Stabilised yeast improves dairy cow performance

Exploiting cows’ genetic potential by using a stabilised yeast can boost yields, new research has found.

Dairy farmers can exploit their cows’ genetic potential, cost efficiently, by introducing a stabilised yeast to their diet after turn out according to results from trials carried out at Aberystwyth University. Milk yield increased 1.5 litres a day, an increment worth an additional margin over purchased feeds (MOPF) of 20p a cow a day during the grazing season, or £56/day for the 280-cow herd.

A group of 37 cows from the university’s spring calving Holstein herd, currently averaging approximately 8000 litres at Trawscoed Farm, featured in the trial over a three-month period last summer. After one month on the control diet – grazed grass plus parlour and supplementary concentrate, the cows were introduced to Lactaid fed at the recommended rate of 50gm a head a day over a four-week period, before they returned to the control diet for the final four weeks.

“Within days of introducing the stabilised yeast to the diet, a milk yield increase was recorded, which over the month long period averaged 1.5 litres a cow a day higher than the average predicted lactation curve,” commented Michael Rose, of the university’s Animal Science department. “The stabilised yeast clearly demonstrated it could help dairy farmers to improve their herd’s efficiency during the grazing period.” See table 1.

Those same benefits were mirrored after housing and introducing the herd to a total mixed ration. “We decided to continue supplementing the diet with Lactaid and designed a similar trial, this time over an eight-week period featuring 100 cows in the latter stages of lactation,” Dr Rose explained. The control TMR diet was fed for two weeks pre- and post-Lactaid being incorporated into the same TMR for one month.

“Adding the stabilised yeast to the diet once again clearly helped to increase yield. This time we witnessed an increment of 1.61 litres a cow a day, in addition, while butterfat levels were maintained, protein content increased from an average 3.07% to 3.13%.”

Agri-Lloyd’s veterinary adviser Peter Townley explains: “One of the limitations of grazed grass as a feed for high yielding dairy cows is the variation in feed quality due to changes such as the weather, the pastures grazed and the season. The rumen microbes need to adapt to these changes in grazed grass and the metabolites contained in the fermented stabilised yeast cultures provide support for the fibre digesting microbes.

“In turn, improved utilisation of the fibre from the forage component of the diet leads to better rumen function and accounts for the increased yields shown in this trial,” he says. “Furthermore, trials at West Virginia University have shown that dairy cow diets supplemented with stabilised yeast resulted in rumen microbial out flow to the small intestine increasing by 256gms a day providing the equivalent to feeding over 300gms per day of a high quality protein.”

Mr Townley adds: “The trial in the Trawscoed herd clearly shows that by feeding stabilised yeast cultures we can increase lactation persistency in both mid lactation cows at grass as well housed late lactation cows by around 1.5 litres per day making a significant improvement to profitability.”

Trawscoed dairy herd at grass: Lactaid performance and cost benefits

Extra milk yield per day (l)

1.5 litres

Extra milk yield MOPF per litre per day at 19.3ppl (p)


Lactaid cost/cow/day (p)


Additional MOPF/cow (p/day)


Additional herd MOPF/day (£)


Source: University of Aberystwyth


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