Influence of ensiling, exogenous protease addition, and bacterial inoculation on fermentation profile, nitrogen fractions, and ruminal in vitro starch digestibility in rehydrated and high-moisture corn

Abstract

Exogenous protease addition may be an option to increase proteolysis of zein proteins and thus starch digestibility in rehydrated and high-moisture corn (HMC) ensiled for short periods. In addition, microbial inoculation may accelerate fermentation and increase acid production and thus increase solubilization of zein proteins. Four experiments were performed to evaluate the effect on fermentation profile, N fractions, and ruminal in vitro starch digestibility (ivSD) of the following: (1) rehydration and ensiling of dry ground corn; (2) exogenous protease addition to rehydrated un-ensiled and ensiled corn; (3) exogenous protease addition or inoculation in rehydrated ensiled corn; and (4) exogenous protease addition or inoculation in HMC. Experiments 1, 2, and 3 were performed with 7 treatments: dry ground corn (DGC); DGC rehydrated to a targeted dry matter content of 70% (REH); REH treated with exogenous protease (REH+); REH ensiled for 30 d (ENS); ENS treated with exogenous protease (ENS+); ENS treated with a microbial inoculant containing Lactobacillus plantarum, Lactobacillus casei, Enterococcus faecium, and Pediococcus sp. (ENSI); and ENS treated with exogenous protease and microbial inoculant (ENSI+). Experiment 1 compared DGC, REH, and ENS with ivSD being greater for ENS (64.9%) than DGC and REH (51.7% on average). Experiment 2 compared REH and ENS without or with exogenous protease addition (REH+ and ENS+, respectively). Ensiling and exogenous protease addition increased ivSD, but exogenous protease addition was more effective in ENS than REH (6.4 vs. 2.6 percentage unit increase). Experiment 3 compared the effects of exogenous protease addition and inoculation in ENS corn (ENS, ENS+, ENSI, and ENSI+). The addition of protease, but not inoculant, increased ivSD. Inoculation reduced pH and acetate, propionate, and ethanol concentrations, and increased lactate and total acid concentrations. In experiment 4, 8 treatments were a combination of HMC noninoculated or inoculated with 1 of 3 microbial inoculants and with or without exogenous protease addition. The inoculant treatments contained (1) Lactobacillus buchneri 40788 and Pediococcus pentosaceus, (2) L. buchneri 40788, and (3) a mixture of P. pentosaceus and Propionibacterium freudenreichii. Protease, but not inoculation, increased ivSD by 7.5 percentage units (44.4 vs. 51.9%). Protease addition increased ivSD in rehydrated corn and HMC. Microbial inoculation improved fermentation profiles but did not affect ivSD.

Effect of substituting dry corn with rehydrated ensiled corn on dairy cow milk yield and nutrient digestibility

“…This increase of total tract digestibility of starch and CP may have occurred as a result of greater degradation of some zein protein in the starch-protein matrix of REC, as described by Hoffman et al (2011). Therefore, protein matrix solubilization may occur in REC (Ferraretto et al, 2015) and, consequently, it may increase starch granule surface area for bacterial attachment in the rumen (Huntington et al, 2006). In addition, increased corn starch digestibility in high-moisture corn may be accelerated by the inclusion of proteases during the ensiling process, which also indicates the inhibitory role of zein on corn starch digestibility (Kung et al, 2014).…”

“…In addition, increased corn starch digestibility in high-moisture corn may be accelerated by the inclusion of proteases during the ensiling process, which also indicates the inhibitory role of zein on corn starch digestibility (Kung et al, 2014). Additionally, a recent study described that addition of exogenous protease, increased in vitro digestibility of starch in REC (Ferraretto et al, 2015). However, a possible limitation of our study could be the overestimation of the digestibility of CP, since fecal samples were dried using a forced air oven, which may result in loss of N and consequently an underestimation of fecal N excretion (Spanghero and Kowalski, 1997).…”

“…Aldrich et al (1993) reported higher starch digestibility when feeding dairy cows high moisture ensiled shelled corn in substitution with dry ear corn. Therefore, ensiling, besides being considered a forage conservation method, can also be used to increase the digestibility of corn grain dry matter (DM) and starch (Benton et al, 2005;Ferraretto et al, 2015). The ensiling process of corn grain reduced the integrity of the protein matrix that surrounds the corn starch granule, which increased the availability of starch to bacterial enzymatic activity, and, consequently, the in vitro starch digestibility (ivSD) (Hoffman et al, 2011;Ferraretto et al, 2015).…”

“…Therefore, ensiling, besides being considered a forage conservation method, can also be used to increase the digestibility of corn grain dry matter (DM) and starch (Benton et al, 2005;Ferraretto et al, 2015). The ensiling process of corn grain reduced the integrity of the protein matrix that surrounds the corn starch granule, which increased the availability of starch to bacterial enzymatic activity, and, consequently, the in vitro starch digestibility (ivSD) (Hoffman et al, 2011;Ferraretto et al, 2015). Recent studies suggested that an extended ensiling period increases ruminal ivSD, which indicated that maximum starch digestibility occurs only after several months of storage Kung et al, 2014).…”

A fermentação de grãos de milho reidratados influenciada pela aplicação de aditivos: aspectos da conservação e do valor nutritivo para vacas leiteiras

“…Para elucidar o efeito da aplicação dos aditivos em silagens de grãos de milho foi realizado um estudo meta-analítico a partir de 24 artigos publicados na íntegra (BIRO et al, 2006(BIRO et al, , 2009CANIBE et al, 2014;Da SILVA, T. et al, 2015;DAWSON;RUST;YOKOYAMA, 1998;DOLEZAL;ZEMAN, 2005;DUTTON;OTTERBY, 1971;FERRARETTO;FREDIN;SHAVER, 2015;FLORES-GALARZA et al, 1985;GÁLIK et al, 2007GÁLIK et al, , 2008ÍTAVO et al, 2006ÍTAVO et al, , 2009JOBIM et al, 2008;KUNG Jr. et al, 2004, 2007WINDLE;WALKER, 2014;LOUCKA, 2010;MORAIS et al, 2012;PRIGGE et al, 1976;PYŚ et al, 2009;REIS et al, 2008;TAYLOR;KUNG, 2002;WARDYNSKI; RUST; YOKOYAMA, 1993) uma nota científica (BASSO et al, 2012) e 10 resumos publicados nos principais simpósios internacionais sobre silagens e não publicados como artigos até o momento (AUERBACH et al, 2015;COUDURE et al, 2012;DA SILVA, N. et al, 2015;DAVIES et al, 2009 …”