The “fine” details on silage storage and particle size – Margaret Quaassdorff, Vita Plus

Posted on September 23, 2016 in Forage Foundations
By Margaret Quaassdorff, Vita Plus Lake Mills dairy specialist
In the July 2016 Forage Foundations, we reported particle size differences existed in haylage and corn silage when stored in bags versus bunkers and piles.  We’ll now focus on the implications of those differences on the rate of digestion and passage, rumen and overall cow health, production, and whether the cow will consume the entire balanced ration.

Although some debate over the exact cut-off length exists, it’s clear that large particles (greater than 0.75 inches) consumed in the diet contribute to the floating rumen mat and encourage rumination.  While other nutritionists have noted differences in the percentage of these large particles in the top sieve of the four-part Penn State Particle Separator, our survey showed little difference between corn silage stored in bags versus bunkers and piles with only subtle differences in haylage stored in those structures.

However, on average, we saw an increase in fines in both corn silage and haylage stored in bags compared with bunkers and piles, based on the yield in the bottom pan of a particle separator.  We feel it is important to note those differences in Figure 1.
Why do increased “fines” matter?
Rumination and the act of chewing increases saliva production.  Saliva acts as a buffer to stabilize rumen pH at the correct level for fiber-digesting rumen microbes to thrive and contribute to overall digestibility, animal health, and production.

Our field study showed, on average, haylage and corn silage stored in bags had nearly double the amount of fine particles (less than 0.07 inches) in the bottom pan compared to bunkers.  This means, on average, at least 8.6 percent of haylage particles and 9.3 percent of corn silage particles pass through the rumen without contributing to rumination stimulation – a lot of ineffective particles compared to the 5.0 percent or less guideline for fine particles.

If a diet is not “physically” balanced, possibly due to forages contributing greater than 5.0 percent particles of 0.07 inches or less, inadequate fiber could lower the rumen pH, creating an environment with inefficient fiber digesting rumen microbes and decreased dairy cow health and production.  A lower rumen pH may also be associated with subacute rumen acidosis and milkfat depression.  This increases the potential for reduced dry matter intake (DMI) and the chances of displaced abomasum, laminitis, and hemorrhagic bowel syndrome – one big mess!  In contrast, too much fiber in the diet may displace more digestible nutrients and contribute to reduced DMI via gut fill.

Understand your crop and find the happy medium!
Based on our understanding that feed stored in a bag is processed more than other storage methods, corn silage harvested too dry may benefit from being stored in a bag because the bagger could process it more and break up hard kernels to increase surface area and digestibility, theoretically.  Increased starch digestibility leads to less dietary energy waste and more efficient milk production.  Haylage cut too long could also benefit from being bagged because of the bagger’s processing effects.  On the other hand, if the bagged corn silage has been properly harvested with a high amount of available starch, you may consider adding longer forages – like haylage, hay or straw – to avoid negative health and production effects from a diet that may decrease rumen pH.

Overall, when balancing diets, consider both the nutrient content and the physical properties of forages.  Be sure to track the physical properties of your forages because they may change depending on storage structure and perform differently for your herd.

Category: Facility design
Feed quality and nutrition
Forage Foundations
Forage storage and management