Farming Magazine - November, 2012

COLUMNS

Forages: Corn Hybrids for Silage: Decision Time for 2013

By Everett D. Thomas

A high percentage of the seed corn orders for spring planting will occur in the coming weeks, so now is the time to consider what's most important as you look through seed catalogs and listen to sales pitches from seed dealers. Visiting seed company test plots can be useful, but university corn silage hybrid trials are even better since they include hybrids from a number of seed companies and are both replicated and statistically analyzed. However, even university trials don't tell the whole picture. Following are a few considerations as you decide on corn hybrids for 2013 silage harvest.

Kernel texture: a controversial subject

Flinty and vitreous are terms used to describe hard kernel texture, while non-vitreous and floury describe soft kernel texture. There seems to be general agreement that kernel texture is a factor in the digestibility of dry shelled corn and high-moisture corn, but even "the experts" don't agree on the importance of kernel texture when corn is harvested for whole-plant silage.

Some seed companies promote certain hybrids as having soft kernel texture, claiming that the silage from these hybrids is more readily digested by livestock. Other seed companies, if they rate their hybrids for kernel texture at all, make no nutritional claims relating to this trait. There are some respected dairy nutrition consultants who think that kernel texture is an important factor in selecting hybrids for silage, but much of the research on this topic has failed to find meaningful differences. In one study two hybrids were planted, one supposedly having highly vitreous kernels, and the other with floury kernel texture. However, when the hybrids were harvested at two-thirds milk line, both had 48 percent starch digestibility. Based on this and other data, Dr. Jeffrey Firkins of Ohio State University has stated that "vitreousness of corn grain in silage seems to be of little value."

Kernel texture, "stay-green" and processing interactions

Adding to the confusion over kernel texture is the fact that kernel processing increases starch digestibility. (Kernel processing is also called silage processing, which is a more accurate term, because processing affects more than just the kernels.) The more mature the corn, the more advantage there is to be gained from processing the crop.

Then there's the "stay-green" trait, which is the corn plant's ability to remain green and healthy as the kernels become progressively more mature. This is of great benefit for farmers growing grain corn and high-moisture corn, since the ideal is keeping the plant healthy as long as possible. But a high stay-green rating (8 or 9 on a scale of 1 to 9) can actually be a disadvantage if the crop isn't processed, since as the corn plant matures it may have an ear with increasingly hard, mature kernels on a stalk that's still very high in moisture content.

Conventional corn choppers usually break only about two-thirds of the kernels - fewer if knives are dull or with long chop lengths - while a silage processor set at the correct roll clearance breaks over 95 percent of the kernels. Therefore, your hybrid selection for whole-plant silage may depend to some extent on whether or not the crop will be processed.

BMR corn hybrids

A number of seed companies are now selling BMR (brown midrib) corn hybrids, and while BMR's percentage of the total silage corn market is still quite small, it's increasing and will probably continue to do so. This is only partly because there are more seed companies selling these hybrids. High grain prices make high-forage rations increasingly popular, but high-forage dry matter intake is only possible with highly digestible forages, and that's a big advantage of BMR corn.

There are some disadvantages to BMR, including moderately lower yields and higher seed prices. Newer BMR hybrids are more competitive for yield, but current university trial results still show some "yield drag." Concerns about standability have followed BMR corn like a bad odor, but good management can often minimize this problem. University silage trials don't evaluate standability, so we're lacking in trial data, but Cornell University's Bill Cox, who manages the New York corn silage hybrid trials, says that he hasn't had any problems with the standability of BMR hybrids. There have been some lodging problems in California, where the combination of hot temperatures and irrigation results in fast growth, long internodes and very high ear placement. BMR has consistently lower lignin content than other hybrids, contributing to its higher digestibility, and the combination of low lignin levels and a top-heavy plant is challenging, to say the least. That's why the proper plant population of BMR hybrids is critical, and why it's recommended to be kept at moderate rates out on the "Left Coast." I was in California twice last winter and learned that sales of BMR seed corn there have rapidly increased in the past few years, so obviously dairy farmers there are making BMR work in their herds.

Miner Institute has used BMR corn for years and has been pleased with the results. However, it's not for everyone. BMR works best where dry matter intake is most important, which is for transition and high-producing cows. It has little impact on non-milking heifers and low group cows - those making less than 50 to 60 pounds of milk per day.

The combination of higher seed cost and lower yield makes every ton of BMR corn silage more expensive than conventional corn silage, so ideally you want to feed it to those animals that will respond positively. This means putting it in a separate silo and feeding it only to the "right" groups of cows. One-group TMRs aren't the best fit for BMR. The owners of a few very high-producing herds have decided to feed "all BMR, all the time" and seem pleased with the decision, but so far they're the exceptions.

BMR is ideal for high-corn-silage rations, and I discourage its use in herds feeding low rates of corn silage. Farmer and university experience has shown that you need to be feeding at least 10 pounds of BMR corn silage dry matter per cow per day to capture the benefits, and more may be better. If using BMR corn silage, my preference is to feed a minimum of 20 pounds of corn silage dry matter, with at least half of this as BMR.

Ev Thomas has worked as an agronomist in New York for 45 years. He continues to work part-time for Miner Institute and is now an agronomist at Oak Point Agronomics. He has written our Forages column for over 13 years and has been an expert contributor on a number of other topics.