Corn silage’s energy comes from the high moisture portion of the plant. That grain portion is approximately 65 percent of the total plant’s energy. “When selecting a hybrid, start with a good grain hybrid,” encouraged Bill Mahanna, “because you cannot overcome the lack of starch with small increases in fiber digestibility.” He also cautioned, “Not every grain hybrid makes a good silage hybrid because they may be too short and not deliver the desired yields.”
Mahanna presented “Guidelines for selecting a silage hybrid” during a Hoard’s Dairyman webinar. With extensive experience in dairy nutrition, he serves as Pioneer’s Global Nutritional Sciences Manager and is an adjunct professor at Iowa State University. He shared details with the live audience on this crucial topic, as corn silage is extremely important in milking cow rations to achieve high production levels.
The key drivers of corn silage are yield, fiber digestibility, and starch. In a perfect world, we would want all three. But the research shows that the same hybrid grown in different locations can have varying results for these three entities.
Differences are a result of the environment, management, and genetics.
Environment factors includes such things as water amounts, light exposure, heat exposure, soil fertility, field history, and disease/pesticide exposure.
Results are also impacted by management. Details like planting date, harvest maturity, chop height, processing, and ensiling are influenced by the people-side of the business.
The third item is the science – genetics. And by that, Mahanna was referring to brown midrib (BMR) versus standard varieties.
What should you focus on when selecting a corn silage hybrid?
When choosing a hybrid, the three items Mahanna addressed were agronomic traits, dry matter yield, and starch content. “Absolutely, the most important thing we have to select on, initially, is agronomic traits because that will contribute to yield stability,” he said. Those items include heat units to silk and maturity, stress emergence, drought tolerance, disease resistance, fungicide response, ear molds, and others. These all have an impact on starch and fiber digestibility.
Corn plant height is also something to consider. Short-statured plants can be high in starch, but they may lack overall tonnage. Dry matter yield is really influenced by the corn plant height (at the ear) and starch (grain) content. Silage yield is driven by the harvest timing, hybrid genetics, and the planting date. Two factors to observe at harvest time are dry matter and kernel maturity. For each additional two days in the field, there is an increase of 1 percent more starch deposited in a ton of corn silage.
What should you not focus on when selecting hybrid genetics?
The two criteria Mahanna suggested to minimize when looking at hybrids were starch digestibility and fiber digestibility (unless discussing BMR varieties).
Fiber digestibility is an area that should not be given consideration as various hybrids are not statistically different. Fiber digestibility is already very high and, therefore, it is hard to make additional progress without sacrificing yield. “Putting selection pressure on fiber digestibility is not warranted,” remarked Mahanna.
The main influencer of fiber digestibility is the growing environment, rather than genetics. Late-season plant health can also influence fiber digestibility, as diseases can decrease neutral detergent fiber digestibility (NDFD). Fiber digestibility does not change due to the ensiling process.
In dealing with BMR expectations, there will be about a 5 to 15 percent reduction in yield. There will be less yield, yet a higher intake volume from the cows. There is also potential for more agronomic risk and need a for fungicides with a BMR selection.
Crop genetics certainly influence the crop’s results, but Mahanna was consistent in reminding attendees that the same corn hybrid is heavily impacted by the growing environment and its geographical location. In fact, the growing environment is more influential on neutral detergent fiber digestibility than genetics.
The growing environment also has a huge impact on starch digestibility, as well as kernel maturity, and degree of processing. Keep in mind that the starch levels (unlike fiber digestibility) will change in fermented storage. Forage management post-harvest influences the starch levels and rations should be updated accordingly at feed-out. Starch digestion should not be a selection criteria for a hybrid, but a feeding consideration.
The author is the online media manager and is responsible for the website, webinars, and social media. A graduate of Modesto Junior College and Fresno State, she was raised on a California dairy and frequently blogs on youth programs and consumer issues.