This thesis summarizes an investigation of antimicrobial resistance (AMR) and antimicrobial use (AMU) in cow-calf herds. The specific objectives of this project were to describe common reasons for treatment and the types of antimicrobials used in cow-calf herds, to describe the frequency of AMR in generic fecal Escherichia coli isolated from various age groups commonly found on cow-calf farms, to determine risk factors associated with the occurrence of AMR, and finally to investigate the underlying molecular mechanisms of AMR in cow-calf herds. At least 86% of the herds treated one or more calves or cows during the study period; however, the overall proportion of both calves and cows reported as treated was less than 14% for calves and 3% for cows. The majority of antimicrobials reported as used in cow-calf operations were for individual therapeutic use rather than prophylaxis, metaphylaxis, or growth promotion. Injectable formulations were the most commonly reported method of antimicrobial administration on cow-calf farms. Cow-calf herds in Wetern Canada are not a significant reservoir for resistance to antimicrobials classified as very important to human medicine such as ciprofloxacin and ceftiofur. The three most common resistances detected were to tetracycline, sulphamethoxazole, and streptomycin regardless of age group. Young calves sampled in the spring of the year were more likely to be shedding AMR E. coli than older calves sampled in the fall of the year or than cows sampled in the spring of the year. The cow-calf pair relationship was not an important factor in transfer of AMR from the individual cow to her calf, but the presence of AMR in the general cow herd was associated with AMR in the calf population. The potential importance of co-selection for AMR at the molecular level was demonstrated by both the risk factor analysis and the molecular work. Phenotypic resistance to streptomycin, tetracycline, and sulphamethoxazole were each associated with the presence of resistance genes from all six families of antimicrobials examined in this study. Several statistically significant associations were also detected between the resistance genes considered. No significant associations were detected between any of the AMR phenotypes or genotypes and the STEC virulence factors stx1, stx2 and eae.

This thesis summarizes an investigation of antimicrobial resistance (AMR) and antimicrobial use (AMU) in cow-calf herds. The specific objectives of this project were to describe common reasons for treatment and the types of antimicrobials used in cow-calf herds, to describe the frequency of AMR in generic fecal Escherichia coli isolated from various age groups commonly found on cow-calf farms, to determine risk factors associated with the occurrence of AMR, and finally to investigate the underlying molecular mechanisms of AMR in cow-calf herds. At least 86% of the herds treated one or more calves or cows during the study period; however, the overall proportion of both calves and cows reported as treated was less than 14% for calves and 3% for cows. The majority of antimicrobials reported as used in cow-calf operations were for individual therapeutic use rather than prophylaxis, metaphylaxis, or growth promotion. Injectable formulations were the most commonly reported method of antimicrobial administration on cow-calf farms. Cow-calf herds in Wetern Canada are not a significant reservoir for resistance to antimicrobials classified as very important to human medicine such as ciprofloxacin and ceftiofur. The three most common resistances detected were to tetracycline, sulphamethoxazole, and streptomycin regardless of age group. Young calves sampled in the spring of the year were more likely to be shedding AMR E. coli than older calves sampled in the fall of the year or than cows sampled in the spring of the year. The cow-calf pair relationship was not an important factor in transfer of AMR from the individual cow to her calf, but the presence of AMR in the general cow herd was associated with AMR in the calf population. The potential importance of co-selection for AMR at the molecular level was demonstrated by both the risk factor analysis and the molecular work. Phenotypic resistance to streptomycin, tetracycline, and sulphamethoxazole were each associated with the presence of resistance genes from all six families of antimicrobials examined in this study. Several statistically significant associations were also detected between the resistance genes considered. No significant associations were detected between any of the AMR phenotypes or genotypes and the STEC virulence factors stx1, stx2 and eae.

Cow-calf producers in western Canada are faced with many decisions throughout the production cycle. The choice of calving time impacts production rate, marketability of calves, income and expenses and net revenue. The purpose of this study was to determine whether June calving could increase net revenues and be a preferred choice across different risk aversion levels over March calving in western Canada. Data for this study were taken from a study carried out by Iwaasa et al. (2009), who collected information from three sites; Brandon, MB, Lanigan, SK and Swift Current SK. Stochastic budgets and a simulation model were used to study the economic impact of calving time. In Brandon and Lanigan, It was found that June calving increased net income and was the dominant alternative across all levels of risk aversion, and in Swift Current, June dominated at high-risk aversion levels.

No description available.

Cow-calf producers in western Canada are faced with many decisions throughout the production cycle. The choice of calving time impacts production rate, marketability of calves, income and expenses and net revenue. The purpose of this study was to determine whether June calving could increase net revenues and be a preferred choice across different risk aversion levels over March calving in western Canada. Data for this study were taken from a study carried out by Iwaasa et al. (2009), who collected information from three sites; Brandon, MB, Lanigan, SK and Swift Current SK. Stochastic budgets and a simulation model were used to study the economic impact of calving time. In Brandon and Lanigan, It was found that June calving increased net income and was the dominant alternative across all levels of risk aversion, and in Swift Current, June dominated at high-risk aversion levels.

Previous work has suggested that there exists a relationship between chondrocyte morphology and matrix metabolism. Changes to chondrocyte morphology have been reported in human cartilage however it is unclear if these are involved in the degenerative process associated with osteoarthritis (OA). In this work, the morphology of human and bovine chondrocytes has been characterised under a range of conditions. Bovine chondrocytes have been utilised in these experiments as bovine cartilage is non-degenerate and the chondrocytes have ‘normal’ morphology. However, if human cartilage have been used instead then there is possibility of having chondrocytes of mixed shapes i.e. both ‘normal’ and ‘abnormal’ cells. The thesis aimed at experimentally inducing morphological changes to chondrocytes to determine whether these changes resemble those observed in human cartilage. The ultimate aim is to model these changes to clarify the link between morphology and matrix metabolism by determining how morphological changes influence matrix metabolism. A classification system was developed for chondrocyte morphology allowing the quantification of chondrocyte shapes under different conditions permitting statistical comparisons. The different conditions utilised were (1) non-degenerate and mildly-degenerate human articular cartilage and (2) two in vitro models (a) weak 3D agarose gels to study the effect of gel strength and increasing concentrations of foetal calf serum (FCS) on morphology of bovine chondrocytes and (b) scalpel induced mechanically-injured bovine cartilage model to study in situ chondrocyte viability and morphology at the injured site in various culture conditions. Additionally, the effect of raised medium osmolarity on the response of chondrocytes to injury was studied to determine if the abnormal morphology could be reversed. Using fluorescence-mode confocal laser scanning microscopy (CLSM), chondrocyte viability, volume and morphology were determined and quantified by using VolocityTM 3D image analysis software. Histological evaluation of matrix by using Haematoxylin and eosin, Alcian blue and Masson’s trichrome staining of matrix produced by chondrocytes cultured in strong or weak agarose gels and in injured cartilage was determined. Additionally, immunohistochemical evaluation of matrix (collagen Types I & II) produced by chondrocytes was also performed. Results demonstrated that in non-degenerate human femoral head cartilage, ~83% chondrocytes were normal in morphology and 17±2% chondrocytes had cytoplasmic processes as compared to mildly-degenerate cartilage where 35±5% abnormal chondrocytes with cytoplasmic processes were present. In non-degenerate cartilage, 11±3% chondrocytes formed small sized clusters however clustering was quite evident in the superficial zone of mildly-degenerate human femoral head cartilage where 43±16% chondrocytes had formed large clusters. In mildly-degenerate cartilage the number of abnormal chondrocytes with processes, length of processes and number of processes per cell were greater in the superficial as compared to mid and deep zones. A model was developed to study the effect of external supporting agarose gel on chondrocyte morphology and also to determine the influence of FCS. Bovine chondrocytes cultured in weak gels after 7 days developed similar morphological changes as those observed in degenerate human cartilage. However, in the strong gels only few chondrocytes with morphological changes were present i.e. similar to non-degenerate cartilage. These morphological changes (development of clusters and processes) occurred more rapidly with increasing concentrations of FCS. Histology revealed less Alcian blue staining intensity around chondrocytes cultured in weak gels as compared to strong gels suggesting altered matrix produced by abnormal chondrocytes. FCS and gel strength were therefore proposed as related factors in regulating chondrocyte morphology. In the bovine injured cartilage explant model, after 14 days chondrocytes at the injury in the presence of FCS or synovial fluid (SF) produced morphological changes. These changes comprised cell enlargement, flattening, elongation and production of cytoplasmic processes. In the absence of FCS or SF, chondrocytes at the injury remained unaffected and were morphologically ‘normal’. Throughout the cartilage and even in the absence of subchondral bone, chondrocytes displayed morphological abnormalities in the presence of FCS or SF. These findings suggested that this is not the property of chondrocytes in the superficial layers alone rather it is due to the extent of penetration of the ‘factors’ into the matrix and there is no possibility of interference of injured site with osteocytes or bone factors. Histology revealed that these abnormal chondrocytes showed less staining with Alcian blue at the injury suggesting that these morphological changes might play a role in the changes to matrix metabolism. By raising the osmolarity of the culture medium these changes were inhibited and chondrocytes maintained their normal morphology. The results suggest that morphogenic/proliferative factors in FCS or SF and strength/damage to the matrix may be inter-related and act as potent controllers of chondrocyte morphology. Raised osmolarity was found to inhibit the morphological changes suggesting the possibly that hyperosmolarity can antagonise the effects of these factors. The key conclusions from the thesis were (a) in non-degenerate human femoral cartilage a large percentage of chondrocytes ~83% were normal in morphology and the rest were abnormal however in mildly-degenerate cartilage 35±5% abnormal chondrocytes with processes were present (b) the changes to chondrocyte morphology (development of clusters and processes) were exacerbated with cartilage degeneration (c) chondrocytes cultured in the weak gels produced morphological changes as compared to strong gels (d) chondrocytes at the injury displayed marked morphological changes in the presence of FCS or SF (e) by raising the medium osmolarity these morphological changes to chondrocytes at the injury were inhibited. These results show that chondrocyte morphology is complex and strongly dependent on the environmental settings. Experimental conditions were therefore identified which showed increased chondrocyte volume, abnormal morphology with cytoplasmic processes, enhanced proliferation/cluster formation and matrix changes. These changes to volume and morphology of chondrocytes in the models studied in this work had certain similarities to the changes observed in human cartilage suggesting that these shape changes may play a role in the changes to matrix metabolism occurring in OA. These findings may be of translational relevance in clinical and experimental research into cartilage injury and degeneration by providing new insights in understanding the role played by chondrocyte morphology in cartilage degeneration and injury.

Master of Agribusiness / Department of Agricultural Economics / Elizabeth Yeager / Crossbreeding has long been promoted as the preferred method of production for cow-calf producers. Unfortunately, crossbreeding can add complexity to maintain a consistent cowherd and can drive the need to purchase replacement females from outside the producer’s own herd. This has led some producers to pursue straightbreeding to provide their own supply of replacements and the opportunity to more narrowly select for individuals suited to a carcass quality grid marketing system. The subject of this thesis is a Red Angus based cowherd that breeds females to Red Angus sires in early parities. The same cowherd is bred to Simmental sires in later parities to produce a terminal F1 cross. It is the objective of this thesis to explore whether this operation’s straghtbred or crossbred calf crop provides an economic advantage to the other treatment. Mortality data were collected during pre-weaning for both steers and heifers. Mortality data were collected for steers during backgrounding and feedlot phases. Wean weights and feed conversion performance during the backgrounding phase was unavailable for use in this study. Feedlot and carcass data were captured for steers from both treatments. The straightbred treatment showed an advantage in carcass quality. The composite treatment showed a slight advantage in mortality cost during pre-weaning and feedlot phase, and a slight advantage in feed conversion and cost per pound of gain while in the feedlot. The composite treatment showed a significant disadvantage during the backgrounding phase. The primary advantage for the composite treatment was the difference in actual wean weights. This difference in wean weight carried over to a higher start weight during the feedlot phase. This was the driving factor in providing the composite group the economic advantage in this study and making it the more attractive production option.

Twenty-eight Holstein and crossbred calves of both genders were used to evaluate the effect of milk replacer antibiotics on abundance of selected antibiotic resistance genes (ARG) in the feces. Calves were blocked by breed, gender, and birth order, and assigned to one of three treatments at birth. Treatments were control (containing no antibiotics in the milk replacer), subtherapeutic (neomycin sulfate and oxytetracycline hydrochloride each fed at 10 mg/calf/d), and therapeutic (no antibiotics in the milk replacer until d 36, then neomycin sulfate and oxytetracycline hydrochloride each fed at 1000 mg/calf/d for 14 d). Calves were fed milk replacer twice daily at 0600 h and 1800 h. Fecal and respiratory scores and rectal temperatures were recorded daily. Calves were weighed at birth and weaning to calculate average daily gain. Beginning at six weeks of age fecal grab samples were collected from heifers at 0600 h, 1400 h, 2000 h, and 2400 h for 7 d, while bull calves were placed in metabolism crates for collection of all feces and urine. DNA was extracted from feces, and ARG corresponding to the tetracyclines (tetC, tetG, tetO, tetW, and tetX), macrolides (ermB, ermF), and sulfonamides (sul1, sul2) classes of antibiotics along with the class I integron gene, intI1, were measured by quantitative polymerase chain reaction (qPCR). No tetC or intI was detected. There was no significant effect of antibiotic treatment on the absolute abundance (gene copies/ g wet manure) of any of the ARG except ermF, which was lower in the antibiotic-treated calf manure probably because host bacterial cells carrying ermF were not resistant to tetracycline or neomycin. All ARG except tetC and intI were detectable in feces from 6 weeks onwards, and tetW and tetG significantly increased with time (P < 0.10), even in control calves. Overall, the majority of ARG analyzed for were present in the feces of the calves regardless of exposure to dietary antibiotic. Feed antibiotics had little effect on the ARG monitored; other methods for reducing the ARG pool should also be investigated. / Master of Science

No description available.

In recent years, there has been an increasing demand for newer, more accurate, technologies that can detect and identify biomolecules or biological entities related to health, agriculture or the environment. With the discovery of new properties of nucleic acids beyond the storage and transfer of genetic information, a new class of nucleic acid-based biosensors is emerging, using DNA and RNA as target recognition elements with the advantage of being simpler and more cost-effective compared to antibodies-based biosensor. Two sequences, TrG14MC and TrG10SC, with evidence to suggest that they are capable of inhibit the metalloenzyme CIP, were isolated from a selection conducted by Dr. Razvan Nutiu. Here we study the inhibitory properties of these two aptamer candidates and measure the IC50 value, determined as 94 nM for TrG14MC and 83 nM for TrG10SC. Different bivalent constructs, designed to increase the inhibitory effect of the isolated sequences, are studied showing a pronounce influence of the linker length improving the inhibitory effect over CIP. Modulating the interaction of the isolated sequences and the CIP is of key importance in order to develop a successful biosensor. Therefore, we try to recover CIP from the inhibition effect by using antisense sequences complementary to different segments of the construct. The maximum recovery, 75%, was achieved by an antisense sequence fully complemented to the inhibitory bivalent construct. We also study here the use of a linker in the bivalent construct that forms a secondary hairpin structure, and the effect of linearizing that structure with an antisense sequence complementary to the linker. This resulted in as 12% of the inhibitory effect. The purpose of this investigation was to establish the first steps toward the development of a new class of biosensors capable of disinhibiting CIP upon the recognition of a specific target, taking advantage of the suggested CIP-inhibitory properties of the isolated sequences TrG14MC and TrG10SC. / Thesis / Master of Applied Science (MASc)