Abstract
Our objective was to assess the effect of forage processor roll gap width and storage length on fermentation, nutrient composition, kernel processing score (KPS), and ruminal in situ starch disappearance (isSD) of whole-plant maize silage harvested at different maturities. Samples from a single maize silage hybrid at three harvest maturities (1/4, 1/2, and 3/4 kernel milk line (early, intermediate, and late, respectively)) processed with two roll gap widths (1 and 3 mm) were collected and stored in quadruplicate vacuum pouches for 0, 30, 120, or 240 d. Lactic acid concentrations were greater, and pH was reduced in early and intermediate maturity silage compared to late maturity silage. Ruminal isSD was greatest for early maturity silage, intermediate for the intermediate maturity silage, and lowest for the late maturity silage, but differences in isSD due to maturity were diminished after prolonged storage. Kernel processing score was greatest in late maturity silage processed through a 1 mm roll gap and lowest in late maturity silage processed through the 3 mm roll gap. For early and intermediate maturity silages, no differences in KPS were observed between the two roll gap widths. Minimal effects of maturity and roll gap width on fatty acids (FA) and amino acids (AA) were observed. Concentrations of total AA decreased as storage length progressed. Results support the premise that the silo is a dynamic system that undergoes numerous chemical changes throughout the storage period.
Highlights
Whole-plant maize silage (WPMS) is a vital forage source for the dairy industry in the United States, with approximately 125 million Mg of maize harvested for silage in 2020 [1].Its reduced harvesting costs, elevated yield per area, and the flexibility to harvest maize for forage or grain have contributed to the popularity of WPMS among dairy producers.In many high-producing dairy herds, up to half of the total mixed ration (TMR) DM can be comprised of WPMS
Given the profound effect that plant and management factors can have on the quality and digestibility of WPMS, the objective of this study was to evaluate the effect of forage harvester roll gap width and length of storage on the fermentation profile, nutrient composition, kernel processing score (KPS), and in situ starch disappearance of whole-plant maize silage harvested at three different maturities
Decreases in concentrations of arginine with ensiling have been reported by others as well [53,57]. This experiment demonstrated the influence that plant maturity, processing roll gap width, storage length, and their interactions could have on maize silage fermentation profile, nutrient composition, and starch disappearance
Summary
Whole-plant maize silage (WPMS) is a vital forage source for the dairy industry in the United States, with approximately 125 million Mg of maize harvested for silage in 2020 [1].Its reduced harvesting costs, elevated yield per area, and the flexibility to harvest maize for forage or grain have contributed to the popularity of WPMS among dairy producers.In many high-producing dairy herds, up to half of the total mixed ration (TMR) DM can be comprised of WPMS. Whole-plant maize silage (WPMS) is a vital forage source for the dairy industry in the United States, with approximately 125 million Mg of maize harvested for silage in 2020 [1]. Whole-plant maize silage is nutritionally valuable in that it is simultaneously a source of physically effective fiber (provided by the stover fraction) and energy (primarily from starch in the kernel fraction) for the dairy cow. The endosperm in maize kernels is protected by the pericarp, which is highly resistant to microbial and enzymatic degradation [4]. Many self-propelled forage harvesters are fitted with processing rolls intended to break maize kernels, thereby exposing starch in the endosperm to microbial degradation in the rumen or enzymatic digestion in the small intestine. Reducing the roll gap width has been shown in a metaanalytical review of the literature to increase total tract starch digestibility [5]. Even when the pericarp is successfully broken, ruminal starch degradation can be inhibited by the hydrophobic zein protein matrix that surrounds starch granules [7,8]
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