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Proper use of BMR silage

This a well written article by Maureen Hanson from Dairy Herd Management 2/23/2022
Joe Bradley

Back Off BMR After Transition?
As a guideline, they suggested most dairies should plan to plant about 20-30% of silage acres to BMR, and 70-80% to conventional silage hybrids.

As a guideline, they suggested most dairies should plan to plant about 20-30% of silage acres to BMR, and 70-80% to conventional silage hybrids.

Brown midrib (BMR) corn silage has become the darling of dairy nutritionists and producers alike, thanks to its high NDF content, increased passage rate, and boosts to dry-matter intake (DMI).

But distinct drawbacks make BMR corn silage far from the all-encompassing silver bullet it was once hoped to be.

For on thing, it comes with a yield price. New York agronomic consultant Ev Thomas told the audience at the 2018 Tri-State Dairy Nutrition Conference that BMR hybrids produce a fairly standard yield drag of 10-15% compared to conventional corn. And while BMR varieties have improved in yield over the years, so, too, have conventional hybrids.

Agronomic instability is another issue. The low lignin content in BMR plants that makes it so highly digestible also makes it less hardy under field conditions. Lodging is more common than in higher-lignin varieties, which can contribute to impaired plant development and harvesting headaches.

It’s also a little fussier in the field, prompting Thomas to advise producers to reserve their most fertile and well-drained soils for BMR plantings.

Finally, the fact that cows eat BMR corn silage like candy is a good thing. But it also can be a bad thing in terms of sheer tonnage. Increases in DMI places higher demand on forage supplies, requiring more crop acres to feed the same number of cows, and making the farm’s total forage crop more expensive due to additional inputs like labor, fuel, and inoculants.

All of these BMR nuances make it a valuable-yet-specific feedstuff that should be used strategically to capture its benefits, while also maintaining balance in a farm’s complete agronomic and nutrition plan.

One such approach proposed by Pioneer is to feed BMR corn silage to transition cows, starting at 3-4 weeks pre-calving, then gradually switching them to conventional corn silage starting at 4-5 weeks into lactation.

Their advice is based on research that shows value in feeding BMR corn silage during transition when cows need the energy afforded by a highly digestible forage source, and the intake incentive of a highly palatable feedstuff. But when their intake gets rocking and rolling later in lactation, DMI versus milk yield actually favors conventional corn silage in terms of feed efficiency.

In a Cornell study (Stone et al.), cows were fed BMR corn silage from 4 weeks pre-fresh until 4 weeks postpartum, then switched to conventional corn silage. Compared to a control group fed conventional corn silage throughout, the BMR group showed significantly higher DMI from 2 weeks pre-fresh to 3 weeks post-fresh. But after that, DMI was similar for both groups through 15 weeks.

A Utah State University study using four different feeding configurations showed feeding BMR in the transition phase was important to improving DMI rates immediately before and after calving. But switching from BMR to conventional corn silage a few weeks postpartum resulted in more milk per pound of DMI by 16 weeks into lactation.

A Miner Institute study showed that cows fed BMR corn silage in mid-lactation had 2.6 pounds higher daily DMI, but significantly lower feed efficiency compared to cows fed a standard corn silage diet, because there was negligible difference in milk production between the two groups.

And studies at both the US Dairy Forage Research Center and Cornell University showed that cows fed BMR corn silage in the transition period were able to maintain their advantage in milk production even after being switched to standard corn silage at 4 weeks postpartum.

To make the BMR transition ration strategy work, the Pioneer experts cautioned that dairies should have the ability to maintain separate bunkers or piles of BMR and conventional corn silage, and to segregate transition cows to deliver specialized BMR diets to them.

As a guideline, they suggested most dairies should plan to plant about 20-30% of silage acres to BMR, and 70-80% to conventional silage hybrids.