Relationship between processing score and kernel-fraction particle size in whole-plant corn silage

Abstract

Kernel processing increases starch digestibility in whole-plant corn silage (WPCS). Corn silage processing score (CSPS), the percentage of starch passing through a 4.75-mm sieve, is widely used to assess degree of kernel breakage in WPCS. However, the geometric mean particle size (GMPS) of the kernel-fraction that passes through the 4.75-mm sieve has not been well described. Therefore, the objectives of this study were (1) to evaluate particle size distribution and digestibility of kernels cut in varied particle sizes; (2) to propose a method to measure GMPS in WPCS kernels; and (3) to evaluate the relationship between CSPS and GMPS of the kernel fraction in WPCS. Composite samples of unfermented, dried kernels from 110 corn hybrids commonly used for silage production were kept whole (WH) or manually cut in 2, 4, 8, 16, 32 or 64 pieces (2P, 4P, 8P, 16P, 32P, and 64P, respectively). Dry sieving to determine GMPS, surface area, and particle size distribution using 9 sieves with nominal square apertures of 9.50, 6.70, 4.75, 3.35, 2.36, 1.70, 1.18, and 0.59 mm and pan, as well as ruminal in situ dry matter (DM) digestibilities were performed for each kernel particle number treatment. Incubation times were 0, 3, 6, 12, and 24 h. The ruminal in situ DM disappearance of unfermented kernels increased with the reduction in particle size of corn kernels. Kernels kept whole had the lowest ruminal DM disappearance for all time points with maximum DM disappearance of 6.9% at 24 h and the greatest disappearance was observed for 64P, followed by 32P and 16P. Samples of WPCS (n=80) from 3 studies representing varied theoretical length of cut settings and processor types and settings were also evaluated. Each WPCS sample was divided in 2 and then dried at 60 °C for 48 h. The CSPS was determined in duplicate on 1 of the split samples, whereas on the other split sample the kernel and stover fractions were separated using a hydrodynamic separation procedure. After separation, the kernel fraction was redried at 60°C for 48 h in a forced-air oven and dry sieved to determine GMPS and surface area. Linear relationships between CSPS from WPCS (n=80) and kernel fraction GMPS, surface area, and proportion passing through the 4.75-mm screen were poor. Strong quadratic relationships between proportion of kernel fraction passing through the 4.75-mm screen and kernel fraction GMPS and surface area were observed. These findings suggest that hydrodynamic separation and dry sieving of the kernel fraction may provide a better assessment of kernel breakage in WPCS than CSPS.

Silage review: Recent advances and future technologies for whole-plant and fractionated corn silage harvesting

“…The use of a single sieve to determine degree of kernel processing leads to the assumption that all particles passing through this sieve are equal. Nevertheless, it is well established that kernel particles of varied sizes have different starch digestibility (Dias Junior et al, 2016). Consequently, the utilization of a single sieve to determine kernel breakage and its potential digestibility in WPCS may Means with different superscripts differ (P ≤ 0.0001).…”

Effects of processing, moisture, and storage length on the fermentation profile, particle size, and ruminal disappearance of reconstituted corn grain

“…Higher moisture contents (Szasz et al, 2007;Owens and Basalan, 2013) and longer periods of storage (Benton et al, 2005;Fernandes, 2014;da Silva et al, 2019) typically increase starch and dry matter (DM) digestibility (Hoffman et al, 2011). Moreover, the disruption of the protein-matrix during silage fermentation hypothetically could result in a reduction of kernel particle size during long storage periods, increasing the surface area for digestion (Dias Junior et al, 2016;Saylor et al, 2020).…”

Does longer storage time increase starch digestibility in corn silage?

“…Alguns estudos que testaram o armazenamento prolongado relataram que o pH continuou a diminuir ao longo do tempo devido ao acúmulo de lactato e acetato, mas esses efeitos não foram tão pronunciados no período inicial de estocagem. Por exemplo, dois estudos de silagem de planta inteira de milho (Ferraretto, et al, 2015;Ferraretto et al, 2016) destacaram quedas de pH em até 120 dias de ensilagem. Além disso, Windle et al (2014) relataram um declínio do pH ao longo do tempo em armazenamento para a silagem de planta inteira de milho por até 150 dias, enquanto (Der Bedrosian et al, 2012) observaram queda de pH somente após 180 dias após a ensilagem (em silagem com 41% de MS).…”