Technical note: A comparison of alkali treatment methods to improve neutral detergent fiber digestibility of corn stover

The objective of this study was to compare neutral detergent fiber (NDF) digestibility of corn stover that had been treated by 2 alkali treatment methods. Two experiments were conducted to test a sodium hydroxide (NaOH) treatment method that uses an ethanol/water co-solvent (NaOH/ethanol-H₂O, United States Patent No. 20140220228) and a calcium hydroxide (CaOH) treatment method, which uses water as a solvent (CaOH/H₂O). An in situ trial was conducted to compare NDF digestion kinetics between NaOH/ethanol-H₂O-treated stover, CaOH/H₂O-treated stover, untreated corn stover, and soy hulls. The digestion rate of potentially digestible NDF (k_d) of NaOH/ethanol-H₂O-treated corn stover (5.36%/h) was higher than CaOH/H₂O-treated stover (2.27%/h), or untreated corn stover (1.76%/h) and similar to the k_d of soy hulls (4.93%/h). The indigestible NDF (iNDF) fraction of untreated corn stover (35.1% of NDF) was reduced by CaOH/H₂O treatment (27.3% of NDF) and by NaOH/ethanol-H₂O treatment (2.8% of NDF). The iNDF fraction in soy hulls (3.6% of NDF) was similar to iNDF of NaOH/ethanol-H₂O-treated stover. An in vivo digestibility trial was also conducted to compare fiber digestibility of diets supplemented with untreated corn stover, NaOH/ethanol-H₂O-treated corn stover, or soy hulls. Total-tract apparent dry matter (DM) and NDF digestibility were measured with 8 lactating Holstein cows in a replicated 4 × 4 Latin square with four 21-d periods. Apparent DM digestibility (DMD) was improved when supplemental soy hulls were added to the base diet (60.0% DMD) compared with the base diet with no supplemental fiber (57.7% DMD). Apparent DM digestibility was reduced when diets were supplemented with untreated stover (52.4%). Dry matter digestibility of NaOH/ethanol-H₂O-treated stover was similar (54.8% DMD) to all other treatments. Digestibility of NDF was lowest when cows were fed the diet with supplemented untreated stover (35.5% of NDF), and improved when soy hulls (40.6% of NDF) or NaOH/ethanol-H₂O-treated stover (43.8% of NDF) were added to the diets. The NaOH/ethanol-H₂O treatment process improves the DM and NDF digestibility of corn stover to values similar to those of soy hulls.