An experiment was conducted to evaluate the effects of pasture finishing versus high-concentrate finishing, over time, on fatty acid metabolism in Angus crossbred (n = 24) beef steers. Ruminal fluid, serum, and adipose tissue biposies were obtained on d 0, 28, 84, and 140. Pasture forages and diet ingredient samples were obtained at 14 d intervals to determine nutritive value and fatty acid composition. The high-concentrate diet consisted of corn silage, cracked corn, soybean meal, and a vitamin and mineral supplement. The pasture-finished steers grazed sequentially on triticale (Triticale hexaploide)/annual ryegrass (Lolium multiflorum), alfalfa (Medicago sativa)/orchardgrass (Dactylis glomerata), and a cool-season grass/legume mixture. The high-concentrate diet consisted of 57 % linoleic acid and 7 % linolenic acid (of total fatty acids). The pasture forages contained an average 9 % linoleic acid and 66 % linolenic acid (of total fatty acids). Adipose tissue concentrations of 18:2 cis-9, trans-11 CLA were higher (P < 0.05) in the pasture-finished steers than high-concentrate finished steers. Concentrations of 18:2 cis-9, trans-11 CLA declined in the high-concentrate finished steers (P < 0.05) from d 0 to 28 and d 28 to 84. In the pasture-finished steers concentrations peaked (P < 0.10) on d 28, and remained high throughout the duration of the study. Concentrations of linolenic acid were higher (P < 0.05) in adipose tissue, ruminal fluid, and serum of the pasture-finished steers, compared to the high-concentrate finished steers. In the pasture-finished steers linolenic acid concentrations peaked (P < 0.05) on d 28, and remained high throughout the study. Concentrations of linolenic acid gradually decreased (P < 0.05) over time within the high-concentrate finished steers. Thus, it appears that only a short time is needed to alter the omega-3 and CLA composition of adipose tissue in cattle finished on pasture. / Ph. D.

Ruminant livestock maintain an important role in meeting the nutrient requirements of the global population through their unique ability to convert plant fiber into human-edible meat and milk products. Volatile fatty acids (VFA) produced by rumen microbial fermentation of feed substrates represent around 70% of the ruminant animal's metabolic energy supply. Rumen fermentation profiles may directly impact productivity because the types of VFA produced are utilized at differing efficiencies by the animal. Improving our understanding of factors that control these fermentative outcomes would therefore aid in optimizing the productive efficiency of ruminant livestock. Improvements in animal efficiency are now more important than ever as the livestock industry must adapt to continue meeting the nutritional needs of a growing global population in the context of increased resource restrictions and requirements to lower the environmental impact of production. The relationship between diet and VFA ultimately supplied to the animal is complex and poorly understood due to the influence of numerous nutritional, biochemical, and microbial variables. The central aim of this body of work was therefore to explore and characterize how fermentation dynamics, rumen environmental characteristics, and the rumen microbiome behave in response to variations in the supply of fermentative substrate. The objective of our first experiment was to describe a novel in vitro laboratory technique to rank livestock feeds based on their starch degradability. This experiment also compared the starch degradation rates estimated by the in vitro method to the rates estimated by a traditional in situ method using sheep. A relationship between the degradation rates determined by these two procedures was observed, but only when feed nutrient content was accounted for. While this in vitro approach may not be able to reflect actual ruminal starch degradation rates, it holds potential as a useful laboratory technique for assessing relative differences in starch degradability between various feeds. Our second experiment aimed to measure changes in VFA dynamics, rumen environmental characteristics, and rumen epithelial gene expression levels in response to dietary sources of fiber and protein designed to differ in their rumen availabilities. Conducted in sheep, this study utilized beet pulp and timothy hay as the more and less available fiber source treatments, respectively, and soybean meal and heat-treated soybean meal as the more and less available protein source treatments, respectively. Results indicated that rumen environmental parameters and epithelial gene expression levels were not significantly altered by treatment. However, numerous shifts in response to both protein and fiber treatments were observed in fermentation dynamics, especially in interconversions of VFA. The objective of the third investigation was to assess whether the rumen microbiome can serve as an accurate predictor of beef and dairy cattle performance measurements and compare its predictive ability to that of diet explanatory variables. The available literature was assembled into a meta-analysis and models predicting dry matter intake, feed efficiency, average daily gain, and milk yield were derived using microbial and diet explanatory variables. Comparison of model quality revealed that the microbiome-based predictions may have comparable accuracy to diet-based predictions and that microbial variables may be used in combination with diet to improve predictions. In our fourth experiment, the objective was to investigate rumen microbial responses to the fiber and protein diet treatments detailed in Experiment 2. Responses of interest included relative abundances of bacterial populations at three taxonomic levels (phylum, family, and genus) in addition to estimations of community richness and diversity. Numerous population shifts were observed in response to fiber treatment. Prominent fibrolytic population abundances as well as richness and diversity estimations were found to be greater with timothy hay treatment and lower with beet pulp whereas pectin degraders increased in abundance on beet pulp. Microbial responses associated with protein treatment were not as numerous but appeared to reflect taxa with roles in protein metabolism. These four investigations revealed that significant changes can occur in VFA fermentation and rumen microbial populations when sources of nutrient substrates provided in a ruminant animal's diet are altered and that a new approach may be useful in investigating degradation of another important substrate for fermentation (starch) in a laboratory setting. Our findings also determined that animal performance can be predicted to a certain extent by rumen microbial characteristics. Collectively, these investigations offer an improved understanding of factors that influence the process of converting feed to energy sources in the ruminant animal. / Doctor of Philosophy / Ruminant animals, such as beef cattle, dairy cattle, and sheep, play a major role in delivering essential nutrients to the human population through their provision of meat and dairy products. The current growth projections of the global population, in addition to increased concerns surrounding greenhouse gas emissions and restrictions on resources such as land and water make it important for us to consider ways of optimizing the productivity of these animals. A unique feature of ruminants is their ability to conduct microbial fermentation of large amounts of plant matter in their rumens to produce energetically valuable compounds called volatile fatty acids (VFA), which are the primary source of energy that the animals use for growth, reproduction, and milk production. One promising way of improving animal productivity is to increase the amount of energy from the diet that becomes available to fuel the animal's body processes; however, the process of converting feed to VFA is complicated and currently not well understood. The overall aim of this body of work was therefore to explore various nutritional, ruminal, and microbial factors that are known to impact fermentation in order to 1) increase our understanding of how these factors interconnect and 2) put us in a better position to manipulate these factors for optimal animal performance. The goal of our first experiment was to devise and use a novel laboratory technique to rank livestock feeds based on the degradability of their starch content, which is an important substrate for VFA fermentation. Our observations indicate that this technique may be a useful tool to help us determine relative differences between feeds based on their starch degradabilities in a laboratory setting. Our second experiment investigated the effects of feeding varying sources of fiber (beet pulp and timothy hay) and protein (heat-treated and untreated soybean meals) to sheep in terms of their VFA fermentation, rumen conditions, and the expression of certain key genes in the epithelial tissue of the rumen wall. While rumen environmental characteristics and epithelial gene expression remained largely unchanged, numerous key aspects of VFA fermentation, predominantly carbon exchanges between different VFA, were altered in response to nutrient source. The third investigation described in this work examined the ability of the microbial populations responsible for rumen fermentation to explain variation in beef and dairy cow productivity compared with the ability of diet characteristics to explain this variation. Using statistical methods to analyze the reports currently available in scientific literature, our findings indicate that the rumen microbiome and diet may exert independent effects on productivity levels and that the microbiome may be used to enhance diet-based predictions of animal performance. Finally, we explored variations in the sheep rumen microbiome in response to the diet treatments utilized in Experiment 2. We observed minimal impact of protein source on the microbiome, but numerous microbial responses were evident when fiber source was varied. These responses included decreases of fiber-degrading bacterial populations and increases in pectin-degrading populations when beet pulp was fed compared to timothy hay. Taken together, these experiments help to provide us with a more comprehensive picture of the numerous factors involved in the process of converting feed to a usable form of energy for ruminant livestock.

The purpose of this study was to examine the relationship between metabolic adaptive response to 5 days of high SFA feeding, independent of positive energy balance, and diet-induced agonism of pro-inflammatory pathways. A secondary aim was to determine if the metabolic adaptive response in skeletal muscle to a single, high fat meal was altered by 5 days of high saturated fat feeding. Twelve college-age, non-obese males were studied and skeletal muscle samples were obtained prior to and concluding the consumption of a high SFA diet. In a subset of volunteers (N=6), we fed participants a high fat meal after the initial skeletal muscle biopsy and measured changes in postprandial endotoxin concentrations for four hours following the meal challenge. A second biopsy was obtained four hours after the meal challenge. Skeletal muscle samples were used to measure fatty acid oxidation, glucose oxidation, oxidative enzyme activities, mRNA expression of metabolic targets, and phosphorylation and total content of inflammatory proteins. In response to five days of high SFA feeding, skeletal muscle glucose and complete palmitate oxidation were significantly reduced as was the ratio of complete to incomplete fatty acid oxidation. Five days of high SFA feeding also attenuated the meal challenge-induced up-regulation of oxidative genes while augmenting postprandial increases in plasma endotoxin concentrations. To assess the relationship between metabolic adaptability and diet-induced inflammatory response we categorized volunteers by the diet induced percent change in fatty acid oxidation. Volunteers who were the least capable to adapt to high SFA feeding displayed the most robust increases in phosphorylation of inflammatory proteins. Lastly, we measured the correlation between the meal challenge associated percent change in oxidative and inflammatory markers in samples obtained prior to and following five days of high SFA feeding. We observed positive associations between the percent change in oxidative and inflammatory markers in samples obtained prior to the high SFA diet that were not observed following five days of high SFA feeding. These findings suggest that diet induced inflammatory response is involved in the regulation of adaptive response to high SFA feeding and that this relationship becomes dysregulated with chronic high SFA intake. / Ph. D.

Three experiments were conducted to contrast the effect of dissimilar lipid sources on broiler chicken metabolism. In Experiment 1, the nitrogen-corrected apparent metabolizable energy values (AME_n) of soybean oil (SBO) and hydrogenated soybean oil (HSBO) were determined. Trans monoenes, present only in HSBO, comprised 41% of total fatty acids. The AME_n contents of SBO and HSBO were determined to be 8,739 and 7,657 kcal/kg, respectively. The influence of dietary fatty acids on the lipid composition of the intestinal brush border membrane (BBM) was studied in Experiment 2. Beginning at hatch, chickens were provided isocaloric diets, identified as being either a minimal-lipid (1% 18:2n6) basal diet (ML) or one of three diets in which one-sixth of the caloric content of the basal diet was replaced by oils high in either polyunsaturates (HP), saturates (HS), or trans (HT) monoenes. The BBM alkaline phosphatase specific activity was greater in chickens fed HT than in those fed ML, HP, and HS. The BBM concentrations of palmitic, stearic, and oleic acids were not affected by treatment. Less linoleate (P<.06) and linolenate (P<.05) were present in the BBM of chickens receiving HT and HS than in those fed ML and HP. Arachidonate was present in greater concentrations when birds were fed ML, HP, and HS than when fed HT. Trans isomers were present only in the BBM from chickens fed HT. In Experiment 3, the effects of supplemental dietary lipidS on 1) the lipid composition of intestinal tissue and 2) the in vitro absorptive rate of differing dietary nutrients were studied. Diets similar to those in Experiment 2 were offered to broiler chicks from hatch to 28 days of age. Intestinal membrane concentrations of palmitic and oleic acids were not affected by dietary treatment. Chickens receiving the HSBO or the palm oil diet had less intestinal 18:0, 18:2n6, 18:3n3, and 20:4n6 than did those offered SBO or the control diet. In all treatments, linoleate and oleate were absorbed at a faster rate than stearate across all treatments. The in vitro uptake rates of oleate and linoleate were not affected by dietary treatment. Stearate and glucose uptakes were reduced in chickens fed HSBO or palm oil compared to those offered either the control diet or SBO diet. / Ph. D.

The theory involved in actual distillation phenomena encountered in molecular distillation has, to the present date, been only lightly explored. Scientific research has been replaced mainly with the need for improving the practical applications ot the process. As a result, although few theoretical correlations have been evolved, the present day high-speed centrifugal molecular stills are capable of effecting separations and purifications economically impossible by any other means. Molecular distillation has found wide commercial application in the separation and purification of such normally non-distillable, high molecular weight, thermally unstable substances as vitamins A and E, industrial synthetics, plasticizers, fatty acid dimers, and the like. In investigating the theory underlying molecular distillation, only a few classes of compounds have been used; the most important of these being pilot dyes, and to a lesser extent, fatty acids. The use of the latter class of compounds has been slight, despite their ease of analysis, ready, solubility in various carrier oils, and the availability of a large number of the series for investigative purposes. It was the purpose of this investigation to molecular distill a number of these fatty acids and, from a study of the elimination curves obtained, to determine the effects of molecular weight, molecular structure, and degree of unsaturation on these maxima. The five-inch magnetically-driven centrifugal molecular still employed for the investigation was modified slightly from a previous design. Two metal diffusion pumps which were a part of the vacuum pumping system were replaced by a third megavac forepump, which was in turn connected through a manifold arrangement with the original two that were in the system. A gravity-feed system was also installed; the modification consisted of elevating the feed tank above the still head assembly, and installing a needle valve in the feed line for accurate feed rate control. Preliminary vacuum tests were roads on the modified still, and the development of a synthetic constant-yield oil for use in the investigation was undertaken. From a number of distillation tests made on individual and blended mixtures of various petroleum oils, it was found that a blend of 225 milliliters of Voltesso No 36, 175 milliliters of light mineral, and 425 milliliters of heavy mineral oil distilled in approximately constant volumetric quantities over the temperature range of 86 to 146 degrees Centigrade. The development of a constant-yield oil led to the standardization of an operating procedure which was to be used for all the tests. The operating variables that were held constant for the distillation studies included: feed rate 60 to 65 milliliters per minute; operating pressure, 12 ± 2 microns of mercury; feed-residue temperature difference, 24 ± 1/2 degrees Centigrade; rotor speed, 1000 ± 50 revolutions per minute; condenser water temperature, 45 ± 1 degrees Centigrade; and one pass of the feed mixture across the rotor per fraction. Six saturated fatty acids, pentadecylic, palmitic, margaric, stearic, nonadecylic, and arachidic; one monoethenoid, oleic; and one diethenoid, linoleic, were then individually distilled using the standardized operating procedure devised in the investigation. The elimination curves were plotted and the maxima were found to be 100, 102, 110, 112, 127, 122, 110, 108 degrees Centigrade, respectively. These maxima were then compared to determine what effect molecular weight, molecular structure, and degree of unsaturation had on the maxima. It was concluded from this investigation that the addition of two CH₂ groups in the molecule of a homologous series of long-chain even numbered carbon atom aliphatic fatty acids raises the elimination maximum 10 degrees Centigrade. It was found that no valid prediction as to the effect of the addition of one CH₂ group to a homologous series of long-chain aliphatic fatty acids can be made. The study indicated that molecular structure; that is, chain length, has a definite, but unpredictable influence on the elimination maximum. It was also found that the addition of each unconjugated double bond in a molecule of a homologous series of fatty acids lowers the elimination maximum two degrees Centigrade. / Master of Science

The Southern Regional Nutrition Research Project Number S-28 has as its objective the study of metabolic patterns in preadolescent children. In the summer of 1962, twelve preadolescent girls were housed and cared for in one of the women's residences at the Virginia Polytechnic Institute. During a period of almost seven weeks the subjects consumed controlled diets; excreta were collected and blood samples were obtained for future analysis. The experimental diets were designed to include only foods from plant sources. This part of the metabolic study was planned to determine the amount and distribution of the fatty acids in those diets. Methods and procedures were developed for extracting the fatty acids from the lyophilized food composite composed of plant foods only. The fatty acids were extracted and methylated. Their methyl esters were separated and determined quantitatively by gas-liquid chromatography. The total amount of fatty acids in Diet 11 and 12 was twice that of Diet 9 and 10. The most abundant fatty acid was oleic, accounting for nearly SO percent of the total fatty acids in the food composites. Linoleic acid was the next most abundant fatty acid present in the diets. The average values for the six days of the two diets had almost identical fatty acid patterns. As would be expected, the ratio of polyunsaturated to saturated fatty acids was very high for these two diets (1.17) as compared to ratios found for representative American diets of plant and animal foods (0.20 - 0.41). / Master of Science

The ubiquitous distribution of the pentose molecule in nature and particularly its presence in certain enzymes and in nucleic acids emphasizes the metabolic significance of these carbohydrates. In living systems the pentoses are undergoing continuous metabolic changes. It thus appeared that investigations concerning the metabolic decomposition of the pentose molecule would be important from a comparative biochemical point of view. The advantages of a microbial system as a working model for biochemical investigations are well known. Investigations concerning pentose metabolism were, therefore, carried out with a washed bacterial cell suspension utilizing xylose as a sole substrate. Previous investigators have obtained evidence that one of the first reactions in the fermentation of pentoses was a carbon bond cleavage resulting in the production of a C₃ and a C₂ fragment. The importance of the C₂ fragment in enzymatic systems is well recognized and it thus seemed plausible that investigations on bacterial pentose fermentations would be of significant value to the field of intermediary metabolism. Preliminary investigations revealed that cells of Escherichia coli K-12 grown in the presence of pentose possessed the ability to ferment pentoses in the nonproliferating cell state. Additional experiments concerning the anaerobic decomposition of xylose re-emphasized the metabolic importance of the C₂ fragment. In fermentations conducted at low pH, lactic acid was produced in a ratio of approximately 1.3 moles per mole of xylose fermented. Since a maximum of only 1.0 moles of lactic acid could have been derived from the C₃ portion of the xylose molecule this was taken as a priori evidence that the C₂ portion of the C₅ molecule was also involved in the formation of lactic acid. Furthermore, at low pH, there was a net fixation of C0₂ which indicated that a direct participation of C0₂ was involved in the production of lactate. There were a number of pathways by which lactate could have been formed from C₂ and carbon tracer experiments were conducted in order to determine the main mechanism of C₂⟶C₃ in this system. These experiments demonstrated that C₂ tracers (C¹⁴H₃C00H and C¹⁴H₃CH₂0H) were converted to the CH₃-CH0H-portion of lactate while C₁ tracers (c¹³0₂ and HC¹⁴OOH) appeared in the lactate carboxyl. This latter piece of evidence was a further indication that lactate was formed via a C₂ + C₁ condensation. This condensation functioned at pH 7.4 as well as at pH 5.3. With C¹⁴H₃C00H as tracer succinate was labeled exclusively in the methylene carbons and it was concluded that the lactate was not in close equilibrium with succinate. The production of lactate via C₂ + C₁ condensation further emphasizes the general role of this reaction in intermediary metabolism. The fact that C₂ produced from pentoses apparently can be converted to C₃ also provides a mechanism for the conversion of pentoses into hexoses and vice versa. / Ph. D.

Data on characteristics of cakes is desirable to have for use by interested parties in making decisions about use of the product. Measurements on apparent viscosity, batter and cake characteristics: height, compressibility and moisture content were determined for cakes made with four fats and three egg products. Apparent viscosity of batter prepared did not predict the kind of cake that was produced. However, a viscous batter was obtained from cakes made with hydrogenated vegetable shortening and any of the egg products used. In addition, a thick batter was produced with Scramblers and any of the fats used. Considering the baked cake, height measurements were in agreement with those of compressibility. These characteristics (height and compressibility) were influenced by fresh whole eggs and hydrogenated vegetable shortening. However, fresh whole eggs did not have any effect on moisture content. In addition, it was concluded that using Lowe's (1955) mixing method, it was possible to use a vegetable oil with fresh whole eggs and get an acceptable cake. With egg substitutes, it was observed that a less tender cake with less height was obtained, but that the cakes were generally acceptable. Though not so much as a characteristic of cakes, but a measurement that was taken on the baked cakes, fatty acids were determined using gas liquid chromatography. / Master of Science

No description available.

Three experiments were conducted to determine how dietary lipid sources influence lipid and polyunsaturated fatty acid (PUFA) metabolism when fed to young, growing chickens. In the first experiment, commercial meat-type chickens were fed one of four dietary lipids: 1) linseed oil (LO); 2) menhaden oil (MO); 3) soybean oil (SBO); or 4) chicken fat (CF). Chickens fed the polyunsaturated lipids, LO, MO, and SBO all had similar very low density lipoprotein + low density lipoprotein (VLDL + LDL) triacylglycerol concentrations which were lower than those for chickens fed CF. Tissue lipids from chickens fed LO contained more 20:5n3 compared with those fed SBO or CF. The amounts of 20:5n3 in tissues from chickens fed LO approached those found in tissues from chickens fed MO. Tissue lipids from LO and MO treatments exhibited decreased 20:4n6 concentrations compared with SBO or CF treatments. The data indicate that dietary n-3 lipid sources influence the fatty acid compositions of tissues and can be effectively used to enrich edible chicken tissues. The second experiment examined the effects of varying combinations of CF and MO on plasma triacylglycerols in broiler chickens. As the amount of dietary n-3 fatty acids and the polyunsaturate:saturate ratio increased, the concentration of triacylglycerols in plasma and the plasma VLDL + LDL fraction decreased. On the other hand, plasma triacylglycerol levels increased as the dietary n-6 fatty acids increased. The dietary n-3 fatty acids in the MO treatment led to higher levels of PUFA in the tissues evaluated. In the third experiment, female chickens from two genetic lines, high body weight (HW) and low body weight (LW), were fed SBO (rich in n-6 polyunsaturates) or MO (rich in n-3 polyunsaturates). The amounts of triacylglycerols in the plasma VLDL + LDL fractions were elevated in the LW chickens compared with the HW groups. Amounts of 18:1 isomers and total monounsaturates were highest in the livers and hearts of HW chickens. Feeding MO enriched the plasma, liver and heart tissues with n-3 polyunsaturates in both genetic lines. Plasma triacylglycerol concentrations were decreased in chickens fed MO at 56, but not at 84 days of age. The data suggest differences in lipid metabolism between the HW and LW lines which were not greatly affected by dietary n-6 or n-3 polyunsaturated fatty acids. / Ph. D.