Silage corn harvested without grain has a higher sugar content than normal silage. But factors that inhibit grain production also retard increases in plant dry matter content, resulting in much lower yields of digestible nutrients.

That’s according to researchers at Illinois State University and DuPont Pioneer, who first compared two tropical hybrids that failed to produce grain with six temperate grain-bearing hybrids. Sets of whole plants were harvested at seven-day intervals starting 102 days after planting.

The tropical hybrids averaged 37% less dry matter per plant than the temperate hybrids across harvest dates. Their NDF digestibility was lower, but their soluble sugar content was higher. Their calculated milk and beef production per ton and per acre were 50% and 74% lower, respectively.

In a second trial, pollination was prevented in three silage hybrids by covering emerging ear silks with paper bags. Pollinated and non-pollinated plants were harvested on 16 dates.

When pollinated plants were 28% dry matter, their dry plant weights and compositions were similar to those of the non-pollinated plants. But when they reached 40% dry matter, the dry weight of plants without grain was 45% lower. Those plants stayed below 30% dry matter, though their sugar content exceeded 20% of the dry matter.

Averaged across harvest dates, dry matter, starch, ADF, NDF and NDF digestibility were all lower for non-pollinated plants. Preventing pollination reduced milk and beef per ton by 50% and per acre by 65%, the researchers report.

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