Development of highly digestible animal feed from lignocellulosic biomass Part 1: Oxidative lime pretreatment (OLP) and ball milling of forage sorghum.

To feed a growing population, alternative sources of animal feed (e.g., lignocellulose) are needed to replace grains (e.g., corn). Oxidative lime pretreatment (OLP) increases lignocellulose digestibility by removing lignin and hemicellulose acetyl content. Adding a mechanical pretreatment (e.g., ball milling) further improves digestibility. This study determines the effectiveness of OLP and ball milling to enhance the ruminant digestibility of lignocellulose. For forage sorghum, the 48-h in vitro TDN were 40, 64, and 84 g nutrients digested/100 g organic matter (OM) for raw, short-term OLP, and short-term OLP + ball milling, respectively. In terms of compositional changes, OLP increases NDF and decreases non-fiber carbohydrate (NFC) and crude protein (CP), all of which would normally be associated with a decrease in digestibility. However, because OLP and ball milling beneficially change composition (lignin removal) and structural features (reduced crystallinity), digestibility actually increases. Although ball milling increases digestibility according to standard laboratory assays, it reduces particle size possibly allowing fine particles to escape from the rumen before they are digested, thus limiting its practical application. Nonetheless, this study indicates that mechanical pretreatment greatly increases digestibility, and therefore it is desirable to identify an effective mechanical treatment that retains fiber integrity.

Development of highly digestible animal feed from lignocellulosic biomass Part 2: Oxidative lime pretreatment (OLP) and shock treatment of corn stover.

Oxidative lime pretreatment (OLP) increases lignocellulose digestibility by removing lignin and hemicellulose acetyl content. Digestibility is improved further by adding mechanical shock treatment, which subjects aqueous slurry of biomass to an explosive pressure pulse. Shock treatment mechanically disrupts the microscopic structure while maintaining the macroscopic integrity of the biomass particle. This study determined the effectiveness of these pretreatments to enhance the ruminant digestibility of corn stover. In terms of compositional changes, OLP and shock treatment should negatively affect the feed value of corn stover; however, digestibility analysis provides a significantly different conclusion. With corn stover, shock + OLP improved the 48-h neutral detergent fiber digestibility (NDFD) to 79.0 g neutral detergent fiber (NDF) digested/100 g NDF fed, compared to 49.3 for raw corn stover. The 48-h in vitro total digestible nutrients (TDNom, g nutrients digested/100 g OM) was 51.9 (raw), 59.7 (OLP), and 72.6 (shock + OLP). Adding extracted corn stover solubles to shock + OLP increased TDNom to 74.9. When enough solubilized chicken feathers were added to match the protein content of corn grain, TDNom increases to 75.5, which is only 12.6 less than corn grain.