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DAIRY SPECIAL: Impact of perennial rye-grass deterioration

The benefits of reseeding and the use of a silage inoculant were discussed at a recent milk from forage press briefing. Hannah Noble reports.

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Research showed by year 10 there could be up to 90 per cent weed grasses in the ley.
Research showed by year 10 there could be up to 90 per cent weed grasses in the ley.

Dairy farmers operating a composite-style system, combing an intensive, high output system with grazing have the potential to increase their milk from forage figure.

 

This was the message from Ben Wixey, of Germinal GB, who said block calving herds knew how to grow and manage grass and high input intensive herds knew how to make quality silage, but often farmers operating a composite-style system were not achieving their potential and there were great gains to be made.

 

Mr Wixey said it was widely understood that after reseeding with a non-native perennial rye-grass (PRG), deterioration occurred over time and weed grasses took over. Research showed by year 10 there could have been up to 90 per cent weed grasses in the ley.

 

But recent investment in their research station in Melksham has allowed Germinal to look more closely at the effect this deterioration had on the dry matter (DM) and energy potential of the ley and consequently the financial losses incurred.

 

Germinal’s research compared a new ley comprising 90 per cent PRG and 10 per cent weed grasses such as Yorkshire fog, rough stalked meadow grass and annual meadow grass whose seeds were naturally in the soil, with a five-year-old ley which had degraded to a 50:50 blend of PRG and weed grasses.

 

The difference in yield from second cut alone, which was taken in July, six weeks after first cut, meant there was an increased fresh weight forage of over 3.3t/hectare on the new ley versus the older ley, and an increase in DM of over one tonne per hectare.

 

Mr Wixey said: “There was a 26 per cent increase in the yield of PRG over weed grasses in this field just from having better grasses in a higher population.”

 

The domination by the energy-rich PRG meant the extra energy per hectare equated to 11,000MJ.

 

He added: “Because we know it takes 5.3MJ of energy to produce a litre of milk if everything else is the same, this extra energy equates to 2,000 litres more milk, and at 27p/litre that is an extra £550 of revenue.”

 

The same pattern was seen to a greater extent in a 10-year-old ley, which had just 25 per cent PRG remaining.

 

There was an additional 5.5t/ha of fresh weight forage which equated to an increase in energy of 18,000MJ/ha which had the potential to produce more than 3,000 litres of extra milk and £920 from the increased production alone.

 

Mr Wixey said a proportion of the increase in milk from forage target had to be as part of an annual reseeding policy. He said a one year in 10 reseeding policy was adequate but grassland management must be good.

Silage inoculant usage in multi-cut system

Adopting a multi-cut silage system of more than three cuts per year meant harvesting a younger crop which provided higher digestibility and energy, higher protein, improved clamp consolidation and a comparable yield according to Volac microbiologist Mark Leggett.

 

However he said there were some down-sides to the increasingly popular silage technique which included increased contractor costs, increased difficulty in reaching the desired drop in pH due to the increased protein content of the crop and possibly an increased risk of slurry contamination with a reduced period between cuts.

 

Therefore Mr Leggett said despite only 60 per cent of beef and dairy farmers doing so, it paid to use a silage inoculant.

Volac carried out a study using four cuts of silage taken over a season, half the grass was treated with its own inoculant, Ecosyl, and half was left untreated.

 

There was a wide range of DM values between 28 per cent and 50 per cent across the four crops.

 

Mr Leggett said the success of the ensiling process depended on quickly reducing the pH of the forage to restrict the activity of the bad bacteria, preserving more of the nutrient and DM content of the crop.

 

“The aim is for silage to reach 4.5pH as quickly as possible, certainly within the first seven to 10 days.”

 

The untreated silage struggled to reach the desired pH and within 10 days all four of the samples were still higher than pH 10 which he said was not ideal for preservation. Even after 90 days none of the samples were below 4.5 which meant dry matter losses and spoilage would have been expected.

 

Mr Leggett said there was a much faster acidification process when an inoculant was used. In all four cuts the pH was below 4.5 in the first 10 days which had a beneficial effect on preventing the activity of bad bacteria in the clamp.

 

The levels of undesirable enterobacteria, which are common in slurry and responsible for DM losses and decreases in nutritional value were also measured. The untreated silage saw a large spike in the number of enterobacteria following the failure to decrease the pH which allowed the bacteria to reach levels of 1 billion/g of silage in some cases.

 

He said butyric acid in silage was usually associated with the presence of clostridia which were found in soil, they were undesirable and caused high DM and energy losses in the crop when they are allowed to proliferate in the silage.

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