A diarréia em bezerros é comprovadamente uma das principais causas de perdas econômicas em rebanhos de corte, sendo os prejuízos diretamente derivados da redução do ganho de peso e custos com tratamento. Considerando-se que, para o delineamento de medidas profiláticas adequadas ao controle de uma doença é necessário o conhecimento de suas causas, o presente trabalho teve por objetivo estudar de modo longitudinal a freqüência de ocorrência de coronavírus bovino (BCoV), rotavírus do grupo A (RV-A), protozoários, helmintos e enterobactérias em uma propriedade com casos esporádicos e em outra com casos recorrentes de diarréia em bezerros. Investigou-se, ainda, a presença de genes codificadores de para as toxinas shiga-like 1 e 2 , para as adesinas K99 e F41 e para a intimina (eae) nas E. coli isoladas. Para a detecção de BCoV, utilizou-se uma nested-RT-PCR direcionada ao gene codificador da RNA polimerase RNA dependente, e para a detecção de RV-A utilizou-se ELISA direto duplo sanduíche. O isolamento e caracterização bioquímica das colônias de bactérias foram conduzidos de acordo com técnicas de bacteriologia clássica. A caracterização genotípica das colônias de E. coli isoladas foi realizada através de uma Multiplex-PCR, utilizando primers para os genes codificadores dos seguintes fatores de virulência: Stx1, Stx2, Sta, K99, F41 e eae. A detecção de parasitas foi realizada por centrífugo sedimentação em água-eter e centrífugo-flutuação em solução supersaturada de sacarose, considerando-se como resultado final do exame coproparasitológico todos os parasitas encontrados em ambas as técnicas em sua maior contagem. A freqüência de ocorrência de coronavírus bovino e rotavírus do grupo A foi baixa, restrita a animais com até quatro meses de idade, enquanto que protozoários, helmintos e enterobactérias apresentaram tendência crescente em freqüência relacionada à progressão da idade dos animais. Foram identificados os patotipos STEC, AEEC e um padrão atípico com os genes de K99 e eae. Além disso, encontrou-se associação entre baixo padrão sanitário e maior freqüência de ocorrência de Eimeria spp, Strongyloidea, Strongyloides spp, Trichuris spp e Escherichia coli portadora de fatores de virulência Stx1, Stx2, K99 e eae. O presente trabalho colabora para a caracterização da microbiota entérica de bezerros, mas mantém abertas as questões relativas às diferenças específicas entre as biotas entéricas de bezerros sadios e com diarréia, enfatizando a importância de se realizarem mais estudos que investiguem simultaneamente diversos enteropatógenos potenciais nestes animais / Diarrhea in calves is proved to be one of the main causes of economic loss in beef herds, which is direct originated by reduction of weight gain and increment of treatment costs. It is known that the determination of appropriate preventive measures to control a disease depends on the knowledge of its causes. In this manner, the present work aimed to study longitudinally the frequency of occurrence of bovine coronavirus (BCoV), group A rotavirus (RV-A), protozoa, helminths and enterobacteria in a beef farm presenting sporadic cases and other with recurrent cases of diarrhea. Moreover, the presence of genes that express the following virulence factors were investigated in the isolated E. coli: shiga-like toxins 1 and 2, adhesins K99 and F41 and intimin (eae). A nested-RT-PCR targeted to the RNA-dependent RNA polimerase gene was conducted to detect BCoV, and a double-sandwich direct ELISA was used to detect RV-A. Classical bacteriology techniques were used to isolate and indentify bacterial colonies. A Multiplex-PCR, with primers designed to previously described E. coli genes, was used to genotype these colonies. Centrifuge sedimentation in water-ether and centrifuge flotation in sucrose supersaturated solution were used to detect the presence of parasites. The final result was achieved by the highest count of all the parasites found. The observed frequency of occurrence of both BCoV and RV-A was low and restricted to animals up to 4 months of age whereas protozoa, helminths and enterobacteria showed an increasing tendency on its frequency related to progression of animals aging. STEC, AEEC and an atypical pathotype of E. coli, with K99 and eae genes were found. Moreover, an association between low sanitary pattern and a higher frequency of Eimeria spp, Strongyloidea, Strongyloides spp, Trichuris spp and Escherichia coli bearing Stx1, Stx2, K99 and eae genes was observed. The present study contributes to the characterization of calf enteric microbiota. However, the points related to the specific differences between healthy and diarrheic calves enteric microbiota remain unclear, emphasizing the importance of future studies to investigate different potential enteropathogens in beef calves simultaneously

Master of Science / Department of Animal Sciences and Industry / Karol Fike / The United States beef cattle industry is continuously evolving and changing to meet buyer demands while considering environment factors for production. Cow-calf producers make decisions within their herds that impact their profitability. Previous research shows producers can add value to beef calves through management and marketing decisions in areas such as genetics, herd health, and nutrition. It is well documented that there are numerous factors that influence the sale price of beef calves, no matter the venue through which they are sold. Historically, steer calves sold for a greater price compared to heifer calves. Apparent breed composition also influences value of lots of beef calves. Black-hided calves recently sold for a greater sale price than calves of other hide colors due to perceived differences in potential performance. Calves with Bos indicus influence usually sell for a lower price than other breed types. Marketing of beef calves through video auction allows sellers to market lots of calves to a buyer basis nationwide. A national market provides a basis for buyer preferences and potential national trends for changes in characteristics valued by buyers. Evaluation of national breed composition trends can indicate potential changes in the industry. The opportunity to evaluate if and how breed description as described by producers influenced calf sale price from 1995 through 2016 was available through a livestock video auction service. Chapter 1 is a review of the literature and an overview of the beef industry and factors affecting sale price of lots of beef calves. Chapter 2 is an analysis of breed composition influencing sale price for lots of steer calves and lots of heifer calves. Chapter 3 investigates national and regional breed description and sire breed trends over a 23-year period.

A diarréia em bezerros é comprovadamente uma das principais causas de perdas econômicas em rebanhos de corte, sendo os prejuízos diretamente derivados da redução do ganho de peso e custos com tratamento. Considerando-se que, para o delineamento de medidas profiláticas adequadas ao controle de uma doença é necessário o conhecimento de suas causas, o presente trabalho teve por objetivo estudar de modo longitudinal a freqüência de ocorrência de coronavírus bovino (BCoV), rotavírus do grupo A (RV-A), protozoários, helmintos e enterobactérias em uma propriedade com casos esporádicos e em outra com casos recorrentes de diarréia em bezerros. Investigou-se, ainda, a presença de genes codificadores de para as toxinas shiga-like 1 e 2 , para as adesinas K99 e F41 e para a intimina (eae) nas E. coli isoladas. Para a detecção de BCoV, utilizou-se uma nested-RT-PCR direcionada ao gene codificador da RNA polimerase RNA dependente, e para a detecção de RV-A utilizou-se ELISA direto duplo sanduíche. O isolamento e caracterização bioquímica das colônias de bactérias foram conduzidos de acordo com técnicas de bacteriologia clássica. A caracterização genotípica das colônias de E. coli isoladas foi realizada através de uma Multiplex-PCR, utilizando primers para os genes codificadores dos seguintes fatores de virulência: Stx1, Stx2, Sta, K99, F41 e eae. A detecção de parasitas foi realizada por centrífugo sedimentação em água-eter e centrífugo-flutuação em solução supersaturada de sacarose, considerando-se como resultado final do exame coproparasitológico todos os parasitas encontrados em ambas as técnicas em sua maior contagem. A freqüência de ocorrência de coronavírus bovino e rotavírus do grupo A foi baixa, restrita a animais com até quatro meses de idade, enquanto que protozoários, helmintos e enterobactérias apresentaram tendência crescente em freqüência relacionada à progressão da idade dos animais. Foram identificados os patotipos STEC, AEEC e um padrão atípico com os genes de K99 e eae. Além disso, encontrou-se associação entre baixo padrão sanitário e maior freqüência de ocorrência de Eimeria spp, Strongyloidea, Strongyloides spp, Trichuris spp e Escherichia coli portadora de fatores de virulência Stx1, Stx2, K99 e eae. O presente trabalho colabora para a caracterização da microbiota entérica de bezerros, mas mantém abertas as questões relativas às diferenças específicas entre as biotas entéricas de bezerros sadios e com diarréia, enfatizando a importância de se realizarem mais estudos que investiguem simultaneamente diversos enteropatógenos potenciais nestes animais / Diarrhea in calves is proved to be one of the main causes of economic loss in beef herds, which is direct originated by reduction of weight gain and increment of treatment costs. It is known that the determination of appropriate preventive measures to control a disease depends on the knowledge of its causes. In this manner, the present work aimed to study longitudinally the frequency of occurrence of bovine coronavirus (BCoV), group A rotavirus (RV-A), protozoa, helminths and enterobacteria in a beef farm presenting sporadic cases and other with recurrent cases of diarrhea. Moreover, the presence of genes that express the following virulence factors were investigated in the isolated E. coli: shiga-like toxins 1 and 2, adhesins K99 and F41 and intimin (eae). A nested-RT-PCR targeted to the RNA-dependent RNA polimerase gene was conducted to detect BCoV, and a double-sandwich direct ELISA was used to detect RV-A. Classical bacteriology techniques were used to isolate and indentify bacterial colonies. A Multiplex-PCR, with primers designed to previously described E. coli genes, was used to genotype these colonies. Centrifuge sedimentation in water-ether and centrifuge flotation in sucrose supersaturated solution were used to detect the presence of parasites. The final result was achieved by the highest count of all the parasites found. The observed frequency of occurrence of both BCoV and RV-A was low and restricted to animals up to 4 months of age whereas protozoa, helminths and enterobacteria showed an increasing tendency on its frequency related to progression of animals aging. STEC, AEEC and an atypical pathotype of E. coli, with K99 and eae genes were found. Moreover, an association between low sanitary pattern and a higher frequency of Eimeria spp, Strongyloidea, Strongyloides spp, Trichuris spp and Escherichia coli bearing Stx1, Stx2, K99 and eae genes was observed. The present study contributes to the characterization of calf enteric microbiota. However, the points related to the specific differences between healthy and diarrheic calves enteric microbiota remain unclear, emphasizing the importance of future studies to investigate different potential enteropathogens in beef calves simultaneously

Bovine respiratory disease (BRD) is a significant health problem for cattle producers in terms of economic cost and animal welfare. In the United States (US), it is one of the leading causes of sickness and death in beef calves prior to weaning. Although much research has been conducted to develop vaccines for prevention and antibiotics for treatment, the morbidity and mortality of BRD in beef calves prior to weaning has not improved over the years. The identification of risk factors associated with BRD is an area of focus which might ultimately allow producers to minimize morbidity and mortality from BRD. Little research has been performed to understand factors contributing to the risk of BRD in beef calves prior to weaning. BRD affects the beef cattle industry through losses due to mortality, prevention cost, treatment cost, or morbidity effect on productivity. Currently, the economic losses due to BRD for beef calves prior to weaning is not available. Price paid for feeder cattle is a major factor influencing the income of producers. The effect of BRD is a complicated problem since the parameters associated with the cost of BRD in beef cow-calf production are variable and interrelated. To better understand the economic effect of BRD in beef calves prior to weaning, concepts of uncertainty, variability, stochasticity, nonlinearity, and feedback might be involved during the process of assessing risk. The objectives of this dissertation are the following: 1) to test if calf sex, birth weight, and age of dam are associated with BRD of beef calves prior to weaning in different age periods; 2) to identify factors affecting the national market price of beef feeder cattle in the US and how the prices change over time; 3) to investigate the prevention and treatment cost of BRD in beef calves prior to weaning; 4) to estimate the economic cost of BRD in US beef calves prior to weaning; and 5) to understand the effect of BRD occurrence or absence on the national net income of the US beef cow-calf industry.

This study investigated proteomic changes in bronchoalveolar lavage fluid (BALF) of beef calves to identify alterations related to development of naturally occurring bovine respiratory disease. BALF was collected from 162 healthy beef calves soon after weaning and transportation. Two-dimensional gel electrophoresis and mass spectrometric analysis revealed calves that later developed pneumonia had significantly lower levels of anti-inflammatory proteins including annexin A1, RAGE-binding protein, apolipoprotein-A, heat shock protein beta-1 and thioredoxin, but higher levels of antioxidant and pro-inflammatory proteins such as immunoglobulin light chain variable region, cyclophilin A, serum albumin precursor and glutathione S-transferase P. Difference in gel electrophoresis-based analysis further showed lower levels of annexin A1, annexin A2, peroxiredoxin I, calycyphosin, superoxide dismutase, macrophage capping protein and dihydrodiol dehydrogenase 3 in the calves that later developed pneumonia. Differences in annexin levels were partially confirmed by Western blot analysis. In healthy calves, immunohistochemistry revealed cytoplasmic expression of annexin A1 in surface epithelium of large airways, tracheobronchial submucosal glands, and goblet cells, and to a lesser degree in small airways but not in alveolar epithelium. Flow cytometry and immunocytochemistry labeled annexin A1 in blood and bronchoalveolar lavage neutrophils, monocytes, macrophages and lymphocytes. Annexin A2 expression was detected in surface epithelium of small airways, some mucosal lymphocytes, and endothelium, with weak expression in large airways, tracheobronchial submucosal glands and alveolar epithelium. For both proteins, the level of expression was similar in tissues collected 5 days after intrabronchial challenge with M. haemolytica compared to that from sham-inoculated calves. A sandwich ELISA for annexin A1 was developed. For use with BALF, the working range was 0.3-317 ng/ml and the sensitivity was 0.8 ng/ml. The coefficient of variation of intra-assay and the between assays was less than 20%. Together, these findings reveal annexins A1 and A2 as promising biomarkers of susceptibility to BRD in healthy at-risk calves. Further, the anti-inflammatory and pro-resolving functions of these proteins suggest roles in the pathogenesis of bacterial pneumonia of feedlot cattle. / Natural Sciences and Engineering Council (NSERC), Ontario Cattlemen’s Association, Ontario Ministry of Agriculture and Food and Ontario Veterinary College Fellowship Program

This study was conducted to compare animal performance, presence of skin reactions and immune response following vaccination of beef calves via needle-free (NF) and needle-syringe (NS) vaccination techniques. Spring-born (Study A) and fall-born (Study B) calves were vaccinated against bovine viral diarrhea virus (BVDV) and Clostridium chauvoei (C. chauvoei) via NF and NS vaccination techniques. The parameters measured in this study included body weight (BW), skin reactions and serum antibodies. Animal performance and antibody levels against BVDV and C. chauvoei did not differ between vaccination techniques. However, NF vaccinated calves had a greater frequency of skin reactions when compared to NS vaccinated calves, except for day 42 of Study B. It can be concluded that a needle-free injection device (NFID) can be used effectively to stimulate an immune response without impacting animal performance, but may cause a greater frequency of skin reactions.

This study was conducted to compare animal performance, presence of skin reactions and immune response following vaccination of beef calves via needle-free (NF) and needle-syringe (NS) vaccination techniques. Spring-born (Study A) and fall-born (Study B) calves were vaccinated against bovine viral diarrhea virus (BVDV) and Clostridium chauvoei (C. chauvoei) via NF and NS vaccination techniques. The parameters measured in this study included body weight (BW), skin reactions and serum antibodies. Animal performance and antibody levels against BVDV and C. chauvoei did not differ between vaccination techniques. However, NF vaccinated calves had a greater frequency of skin reactions when compared to NS vaccinated calves, except for day 42 of Study B. It can be concluded that a needle-free injection device (NFID) can be used effectively to stimulate an immune response without impacting animal performance, but may cause a greater frequency of skin reactions.

Résumé L’objectif de cette étude était de déterminer les effets de la source de sélénium sur les concentrations de Se et de GSH-Px des vaches de boucherie (n =33) et leurs veaux et sur des paramètres immunitaires des veaux. Deux groupes de vaches ont reçu 3 mg/j/animal de Se organique ou inorganique dans le minéral. Le troisième groupe n'a pas été supplémenté en Se et leurs veaux ont été divisés en deux sous-groupes, l’un des deux a reçu une injection de sélénite de sodium (0,087 mg/Kg) à la naissance. Le Se et la GSH-Px ont été respectivement mesurés par HPLC-UV et par cinétique enzymatique. La phagocytose, la flambée respiratoire et le ratio CD4:CD8ont été évalués par des kits commerciaux et les IgG totales ont été mesurés par immunodiffusion radiale. La supplémentation de Se a augmenté significativement le Se sérique et colostral (P<0,02) et la GSH-Px(P≤0,04) pour les vaches et leurs veaux avec un effet significativement plus élevé pour le Se organique. Le Se du lait a augmenté de façon significative uniquement avec la source organique du Se (P≤0,0007). L’injection du Se chez les veaux a permis une augmentation significative mais temporaire (P<0,0001) du Se sérique. La supplémentation en Se n’a pas influencé les paramètres immunitaires mesurés (P>0,01, non significatif après correction de Bonferroni). Nous concluons que la supplémentation en Se améliore le niveau du Se colostral, lacté et sérique ainsi que la GSH-Px pour les vaches et leurs veaux sans effet sur les paramètres immunitaires mesurés des veaux. Mots clés: Sélénium, veaux de boucherie, phagocytose, flambée respiratoire, anticorps, ratio CD4:CD8, GSH-Px. / Abstract The aims of this study were to determine the effects of selenium (Se) supplementation sources (organic and inorganic) on Se and GSH-Px concentrations of beef cows (n=33) and their calves and on immune parameters of the calves. Two groups of cows were given daily 3 mg of either organic or inorganic Se in mineral supplement starting from 12 weeks before calving until weaning. The third group had no Se added into the diet and their calves were divided into two subgroups either injected or not with 0.087 mg/kg of sodium selenite after birth. Serum Se and whole blood GSH-Px were respectively measured by HPLC-UV and by kinetic-enzymatic technique. Calves immune parameters were evaluated using commercial kits for phagocytosis, respiratory burst and CD4:CD8 ratio and radial immunodiffusion for total IgG concentrations. In cows and calves, Se supplementation increased significantly serum and colostrum Se concentrations (P<.02) with significant higher effect for organic source. However, milk Se concentrations increased significantly only with the organic source (P≤.0007). Se supplementation increased GSH-Px concentrations in cows (P≤.04) and their calves (P≤.0004); organic source induced a higher effect than inorganic one in calves (P≤.0004). Se injection in calves allowed a temporary increase (P<.0001) of serum Se concentrations. No significant differences were noticed throughout the experiment for all of the immune parameters measured (P>.01, not significant after Bonferroni adjustment). Our results showed that Se supplementation improved colostrum, milk and serum Se and GSH-Px concentrations in cows and their calves without effect on the measured immune parameters in calves. Key words: selenium, beef calves, phagocytosis, respiratory burst, antibodies, CD4:CD8 ratio, GSH-Px.

Résumé L’objectif de cette étude était de déterminer les effets de la source de sélénium sur les concentrations de Se et de GSH-Px des vaches de boucherie (n =33) et leurs veaux et sur des paramètres immunitaires des veaux. Deux groupes de vaches ont reçu 3 mg/j/animal de Se organique ou inorganique dans le minéral. Le troisième groupe n'a pas été supplémenté en Se et leurs veaux ont été divisés en deux sous-groupes, l’un des deux a reçu une injection de sélénite de sodium (0,087 mg/Kg) à la naissance. Le Se et la GSH-Px ont été respectivement mesurés par HPLC-UV et par cinétique enzymatique. La phagocytose, la flambée respiratoire et le ratio CD4:CD8ont été évalués par des kits commerciaux et les IgG totales ont été mesurés par immunodiffusion radiale. La supplémentation de Se a augmenté significativement le Se sérique et colostral (P<0,02) et la GSH-Px(P≤0,04) pour les vaches et leurs veaux avec un effet significativement plus élevé pour le Se organique. Le Se du lait a augmenté de façon significative uniquement avec la source organique du Se (P≤0,0007). L’injection du Se chez les veaux a permis une augmentation significative mais temporaire (P<0,0001) du Se sérique. La supplémentation en Se n’a pas influencé les paramètres immunitaires mesurés (P>0,01, non significatif après correction de Bonferroni). Nous concluons que la supplémentation en Se améliore le niveau du Se colostral, lacté et sérique ainsi que la GSH-Px pour les vaches et leurs veaux sans effet sur les paramètres immunitaires mesurés des veaux. Mots clés: Sélénium, veaux de boucherie, phagocytose, flambée respiratoire, anticorps, ratio CD4:CD8, GSH-Px. / Abstract The aims of this study were to determine the effects of selenium (Se) supplementation sources (organic and inorganic) on Se and GSH-Px concentrations of beef cows (n=33) and their calves and on immune parameters of the calves. Two groups of cows were given daily 3 mg of either organic or inorganic Se in mineral supplement starting from 12 weeks before calving until weaning. The third group had no Se added into the diet and their calves were divided into two subgroups either injected or not with 0.087 mg/kg of sodium selenite after birth. Serum Se and whole blood GSH-Px were respectively measured by HPLC-UV and by kinetic-enzymatic technique. Calves immune parameters were evaluated using commercial kits for phagocytosis, respiratory burst and CD4:CD8 ratio and radial immunodiffusion for total IgG concentrations. In cows and calves, Se supplementation increased significantly serum and colostrum Se concentrations (P<.02) with significant higher effect for organic source. However, milk Se concentrations increased significantly only with the organic source (P≤.0007). Se supplementation increased GSH-Px concentrations in cows (P≤.04) and their calves (P≤.0004); organic source induced a higher effect than inorganic one in calves (P≤.0004). Se injection in calves allowed a temporary increase (P<.0001) of serum Se concentrations. No significant differences were noticed throughout the experiment for all of the immune parameters measured (P>.01, not significant after Bonferroni adjustment). Our results showed that Se supplementation improved colostrum, milk and serum Se and GSH-Px concentrations in cows and their calves without effect on the measured immune parameters in calves. Key words: selenium, beef calves, phagocytosis, respiratory burst, antibodies, CD4:CD8 ratio, GSH-Px.