Thesis (Ph. D.)--University of Delaware, 2008. / Principal faculty advisor: Limin Kung, Jr., Dept. of Animal & Food Sciences. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Several countries have enacted regulations on tolerance limits for common mycotoxins because of the hazardous nature and widespread occurrence of these fungal secondary metabolites in agricultural commodities. Screening of agricultural commodities destined for animal consumption for the presence of mycotoxins is now becoming a prerequisite in several countries as a means of minimizing ingestion of these toxins. Silage samples were analyzed for pH, % dry matter (DM) content, and the presence of total fungi, yeasts and the types of lactic acid bacteria present. The samples were also analyzed for mycotoxins that have been reported to commonly occur in silage. The pH of the samples was found to be acidic ranging from pH 3.4 to 4.7, with few samples having pH values above 6. There was a significant difference in the % DM content amongst the sampling regions. There was no significant difference in the extent of fungal contamination amongst the different regions. Aspergillus fumigatus was the predominant species from all the samples. Most of the yeast species were isolated from the Bergville region. The yeast species isolated from all samples were Trichosporon, Cryptococcus and Candida species, which are all regarded as nonlactate fermenters. Lactobacillus plantarum and Lactobacillus buchneri were the only two lactic acid producers isolated from the samples. Aflatoxins, citrinin and patulin were the most predominant toxins in the samples. Ochratoxin A and deoxynivalenol was not detected in all samples using thin layer chromatography, while the latter two toxins were only detected in two samples using VICAM fluorometry. The level of fumonisins that was found in the forage crops used for silage production was fairly low with the highest level being 9.36 ppb. Most of the mycotoxin extracts were found to reduce the % cell viability of human lymphocytes after 18 hours of incubation as determined by the MTT assay. / Professor Mike Dutton Mr. F. E. Van Zyl

In this study, the bioconversion of manure and silage to biogas by an anaerobic digestion process in batch reactors was studied. Biogas is a valuable alternative energy source, mainly in rural areas. The main aim for the environment is to use biogas as a fuel instead of crude oil or natural gas. In this study, two different parameters were studied to observe the changes in methane productivity. The first three reactors were shaken once per week and the following three reactors were shaken 5 times per week. The results showed that mixing has no major effect on the methane production yield. In the second six reactors a mixture of 1% and 3% silage was added and the results were recorded. When the data from the reactors with just manure was compared to the reactors with 1% and 3% silage, it was seen that the silage increased the production rate and total gas produced. The process stabilization took a long time for digestion with the 3% silage possibly caused by release of too much fatty acids.

Silage is fermented forage plants. It is a succulent and nutritious feed, which can be used especially when green forage is not available. The methods by which it is made were first developed from a nineteenth century German process for making sour hay. / Master of Science

Glyphosate (N-(phosphonomethyl)glycine)-containing herbicides are a common and highly effective method to terminate alfalfa (Medicago sativa) stands. With the development and use of glyphosate-resistant (Roundup Ready®) alfalfa, this tool is no longer an option. The purpose of this research was to determine the optimal strategy to rotate from glyphosate-resistant alfalfa into silage corn (Zea mays). Studies were conducted in 2012 and 2013 at sites near Cache Junction and Cornish, Utah to determine the effect of tillage type and timing [fall conventional till (FCT), spring conventional till (SCT), fall strip-till (FST), spring strip-till (SST), and no-till (NT)], 2,4-D plus dicamba herbicide timing (fall, spring, in-crop, and a control), and N rate (0, 56, 112, and 224 kg N ha-1) on soil penetration resistance (PR), alfalfa re-growth, and corn emergence rate index (ERI), silage yield, quality, and economic return. The fall, spring, and in-crop herbicide timings across all tillage treatments reduced alfalfa stem count and biomass by at least 95% and 98%, respectively. Tillage reduced PR compared to NT to or near the depth of tillage. The ERI was significantly higher under FCT, SCT, and SST and when herbicides were applied in fall or spring. Silage yield, quality, and economic return were the highest when spring herbicide timing was used with all tillage types and timings and the fall herbicide timing under conventional tillage. Increasing N rates increased crude protein, milk ha-1, and dry matter yield. However, optimal yield and quality can be obtained with no additional N fertilizer. First-year silage corn yield, quality, and economic return can be optimized under fall or spring conventional till, strip-till, and no-till at the spring herbicide timing along with the fall herbicide timing for conventional tillage with no additional N fertilizer.

Alfalfa is difficult to ensile because of its low water soluble carbohydrate content, low dry matter content, and high buffering capacity. Therefore, the isolation of mutants of L. plantarum was undertaken to develop a strain(s) which could improve the fermentation of alfalfa silage when used as an inoculum. Efforts to isolate starch- or hemicellulose-utilizing strains proved unsuccessful as did the isolation of high temperature resistant mutants and oxygen resistant mutants. Mutants resistant to plumbagin (an intracellular O₂- generator) and citrate were isolated. Of these mutants, some were found to be more sensitive to cadmium than the parent strain. Though these three characteristics point to an enhanced manganese accumulation since O₂- is scavenged by manganese, citrate will chelate manganese, making it unavailable to the organism, and cadmium is transported by the manganese transport system, the rates of 54_Mn transport were no greater than the parent. When grown aerobically on a glucose-limited medium, the parent strain consumed oxygen and produced high concentrations of acetic acid and low concentrations of lactic acid. By contrast, one mutant (strain MC226), produced high concentrations of lactic acid and demonstrated low rates of O₂ consumption and low levels of acetic acid. The parent strain and two plumbagin- and citrate-resistant mutants were used to inoculate alfalfa for silage production. The inoculated silages showed a lower pH and higher titratable acidity than that of an uninoculated control. Silages inoculated with the parent strain exhibited high levels of acetic acid and low levels of lactic acid, indicative of oxygen consumption by the parent strain. Less acetic acid was evident in silages inoculated with the mutant strains. All silages contained a high level of butyric and isobutyric acids and propionic and isovaleric acids were also detected, indicative of clostridial growth. / Master of Science

Corn silages were selected from samples analyzed in the Virginia Tech Forage Testing Laboratory. A sample selection scheme employing observation of silage quality indicators (color, mold, aroma, fermentation type) was utilized to obtain a sample set encompassing a wide range in deterioration. In vitro digestible organic matter (IVDOM) was the criteria used to estimate feeding value. The full data set contained 142 corn silages which averaged 59.8 ± 6.6% and ranged from 38.5 to 74.7% IVDOM. Simple and multiple regression of IVDOM on chemical constituents were performed for the full data set and within fermentation groups. Coefficients of determination (R² ) revealed that acid detergent fiber (ADF) and dry matter (DM) explained the largest proportion of variation in IVDOM. The simple regression on the full data set resulted in R² of .352 and .208 with standard errors of the prediction S_y.x of 5.29 and 5.86 for ADF and DM, respectively. Multiple regression analyses resulted in minor improvements in S_y.x. These data suggest the inclusion of other variables besides ADF and DM in the prediction equation is unwarranted. Corn silage IVDOM was predicted employing Near-infrared reflectance techniques. A calibration resulted in R² of .77, S_y.x of 5.38. The calibration equation was tested for the prediction of IVDOM for an additional 90 corn silages. The regression of NIR predicted IVDOM resulted in an R² of .37 and S_y.x of 4.04. The prediction of corn silage IVDOM by NIR or ADF were similar. / Master of Science

Beef cattle producers in the southeastern US often stockpile forage in late summer to extend the grazing season and reduce feeding costs. Three stockpiled grass-legume mixtures were evaluated for winter grazing. In addition, stockpiled forages were ensiled and evaluated as livestock feed. Four accumulation dates and seven harvest dates were randomized to small plots of tall fescue (Festuca arundinacea Schreb.) -red clover (Trifolium pratense L.), orchardgrass (Dactylis glomerata L.) -red clover, and orchardgrass-alfalfa (Medicago sativa L.). The amount of grass and legume in the fescue-red clover mixture shifted from less than 30% grass and more than 60% legume in October to over 60% grass and less than 10% legume in April. All forage mixtures contained at least 15% CP from November to March. Fescue-red clover was higher in TNC and lower in NDF, ADF and cellulose in January and March than the orchardgrass-legume mixtures. Fescue-red clover was higher in yield than the orchardgrass-legume mixtures from November to February. Delaying stockpiling until September 1 or 15 increased (P <.05) legume content and decreased dead grass content in orchardgrass-clover and orchardgrass-alfalfa. Accumulating growth from September 15 increased percent CP in fescue-red clover and orchardgrass-clover, compared to August 15, and decreased percent NDF in all forage mixtures. Percent IVDMD increased in orchardgrass-clover when stockpiling was delayed until September 15. May yields decreased only in orchardgrass-alfalfa when stockpiling was delayed until September. Orchardgrass stockpiled on August 3 and September 3, and alfalfa stockpiled on September 3 were ensiled alone. Chemical composition of silages was determined after 90 d of fermentation. Silages averaged 16.0% CP and 44.7% NDF. Digestibility of the ensiled stockpiled forages was estimated using acid insoluble ash as a marker with 18 wether lambs. No differences were observed in DM or CP digestibility, but NDF digestibility was lower for alfalfa silage than for orchardgrass silages. All stockpiled grass-legume mixtures provided high quality winter grazing, and all silages were of good quality and digestibility. Fescue-red clover maintained both good quality and higher yield than the other mixtures. Ensiling stockpiled alfalfa and orchard grass provided a method of maintaining CP and digestibility for subsequent feeding. / Master of Science

Three studies were conducted to assess if the ability of Enterococcus spp. surviving the ensiling process and bovine gastrointestinal tract could impact risk of bovine mastitis. The first study determined ability of enterococci to survive 3 wk ensiling. Grass and corn crops were divided into 3 treatments: 2 commercial silage inoculants, 1 negative control. After wk 1, 2, and 3 of ensiling, dry matter and bacterial enumeration were performed. Addition of silage inoculant led to greater levels of enterococci in grass silage compared with negative control levels, but showed less difference in inoculated corn silage. The second study quantified enterococci shedding rates in lactating dairy cows. Using a 4 x 4 Latin Square design, lactating, ruminally fistulated Holsteins were inoculated with enterococcal isolates from silage inoculants, ensiled forages, or clinical mastitis cases. Over the 4-period study, each period consisted of rumen and fecal sampling (2 wk) followed by a wash period (10 d). There were no significant differences in rumen or fecal enterococci levels between the 4 treatments. Both rumen and fecal enterococci levels showed significant differences between baseline and treatment periods (period 3, 4). The third study analyzed similarity in enterococcal isolates of silage and bovine origin using pulsed-field gel electrophoresis patterns from SmaI restrictions. Dendogram analysis showed none of the isolates met or were greater than a 75% genetic similarity and produced a genetically diverse population. Results suggest Enterococcus spp. from silage inoculants are not likely to contribute to an increased risk of enterococcal bovine mastitis. / Master of Science