Feeding high corn silage diets presents opportunities and challenges for cattle producers.
By: Stan Moore, Michigan State University
In part one of this two part series by Michigan State University Extension, the first two keys to success in feeding high corn silage diets were covered: Timeliness of corn silage harvest, and hybrid selection, percent NDF. In part two we will continue with hybrid selection and also cover grouping and feeding, processing considerations, and allowing for breakdown of corn grain in storage.
Hybrid selection (continued)
Just as the percent NDF varies considerably between hybrids, so does the NDF digestibility. Hybrids can easily vary by 10 percentage units, and each unit increase in NDF digestibility has been shown to increase dry matter intake by .37 pounds per day, and increase 4 percent fat corrected milk by .55 pounds per day according to a 1999 report by Oba and Allen in the Journal of Dairy Science. In other words, choosing hybrid A that has a NDF digestibility of 50 percent over hybrid B that has a NDF digestibility of 40 percent would equate to an increase of 5.5 pounds per day in milk production per cow! Oba and Allen also showed that higher producing cows show an even higher response to improved NDF digestibility.
Hybrids also vary significantly in starch digestibility. Allen showed variation across 6 hybrids to be 49.8 percent to 60.3 percent in starch digestibility in the 2003 Journal of Dairy Science.
With large variation in NDF, NDF digestibility, and Starch digestibility across hybrids, producers would be wise to do partial budgeting when it comes to silage hybrid selection. Cost of production, land base, corn silage concentration in diets, and cost of supplementation are all important in making hybrid selections.
Grouping and feeding
Feeding one group total mixed rations (TMR) will not allow growers to take full advantage of improvements in timely harvest and hybrid selection. This is due to the fact that high producing cows benefit most from increased fiber digestibility. High producing cows are the ones that are going to show an increase in dry matter intake and milk production. Low producing cows will not respond (or show less response) and thus will wash out the benefits of the improvements growers make in hybrid selection. One group TMR’s also do not allow producers to mitigate the effects of poor NDF digestible forage. Because all cows are being fed the same ration, producers are limited in their ability to feed the best corn silage to the highest producing cows.
In general processing corn silage has shown benefits to increased starch and fiber digestibility, as it increases access to rumen bacteria by increasing surface area. However, growers need to be cautious of over-processing silage, especially as we choose higher NDF digestible varieties and harvest in a timely way. Over processing will reduce dry matter intake and result in milk fat depression.
Allowing for breakdown of corn grain in storage
Increasing storage time prior to feeding will increase starch digestibility and corn silage quality will be more consistent as it is fed out. Starch digestibility can improve by 15 percent units when harvest at adequate moisture according to Allen in the 2003 Journal of Dairy Science. It is recommended to store corn silage 3-6 months prior to feeding. This will require extra storage, and higher inventory cost, but the results are improved starch digestibility and insurance for low corn silage production years.
Following these five keys to success will help optimize the benefits of feeding high corn silage diets to dairy cows.