As we approach midsummer, there is much discussion among dairy farmers about low butterfat levels in milk. A decline in butterfat percentages is a common occurrence during spring months, since cows are grazing lush grass high in sugars at that time, but this issue can continue through the summer.

Decline in butterfat

Butterfat production can be compromised when rapidly digestible grass is consumed. Butterfat is derived from acetate, a volatile fatty acid (VFA). Acetate is produced when the bacteria in the rumen break down fibre, but because rapidly digestible grass has low levels of effective fibre, it produces little acetate and, as a result, hinders butterfat production.

This can also cause a drop in rumen pH, which leads to sub-acute rumen acidosis (SARA). If the rumen pH is below 6 (the optimal number), bacteria will not work as effectively, resulting in the reduced production of VFAs from the diet, particularly acetate.

Low rumen pH can also cause damage to the lining of the cow’s rumen — which, in turn, can have a negative effect on both feed intake and digestion, leading to depressed milk production, decreased fertility and other health problems.

Low milk fat can be a sign that cows are suffering from SARA.

Improving butterfat levels

There are multiple ways to help improve butterfat levels, including boosting rumen pH levels, increasing the fibre-digesting bacteria in the rumen and following a good grassland management plan.

Don’t allow the cow to pick and choose what she eats, as she is more likely to only eat the leaf, which is higher in sugar and lower in fibre.

Choose a concentrate with a high level of digestible fibre — for example, beet pulp.

Do not feed mouldy feed or forages, as mould is a potential indicator of mycotoxins, which can kill rumen bacteria and inhibit fibre digestion, resulting in lower acetate production and, therefore, lower butterfat levels.

Proven solution

Avoiding conditions that can lead to SARA and improving rumen pH are central to ensuring that the rumen is working at its best; the bacteria in the rumen will be working more efficiently, optimising the breakdown of grazed grass and concentrates as well as nutrient availability.

Commonly live yeasts are used to help achieve these prime conditions, but while many yeasts claim to have a positive effect, only one — Yea-Sacc® from Alltech — is supported by published and proven research in Ireland.

In fact, studies of Yea-Sacc constitute almost 50% of the total research on all yeast products worldwide. Yea-Sacc is also the only live yeast that has produced positive results on dairy cow performance at Irish research centres, such as University College Dublin (UCD).

Figure 1: Effect of Yea-Sacc supplementation on rumen pH (p=0.0037)

Controlling rumen pH

Yea-Sacc — a special, active strain of live yeast with a specific impact on rumen activity — has been developed on the backs of more than 100 controlled animal performance research trials. Yea-Sacc works by metabolising excess oxygen and increasing the amount of lactic acid-utilising bacteria, which help remove acid and increase rumen pH.

Trials studying Yea-Sacc conducted at the UCD Lyons Farm highlighted the ability of Yea-Sacc to significantly increase the rumen pH of cows on grass-based systems throughout the day, as compared with cows that did not receive Yea-Sacc (Figure 1).

As these results illustrate, adding Yea-Sacc to your feed can help maintain optimal rumen pH levels and prevent SARA.

Figure 2: Effect of Yea-Sacc supplementation on rumen VFA

Increasing VFA production

An increase in VFA production in the rumen signifies that more energy is being produced from the diet — and increasing acetate, a key VFA, can help increase butterfat levels.

In the same study mentioned above, UCD demonstrated that cows fed Yea-Sacc had significantly higher levels of VFAs (Figure 2). This increase in VFA production was a by-product of increased rumen function and a more stable rumen pH.

Additionally, Yea-Sacc produced small peptides that increased the bacteria responsible for fibre digestion, improving the butterfat percentage.

Cows fed Yea-Sacc were able to produce more energy from their feed, meaning they needed to mobilise fewer body reserves.

Summary

While many factors can help prevent a drop in milk solids, the addition of a live yeast product, such as Yea-Sacc, has been proven to consistently improve rumen function by maintaining a higher rumen pH, increasing fibre-degrading bacteria and increasing VFA production — all of which play an important role in improving butterfat production and overall milk solids.

Different rumen buffers will have different effects, but Yea-Sacc is the only live yeast studied in Irish grazing conditions to produce consistent, proven results, including increased milk solids, improved feed efficiency and better fertility.

Dairy farmers must give more consideration to which live yeast product they are choosing for their own farms.

For management tips on maintaining milk solids visit go.alltech.com/beat-the-drop