Storage length interacts with maturity to affect nutrient availability in unprocessed flint corn silage

Jonatas Lopes Bueno Dheyme Cristina Bolson Fernando Alberto Jacovaci Ana Luiza Mendonça Gomes Matheus Gonçalves Ribeiro Antonio Vinicius Iank Bueno Clóves Cabreira Jobim João Luiz Pratti Daniel About the authors

ABSTRACT

Our objective was to determine the effects of maturity and storage length on the fermentation pattern, ruminal disappearance of nutrients, and recovery of digestible nutrients in flint corn (Zea mays L.) silage harvested with a pull-type machine without a kernel processor. Corn plants were harvested at 300 g kg−1 DM (low dry matter, LDM) or 400 g kg−1 DM (high dry matter, HDM) and stored for 0, 7, 14, 30, 60, 90, 120, and 180 d in laboratory silos. Corn harvested at HDM had a higher proportion of long particles (>19 mm), more intact kernels, and lower kernel processing score. There was an interaction between maturity and storage length for several fermentation end-products, DM recovery, ruminal disappearance of nutrients, and recovery of digestible DM. Overall, the concentrations of fermentation end-products were higher in LDM than in HDM silage. The DM recovery decreased over time, mainly for LDM silage. Ruminal disappearance of nutrients (starch, CP, and DM) increased with storage length, with greater values for LDM silage at shorter storage, but closer values among LDM and HDM at longer storage periods. The recovery of digestible DM (DM recovery × ruminal disappearance) slightly increased in LDM silage up to 26 d of fermentation, but it markedly increased in HDM silage, mainly up to 60 d of storage. Storing for longer periods is a strategy to partially offset the negative impact of maturity on the digestibility of flint corn silage harvested with pull-type machines without kernel processor.

Keywords:
digestibility; fermentation; proteolysis; starch

Introduction

In Brazil, pull-type forage harvesters without a kernel processor are still widely used by farmers (Bernardes and Do Rêgo, 2014Bernardes, T. F. and Do Rêgo, A. C. 2014. Study on the practices of silage production and utilization on Brazilian dairy farms. Journal of Dairy Science 97:1852-1861. https://doi.org/10.3168/jds.2013-7181
https://doi.org/10.3168/jds.2013-7181...
; Daniel et al., 2019Daniel, J. L. P.; Bernardes, T. F.; Jobim, C. C.; Schmidt, P. and Nussio, L. G. 2019. Production and utilization of silages in tropical areas with focus on Brazil. Grass and Forage Science 74:188-200. https://doi.org/10.1111/gfs.12417
https://doi.org/10.1111/gfs.12417...
). Pull-type forage harvesters typically result in poor kernel processing and, in turn, lower starch digestibility (Salvati et al., 2017Salvati, G. G. S.; Santos, W. P.; Silveira, J. M.; Gritti, V. C.; Arthur, B. A. V.; Salvo, P. A. R.; Ribeiro, A. P.; Lima, T. A. D.; Morais Jr., N. N. and Nussio, L. G. 2017. Impact of kernel processing and particle size in whole plant corn silage on the performance of dairy cows. In: Proceedings of the V International Symposium on Forage Quality and Conservation, Piracicaba.; Ferraretto et al., 2018Ferraretto, L. F.; Shaver, R. D. and Luck, B. D. 2018. Silage review: Recent advances and future technologies for whole-plant and fractionated corn silage harvesting. Journal of Dairy Science 101:3937-3951. https://doi.org/10.3168/jds.2017-13728
https://doi.org/10.3168/jds.2017-13728...
). Additionally, corn hybrids grown in tropical areas predominantly have a greater proportion of vitreous endosperm, which is also associated with lower starch digestibility (Correa et al., 2002Correa, C. E. S.; Shaver, R. D.; Pereira, M. N.; Lauer, J. G. and Kohn, K. 2002. Relationship between corn vitreousness and ruminal in situ starch degradability. Journal of Dairy Science 85:3008-3012. https://doi.org/10.3168/jds.S0022-0302(02)74386-5
https://doi.org/10.3168/jds.S0022-0302(0...
). Consequently, many Brazilian farmers are harvesting corn crop earlier than desirable (< 300 g kg−1 of DM), which result in lower DM yield and silages with lower starch content (Daniel et al., 2019Daniel, J. L. P.; Bernardes, T. F.; Jobim, C. C.; Schmidt, P. and Nussio, L. G. 2019. Production and utilization of silages in tropical areas with focus on Brazil. Grass and Forage Science 74:188-200. https://doi.org/10.1111/gfs.12417
https://doi.org/10.1111/gfs.12417...
). Meanwhile, ensiling wetter crops are also associated with higher fermentative losses (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.) and greater formation of volatile organic compounds (e.g. volatile fatty acids, alcohols, esters, aldehydes, ketones), which has been claimed to have negative impacts on animal performance (Weiss, 2017Weiss, K. 2017. Volatile organic compounds in silages – Effects of management factors on their formation: A review. Slovak Journal of Animal Science 50:55-67.) and the environment (Howard et al., 2010Howard, C. J.; Kumar, A.; Malkina, I.; Mitloehner, F.; Green, P. G.; Flocchini, R. G. and Kleeman, M. J. 2010. Reactive organic gas emissions from livestock feed contribute significantly to ozone production in central California. Environmental Science and Technology 44:2309-2314. https://doi.org/10.1021/es902864u
https://doi.org/10.1021/es902864u...
; Hafner et al., 2013Hafner, S. D.; Howard, C.; Muck, R. E.; Franco, R. B.; Montes, F.; Green, P. G.; Mitloehner, F.; Trabue, S. L. and Rotz, C. A. 2013. Emission of volatile organic compounds from silage: Compounds, sources, and implications. Atmospheric Environment 77:827-839. https://doi.org/10.1016/j.atmosenv.2013.04.076
https://doi.org/10.1016/j.atmosenv.2013....
).

Several studies have shown that the negative impact of the protein matrix surrounding starch granules in corn vitreous endosperm is attenuated over the ensiling period (Hoffman et al., 2011Hoffman, P. C.; Esser, N. M.; Shaver, R. D.; Coblentz, W. K.; Scott, M. P.; Bodnar, A. L.; Schmidt, R. J. and Charley, R. C. 2011. Influence of ensiling time and inoculation on alteration of the starch-protein matrix in high-moisture corn. Journal of Dairy Science 94:2465-2474. https://doi.org/10.3168/jds.2010-3562
https://doi.org/10.3168/jds.2010-3562...
; Der Bedrosian et al., 2012Der Bedrosian, M. C.; Nestor Jr., K. E. and Kung Jr., L. 2012. The effects of hybrid, maturity, and length of storage on the composition and nutritive value of corn silage. Journal of Dairy Science 95:5115-5126. https://doi.org/10.3168/jds.2011-4833
https://doi.org/10.3168/jds.2011-4833...
), mainly due to the proteolytic activity of bacteria and plant enzymes (Junges et al., 2017Junges, D.; Morais, G.; Spoto, M. H. F.; Santos, P. S.; Adesogan, A. T.; Nussio, L. G. and Daniel, J. L. P. 2017. Short communication: Influence of various proteolytic sources during fermentation of reconstituted corn grain silages. Journal of Dairy Science 100:9048-9051. https://doi.org/10.3168/jds.2017-12943
https://doi.org/10.3168/jds.2017-12943...
). Hence, storing corn silages (whole crop or grain) for longer periods typically increases starch and protein digestibility, with minor or no effect on fibre digestibility (Benton et al., 2005Benton, J. R.; Klopfenstein, T. J. and Erickson, G. E. 2005. Effects of corn moisture and length of ensiling on dry matter digestibility and rumen degradable protein. Nebraska Beef Cattle Reports No. 151. University of Nebraska, Lincoln.; Daniel et al., 2015Daniel, J. L. P.; Junges, D. and Nussio, L. G. 2015. A meta-analysis of the effects of length of storage on starch digestibility and aerobic stability of corn silages. p.306-307. In: Proceedings of the XVII International Silage Conference, Piracicaba.; Kung Jr. et al., 2018Kung Jr., L.; Shaver, R. D.; Grant, R. J. and Schmidt, R. J. 2018. Silage review: Interpretation of chemical, microbial, and organoleptic components of silages. Journal of Dairy Science 101:4020-4033. https://doi.org/10.3168/jds.2017-13909
https://doi.org/10.3168/jds.2017-13909...
). However, the extension of this benefit is unknown in corn hybrids with a high proportion of vitreous endosperm when harvested with forage harvesters without a kernel processor.

The main objective of our study was to determine the effects of maturity and storage length on the fermentation pattern, ruminal disappearance of nutrients, and recovery of digestible DM in flint corn silage harvested with a pull-type machine without a kernel processor. We hypothesised that although a more mature crop may lead to a less intense fermentation, it would achieve similar levels of ruminal DM disappearance of the early-harvested corn at longer storage periods. A second objective was to verify if the DM content at harvesting affects the recommendation of minimal storage length to improve DM digestibility.

Material and Methods

On October 15, 2015, a corn hybrid with flint endosperm (2B877PW, Dow Agrosciences, São Paulo, Brazil) was sown in four plots (10×18 m) in the municipality of Maringá, (23°25'38" S and 51°56'15" W), state of Paraná, Brazil. Five seeds were distributed per linear meter (62,500 plants per ha). Each plot contained 12 rows with a spacing of 80 cm between rows. To reduce border effects, only the six central rows were used. At seeding, 250 kg ha−1 of a commercial NPK (19:15:16) fertilizer was applied in the furrow. Four weeks after seeding, 150 kg ha−1 of urea, and 100 kg ha−1 of KCl were spread over the plots.

Two weeks after silking, the DM content was monitored once a week. At 91 d after seeding, plants achieved approximately 300 g kg−1 of DM (LDM), then three of those six central rows in each plot were mechanically harvested. The remaining three central rows were harvested 12 d later, at 400 g kg−1 of DM (HDM). In both maturities, plants were harvested at 25-cm cut height with a pull-type forage harvester set for a 7-mm theoretical cut length and without a kernel processor (JF192C12 single row, JF Máquinas Agrícolas, Itapira, Brazil).

In each maturity stage (LDM and HDM), chopped forage from each plot was placed in eight nylon-polyethylene bags (33×45 cm, 160 µm) without any additive, subsequently sealed under vacuum (∼1.8 kg per mini-silo), and stored for 0 (opened immediately after sealing), 7, 14, 30, 60, 90, 120, and 180 d. A total of 64 silos were prepared [four replicates (blocks) per maturity per storage time]. At ensiling and at opening, silos were weighed and sampled. Dry matter recovery was determined by DM weight change, as a fraction of ensiled DM mass. Silage samples were frozen at −20 °C for further analysis.

Additionally, fresh chopped forage from each plot were sampled for measuring particle size distribution using the Penn State Particle Separator (Three-sieve model with 1.18-mm sieve). The mean particle length and geometric standard deviation were calculated according to Kononoff et al. (2003)Kononoff, P. J.; Heinrichs, A. J. and Buckmaster, D. R. 2003. Modification of the Penn State forage and total mixed ration particle separator and the effects of moisture content on its measurements. Journal of Dairy Science 86:1858-1863. https://doi.org/10.3168/jds.S0022-0302(03)73773-4
https://doi.org/10.3168/jds.S0022-0302(0...
. The number of intact kernels per 250 g of fresh forage (including whole and slightly damaged kernels) and the length of ten longest particles were recorded. A subsample of chopped forage from each plot was dried at 55 °C for measuring the kernel processing score (KPS), which represents the proportion of starch passing through a 4.75-mm sieve (Ferreira and Mertens, 2005Ferreira, G. and Mertens, D. R. 2005. Chemical and physical characteristics of corn silages and their effects on in vitro disappearance. Journal of Dairy Science 88:4414-4425. https://doi.org/10.3168/jds.S0022-0302(05)73128-3
https://doi.org/10.3168/jds.S0022-0302(0...
; Mertens, 2005Mertens, D. R. 2005. Particle size, fragmentation index, and effective fiber: Tools for evaluating the physical attributes of corn silages. In: Proceedings of the Four-State Dairy Nutrition and Management. Dubuque, IA.).

For the in situ ruminal degradability, approximately 40 g of fresh thawed samples were placed into polyamide bags (15×35 cm, 60 μm porosity) and incubated for 24 h in the rumen ventral sac of two rumen-cannulated non-lactating Holstein cows fed corn silage (ad libitum) and concentrate (2 kg d−1). One sample from each silo was incubated in each cow. Immediately after retrieving, bags were submerged in cold water (0 °C) for 5 min and washed in a washing machine (three cycles, followed by a final spin). Washed bags were dried in a forced-air oven at 55 °C for 72 h and weighed to calculate DM disappearance.

Fresh subsamples of silages were used to prepare an aqueous extract (Kung Jr. et al., 1984Kung Jr., L.; Grieve, D. B.; Thomas, J. W. and Huber, J. T. 1984. Added ammonia or microbial inocula for fermentation and nitrogenous compounds of alfalfa ensiled at various percents of dry matter. Journal of Dairy Science 67:299-306. https://doi.org/10.3168/jds.S0022-0302(84)81302-8
https://doi.org/10.3168/jds.S0022-0302(8...
). Aqueous extracts were used for measuring pH and fermentation end-products. Lactic acid (Pryce, 1969Pryce, J. D. 1969. A modification of Barker-Summerson method for the determination of lactic acid. Analyst 94:1151-1152. https://doi.org/10.1039/AN9699401151
https://doi.org/10.1039/AN9699401151...
) and NH3-N (Chaney and Marbach, 1962Chaney, A. L. and Marbach, E. P. 1962. Modified reagents for determination of urea and ammonia. Clinical Chemistry 8:130-132. https://doi.org/10.1093/clinchem/8.2.130
https://doi.org/10.1093/clinchem/8.2.130...
) were analysed by colorimetric methods. Volatile fatty acids, alcohols, and esters were determined by gas chromatography-mass spectrometry (GCMS QP 2010 plus, Shimadzu, Kyoto, Japan) using a capillary column (Stabilwax, Restek, Bellefonte, PA; 60 m, 0.25 mm ø, 0.25 μm crossbond carbowax polyethylene glycol). Compounds were identified based on their retention time and mass spectra and quantified with external standards.

Dried samples were ground in a Wiley mill through 1-mm screen and analysed for crude protein (CP; AOAC, 1990AOAC - Association of Official Analytical Chemistry. 1990. Official methods of analysis. 15th ed. AOAC International, Arlington, VA.; method 984.13), neutral detergent fibre (NDF; assayed with a heat stable α-amylase and sodium sulphite, and expressed inclusive of residual ash; Mertens, 2002Mertens, D. R. 2002. Gravimetric determination of amylase-treated neutral detergent fiber in feeds with refluxing in beakers or crucibles: Collaborative study. Journal of AOAC International 85:1217-1240.), starch (Hall, 2015Hall, M. B. 2015. Determination of dietary starch in animal feeds and pet food by an enzymatic-colorimetric method. Collaborative study. Journal of AOAC International 98:397-409. https://doi.org/10.5740/jaoacint.15-012
https://doi.org/10.5740/jaoacint.15-012...
), and dry matter (DMoven; AOAC, 1990AOAC - Association of Official Analytical Chemistry. 1990. Official methods of analysis. 15th ed. AOAC International, Arlington, VA.; method 934.01). The DMoven was corrected for volatiles as follows (Weissbach, 2009Weissbach, F. 2009. Correction of dry matter content of silages used as substrate for biogas production. p.483-484. In: Proceedings of the XV International Silage Conference. Madison, WI.): DM (g kg−1 FM) = DMoven (g kg−1 FM) + n-alcohols (g kg−1 FM) + i-propyl alcohol (g kg−1 FM) + 2,3-butanediol (g kg−1 FM) + esters (g kg−1 FM) + 0.95 × volatile fatty acids (g kg−1 FM) + 0.77 × 1,2-propanediol (g kg−1 FM) + 0.08 × lactic acid (g kg−1 FM). The n-alcohols included methanol, ethanol, and propanol; esters included ethyl lactate, ethyl acetate, and propyl acetate; and volatile fatty acids included acetic, propionic, i-butyric, butyric, i-valeric, and valeric acids.

Residues from in situ incubation were ground in a Wiley mill through 1-mm screen and analysed for NDF, CP, and starch to calculate the ruminal disappearance of those fractions. The recovery of digestible DM was calculated by multiplying DM recovery in the silo by DM disappearance in the rumen.

Data were analysed using the Mixed procedure of SAS (Statistical Analysis System, version 9.4). Forage processing outcomes (particle size, KPS, intact kernels) were analysed with a model including fixed effect of maturity and random effect of plot.

Fermentation pattern, chemical composition and in situ disappearance were analysed as a split-plot arrangement (two maturities × eight storage periods) with the same model described above including the effects of storage length and its interaction with maturity. The interaction between plot and maturity was defined as subject. Covariance structures were chosen for each outcome based on the smaller value for the corrected Akaike Information Criterion.

Ruminal disappearance of DM, starch, and protein and recovery of digestible DM were modelled with a segmented regression (first segment quadratic, second segment linear) to define the curve breakpoint and infer on the minimal length of storage required to improve those responses (Robbins et al., 2006Robbins, K. R.; Saxton, A. M. and Southern, L. L. 2006. Estimation of nutrient requirements using broken-line regression analysis. Journal of Animal Science 84:E155-E165. https://doi.org/10.2527/2006.8413_supple155x
https://doi.org/10.2527/2006.8413_supple...
; Daniel et al., 2015Daniel, J. L. P.; Junges, D. and Nussio, L. G. 2015. A meta-analysis of the effects of length of storage on starch digestibility and aerobic stability of corn silages. p.306-307. In: Proceedings of the XVII International Silage Conference, Piracicaba.).

Results

Forage harvested at HDM had greater proportion of particles >19 mm and tended to have more fine particles (retained on 1.18-mm sieve and pan). The LDM forage had a higher proportion of particles retained on the 8-mm sieve. The mean particle length was similar between treatments, whereas the geometric standard deviation was higher in HDM than in LDM forage. Corn harvested at HDM had more intact kernels, lower KPS, and greater proportion of coarse particles than LDM corn (Table 1).

Table 1
Particle size distribution and kernel processing score in corn forage harvested with a pull-type forage harvester without kernel processor

For the outcomes measured across fermentation, when the interaction between maturity and storage length or the main effect of maturity was significant (Table 2), data were presented in graphic form. For the remaining few responses, means were described along the text.

Table 2
Statistical analysis (P-values) of the influence of maturity (M) and storage length (S) on the fermentation profile and nutritive value of corn silage

There was an interaction between maturity and storage length for pH, lactic acid, 1,2-propanediol, and DM recovery, whereas NH3-N, acetic acid, propionic acid, methanol, ethanol, 1-propanol, and ethyl esters were affected by the main effects of maturity and storage length. Propyl acetate was only affected by maturity.

The pH dropped during the onset of fermentation (first week of storage) and remained low (around 3.7), with slight variations thereafter. Lactic acid steeply increased during the first 14 d of fermentation, with higher values for the LDM silage (Figure 1).

Figure 1
Influence of maturity (low dry matter ●; high dry matter ■) and storage length on pH (A) and lactic acid (B) in flint corn silage.

The concentration of acetic acid increased with storage length and remained higher in LDM than in HDM silage up to 180 d. The content of 1,2-propanediol remained low across storage in HDM silage, while steeply increased from 60 d up to 120 d in LDM silage. The LDM silage also had a higher level of 1-propanol, which increased mainly during the first 30 d. In HDM silage, 1-propanol slowly increased up to 180 d of fermentation. Propionic acid was primarily synthetized in LDM silage up to 7 d of fermentation with minimal fluctuation thereafter. In HDM silage, propionic acid concentration was lower than in LDM and gradually increased up to 90 d of storage (Figure 2).

Figure 2
Influence of maturity (low dry matter ●; high dry matter ■) and storage length on acetic acid (A), 1,2-propanediol (B), 1-propanol (C), and propionic acid (D) in flint corn silage.

In LDM and HDM silages, ethanol increased over time, mainly during the first 30 d of fermentation, with higher levels in LDM than in HDM silage. Ethyl lactate and ethyl acetate concentrations were greater in LDM silage. In both silages, ethyl esters were formed mostly during the first 30 d of fermentation. Propyl acetate was only found in LDM silage (Figure 3). The formation of methanol occurred during the first 14 d of fermentation and was higher in LDM silage (Figure 4).

Figure 3
Influence of maturity (low dry matter ●; high dry matter ■) and storage length on ethanol (A), ethyl lactate (B), ethyl acetate (C), and propyl acetate (D) in flint corn silage.
Figure 4
Influence of maturity (low dry matter ●; high dry matter ■) and storage length on methanol in flint corn silage.

The content of NH3-N increased during fermentation and was higher in LDM silage. Although the DM recovery markedly decreased during the first 60 d of fermentation, it continued until 180 d of storage in both silages. In comparison with HDM, ensiling corn with LDM reduced DM recovery during silage fermentation (Figure 5).

Figure 5
Influence of maturity (low dry matter ●; high dry matter ■) and storage length on NH3-N (A) and DM recovery (B) in flint corn silage.

The concentrations of i-butyric acid, i-valeric acid, i-propyl alcohol, and 2,3-butanediol were only affected by storage length and increased from 6.30 to 9.37 mg kg−1 DM, 14.7 to 12.5 mg kg−1 DM, 0.49 to 1.98 mg kg−1 DM, and 8.24 to 10.7 g kg−1 DM, respectively, from ensiling to 180 d of storage. Butyric (average 10.0 mg kg−1) and valeric (average 2.06 mg kg−1 DM) acids did not change among maturities and storage lengths (data not shown in figures).

The contents of DM, starch, NDF, and CP were only affected by maturity. The HDM silage had higher levels of DM and starch, whereas LDM silage had greater concentrations of NDF and CP (Figure 6). The ruminal NDF disappearance was not affected by storage length and was higher in LDM than in HDM silage (387 vs. 338 g kg−1 DM; P<0.01; data not shown in figures). There was an interaction between maturity and storage length for the ruminal disappearance of starch, CP, and DM and recovery of digestible DM. Ruminal CP disappearance increased primarily during the first month of storage and was higher in LDM silage. Ruminal starch disappearance was greater in LDM but increased in both LDM and HDM silages, especially during the first month of storage. After 30 d, ruminal starch disappearance continued improving in HDM silage. The ruminal DM disappearance increased along the storage and was higher in LDM than in HDM silage. In both silages, the breakpoint for ruminal disappearance of DM, CP, and starch modelled with segmented regressions occurred around 30 d of storage. After the first month of fermentation, ruminal DM disappearance reached a plateau in LDM, while linearly increased in HDM up to 180 d. The recovery of digestible DM increased along the storage in both LDM and HDM silages. In LDM, the recovery of digestible DM reached a plateau at 26 d of storage, whereas it increased during 180 d in HDM silage, but the main increase occurred during the first 60 d of storage (breakpoint) (Figure 7).

Figure 6
Influence of maturity (low dry matter ●; high dry matter ■) and storage length on DM (A), starch (B), aNDF (C), and CP (D) in flint corn silage.
Figure 7
Influence of maturity (low dry matter ●; high dry matter ■) and storage length on ruminal CP disappearance (A), ruminal starch disappearance (B), ruminal DM disappearance (C) and recovery of digestible DM (D) in flint corn silage harvested with a pull-type machine without a kernel processor.

Discussion

In tropical areas, many farmers are harvesting corn crop earlier than desirable (<300 g kg−1 of DM), mainly due to the use of forage harvesters without a kernel processor (Bernardes and Do Rêgo, 2014Bernardes, T. F. and Do Rêgo, A. C. 2014. Study on the practices of silage production and utilization on Brazilian dairy farms. Journal of Dairy Science 97:1852-1861. https://doi.org/10.3168/jds.2013-7181
https://doi.org/10.3168/jds.2013-7181...
; Daniel et al., 2019Daniel, J. L. P.; Bernardes, T. F.; Jobim, C. C.; Schmidt, P. and Nussio, L. G. 2019. Production and utilization of silages in tropical areas with focus on Brazil. Grass and Forage Science 74:188-200. https://doi.org/10.1111/gfs.12417
https://doi.org/10.1111/gfs.12417...
) and high vitreousness of the corn hybrids (Correa et al., 2002Correa, C. E. S.; Shaver, R. D.; Pereira, M. N.; Lauer, J. G. and Kohn, K. 2002. Relationship between corn vitreousness and ruminal in situ starch degradability. Journal of Dairy Science 85:3008-3012. https://doi.org/10.3168/jds.S0022-0302(02)74386-5
https://doi.org/10.3168/jds.S0022-0302(0...
), which has been called harder to processing.

Harvesting corn plants with high DM content has been associated with poorer processing of both stover and kernel fractions (Ferraretto et al., 2018Ferraretto, L. F.; Shaver, R. D. and Luck, B. D. 2018. Silage review: Recent advances and future technologies for whole-plant and fractionated corn silage harvesting. Journal of Dairy Science 101:3937-3951. https://doi.org/10.3168/jds.2017-13728
https://doi.org/10.3168/jds.2017-13728...
). In this study, harvesting at HDM with a pull-type machine without a kernel processor affected forage processing by increasing the proportion of very long (>19 mm) and fine particles (<8 mm) in comparison with LDM. Bernardes et al. (2012)Bernardes, T. F.; Carvalho, I. Q. and Silva, N. C. 2012. A snapshot of maize silage quality on dairy farms in South Brazil. p.322-323. In: Proceedings of the XVI International Silage Conference. Hämeenlinna, Finland. also reported a higher proportion of particles >19 mm in corn harvested at higher DM content, whereas a positive correlation between DM content and particles >19 mm was higher in corn silages harvested with pull-type rather than self-propelled machines. In our study, harvesting at HDM also tended to increase the proportion of fine particles (<8 mm), besides the greater proportion of particles >19 mm. Therefore, the mean particle length was similar between LDM and HDM, but the geometric standard deviation was higher in HDM corn. Higher proportion of very long particles increases the resistance to packing at ensiling, resulting in higher silage porosity (Muck et al., 2003Muck, R. E.; Moser, L. E. and Pitt, R. E. 2003. Postharvest factors affecting ensiling. p.251-304. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI. https://doi.org/10.2134/agronmonogr42.c6
https://doi.org/10.2134/agronmonogr42.c6...
; Pries et al., 2018Pries, M.; Denissen, J. and Speit, J. H. 2018. Effects of particle size distribution of maize silage on silage quality, dry matter intake and performance of dairy cows. p.65-74. In: Proceedings of 45th Viehwirtschaftliche Fachtagung, Raumberg, Austria. (in German).). Long particles also increase the risk of sorting in the feedbunk (Leonardi and Armentano, 2003Leonardi, C. and Armentano, L. E. 2003. Effect of quantity, quality and length of alfalfa hay on selective consumption by dairy cows. Journal of Dairy Science 86:557-564. https://doi.org/10.3168/jds.S0022-0302(03)73634-0
https://doi.org/10.3168/jds.S0022-0302(0...
). Excessive sorting increases the risk of ruminal acidosis and reduces the nutritive value of the ration remaining in the feedbunk, particularly in the later hours past the time of feed delivery (DeVries et al., 2008DeVries, T. J.; Dohme, F. and Beauchemin, K. A. 2008. Repeated ruminal acidosis challenges in lactating dairy cows at high and low risk for developing acidosis: Feed sorting. Journal of Dairy Science 91:3958-3967. https://doi.org/10.3168/jds.2008-1347
https://doi.org/10.3168/jds.2008-1347...
), resulting in lower milk yield (Sova et al., 2013Sova, A. D.; LeBlanc, S. J.; McBride, B. W. and DeVries, T. J. 2013. Associations between herd-level feeding management practices, feed sorting, and milk production in freestall dairy farms. Journal of Dairy Science 96:4759-4770.). On the other hand, a larger proportion of fine particles (<8 mm) decrease the content of physically effective NDF and increase the risk of ruminal acidosis (Zebeli et al., 2012Zebeli, Q.; Aschenbach, J. R.; Tafaj, M.; Boguhn, J.; Ametaj, B. N. and Drochner, W. 2012. Invited review: Role of physically effective fiber and estimation of dietary fiber adequacy in high-producing dairy cattle. Journal of Dairy Science 95:1041-1056. https://doi.org/10.3168/jds.2011-4421
https://doi.org/10.3168/jds.2011-4421...
).

Harvesting corn plants at HDM usually increases starch concentration, while decreases starch digestibility (Allen et al., 2003Allen, M. S.; Coors, J. G. and Roth, G. W. 2003. Corn silage. p.547-608. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.). Kernel maturation is associated with development of the protein matrix that surrounds the starch granules and increases the proportion of vitreous endosperm, especially in flint genotypes (Philippeau and Michalet-Doreau, 1997Philippeau, C. and Michalet-Doreau, B. 1997. Influence of genotype and stage of maturity of maize on rate of ruminal starch degradation. Animal Feed Science and Technology 68:25-35. https://doi.org/10.1016/S0377-8401(97)00042-4
https://doi.org/10.1016/S0377-8401(97)00...
; Pereira et al., 2004Pereira, M. N.; Von Pinho, R. G.; Bruno, R. G. S. and Calestine, G. A. 2004. Ruminal degradability of hard or soft texture corn grain at three maturity stages. Scientia Agricola 61:358-363. https://doi.org/10.1590/S0103-90162004000400002
https://doi.org/10.1590/S0103-9016200400...
; Ngonyamo-Majee et al., 2009Ngonyamo-Majee, D.; Shaver, R. D.; Coors, J. G.; Sapienza, D. and Lauer, J. G. 2009. Influence of single-gene mutations, harvest maturity and sample processing on ruminal in situ and post-ruminal in vitro dry matter and starch degradability of corn grain by ruminants. Animal Feed Science and Technology 151:240-250. https://doi.org/10.1016/j.anifeedsci.2009.02.002
https://doi.org/10.1016/j.anifeedsci.200...
). Endosperm vitreousness is negatively correlated with starch digestibility in non-fermented corn (Correa et al., 2002Correa, C. E. S.; Shaver, R. D.; Pereira, M. N.; Lauer, J. G. and Kohn, K. 2002. Relationship between corn vitreousness and ruminal in situ starch degradability. Journal of Dairy Science 85:3008-3012. https://doi.org/10.3168/jds.S0022-0302(02)74386-5
https://doi.org/10.3168/jds.S0022-0302(0...
; Pereira et al., 2004Pereira, M. N.; Von Pinho, R. G.; Bruno, R. G. S. and Calestine, G. A. 2004. Ruminal degradability of hard or soft texture corn grain at three maturity stages. Scientia Agricola 61:358-363. https://doi.org/10.1590/S0103-90162004000400002
https://doi.org/10.1590/S0103-9016200400...
). Moreover, more mature kernels are more vitreous and harder to damage upon forage chopping. Philippeau and Michalet-Doreau (1998)Philippeau, C. and Michalet-Doreau, B. 1998. Influence of genotype and ensiling of corn grain on in situ degradation of starch in the rumen. Journal of Dairy Science 81:2178-2184. https://doi.org/10.3168/jds.S0022-0302(98)75796-0
https://doi.org/10.3168/jds.S0022-0302(9...
reported larger particle size for flint than dent corn ground through the same screen, and Ngonyamo-Majee et al. (2009)Ngonyamo-Majee, D.; Shaver, R. D.; Coors, J. G.; Sapienza, D. and Lauer, J. G. 2009. Influence of single-gene mutations, harvest maturity and sample processing on ruminal in situ and post-ruminal in vitro dry matter and starch degradability of corn grain by ruminants. Animal Feed Science and Technology 151:240-250. https://doi.org/10.1016/j.anifeedsci.2009.02.002
https://doi.org/10.1016/j.anifeedsci.200...
mentioned a larger particle size for ground corn kernels harvested at black layer than at half-milk line stage. Pericarp integrity and larger pieces of endosperm, with lower surface area available for enzymatic hydrolysis and microbial attachment, are physical constrains to starch digestibility (McAllister et al., 1994McAllister, T. A.; Bae, H. D.; Jones, G. A. and Cheng, K. J. 1994. Microbial attachment and feed digestion in the rumen. Journal of Animal Science 72:3004-3018. https://doi.org/10.2527/1994.72113004x
https://doi.org/10.2527/1994.72113004x...
). In our study, harvesting at HDM increased the proportion of intact kernels and decreased the KPS compared with LDM. Lower KPS has been associated with lower starch digestibility and milk yield (Ferraretto and Shaver, 2012Ferraretto, L. F. and Shaver, R. D. 2012. Meta-analysis: Effect of corn silage harvest practice on intake, digestion and milk production by dairy cows. The Professional Animal Scientist 28:141-149.; Braman and Kurtz, 2015Braman, W. L. and Kurtz, J. E. 2015. Effect of corn silage kernel processing score on dairy cow starch digestibility. p.160-161. In: Proceedings of the XVII International Silage Conference, Piracicaba.; Salvati et al., 2017Salvati, G. G. S.; Santos, W. P.; Silveira, J. M.; Gritti, V. C.; Arthur, B. A. V.; Salvo, P. A. R.; Ribeiro, A. P.; Lima, T. A. D.; Morais Jr., N. N. and Nussio, L. G. 2017. Impact of kernel processing and particle size in whole plant corn silage on the performance of dairy cows. In: Proceedings of the V International Symposium on Forage Quality and Conservation, Piracicaba.).

Harvesting corn at HDM increased starch concentration by 28%, while reduced the ruminal disappearance of nutrients (starch, CP, and NDF) at ensiling, compared with LDM. Therefore, ruminal DM disappearance decreased by 36% at ensiling in HDM compared with LDM. However, the ruminal DM disappearance increased during storage for both LDM and HDM silages by 14 and 70%, respectively. The large difference in ruminal DM disappearance at ensiling markedly decreased during storage.

Ensiling corn causes degradation of endosperm hydrophobic proteins (Hoffman et al., 2011Hoffman, P. C.; Esser, N. M.; Shaver, R. D.; Coblentz, W. K.; Scott, M. P.; Bodnar, A. L.; Schmidt, R. J. and Charley, R. C. 2011. Influence of ensiling time and inoculation on alteration of the starch-protein matrix in high-moisture corn. Journal of Dairy Science 94:2465-2474. https://doi.org/10.3168/jds.2010-3562
https://doi.org/10.3168/jds.2010-3562...
) mainly due to the proteolytic activity of bacteria and plant enzymes (Junges et al., 2017Junges, D.; Morais, G.; Spoto, M. H. F.; Santos, P. S.; Adesogan, A. T.; Nussio, L. G. and Daniel, J. L. P. 2017. Short communication: Influence of various proteolytic sources during fermentation of reconstituted corn grain silages. Journal of Dairy Science 100:9048-9051. https://doi.org/10.3168/jds.2017-12943
https://doi.org/10.3168/jds.2017-12943...
). In corn silage, the occurrence of proteolysis is positively correlated with starch digestibility (Ferraretto et al., 2015Ferraretto, L. F.; Shaver, R. D.; Massie, S.; Singo, R.; Taysom, D. M. and Brouillette, J. P. 2015. Effect of ensiling time and hybrid type on fermentation profile, nitrogen fractions, and ruminal in vitro starch and neutral detergent fiber digestibility in whole-plant corn silage. The Professional Animal Scientist 31:146-152. https://doi.org/10.15232/pas.2014-01371
https://doi.org/10.15232/pas.2014-01371...
; Kung Jr. et al., 2018Kung Jr., L.; Shaver, R. D.; Grant, R. J. and Schmidt, R. J. 2018. Silage review: Interpretation of chemical, microbial, and organoleptic components of silages. Journal of Dairy Science 101:4020-4033. https://doi.org/10.3168/jds.2017-13909
https://doi.org/10.3168/jds.2017-13909...
). Therefore, harvesting corn at LDM and storing silages for longer periods increased NH3-N concentration and ruminal starch disappearance, and in turn, ruminal DM disappearance. Plant enzymes (proteases and deaminases) and bacteria (e.g. enterobacteria, clostridia, and bacilli) are involved in protein breakdown (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.; Pahlow et al., 2003Pahlow, G.; Muck, R. E.; Driehuis, F.; Oude Elferink, S. J. W. H.; Spoelstra, S. F. 2003. Microbiology of ensiling. p.31-93. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.; Rooke and Hatfield, 2003Rooke, J. A. and Hatfield, R. D. 2003. Biochemistry of ensiling. p.95-139. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.). Although low pH is recognized in reducing proteolysis (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.), it should be noted that LDM silage had higher NH3-N concentration despite a tendency to lower pH. Hence, the higher moisture content in LDM must have prevailed in determining the extent of protein breakdown. Such increase in proteolysis was in line with the higher ruminal CP disappearance.

In both silages, the increase in ruminal DM disappearance occurred mainly during the first month of storage, due to an increase in both CP and starch disappearance in the same period. Despite the lower KPS in HDM silage, longer storage periods decreased the negative impact of maturity on nutrient availability. Although a minimum storage period of one month has been generally recommended for corn silage (Daniel et al., 2015Daniel, J. L. P.; Junges, D. and Nussio, L. G. 2015. A meta-analysis of the effects of length of storage on starch digestibility and aerobic stability of corn silages. p.306-307. In: Proceedings of the XVII International Silage Conference, Piracicaba.), flint hybrids harvested at high DM contents (e.g. 400 g kg−1) using pull-type forage harvesters without kernel processors requires longer storage periods (e.g. at least two months) to attenuate the negative impact of maturity on digestibility.

As expected, LDM silage showed a more intense fermentation. Most volatile organic compounds were detected in higher concentrations in LDM silage. Typically, wetter forages favour microbial development due to the higher water activity (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.; Pahlow et al., 2003Pahlow, G.; Muck, R. E.; Driehuis, F.; Oude Elferink, S. J. W. H.; Spoelstra, S. F. 2003. Microbiology of ensiling. p.31-93. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.). In this study, both LDM and HDM silages were well preserved, as noticed by low concentrations of butyric acid, whereas a more heterofermentative pattern was stimulated in LDM silage.

A wide range of bacteria produces acetic acid (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.). During earlier stages of fermentation, enterobacteria play an important role in acetic acid synthesis; however, other microorganisms such as heterolactic bacteria can also produce acetic acid in silage (Pahlow et al., 2003Pahlow, G.; Muck, R. E.; Driehuis, F.; Oude Elferink, S. J. W. H.; Spoelstra, S. F. 2003. Microbiology of ensiling. p.31-93. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.). Nevertheless, the activity of Lactobacillus buchneri-like strains probably had a secondary contribution to acetic acid formation, once acetic acid was mostly produced during the first month of storage in both silages. Moreover, a significant accumulation of 1,2-propanediol (a marker of L. buchneri activity; Oude-Elferink et al., 2001Oude-Elferink, S. J. W. H; Krooneman, J.; Gottschal, J. C.; Spoelstra, S. F.; Faber, F. and Driehuis, F. 2001. Anaerobic conversion of lactic acid to acetic acid and 1,2-propanediol by Lactobacillus buchneri. Applied and Environmental Microbiology 67:125-132. https://doi.org/10.1128/AEM.67.1.125-132.2001
https://doi.org/10.1128/AEM.67.1.125-132...
) was noticed after 60 d of storage, almost exclusively in LDM silage. Interestingly, this accumulation in 1,2-propanediol in LDM silage was not followed by an increase in 1-propanol and propionic acid, as often reported in the literature (Raun and Kristensen, 2010Raun, B. M. L. and Kristensen, N. B. 2010. Propanol in maize silage at Danish dairy farms. Acta Agriculturae Scandinavica, Section A – Animal Science 60:53-59. https://doi.org/10.1080/09064701003796742
https://doi.org/10.1080/0906470100379674...
; Kleinshmitt et al., 2013Kleinshmitt, C.; Morais, G.; Custódio, L.; Fernandes, J.; Santos, M. C.; Daniel, J. L. P. and Nussio, L. G. 2013. Performance of lactating dairy cows fed maize silage with increased dosages of L. buchneri. p.141-142 In: Proceedings of the 15th International Conference on Forage Conservation. High Tatras, Slovakia.; Gomes et al., 2019Gomes, A. L. M.; Jacovaci, F. A.; Bolson, D. C.; Nussio, L. G.; Jobim, C. C. and Daniel, J. L. P. 2019. Effects of light wilting and heterolactic inoculant on the formation of volatile organic compounds, fermentative losses and aerobic stability of oat silage. Animal Feed Science and Technology 247:194-198. https://doi.org/10.1016/j.anifeedsci.2018.11.016
https://doi.org/10.1016/j.anifeedsci.201...
). Krooneman et al. (2002)Krooneman, J.; Faber, F.; Alderkamp, A. C.; Oude Elferink, S. J. H. W.; Driehuis, F.; Cleenwerk, L.; Swings, J.; Gottschal, J. C. and Vancaneyt, M. 2002. Lactobacillus diolivorans sp. nov., a 1,2-propanediol-degrading bacterium isolated from aerobically stable maize silage. International Journal of Systematic and Evolutionary Microbiology 52:639-646. https://doi.org/10.1099/00207713-52-2-639
https://doi.org/10.1099/00207713-52-2-63...
demonstrated that Lactobacillus diolivorans, an indigenous strain in corn silage, is capable of converting 1,2-propanediol to approximately equimolar amounts of 1-propanol and propionic acid. In our study, the concentration of propionic acid was much greater than 1-propanol in both silages (on average 18-fold), suggesting that propionic acid might have been synthetized in small amounts by a variety of microorganisms, such as clostridia, yeasts, and, perhaps, propionibacteria (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.; Rooke and Hatfield, 2003Rooke, J. A. and Hatfield, R. D. 2003. Biochemistry of ensiling. p.95-139. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.).

Ethanol is the alcohol most commonly found in silages (Pahlow et al., 2003Pahlow, G.; Muck, R. E.; Driehuis, F.; Oude Elferink, S. J. W. H.; Spoelstra, S. F. 2003. Microbiology of ensiling. p.31-93. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.). Higher concentrations (>30-40 g kg−1 DM) of ethanol are often associated with yeast development in silage (Kung Jr. et al., 2018Kung Jr., L.; Shaver, R. D.; Grant, R. J. and Schmidt, R. J. 2018. Silage review: Interpretation of chemical, microbial, and organoleptic components of silages. Journal of Dairy Science 101:4020-4033. https://doi.org/10.3168/jds.2017-13909
https://doi.org/10.3168/jds.2017-13909...
). However, low concentrations of ethanol were found in this trial (<7 g kg−1 DM), which can be considered within normal range for whole-plant corn silage (Kung Jr. et al., 2018Kung Jr., L.; Shaver, R. D.; Grant, R. J. and Schmidt, R. J. 2018. Silage review: Interpretation of chemical, microbial, and organoleptic components of silages. Journal of Dairy Science 101:4020-4033. https://doi.org/10.3168/jds.2017-13909
https://doi.org/10.3168/jds.2017-13909...
). Such levels indicate that ethanol was probably produced in small amounts by a variety of microbes, such as yeasts, enterobacteria, heterolactic bacteria, bacilli, and clostridia (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.; Rooke and Hatfield, 2003Rooke, J. A. and Hatfield, R. D. 2003. Biochemistry of ensiling. p.95-139. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.).

Low molecular weight esters are likely formed in silages by abiotic esterification of carboxylic acids and alcohols under low pH conditions (Hangx et al., 2001Hangx, G.; Kwant, G.; Maessen, H.; Markusse, P. and Urseanu, I. 2001. Reaction kinetics of the esterification of ethanol and acetic acid towards ethyl acetate. Deliverable 22, Workpackage 6, Technical report. Intelligent column internals for reactive separations (INTINT), project no. GRD1 CT199910596. European Industrial Research magazine. European Commission, Research DG, Directorate G (Industrial Technologies). ESN, Brussels, Belgium.). Therefore, ethyl acetate and ethyl lactate are positively correlated with ethanol concentrations, whereas propyl acetate is correlated with 1-propanol concentration (Weiss, 2017Weiss, K. 2017. Volatile organic compounds in silages – Effects of management factors on their formation: A review. Slovak Journal of Animal Science 50:55-67.). In this study, LDM silage had higher concentrations of lactic and acetic acids, ethanol, and 1-propanol, resulting in higher concentrations of ethyl lactate, ethyl acetate, and propyl acetate. Interestingly, propyl acetate was only formed in LDM silage, suggesting that a minimal concentration of alcohol is required for ester formation. The concentration of 1-propanol was lower than 5 mg kg−1 DM in HDM silage. Although the possible impacts of esters on feed intake have been conjectured (Weiss, 2017Weiss, K. 2017. Volatile organic compounds in silages – Effects of management factors on their formation: A review. Slovak Journal of Animal Science 50:55-67.), Gerlach et al. (2019)Gerlach, K.; Weiß, K. and Südekum, K. H. 2019. Effects of ethyl ester supplementation to forage on short-term dry matter intake and preference by goats. Archives of Animal Nutrition 73:127-139. https://doi.org/10.1080/1745039X.2019.1575656
https://doi.org/10.1080/1745039X.2019.15...
reported that ethyl esters, as single substance or in combination with ethanol, did not affect the feeding behaviour of goats, then suggesting that esters are unlikely to impair the feed intake of ruminants.

The mechanisms of methanol production in silages are not clear. Although methanol may be produced by clostridia (Hippe et al., 1992Hippe, H.; Andreesen, J. and Gottschalk, G. 1992. The genus Clostridium – nonmedical. p.1800-1866. In: The Prokaryotes. Balows, A.; Trüper, H. G.; Dworkin, M.; Harder, W. and Schleifer, K. H., eds. Springer-Verlag, New York, USA.), in the current study, the low concentrations of butyric acid suggest that methanol was probably a product of pectin demethylation by plant and bacterial enzymes (Fall and Benson, 1996Fall, R. and Benson, A. A. 1996. Leaf methanol - the simplest natural product from plants. Trends in Plant Science 1:296-301. https://doi.org/10.1016/S1360-1385(96)88175-0
https://doi.org/10.1016/S1360-1385(96)88...
; Steidlová and Kalac, 2002Steidlová, S. and Kalac, P. 2002. Levels of biogenic amines in maize silages. Animal Feed Science and Technology 102:197-205. https://doi.org/10.1016/S0377-8401(02)00217-1
https://doi.org/10.1016/S0377-8401(02)00...
). The higher concentrations of methanol suggest that pectin demethylation must have occurred under greater intensity in LDM silage, perhaps due to the less mature cell wall and higher moisture content.

These large alterations in fermentation patterns led to a marked difference in DM recovery among silages. The greater formation of fermentation end-products from pathways associated with CO2 production resulted in lower DM recovery in LDM than in HDM silage (McDonald et al., 1991McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.; Rooke and Hatfield, 2003Rooke, J. A. and Hatfield, R. D. 2003. Biochemistry of ensiling. p.95-139. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.).

Lastly, the recovery of digestible DM (= DM recovery × ruminal DM disappearance) followed a similar pattern as observed for ruminal DM disappearance. In this way, the delay in harvest reduced the recovery of digestible DM, but this effect was counterbalanced by prolonged storage, despite the occurrence of DM loss during silage fermentation. In LDM silage, the recovery of digestible DM slightly changed over time, but it markedly increased in HDM silage, mainly up to 60 d of fermentation.

Conclusions

Corn silage harvested at low dry matter (300 g kg−1) had less starch and a more intense fermentation with higher dry matter loss during storage. On the other hand, harvesting corn at a more mature stage (400 g kg−1 of DM) with a pull-type forage harvester without a kernel processor worsened forage processing and decreased the ruminal disappearance of nutrients. However, in both silages, there was an increase in ruminal dry matter disappearance during fermentation, mainly in the first month of storage. Afterwards, the ruminal dry matter disappearance reached a plateau in low dry matter silage, whereas it continued increasing in high dry matter silage. Therefore, longer storage of high dry matter silage is a plausible strategy to attenuate the negative effect of maturity on digestibility of flint corn silage harvested with a pull-type forager without a kernel processor.

References

  • Allen, M. S.; Coors, J. G. and Roth, G. W. 2003. Corn silage. p.547-608. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.
  • AOAC - Association of Official Analytical Chemistry. 1990. Official methods of analysis. 15th ed. AOAC International, Arlington, VA.
  • Benton, J. R.; Klopfenstein, T. J. and Erickson, G. E. 2005. Effects of corn moisture and length of ensiling on dry matter digestibility and rumen degradable protein. Nebraska Beef Cattle Reports No. 151. University of Nebraska, Lincoln.
  • Bernardes, T. F.; Carvalho, I. Q. and Silva, N. C. 2012. A snapshot of maize silage quality on dairy farms in South Brazil. p.322-323. In: Proceedings of the XVI International Silage Conference. Hämeenlinna, Finland.
  • Bernardes, T. F. and Do Rêgo, A. C. 2014. Study on the practices of silage production and utilization on Brazilian dairy farms. Journal of Dairy Science 97:1852-1861. https://doi.org/10.3168/jds.2013-7181
    » https://doi.org/10.3168/jds.2013-7181
  • Braman, W. L. and Kurtz, J. E. 2015. Effect of corn silage kernel processing score on dairy cow starch digestibility. p.160-161. In: Proceedings of the XVII International Silage Conference, Piracicaba.
  • Chaney, A. L. and Marbach, E. P. 1962. Modified reagents for determination of urea and ammonia. Clinical Chemistry 8:130-132. https://doi.org/10.1093/clinchem/8.2.130
    » https://doi.org/10.1093/clinchem/8.2.130
  • Correa, C. E. S.; Shaver, R. D.; Pereira, M. N.; Lauer, J. G. and Kohn, K. 2002. Relationship between corn vitreousness and ruminal in situ starch degradability. Journal of Dairy Science 85:3008-3012. https://doi.org/10.3168/jds.S0022-0302(02)74386-5
    » https://doi.org/10.3168/jds.S0022-0302(02)74386-5
  • Daniel, J. L. P.; Junges, D. and Nussio, L. G. 2015. A meta-analysis of the effects of length of storage on starch digestibility and aerobic stability of corn silages. p.306-307. In: Proceedings of the XVII International Silage Conference, Piracicaba.
  • Daniel, J. L. P.; Bernardes, T. F.; Jobim, C. C.; Schmidt, P. and Nussio, L. G. 2019. Production and utilization of silages in tropical areas with focus on Brazil. Grass and Forage Science 74:188-200. https://doi.org/10.1111/gfs.12417
    » https://doi.org/10.1111/gfs.12417
  • Der Bedrosian, M. C.; Nestor Jr., K. E. and Kung Jr., L. 2012. The effects of hybrid, maturity, and length of storage on the composition and nutritive value of corn silage. Journal of Dairy Science 95:5115-5126. https://doi.org/10.3168/jds.2011-4833
    » https://doi.org/10.3168/jds.2011-4833
  • DeVries, T. J.; Dohme, F. and Beauchemin, K. A. 2008. Repeated ruminal acidosis challenges in lactating dairy cows at high and low risk for developing acidosis: Feed sorting. Journal of Dairy Science 91:3958-3967. https://doi.org/10.3168/jds.2008-1347
    » https://doi.org/10.3168/jds.2008-1347
  • Fall, R. and Benson, A. A. 1996. Leaf methanol - the simplest natural product from plants. Trends in Plant Science 1:296-301. https://doi.org/10.1016/S1360-1385(96)88175-0
    » https://doi.org/10.1016/S1360-1385(96)88175-0
  • Ferraretto, L. F. and Shaver, R. D. 2012. Meta-analysis: Effect of corn silage harvest practice on intake, digestion and milk production by dairy cows. The Professional Animal Scientist 28:141-149.
  • Ferraretto, L. F.; Shaver, R. D.; Massie, S.; Singo, R.; Taysom, D. M. and Brouillette, J. P. 2015. Effect of ensiling time and hybrid type on fermentation profile, nitrogen fractions, and ruminal in vitro starch and neutral detergent fiber digestibility in whole-plant corn silage. The Professional Animal Scientist 31:146-152. https://doi.org/10.15232/pas.2014-01371
    » https://doi.org/10.15232/pas.2014-01371
  • Ferraretto, L. F.; Shaver, R. D. and Luck, B. D. 2018. Silage review: Recent advances and future technologies for whole-plant and fractionated corn silage harvesting. Journal of Dairy Science 101:3937-3951. https://doi.org/10.3168/jds.2017-13728
    » https://doi.org/10.3168/jds.2017-13728
  • Ferreira, G. and Mertens, D. R. 2005. Chemical and physical characteristics of corn silages and their effects on in vitro disappearance. Journal of Dairy Science 88:4414-4425. https://doi.org/10.3168/jds.S0022-0302(05)73128-3
    » https://doi.org/10.3168/jds.S0022-0302(05)73128-3
  • Gerlach, K.; Weiß, K. and Südekum, K. H. 2019. Effects of ethyl ester supplementation to forage on short-term dry matter intake and preference by goats. Archives of Animal Nutrition 73:127-139. https://doi.org/10.1080/1745039X.2019.1575656
    » https://doi.org/10.1080/1745039X.2019.1575656
  • Gomes, A. L. M.; Jacovaci, F. A.; Bolson, D. C.; Nussio, L. G.; Jobim, C. C. and Daniel, J. L. P. 2019. Effects of light wilting and heterolactic inoculant on the formation of volatile organic compounds, fermentative losses and aerobic stability of oat silage. Animal Feed Science and Technology 247:194-198. https://doi.org/10.1016/j.anifeedsci.2018.11.016
    » https://doi.org/10.1016/j.anifeedsci.2018.11.016
  • Hafner, S. D.; Howard, C.; Muck, R. E.; Franco, R. B.; Montes, F.; Green, P. G.; Mitloehner, F.; Trabue, S. L. and Rotz, C. A. 2013. Emission of volatile organic compounds from silage: Compounds, sources, and implications. Atmospheric Environment 77:827-839. https://doi.org/10.1016/j.atmosenv.2013.04.076
    » https://doi.org/10.1016/j.atmosenv.2013.04.076
  • Hall, M. B. 2015. Determination of dietary starch in animal feeds and pet food by an enzymatic-colorimetric method. Collaborative study. Journal of AOAC International 98:397-409. https://doi.org/10.5740/jaoacint.15-012
    » https://doi.org/10.5740/jaoacint.15-012
  • Hangx, G.; Kwant, G.; Maessen, H.; Markusse, P. and Urseanu, I. 2001. Reaction kinetics of the esterification of ethanol and acetic acid towards ethyl acetate. Deliverable 22, Workpackage 6, Technical report. Intelligent column internals for reactive separations (INTINT), project no. GRD1 CT199910596. European Industrial Research magazine. European Commission, Research DG, Directorate G (Industrial Technologies). ESN, Brussels, Belgium.
  • Hippe, H.; Andreesen, J. and Gottschalk, G. 1992. The genus Clostridium – nonmedical. p.1800-1866. In: The Prokaryotes. Balows, A.; Trüper, H. G.; Dworkin, M.; Harder, W. and Schleifer, K. H., eds. Springer-Verlag, New York, USA.
  • Hoffman, P. C.; Esser, N. M.; Shaver, R. D.; Coblentz, W. K.; Scott, M. P.; Bodnar, A. L.; Schmidt, R. J. and Charley, R. C. 2011. Influence of ensiling time and inoculation on alteration of the starch-protein matrix in high-moisture corn. Journal of Dairy Science 94:2465-2474. https://doi.org/10.3168/jds.2010-3562
    » https://doi.org/10.3168/jds.2010-3562
  • Howard, C. J.; Kumar, A.; Malkina, I.; Mitloehner, F.; Green, P. G.; Flocchini, R. G. and Kleeman, M. J. 2010. Reactive organic gas emissions from livestock feed contribute significantly to ozone production in central California. Environmental Science and Technology 44:2309-2314. https://doi.org/10.1021/es902864u
    » https://doi.org/10.1021/es902864u
  • Junges, D.; Morais, G.; Spoto, M. H. F.; Santos, P. S.; Adesogan, A. T.; Nussio, L. G. and Daniel, J. L. P. 2017. Short communication: Influence of various proteolytic sources during fermentation of reconstituted corn grain silages. Journal of Dairy Science 100:9048-9051. https://doi.org/10.3168/jds.2017-12943
    » https://doi.org/10.3168/jds.2017-12943
  • Kleinshmitt, C.; Morais, G.; Custódio, L.; Fernandes, J.; Santos, M. C.; Daniel, J. L. P. and Nussio, L. G. 2013. Performance of lactating dairy cows fed maize silage with increased dosages of L. buchneri p.141-142 In: Proceedings of the 15th International Conference on Forage Conservation. High Tatras, Slovakia.
  • Kononoff, P. J.; Heinrichs, A. J. and Buckmaster, D. R. 2003. Modification of the Penn State forage and total mixed ration particle separator and the effects of moisture content on its measurements. Journal of Dairy Science 86:1858-1863. https://doi.org/10.3168/jds.S0022-0302(03)73773-4
    » https://doi.org/10.3168/jds.S0022-0302(03)73773-4
  • Krooneman, J.; Faber, F.; Alderkamp, A. C.; Oude Elferink, S. J. H. W.; Driehuis, F.; Cleenwerk, L.; Swings, J.; Gottschal, J. C. and Vancaneyt, M. 2002. Lactobacillus diolivorans sp. nov., a 1,2-propanediol-degrading bacterium isolated from aerobically stable maize silage. International Journal of Systematic and Evolutionary Microbiology 52:639-646. https://doi.org/10.1099/00207713-52-2-639
    » https://doi.org/10.1099/00207713-52-2-639
  • Kung Jr., L.; Grieve, D. B.; Thomas, J. W. and Huber, J. T. 1984. Added ammonia or microbial inocula for fermentation and nitrogenous compounds of alfalfa ensiled at various percents of dry matter. Journal of Dairy Science 67:299-306. https://doi.org/10.3168/jds.S0022-0302(84)81302-8
    » https://doi.org/10.3168/jds.S0022-0302(84)81302-8
  • Kung Jr., L.; Shaver, R. D.; Grant, R. J. and Schmidt, R. J. 2018. Silage review: Interpretation of chemical, microbial, and organoleptic components of silages. Journal of Dairy Science 101:4020-4033. https://doi.org/10.3168/jds.2017-13909
    » https://doi.org/10.3168/jds.2017-13909
  • Leonardi, C. and Armentano, L. E. 2003. Effect of quantity, quality and length of alfalfa hay on selective consumption by dairy cows. Journal of Dairy Science 86:557-564. https://doi.org/10.3168/jds.S0022-0302(03)73634-0
    » https://doi.org/10.3168/jds.S0022-0302(03)73634-0
  • McAllister, T. A.; Bae, H. D.; Jones, G. A. and Cheng, K. J. 1994. Microbial attachment and feed digestion in the rumen. Journal of Animal Science 72:3004-3018. https://doi.org/10.2527/1994.72113004x
    » https://doi.org/10.2527/1994.72113004x
  • McDonald, P.; Henderson, A. R. and Heron, S. J. E. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publications, Marlow, UK.
  • Mertens, D. R. 2002. Gravimetric determination of amylase-treated neutral detergent fiber in feeds with refluxing in beakers or crucibles: Collaborative study. Journal of AOAC International 85:1217-1240.
  • Mertens, D. R. 2005. Particle size, fragmentation index, and effective fiber: Tools for evaluating the physical attributes of corn silages. In: Proceedings of the Four-State Dairy Nutrition and Management. Dubuque, IA.
  • Muck, R. E.; Moser, L. E. and Pitt, R. E. 2003. Postharvest factors affecting ensiling. p.251-304. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI. https://doi.org/10.2134/agronmonogr42.c6
    » https://doi.org/10.2134/agronmonogr42.c6
  • Ngonyamo-Majee, D.; Shaver, R. D.; Coors, J. G.; Sapienza, D. and Lauer, J. G. 2009. Influence of single-gene mutations, harvest maturity and sample processing on ruminal in situ and post-ruminal in vitro dry matter and starch degradability of corn grain by ruminants. Animal Feed Science and Technology 151:240-250. https://doi.org/10.1016/j.anifeedsci.2009.02.002
    » https://doi.org/10.1016/j.anifeedsci.2009.02.002
  • Oude-Elferink, S. J. W. H; Krooneman, J.; Gottschal, J. C.; Spoelstra, S. F.; Faber, F. and Driehuis, F. 2001. Anaerobic conversion of lactic acid to acetic acid and 1,2-propanediol by Lactobacillus buchneri Applied and Environmental Microbiology 67:125-132. https://doi.org/10.1128/AEM.67.1.125-132.2001
    » https://doi.org/10.1128/AEM.67.1.125-132.2001
  • Pahlow, G.; Muck, R. E.; Driehuis, F.; Oude Elferink, S. J. W. H.; Spoelstra, S. F. 2003. Microbiology of ensiling. p.31-93. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.
  • Pereira, M. N.; Von Pinho, R. G.; Bruno, R. G. S. and Calestine, G. A. 2004. Ruminal degradability of hard or soft texture corn grain at three maturity stages. Scientia Agricola 61:358-363. https://doi.org/10.1590/S0103-90162004000400002
    » https://doi.org/10.1590/S0103-90162004000400002
  • Philippeau, C. and Michalet-Doreau, B. 1997. Influence of genotype and stage of maturity of maize on rate of ruminal starch degradation. Animal Feed Science and Technology 68:25-35. https://doi.org/10.1016/S0377-8401(97)00042-4
    » https://doi.org/10.1016/S0377-8401(97)00042-4
  • Philippeau, C. and Michalet-Doreau, B. 1998. Influence of genotype and ensiling of corn grain on in situ degradation of starch in the rumen. Journal of Dairy Science 81:2178-2184. https://doi.org/10.3168/jds.S0022-0302(98)75796-0
    » https://doi.org/10.3168/jds.S0022-0302(98)75796-0
  • Pries, M.; Denissen, J. and Speit, J. H. 2018. Effects of particle size distribution of maize silage on silage quality, dry matter intake and performance of dairy cows. p.65-74. In: Proceedings of 45th Viehwirtschaftliche Fachtagung, Raumberg, Austria. (in German).
  • Pryce, J. D. 1969. A modification of Barker-Summerson method for the determination of lactic acid. Analyst 94:1151-1152. https://doi.org/10.1039/AN9699401151
    » https://doi.org/10.1039/AN9699401151
  • Raun, B. M. L. and Kristensen, N. B. 2010. Propanol in maize silage at Danish dairy farms. Acta Agriculturae Scandinavica, Section A – Animal Science 60:53-59. https://doi.org/10.1080/09064701003796742
    » https://doi.org/10.1080/09064701003796742
  • Robbins, K. R.; Saxton, A. M. and Southern, L. L. 2006. Estimation of nutrient requirements using broken-line regression analysis. Journal of Animal Science 84:E155-E165. https://doi.org/10.2527/2006.8413_supple155x
    » https://doi.org/10.2527/2006.8413_supple155x
  • Rooke, J. A. and Hatfield, R. D. 2003. Biochemistry of ensiling. p.95-139. In: Silage science and technology. Buxton, D. R.; Muck, R. E. and Harrison, J. H., eds. American Society of Agronomy, Madison, WI.
  • Salvati, G. G. S.; Santos, W. P.; Silveira, J. M.; Gritti, V. C.; Arthur, B. A. V.; Salvo, P. A. R.; Ribeiro, A. P.; Lima, T. A. D.; Morais Jr., N. N. and Nussio, L. G. 2017. Impact of kernel processing and particle size in whole plant corn silage on the performance of dairy cows. In: Proceedings of the V International Symposium on Forage Quality and Conservation, Piracicaba.
  • Sova, A. D.; LeBlanc, S. J.; McBride, B. W. and DeVries, T. J. 2013. Associations between herd-level feeding management practices, feed sorting, and milk production in freestall dairy farms. Journal of Dairy Science 96:4759-4770.
  • Steidlová, S. and Kalac, P. 2002. Levels of biogenic amines in maize silages. Animal Feed Science and Technology 102:197-205. https://doi.org/10.1016/S0377-8401(02)00217-1
    » https://doi.org/10.1016/S0377-8401(02)00217-1
  • Weiss, K. 2017. Volatile organic compounds in silages – Effects of management factors on their formation: A review. Slovak Journal of Animal Science 50:55-67.
  • Weissbach, F. 2009. Correction of dry matter content of silages used as substrate for biogas production. p.483-484. In: Proceedings of the XV International Silage Conference. Madison, WI.
  • Zebeli, Q.; Aschenbach, J. R.; Tafaj, M.; Boguhn, J.; Ametaj, B. N. and Drochner, W. 2012. Invited review: Role of physically effective fiber and estimation of dietary fiber adequacy in high-producing dairy cattle. Journal of Dairy Science 95:1041-1056. https://doi.org/10.3168/jds.2011-4421
    » https://doi.org/10.3168/jds.2011-4421

Publication Dates

  • Publication in this collection
    11 May 2020
  • Date of issue
    2020

History

  • Received
    02 Dec 2019
  • Accepted
    05 Feb 2020
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