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Rumen additive benefits dry cows

Researchers find promising results feeding monensin to dairy cows during their dry period, when nutritional needs are greatest

Getting nutrition right during a dairy cow’s dry period makes a huge difference to her health, the health of her calf, and the milk yield after calving. Now, new research from the University of Illinois has shown that diets that promote consistent energy levels and contain the rumen-boosting supplement monensin are the ideal approach during the dry period.

Monensin is widely used in the beef and dairy industries. It is an ionophore (a chemical that transports an ion across a cell membrane) that selects against certain bacteria in the rumen to increase production of propionic acid (an organic acid), which is a more efficient volatile fatty acid for cows. It keeps more feed energy in the body instead of losing it to methane. In dairy cows, it boosts feed conversion more efficiently, as well as milk protein production.

Farmers typically feed the supplement during lactation to make fermentation in the rumen more efficient and convert nutrients into milk proteins.

Many producers use a “steam up” approach where they gradually increase the energy intake during the dry period to help adjust the rumen and prepare the cow for greater feed intake post calving. But this approach may be of questionable benefit for many farmers and it was this feeding approach variable that prompted the research on dry period diet strategies.

“There was a question about whether monensin would be useful in a controlled-energy dry cow diet in which we are trying to prevent over-consumption of energy during the dry period,” said James Drackley, a professor at the university’s Animal Science Laboratory and co-author of the study.

“Since monensin boosts the energy captured from feed, it might seem counterproductive in such diets. There was also the idea that cows should have a break from monensin so they don’t become resistant to it. Plus, we are interested in whether the close-up diet of higher nutrient density actually provides benefits beyond just a single dry cow ration.”

Drackley said that the idea behind the steam-up diet is to increase energy intake in the face of declining dry matter intake before calving and to adapt the rumen to the higher energy feeds that will be fed after calving.

“Research results on the efficacy (of that approach) are widely unsuccessful,” said Drackley. “It may have advantages for higher producing herds. It is still widely used but the single group dry cow program has increased in popularity.”

The researchers fed dairy cows four diets in the study and they were combinations of two main factors — a single diet or close-up, with or without monensin.

The supplement is typically fed during lactation to make fermentation in the rumen more efficient and convert nutrients into milk proteins. Some producers take the supplement out during the dry period to give rumen microbes a rest period.

“The four diets were single diet no monensin, close up diet no monensin, single diet with monensin, and close-up diet with monensin,” said Drackley. “Statistically, then we can look at the cows that received each of the diets to calculate the response to the main factors of diet and monensin. There was no difference between cows that received the single diet or the close-up diets, but we did show the positive response to keeping in monensin.”

The diets made no difference in how the cows performed or in any of their metabolic indicators after calving.

“Our research showed that if we took monensin out during the dry period, the cows produced about two kilograms less milk in the next lactation,” said Drackley. “The conclusion is that it is better to leave it in and prevent that lost milk production.”

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