Corn Silage: Maximizing A Dairy Nutrition Staple
If anything good came out of the historically high feed prices of the past few years, it's that dairy producers now are placing much greater emphasis on producing excellent forages, according to John Kurtz with Chr. Hansen Animal Health and Nutrition.
"Corn silage is one of the most economical dairy feed sources," says Kurtz. "But varying levels of quality can have a tremendous impact on cow performance and herd profitability. The herds that achieve excellence in their cow health and performance almost universally achieve excellence in their silage production."
While feed and milk prices have moderated, some producers will continue to invest in technologies and equipment that support efficient feed production, processing and delivery. That investment helps them to produce quality corn silage every year.
Besides capital improvements, there are additional measures that producers can take to improve the quality and quantity of their corn silage crop. Limin Kung, Jr., professor of animal science at the University of Delaware, says that, as in most cases of management success, it is a matter of doing many little things well, ultimately resulting in a big difference.
He says harvest maturity is the starting point. Corn silage harvested too early (< 30% dry matter [DM]) often results in an end product with low starch and excessive production of total silage acids (with a large proportion coming from acetic acid produced by "wild bacteria"). Seepage is another danger with immature corn silage, "and that's a problem you definitely don't want to have," says Kung.
Conversely, overly mature plants (>40% DM) will produce a low-acid crop with poor packing density; greater oxygen entrapment; and poor aerobic stability that could result in more shrink. Both immature and over-mature silage can result in decreased palatability and intake. Kung's recommendation for an ideal harvest maturity: 35 ± 2% DM.
"Milk-line stage alone is not an accurate indication of when to start harvesting," advises Kung. "A whole-plant dry-matter test is the only way to precisely pinpoint maturity." He adds that the ideal maturity window can be extremely narrow, as whole-plant moisture can drop up to 2% on just one hot, dry, breezy day.
New methods of processing silage have emerged in the past few years. Kurtz says a greater degree of kernel processing, without sacrificing stover particle size and effective fiber, is the key to maximizing the nutritive value of corn silage. On traditional harvesters, he prefers a chop length of 24 to 26 mm with a roll clearance of 1 to 1.6 mm.
Visual appraisal alone will not accurately portray the degree of processing in batches of corn silage, which is why Kurtz emphasizes the importance of regularly performing laboratory analysis of corn silage processing score (CSPS) and fecal starch as a percentage of dry matter in manure.
"Monitoring CSPS during processing is important to ensure we are putting away a well-processed crop," says Kurtz. "But ongoing CSPS evaluation also is necessary, because CSPS in well-preserved silage typically will continue to increase through the ensiling process." He says silage going into the bunker at a CSPS of
70—already an excellent score—can be expected to feed out several months later at a CSPS of 80 or higher. The payoff is more digestible silage that can be fed at lower rates. Low fecal starch scores correlate with high total tract starch digestibility (TTSD). A score of 5% or lower is considered desirable; 2 to 3% is an even better goal.
To avoid dry-matter loss, forage needs to ferment quickly and remain stable during storage and feed out. Rapid production of lactic acid and a fast drop in pH during ensiling are good signs of a quick fermentation. Inoculating silage with additional lactic acid-producing bacteria can help accelerate the process. In addition, inoculants specifically containing Lactobacillus buchneri can promote stability because they produce moderate amounts of acetic acid that inhibit spoilage yeasts in silage, says Kung.
Kung notes that the temperature of the water used to mix and distribute inoculant solutions is critical. Water exceeding 100°F can kill a large percentage of the live bacteria in an inoculant, resulting in significantly low numbers of effective bacteria actually being distributed in the silage. Kung's research group has measured inoculant mixtures in tanks with temperatures exceeding 130 F! In most cases high water temperatures in inoculant tanks are due to poor placement of the tanks (e.g. too close to an exhaust or engine).
Avoiding silage spoilage is, of course, an important goal once the crop is put away. Excellent packing, tightly covering bunkers and excellent face management all are necessary to limit spoilage. But when spoilage does occur, Kung's advice is: "Pitch it. It's potentially not even a good feedstuff for steers."
What's next on the silage front? Kurtz believes technology will continue to drive the quality and value of corn silage. Specifically, he would like to see agronomic advancements that could lower the content of ash—an inert, unusable compound—in corn plants. He believes activity monitoring that provides frequent, individual-animal data on feed consumption, along with a host of other variables, also will become more widely adopted. Kung says additional research on the hundreds of volatile compounds in silage, such as ethyl lactate, could identify factors that affect silage intake and animal performance.
"We've come to a point at which we can't get any more feed into these animals," says Kurtz. "Our goals now must be centered on doing some of the digestive work for them, so that every bite they take maximizes their performance potential."