Could high-cut silage replace BMR? Here’s what the research suggests

By Cole Diepersloot, Ph.D., Vita Plus forage specialist and dairy nutritionist

When we talk about corn silage, there’s always a balance between quality and yield. One management decision that really highlights this trade-off is cutting height at harvest.

If we increase the cutting height of silage during harvest, we are going to leave more of the more fibrous and less digestible part of the stalk in the field and we are going to increase the proportion of leaf and grain within the remaining silage that we harvest.

That shift improves fiber digestibility and starch concentration, which means the feed becomes more energy dense. But it’s not without cost. If you were to increase cutting height by 10 centimeters, which is a pretty small increase as we look at practical applications, we would be decreasing our dry matter yield by over half a metric ton per hectare. As you can imagine, that can be significant and adds up quickly if a farm decides to harvest all their corn silage at a greater cutting height.

So, if you’re considering raising cutting height, you need a plan. Either grow more acres or find other strategies to offset the yield loss. It’s not a decision to make in isolation.

Corn maturity plays a role

Cutting height interacts with other factors, especially corn maturity at harvest. In a meta-analysis of 33 studies, we grouped silage by dry matter (DM):

• Low DM (<32%)
• Average DM (32–37%)
• High DM (>37%)

The biggest improvement in fiber digestibility came from high-DM silage, which makes sense because stalk digestibility declines as plants mature. Interestingly, starch concentration improved most in the low-DM category — something we didn’t expect. We suspect stay-green genetics may be influencing those results.

A possible alternative to BMR

With brown midrib (BMR) hybrids being phased out, some farms are asking if higher cutting heights could fill that gap. Unlike BMR corn silage, which typically has lower starch concentrations, harvesting a higher cutting height increases starch concentration, and therefore, may increase the energy density of high-cut corn silage more than BMR alone would.

That’s promising, but we need more research before recommending high-cut silage as a full replacement for BMR hybrids. High-cut corn silage will probably not feed the same as BMR silage, but the trade-offs between nutritive value and yield are real, and every farm will need to weigh them carefully.