As feed prices remain high, the drive to get more milk from forage is more important than ever. Providing advice for dairy farmers, Jimmy Goldie, chief technical officer at Carr’s Billington, explains how this can be achieved while also supplying the nutrient needs for high milk production.

“We know that milk from grazed grass is the cheapest way to produce milk, but we need to also look after the nutrition, body condition and fertility of the cow, to ensure that we safeguard long-term performance,” he says.

“In most cases, grass or grass silage is more than 50% of a lactating dairy cow’s diet, and the quality of this forage will directly impact herd performance.”

Grass analysis carried out by the Carr’s Billington team at the start of the typical grass growing season highlighted that due to the cold wet weather, dry matter content was high, protein levels were lower than normal, and energy levels were very high. This meant that once cows were turned out, they performed very well on high quality short grass, but protein has had to be supplemented more than normal.

“To put that in numbers, often in May grass contains 24 to 26% crude protein, but this year many of the results came back below 20% protein, which was due to the weather, slower nitrogen uptake and slower grass growth. This has meant that farmers have had to supplement additional protein to prevent a drop in milk production.”

As a result, farmers are advised to carry out practices which can maintain the nutritional levels of grass, and setting up a rotational grazing plan is one way to achieve this.

Rotational grazing

To maximise milk from grass, Mr Goldie explained that grass needs to be grazed at the optimal height.

“When looking at rotational grazing, grass should be grazed at 2800-3000kg DM/ha, or 12-15cm high. If grass is allowed to grow beyond 3000kg DM/ha, the fibre level increases, the quality decreases, and dry matter intakes per cow per day drop consequently leading to a reduction in milk production. Grass should be grazed down to 1600-1800kg DM/ha to maximise milk production and maintain the quality of the grass re-growth. There is a fine balance between managing grazing to maintain grass quality without compromising milk production,” he said.

When operating a rotational grazing system, cows should ideally have a fresh paddock of grass every 24 hours and be in a paddock for no longer than 48 hours because it will start to compromise re-growth. On average, in Scotland, grass growth at 70kg DM/ha/day will re-grow back to the required height in 21 days, however, when conditions are right, it can take as little as 10-14 days for grass to re-grow back to the required height.

“As growth is variable, I’d really recommend monitoring grass growth once or twice a week to ensure you’re grazing the paddock which meets optimal grazing height. It’s important to remove paddocks from the rotation if there’s a surplus of grass and instead cut this for silage, otherwise the grass will be wasted.”

Roughly 100 cows need one hectare of grass per 24 hours. The total area of grazing required will change throughout the season depending on how fast it’s re-growing. If cows are out day and night, the target is to get between 12-14kg of dry matter from grass per cow per day. This should provide maintenance plus 12-18 litres of milk from grass depending on quality.

“If cows are only grazing through the day, higher yielding herds will also need a buffer feed. However, it’s important to make sure cows don’t take preference of buffer feed and reduce the amount of grass they eat.

“Normally grass is high in energy and protein and low in fibre, so if this is the case, the best supplement is a high energy, high fibre, low protein feed. As this can vary depending on grass conditions, protein balance can be checked by monitoring weekly milk urea levels to ensure correct levels of protein are being supplied."

It’s important to be aware that if cows are eating high volumes of grass which is low in fibre, they can show signs of acidosis. However, feeding a yeast or a rumen buffer can be helpful in this situation to improve rumen function and help maintain milk production and quality.

“A grass only diet doesn’t provide sufficient minerals for a dairy cow, so cows on a high grass diet need to be supplemented. This can be supplied in the form of a mineralised compound. Magnesium supplements will be particularly important if grass supply is short, or growing conditions are poor."

Mineral deficiencies can also lead to other issues, for example ‘pica’ which is where cows eat things that do not have any nutritional value, for example stones and silage sheets.

“Quite a few farmers reported pica issues last year due to the very dry weather and a lack of grass. So this is something to be aware of if dry periods occur again this year. Pica is largely due to insufficient dry matter intake as the animal simply doesn’t have enough to eat. Making sure cows have enough concentrate feed if grass is poor, and sufficient water, can help to prevent this occurring,” concluded Mr Goldie.