MSU Extension Dairy

When corn is growing in the field, we all become spectators of the crop. We look at fields along our travels and compare them to those at home. Not only do we look at corn fields, but also to a certain extent, we judge them on how tall the crop is, how big the ears look as we drive by and even how dark green is the color. Those windshield evaluations really don’t get to the heart of the issue.

Corn silage is not grown as a commodity, it is primarily grown for feeding the cattle you have. Therefore, the feed quality is the heart of the issue when we evaluate corn for silage and should be a primary basis for seed selection. It cannot be evaluated from windshields or even from field inspections. What we need to know is how a hybrid is going to feed? How are cows going to milk or grow on it? What will it do to the cost of the ration? For Michigan State University Extension Dairy educators, those are key questions.

Michigan State University Department of Plant, Soil and Microbial Sciences conducts hybrid trials each year for various crops including corn silage. The data they collect provides some answers to those questions about quality and is valuable information for farmers to use in planning. In 2020, a total of 304 hybrids from 24 brand names comprised 464 entries that were evaluated. The corn silage hybrids were planted at eight locations in four maturity zones based on growing degree days.

Corn silage is analyzed differently than corn for grain, with six quality factors measured and two calculated. The quality factors can be grouped as two component measures (crude protein and starch), two fiber measures (NDF and ADF) and two digestibility measures (in vitro digestibility and NDF digestibility - NDFd). The two calculated measures are milk per ton and milk per acre.

Those measures are recorded for each hybrid at each growing location, allowing comparison between hybrids and highlighting that even hybrids that look similar can differ markedly in feed value. All hybrids were in replicated plots and treated the same.

MSU Extension educator Christian Tollini and I examined the data from corn silage variety trial plots at Double B Dairy in Whittemore, MI, a Zone 4 location, and discussed differences in quality measures in an MSU Extension Dairy Team video. No matter the year, zone, location or number of hybrids, there are important lessons to be learned from evaluating the quality measures.

The 2020 field results show ranges in each of the measures among 17 silage hybrids (97 day and earlier maturity) at this location. Whether for those hybrids, or from a location within your growing zone, you can compare hybrids across quality measures and analyze the impact of the differential between hybrids at either end of the range.

At the Iosco County site in 2020, there was a 1.1 percentage point range in crude protein across the entered hybrids: 8.0 to 9.1%. While that may not seem like much of a difference, it adds up for dairy cows fed a high corn silage ration (60 pounds as fed daily for this example). The one percentage point difference can be translated to the amount of additional soybean meal (SBM) necessary to make up for the difference. In this example, the difference in SBM needed was calculated to be about 120 pounds per day for a pen or group of 250 cows. Over the period of a year, that adds up to almost 22 tons of SBM for that barn or group of 250 cows to feed the same amount of protein as the higher CP corn silage.

While protein is important, fiber is the biggest reason we feed corn silage. The balance between fiber amount, fiber digestibility and dry matter intake is critical in feeding cows, and there were differences among the 17 hybrids at this site. Neutral detergent fiber (NDF) had a range of seven percentage points and the digestibility of that fiber (NDFd) had a 3. 9 percentage point difference. Those differences will impact the dry matter intake and therefore, milk production by cows.

There is a general rule useful for selecting hybrids based on fiber level. When the land base for planting corn for silage is limiting or when supplementation cost is low, we want to feed a higher fiber silage to get the fiber we need for the cows. The inverse is also true; when land base is not the limiting factor or when supplementation cost is high, we want to feed a lower fiber hybrid.

You should also look at the calculated measures of milk per (dry) ton of corn silage and milk per acre. In 2020, the range in milk per ton at this site, among these 17 hybrids, was 248 pounds of milk. If that group of cows was fed a diet with 62 pounds as fed of silage per day (at 35% dry matter), each cow would eat around an average of four tons of corn silage per year. Therefore, the MILK 2006 model predicts that they would produce around 1000 pounds of milk per year more than cows fed the hybrid at the other end of the range in milk per ton.

Selecting corn hybrids for silage is a feed decision. At the rates we feed corn silage today, that is a critical decision that will impact milk production and ration cost for a year. For more information, download MSU “Corn Hybrids Compared” at vartietytrials.msu.edu and be selective in your selection to produce forage that milks.