September 2009
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Why use a grass based system?

Grass based systems are known to:

  • Lower the cost per unit of milk production
  • Have superior milk composition, such as greater fatty acids
  • Have more sustainability with regard to economic, social and environmental effects

Compared to other feed options, Pat Dillon, head of Moorepark Dairy Production Research Centre believes that good grassland management is not only the most viable but also the most productive. The table below shows the relative cost of grass compared to silage and concentrates. As can be seen from the research, feeding concentrates is 3.5 times more costly than applying good grass management.

Table 1: The relative cost of grass, silage and concentrate feed
  Good Grass Management 1st cut grass silage 2nd cut grass silage Concentrate (€200/t) Maize silage with plastic
Total costs (€/tonne DM) inc land value at €350/ha 63 127 142 234 123
No land costs (€/tonne DM) 33 92 112 - 96
€/ 1000 UFL 63 158 184 221 150
Relative to grass total cost 1 2.5 2.9 3.5 2.4
Source: Pat Dillon, Moorepark Dairy Production Research Centre

Research has concluded that the higher the proportion of grazed grass in a cows diet, the lower the costs of production will be. In grass systems such as are in place in New Zealand and Australia, where over 90 per cent of the cows diet is fresh grass costs of production are between €10-15 cents per litre produced. Compare this to an intensive system in the US where cows are housed indoors all year at a cost of €34 cents per litre. The UK and other European countries whom are operating at a diet of approximately 50% fresh grass, have costs of production around €25-30 cent per litre.

What are the key components to a profitable and sustainable grass dairy farm?

  • High milk productivity per hectare
  • High grass production and utilisation
  • High nutrient use efficiency
  • Key components Grazing management Genetics for the system

Mr Dillon demonstrated that there was a significant relationship between pasture harvested and operating profits. The more pasture harvested and consumed by cows the higher the operating profit.

Estimated Breeding Index (EBI) is the breeding programme operated in Ireland which details information such as milk yields, health and fertility. Mr Dillon stressed that it is important for grass based systems to have high quality EBI genetics in order to see high profits. Research carried out showed that cows with high EBI on a grass based system were producing on average 450 kg of milk solids per cow per year. All cows had good body condition scoring and fitness as well as excellent feed conversion efficiency.

Grazing systems like this focus on production per hectare rather than milk yield per cow.

Principals of grassland management

Research shows that leaf production is maximised by grazing to 3.5-4 cm residual height. With good quality grass this should yield 1250 kg/ DM per ha. By keeping the pasture in a growing state, a higher quality of grass will be produced in a green leafy base.

Pre-grazing height should be 8-9 cm (three leaves), if this is grazed down to 3.5-4 cm then growth will be 16 tonnes/ha. Leaf death should be avoided, says Mr Dillon, do not let grass go to seed.

Applying best grazing management practices

It is vital to measure grass in order to optimise grass efficiency. There are two methods to achieve this the first probably most reliable is using a rising plate metre and the second is using scissor clips.

Spring Grazing Period:
This period will run from the beginning of February when cows are turned out, until beginning of April. It is important that grass is the maximum proportion of feed in the cows diet. Management factors to consider here are what cover was available at autumn closing, what stocking rate should be applied, what ground should be kept back for silage and calving patterns.

A spring grazing rotation planner should be in place. By April, 100 per cent of the available grass land should be grazed. A strip wire must be used to allocate grass on a 12-hour basis. By following a simple grazing area plan per day, maximisation of nutrients is achievable. Rotation periods will be longer at the start of the season. By bringing cows out at the start of February, the grazing season is extended and early grazed sward will be better quality than a later grazed sward. It will likely be necessary to apply urea 23kg/ha on 75 per cent of the land. 2,8000 l/ ha of slurry should be applied to 25 per cent of land with the lowest cover. These figures may vary depending on ground type etc. Remember to graze until sward height of 3.5-4cm is achieved.

Spring Grazing Rotation Planner
Week start date Fraction of farm grazed per day % of total farm area grazed at weekend
1 Feb 1/100 7
8 Feb 1/92 15
15 Feb 1/84 23
22 Feb 1/76 32
1 March 1/68 43
8 March 1/60 54
15 March 1/51 68
22 March 1/43 84
29 March 1/35 100
5 April 1/27 Begin rotation 2
Source: Pat Dillon, Moorepark Dairy Production Research Centre

Avoid poaching: When ground is wet restrict access time to pasture to take advantage of the cow's natural instinct to graze. Mr Dillon's research shows that by restricting cows to two three hour periods of grazing, 97 per cent of that time is spent grazing, as opposed to giving cows 24 hour access to grazing, only 41 per cent of the time is spent grazing. Through the two three hour periods, grazing efficiency is increased with 95 per cent of 24 hour intake is achieved with 16.6 DM kg/ cow/ day. Research shows that there is no effect on milk solids production and grassland remains undamaged.

Mid-season grazing management: This will cover the period of early-April until early-August. Again pasture should be grazed to a residual of 3.5-4.5 cm.

""Pre-grazing cover = Stocking rate (4.5 cows/ha) * Allocation (16kg DM/cow) * Rotation length (19 days) + Residual (3.5cm = 0kg DM/ha) = 1369 kg DM/ha""

Grass growth will be strongest at this time of year and there will likely be excess grass - it is therefore important to plan ahead, as during the Autumn months grass growth may not equal grass demand and so there will be a shortage. Using a grass wedge will allow these surpluses and shortages to identified and prevented early on. The target pre-grazing yield should be between 1,200 and 1,500 kg DM/ha. In order to maintain high quality grass it is important cows enter and leave the field at the target grass covers.

Figure 1 shows adequate grass supply although in practice, many will find that when using the grass wedge however it will look more like Figure 2 or Figure 3 or a combination of the two. These issues therefore need to be addressed, if there is inadequate grass - can this be offset against paddocks with over-supply? If not another option could be to feed extra supplements. It is important that if there is a shortage not to speed up the rotation as this will worsen the problem. Instead by elongating the rotations, grass is given more time to grow.

Figure 1

Source: Pat Dillon

Figure 2

Source: Pat Dillon

Figure 3

Source: Pat Dillon

Autumn grazing management: This rotation will commence from mid to end of August and carry on until the cows are turned in. Rotations will need to be made longer as grass supply will begin to decrease. The first paddock for spring grazing should be closed early to mid October. By the first week of November it would be advisable to have 60 per cent of the farm closed. Depending on grass coverage and whether ground is wet, supplementary feeding will likely begin in November. During the Autumn rotation, target cover (kg DM) per cow will decrease as will target kg DM per ha. Stocking rates are likely to be lower to compensate for grass cover.

Research at Moorepark Farm using this system has proven to give a milk yield of 5700 litres per cow, the Irish average is 4700 litres per cow. Milk solids in kg per ha were double that of the national average as stocking rates per ha were higher. Less concentrates were provided per cow. Profits were therefore also double the average per ha.

In conclusion, the profit potential of a grass-based systems are high although to be adopted they require good management skills. Grass measurement is key to success and planning ahead will allow shortages and surpluses to be identified and opportunities used. Cow genotype must be compatible with grass-based systems, research done a Moorepark showed that cows with high EBI were more successful in the system. Finally, the producer must focus on yield per ha, not on production per cow.

September 2009
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