Supporting butterfat production at grazing, by adding a rumen conditioner
to summer buffer rations, improves milk quality and meets milk-buyer
requirements. And this also helps to maximise the milk cheque.
TEXT PHIL EADES
Maximising compositional quality to help increase milk prices will be a vital tactic as producers look to maintain margins as milk prices struggle to match higher overall costs. This will be particularly important this year with delayed turnout increasing winter feed costs.
Falling butterfats at grazing are a familiar issue, but according to Adisseo’s Andrew Grimston, better understanding of the causes of the problem in the rumen mean that it is possible to reduce the drop in milk constituents and, ultimately, milk price.
“On compositional quality-based contracts, butterfat bonuses are typically around 0.25ppl per 0.1%, with many contracts having deductions for low fats,” says Mr Grimston. “For a 200-cow herd averaging 30 litres per day, a 0.2% increase in butterfat would be worth around £900 per month in increased income. Typically, around 40% of milk fat is synthesised in the udder using volatile fatty acids produced in the rumen, while the remaining 60% comes directly from fatty acids absorbed from the diet. So effective rumen fermentation is central to efficient butterfat production,” he explains.
Butterfat production
A number of factors are known to predispose cows to lower butterfat production. These include more oils in the feed, particularly unsaturated fatty acids, as well as lower rumen pH, highly fermentable diets, and diets that are low in fibre.
“The unsaturated fats in grass are typically seen as the main reason for depressed butterfats at grazing. But the rapidly fermented nature of grass, the low fibre content of grazing and the risk of low pH will also have an impact.
“The oils in fresh grass increase the rumen fatty acid load that, in turn, can be toxic to rumen bacteria,” he explains. “As part of the process of producing milk fat, the rumen bacteria have to convert the unsaturated oils in the grass and the rest of the diet into saturated oils. There are two different pathways to achieve this, one of which has a positive effect on milk fat production.
“Under specific rumen conditions, principally low rumen pH, classes of bacteria dominate that produce a fatty acid that directly inhibits butterfat production. The only way to reverse this diet-induced milk fat depression is to restore the microbial balance in the rumen, increase rumen pH and encourage populations of more beneficial bacteria, and reduce the activity of the ‘detrimental’ bacteria.
“If the activity in the beneficial pathway can be increased by supplying substrates required by specific bacteria it is possible to increase the fatty acids available for butterfat production.”
Adisseo’s RumenSmart is a supplement that specifically supports the rumen microbial population, favouring specific bacteria and protozoa to promote milk fat synthesis in the udder.
Bacterial populations
In trials it has been shown to improve butterfat production and is particularly effective in higher risk diets. “Analysis of bacterial populations show it reduces numbers of those strains responsible for the detrimental pathway and encourages the more desirable strains,” adds Mr Grimston.
Roger Cook and his father John run a 450-cow Holstein Friesian herd near Scarborough. “Herd average yield is 8,000 litres, but we can’t push for high yields as we have a long grazing season and cannot house fresh calvers for the first three months,” explains Roger Cook. “We are happy with cows peaking at 40 litres.”
The herd is grazed, on a 65-hectare block, from mid-April to mid-October on a rotational system. “Cows are housed when ground conditions require it or when grass quality falls off,” says Mr Cook.
The business has an Arla CARE contract, which pays on fat and protein, so the Cooks aim to maximise milk quality, maintaining fats at grazing and are currently running at an average of 4.75% fat and 3.48% protein. This means that the herd is producing more than 10,000 litres of fat-corrected milk, and around 660kg fat and protein per cow.
While grass makes up the majority of the summer diet, cows are buffer fed all year round and are topped up with a 16% protein concentrate fed through the parlour. The buffer is fed at night and cows are able to go indoors as they choose.
“We will usually put out between five and six tonnes of buffer, depending on grass availability,” says Mr Cook. “We know the overall diet is not particularly rumen friendly with a lot of grass and up to 8kg/day of parlour compound so we look for the buffer to help address this and prevent milk fats falling. But during the summer butterfat would typically fall to between 3.8% and 3.9%.” The buffer feed is developed by nutritionist Paul Robinson and typically comprises grass silage, a fibre blend, caustic wheat and live and dead yeasts to promote rumen function.
The buffer contained a C16:C18 protected-fat mix, at a rate of 170g per cow per day, which would pass through the rumen to improve milk fat, but there was still a milk fat decline at turnout. Roger and Paul felt there was still potential to improve butterfats and they decided to add RumenSmart to the buffer.
Supportive supplement: buffer now contains a product that better supports
butterfat production
Buffer supplement
The protected fat in the buffer was replaced with the supplement, at a rate of 37.5g per cow per day and at a cost of 15p per cow per day. This is a lower cost than the replaced protected fat.
“In summer 2022 we averaged 4.3% butterfat during the grazing season, but in 2023, after adding RumenSmart, we had no tests lower than 4.5%,” says Mr Cook. “So we now feed it all year round.”
“We had been running at a rolling average butterfat of 4.1% for several years. Adding the protected fat had nudged this up to 4.35%, but now we have a rolling average butterfat content of 4.75% despite taking the fat out of the diet,” says Mr Cook.
“By paying close attention to the diet, we have been able to increase both milk quality and milk price, which is essential given the limitations we have on yields. It shows that high milk quality can be achieved when grazing and that it is possible to make the best of milk contract opportunities.”
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