Feeding high corn silage diets: Part 1
Feeding high corn silage diets presents opportunities and challenges for dairy producers.
Feeding higher levels of corn silage in the diets of dairy cows presents some great opportunities, but also some challenges. Opportunities include the potential to reduce purchased feed cost (especially corn grain), more stability in ration cost throughout the year, increased forage production on limited acres, and the opportunity to make bigger improvements in ration cost and milk production through improved Neutral Detergent Fiber (NDF) digestibility.
Challenges with inclusion of higher amounts of corn silage in the ration include: “more of your eggs are in one basket” so if NDF digestibility is lower in a given year, you will have a more difficult time managing the feed for high milk production; and the importance of knowing your cost of production is magnified as this one forage now has a big impact on your farms profitability.
Five keys to success in high corn silage diets include a timely harvest, hybrid selection for fiber and starch digestibility, grouping and feed allocation, processing considerations, and allowing for breakdown of corn grain in storage.
Timeliness of corn silage harvest affects fiber digestibility and starch digestibility. As the corn plant matures NDF digestibility decreases significantly.Mike Allen of Michigan State University Extension showed a 3 – 6 percentage points difference in NDF digestibility as corn silage matured from 1/8 milk line, approximately 30 percent whole plant dry matter, to black layer, approximately 42 percent whole plant dry matter, depending on hybrid. Starch digestibility also decreases as kernel moisture decreases. This change in starch digestibility occurs as the kernel matures and the kernel endosperm becomes more vitreous. The current recommendation is to harvest corn silage at 35 percent whole plant dry matter or ½ kernel milk line. Farmers filling bunkers or piles will often start harvest around 30 percent dry matter to maintain an average of 35 percent.
Corn hybrids vary significantly in total NDF, NDF digestibility, and starch digestibility. Sample analysis information obtained from Dairy One lab in New York shows that percent NDF in corn silage samples ran from 2000 – 2014 ranged from 37.6 percent to 49.6 percent (one standard deviation, 68 percent of the samples surrounding the mean). Producers may ask, “What is the right NDF level that I should look for in a hybrid”. The answer is, it depends! If land is limiting and/or corn grain price is projected to be low, a producer may be better off to choose a high NDF hybrid even if corn grain content is sacrificed. If a producer has an adequate land base and/or corn grain price is projected to be high, a producer may be better off to choose a low NDF hybrid with higher grain content. Ultimately the producer needs to understand his/her cost of production in order to make this decision wisely.