Carryover Effects of Crude Glycerin Fed During the Growing Phase on Finishing Cattle Performance and Carcass Characteristics

Crude glycerin is a byproduct of biodiesel production, and its use as a feedstuff for cattle has expanded in the last decade due to increased availability and favorable pricing compared with other energy concentrates such as cereal grains. Incorporation of glycerin into cereal-based finishing diets, at levels up to 8%, has been shown to improve cattle performance; however, it decreases activity of cellulolytic microorganisms in the rumen, ultimately decreasing fiber digestion. Most of the studies conducted to date have evaluated glycerin in finishing diets that contain relatively small amounts of fiber, but little is known of its value as an energy source for growing cattle that typically are fed diets containing greater proportions of fiber. Moreover, possible carryover effects from feeding glycerin in the growing phase and effects on finishing performance and carcass characteristics are unknown. In this study, we wanted to evaluate glycerin as a component of diets fed throughout a 90-day backgrounding phase to determine its impact on performance and carcass characteristics of heifers during the subsequent finishing phase when they were no longer fed glycerin

Menthol Supplementation Has Minimal Effects on Blood Components from Holstein Steers

Menthol is a naturally occurring compound classified as an essential oil that gives plants of the Mentha species their characteristic minty aroma and flavor. Menthol is used as a cooling compound in products ranging from common cold medications to pesticides and has been found to have a wide range of biological activities in different systems within the body. More recently, menthol and other essential oils have been identified as potential alternatives to feed antibiotics and growth promotants. Menthol has been observed to directly affect κ-opioid receptors. Kappa opioid receptors are located in the central nervous system, with a high density found in the hypothalamus. Menthol has been hypothesized to be capable of binding to κ-opioid receptors in the hypothalamus, stimulating neuropeptides involved in the production and release of growth hormone and leading to increased insulin-like growth factor-1 concentration, thus increasing growth. The purpose of this experiment was to evaluate changes in blood metabolites when menthol was incorporated into the diets of steers

Factors influencing Escherichia coli O157 colonization of the gastrointestinal tract of feedlot cattle

Doctor of PhilosophyDepartment of Animal Sciences and IndustryJ. S. DrouillardThe first chapter of this dissertation reviews factors affecting E. coli O157:H7 prevalence in the gastrointestinal tracts of cattle. Chapter 2 assessed E. coli O157:H7 ability to use bovine intestinal mucus and its constituents as substrates for growth in vitro in the presence and absence of fecal inoculum and exogenous enzymes. Whole mucus supported the greatest pathogen growth (P 0.05), highlighting potential for glycerin use as a means for controlling fecal prevalence of E. coli O157 in cattle fed conventional grain-based diets. Chapter 4 evaluated transportation and lairage effects on fecal shedding of E. coli in feedlot cattle by mimicking transport to the abattoir. Shedding patterns were influenced by transportation, with significantly lower E. coli O157 prevalence in transported animals 4 hours after transit (P < 0.05). Additional post-transit samplings are, however, needed to confirm effects of transport stress on pathogen prevalence and shedding patterns. The experiment summarized in chapter 5 evaluated the potential for utilizing fecal long-chain fatty acid (LCFA) profiles as an indicator of E. coli O157 status. Out of 39 LCFA evaluated, only eicosapentaenoic acid (EPA) concentration was associated with presence of the pathogen (P < 0.02). The final chapter assessed the impact of dietary menthol, up to 0.3% of diet DM, on antimicrobial resistance in commensal E. coli. Menthol addition affected prevalence of tetracycline resistant E. coli, but contrary to our hypothesis, increased their occurrence after 30 days of treatment (P < 0.006). No hypothesis on mechanism responsible for this increase could be made from the present study

Capacity of the bovine intestinal mucus and its components to support Escherichia coli O157:H7 growth

Escherichia coli O157:H7 contamination of human food products is a major concern for the beef industry. The pathogens responsible for outbreaks often originate from cattle, and E. coli O157:H7 can thrive in healthy cattle. To control contamination in the food chain, it is essential to understand how this pathogen is able to grow and compete with other bacteria in the gastrointestinal tracts of cattle. Previous studies have shown that bovine intestinal mucus supports bacterial colonization and can selectively influence makeup of the bacterial population. Intestinal mucus is made of mucins, which are gel-forming glycoproteins. Mucin molecules contain sialic acid that must be removed by neuraminidase enzyme to allow for complete degradation of mucin. E. coli O157:H7 lacks neuraminidase and should have little ability to degrade the complex mucin molecules. Our objective was to evaluate bovine intestinal mucus and its components in terms of their capacity to support E. coli O157:H7 growth in the presence or absence of feces and to understand the roles various enzymes play in this process

Increased concentrations of bovine intestinal mucus encourage growth of Escherichia coli O157:H7

Cattle have been implicated as carriers of the human pathogen Escherichia coli O157:H7. Contamination of the beef supply by E. coli O157 can occur during harvest and processing, causing costly recalls or human illness. Many interventions have been applied in attempts to prevent contamination of carcasses in processing plants, such as development of HACCP procedures, carcass washes, and steam pasteurization, but contaminations still occur. Mechanisms that allow E. coli O157:H7 to thrive in cattle at sporadic times and in such large numbers are poorly understood. Understanding factors that stimulate E. coli O157 growth in cattle will aid in identifying effective interventions that can be applied in feedlots and processing plants to reduce the numbers of this pathogen. E. coli O157 resides in the intestinal tracts of cattle. Mucin is a major component of intestinal mucus and is composed of proteins, lipids, and carbohydrates, which many bacteria can use as a source of food. The amount of mucin available in the intestinal tract depends on the stimulation of intestinal mucus-producing cells (goblet cells), which may be influenced by the animal’s diet, stress, and a variety of other factors. Our objective in this experiment was to determine if mucin produced in the small or large intestine could affect growth of E. coli O157:H7

Effect of transportation on E. coli O157:H7 prevalence and coliform concentrations in feces of feedlot cattle

Foodborne illness from Escherichia coli O157:H7 is a major concern for the food industry. Contamination of food products can occur at slaughter by contact with hide or feces. Limiting E. coli O157:H7 shedding is important to prevent outbreaks. Previous studies have demonstrated a relationship between stress and levels of pathogens shed in feces. During transport to the slaughterhouse, animals are subjected to large amounts of stress. This stress could increase shedding of E. coli O157:H7 prior to slaughter, and in so doing increase the risk of contamination of beef products by contact with hides or feces. Our objective in this study was to evaluate the effects of transportation on fecal shedding of E. coli 4 and 24 hours after transport compared with non-transported animals

Feeding crude glycerin decreases fecal shedding of E. coli O157:H7 in growing cattle

Crude glycerin is a byproduct of ethanol production and is used as a carbohydrate source for cattle feed. Glycerin levels in previous studies have ranged from 0 to 20% of diet dry matter, and concentrations of 8% or less generally improve feedlot performance. At even low levels of glycerin, however, the activity of cellulolytic bacteria is depressed, ultimately leading to poorer fiber digestion. This observation suggests that glycerin may affect a specific population of bacteria in the gut. Crude glycerin can account for 8 to 10% of the weight of dried distillers grains with solubles, because it is one of the primary end-products when yeast ferments sugars to produce ethanol. Addition of 25% dried distillers grains with solubles to a feedlot diet increased the prevalence of Escherichia coli O157:H7 in feces of cattle. These observations led us to question whether glycerin might be the component of distillers grains responsible for the increases in prevalence of E. coli O157:H7 that often are observed in cattle fed distillers grains. To address this question, we added glycerin to diets of growing cattle and subsequently evaluated fecal shedding of E. coli O157:H7