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Forage particle size influenced by storage method? Absolutely! – Margaret Quaassdorff, Vita Plus

Posted on July 29, 2016 in Forage Foundations

By Margaret Quaassdorff, Vita Plus Lake Mills dairy specialist

You may have taken forage samples from different storage structures, like bags, bunkers or piles, and observed a difference in particle size distribution. Vita Plus National Forage Specialist Jon Urness and I dedicated more thought and observation to find why forage particle sizes may vary coming out of different storage structures and if the distributions truly differ. It seems reasonable to assume that, during harvest, feed going through a bagger would be processed to a greater degree than feed stored in a bunker or pile, due to more aggressive filling and packing mechanisms.

To our knowledge, we know of no effort to quantify the difference in particle size and distribution between forages coming out of bags versus bunkers or piles. To check our theory, we collected forage samples from more than 65 bags, bunkers and piles, and analyzed them using a Penn State Particle Separator to develop a preliminary database.

Intriguing findings

Figure 1 shows particle distribution results from haylage samples taken from bags versus bunkers or piles. In the top sieve, with particles greater than 0.75 inches, haylage bags had a smaller average percentage of large particles versus haylage bunkers or piles. In the middle and lower sieve, with particle sizes 0.31 to 0.75 inches and 0.07 to 0.31 inches, respectively, similar percent differences existed between bags and bunkers or piles – about 0.5 percent.

However, bagged haylage had 4.2 percent more particles in the bottom pan versus haylage from bunkers or piles. This means, not only does bagged haylage differ in particle distribution versus bunkers or piles, but it is also more processed and contains more short and fine particles than a bunker or pile.

Looking at Figure 2, we see corn silage in both bags and bunkers or piles yielded similar percentages of particles greater than 0.75 inches. We also see a smaller percentage of particles on the middle and lower sieves from corn silage coming out of bags versus bunkers or piles, which is accounted for by a larger percentage in the bottom pan with particles less than 0.07 inches (9.3 percent in bags versus 5.0 percent in bunkers or piles). Again, we can conclude the particle distribution from corn silage coming out of bags is different than bunkers or piles, and storing corn silage in bags yields a more highly processed product.

Comparison to PSPS guidelines (2009)

In comparison to the Penn State Particle Size guidelines in table 1 below, haylage out of bags, on average, fell short of the guideline for the lower sieve, but exceeded the guidelines for the bottom pan. Haylage out of a bunker or pile had a higher percentage of particles greater than 0.75 inches than recommended, but fell within the remainder of the guidelines.

On average, corn silage out of bags and bunkers or piles fell within the ranges for the top and middle sieves, though at the respective upper limits for each, but fell short of recommendations on the lower sieve. Corn silage out of a bag exceeded the recommendation of 5.0 percent on the bottom pan, while corn silage out of a bunker or pile was at the high end of the recommended range for the bottom pan.