Graduate Thesis Or Dissertation

 

The effects of aerobic and anaerobic fermentation on the nutritive value of ryegrass straw Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/mw22v852m

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  • A series of in vitro laboratory trials and in vivo sheep digestion trials were used to evaluate aerobically or anaerobically fermented perennial ryegrass straw. The laboratory trials consisted of a silage study, where mini-silos were used in a 9 X 2 factorial design with nine levels of whey (0 to 20%) and two levels of sodium hydroxide (0 and 4%). The laboratory trial also included a study of products derived from a semisolid fermentation of ryegrass straw, which involved the acid hydrolysis, neutralization with ammonia and aerobic fermentation with yeast (Candida utilis). In vivo digestion trials with sheep were used to evaluate 0 and 4% sodium hydroxide (NaOH) treated silages as well as the semisolid fermentation products. Silage pH was higher (P<.01) for silages containing 4% NaOH than for controls. NaOH treated and untreated silages were similar in crude protein, content, however, NaOH treated silages were lower (P<.05) in total soluble nitrogen and soluble nonprotein nitrogen. The concentration of acid detergent fiber (ADF), cell wall constituents (CWC), cellulose and hemicellulose were consistently lower (P<.05) for the NaOH treated silages. Acetic, propionic, and butyric acid concentrations were increased (P<.01) in the 4% NaOH silages as well as the total organic acid concentration (P<,01). In vitro dry matter digestibility (DMD) was also improved (P<.01) by NaOH additions to the silages. Increasing levels of dried whole whey added to both NaOH treated and untreated silages decreased (P<.01) the pH and increased (P<.01) the total organic acid production. Crude protein levels of the silages increased (P<.01) with higher levels of whey, but had no effect on soluble nitrogen fractions. Structural components, ADF, CWC, cellulose and hemicellulose, decreased (P<.01) with increasing levels of whey, however, the NaOH treated silages were lower in total percentages. In vitro DMD was improved (P<.01) by increasing levels of whey. The products derived from the semisolid fermentation process (neutralized and fermented straw) were similar (P<.05) with respect to crude protein and soluble nitrogen fractions. However, the soluble protein of the neutralized products was higher (P<.05) than the fermented product. The fermented product was higher (P<.05) in ADF, CWC, and ADL than the neutralized material. The two products were similar (P<.05) in cellulose and hemicellulose content. In vitro DMD for the fermented and neutralized products did not differ significantly. In vivo evaluation of the whey and NaOH treated ryegrass straw silages indicated no difference (P<.05) in nitrogen retention. Apparent protein digestibility was lower (P<.05) for the 4% NaOH treated silage than for the untreated silage. However, the NaOH treated silage had an increased (P<.05) dry matter, CWC, and ADF digestibility over the untreated silage. The diets for the digestion trials containing the neutralized and fermented products from the semisolid fermentation process were similar in chemical composition to the grass hay control diet, except for being higher (P<.05) in ADF. Nitrogen retention data showed a reduced (P<.05) nitrogen utilization by sheep for the neutralized and fermented product over that of the grass hay diet. The apparent protein digestibility was higher (P<.05) for the neutralized product than the fermented product, however, both were lower (P<.05) than the grass hay diet. Both semisolid fermentation products were lower (P<.05) in dry matter, CWC and ADF digestibilities than the grass hay control.
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