Maximising Milk From Grazed Grass

With very variable milk prices and higher feed costs, due to raw material issues, maximising milk from grazed grass is more important than ever.

Challenges for maximising milk from grass

  • Maintaining consistent high quality grass throughout the season
  • Managing pastures with variable growth rates
  • Supplementing grass to maintain butterfat levels
  • Preserving yield, body condition and fertility

Maintaining high quality grass throughout the season

The ideal grass cover to graze dairy cows is 2800 – 3000 kg per ha (12 – 15cm grass height) This maximises production of the grass plant, achieves the optimum energy and fibre level and maximises dry matter intake and milk yield. If pastures are grazed down to around 1500 – 1600kg per ha, this achieves maximum grass intake and quality of the grass from regrowths. This is relatively easily achieved in dry conditions but more difficult in wet conditions.

If the grass cover increases above 3000kg per ha the fibre (NDF) in the grass increases and the energy drops as the grass plant matures. As fibre levels in the grass increase, dry matter intake drops leading to negative effects on cow performance. If dry matter intake drops by 1kg per head per day and the ME of the grass drops by 1 MJ/kg DM, this is equivalent to a drop of around 4.5 litres of milk per cow per day.

Managing pastures with variable growth

Typically, if grass gets sufficient moisture, temperature and fertiliser, it will attain average growth rates of around 70-80kg per ha per day throughout May and June at least. At this growth level, well managed pasture will regrow to around 2800 – 3000 kg per ha grass cover every 21 days. To provide 14 – 15 kg of dry matter of grass per head per day, 1ha of pasture will grow enough grass for 100 cows for 24 hours. This will then need to be adjusted depending on grass growth which will vary from 50kg per ha per day up to over 125kg per ha per day. Extending or reducing the area available in the rotation appears an easy solution but planning ahead for subsequent grazing adds to the challenge. If grass growth is in excess of 70-80kg per ha per day, surplus paddocks need to be removed from the rotation quickly and cut and allowed to regrow in time for the next round.

Supplementing grass to maintain butterfat levels

Good quality grazed grass tends to be high in energy and protein and low in fibre. While this is essential to achieve good milk yields, this is not always ideal to maximise butterfat levels. Allowing the grass to mature and increase fibre levels will potentially improve Butterfat levels, as mentioned above this will have a detrimental effect on grass quality and subsequent milk yield. Offering a concentrate with some high digestible fibre or a small amount of high fibre forage will help to improve butterfat levels. This has to be balanced carefully as too much supplemented fibre will substitute out grass leading to a milk yield drop. Supplementing cows with C16 protected fat will also have a positive effect on butterfat levels. On average around 300g per head per day of C16 protected fat will increase butterfat levels by 0.3%. The economics of this will depend on the specific milk contract payments for butterfat and the average daily yield.

Preserving yield, body condition and fertility

While maximising milk from grazed grass should always be the key objective, monitoring overall herd performance will result in the best long-term profitability. Feeding regime and amount will depend on farm system and expected yield. As desired milk yield increases, more feed supplement will obviously be required. The balance of this feed in terms of forage and concentrate will determine the benefit from grazed grass. To continue to maximise milk from grazed grass in a higher yielding system, the level and quality of forage is very important. If cows are grazed day and night, assuming there is sufficient grass available, the conserved forage level in the diet can be quite low (around 2-3kg dry matter per head per day) along with a balanced concentrate feed. Both forage and concentrate can be increased if grass availability or quality is reduced. If cows are grazed during the day only, the level of forage can be increased assuming cows will obtain around 6 – 7kg dry matter per head per day from grazing. Monitoring cow body condition closely will ensure energy levels are maintained and therefore yield and fertility will be maintained.

If you would like to discuss your grazing and feeding system in more detail, contact your Carrs Billington representative or contact Customer Services on 01228 518860.

Jimmy Goldie, Chief Technical Officer,
Carrs Billington Agriculture Ltd

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