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Title: The nitrogenous changes during ensilage
Author: Heron, Shirley Jean Elizabeth
ISNI:       0000 0001 3555 0414
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1985
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Gamma-irradiation was used to delineate the effects of plant and microbial enzymes on the nitrogenous changes occurring during ensilage, particularly in the amino acid fraction. The effect of inoculating irradiated grass with lactic acid bacteria was also studied. Results showed that proteolysis is brought about mainly by plant proteases whereas further amino acid metabolism is the result of microbial activity. The effects on individual amino acids are reported. L. plantavum and S. faeoal-is were shown to be non-proteolytic and to have a limited ability to catabolise amino acids. The effect of pH on plant protease activity was investigated using gamma-irradiated aqueous grass extract. Protein breakdown appears to be largely completed within a few days. It was found that, although the overall optimum pH for ryegrass proteases is 5.5 to 6.5, activity still occurred at the pH levels found in silage. The effect of several different types of silage additive on fermentation was studied, particularly with respect to the nitrogenous components. A commercial inoculant ("Clampdown") was applied to grass at three levels (10⁴, 10⁶ and 10⁸ organisms g⁻¹) before ensiling. Silages were also made after mincing both inoculated and uninoculated grass and after addition of glucose (20 gkg⁻¹), to inoculated and uninoculated grass. The homofermentative inoculant stimulated a more efficient fermentation, leading to rapid acidification and silages with high water-soluble carbohydrate and lactic acid contents. There was some reduction in proteolysis and a considerable decrease in deamination. Mincing alone did not encourage acidification nor reduce deamination, but did reduce proteolysis. Mincing the inoculated material did not enhance the effects of inoculation. Glucose treatment was found to be ineffeetive. Formalin (40% w/v formaldehyde) at 1.8 It⁻¹ and "Add-F" (85% w/w formic acid) at three levels (2.3, 4.6 and 6.9 It⁻¹) were applied to grass before ensiling either alone or in combination. Formic acid was found to be a very effective inhibitor of fermentation. When used on its own, it had a limited effect only, in preventing proteolysis, but did reduce deamination substantially. Formaldehyde alone had little effect on fermentation, proteolysis or deamination. Combining the two additives produced a synergistic effect with respect to protein protection. The most satisfactory treatment was a combination of formic acid at 2.3 It⁻¹ with formalin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Microbiology