Background: Northern elephant seals transition from terrestrial nursing pups to pelagic foraging juveniles in a short period of just 8-12 weeks. During the post-weaning period, pups rely solely on the energy reserves gained during nursing for their caloric demands and water supply. The prolonged absence of food after weaning is the first of many fasts for which the seals have evolved adaptations such as decreased urine production and increased blubber reserves. The stressors experienced from learning to dive for the first time are also stressors that they will experience frequently as an adult and for which they have evolved adaptations. The purpose of this study was to understand the tissue-specific molecular fasting- and diving- induced adaptive responses of pups during this critical transition. Methods: To investigate these adaptive responses to fasting and diving, we collected skeletal muscle and (inner and outer) adipose tissue from early-fasting (< 1 week post-weaning) and late-fasting (8 weeks post-weaning) pups. We analyzed the samples with mass-spectrometry-based proteomics using two-dimensional gel electrophoresis. Proteomics is an invaluable tool for analyzing marine mammal physiology, as it provides a large, unbiased data set of proteins that offer a comprehensive set of mechanisms involved with the cellular processes being studied. Proteomics has only been used as analytical tool for marine mammal biology in two other studies, and it can be used as a tool leading to the discovery of novel, unanticipated results. Results and Discussion: Because muscles are utilized during locomotion, we expected the proteome of skeletal muscle to highlight important physiological changes as the pups learn to dive. Inner adipose is more metabolically active than outer adipose, so we anticipated it would show important changes in metabolism throughout their fast. Outer adipose was useful to detect changes in the proteome due to thermoregulation, as it experiences the most drastic change in temperature and pressure while the pups learn to dive. In all tissues, we found significant shifts in energy metabolism proteins that show a decrease in lipid metabolism and urine production, and an increase in alternative metabolic pathways, such as the pentose phosphate pathway, which produces precursors for nucleic acid synthesis. We also found increases in cytoskeletal proteins, skeletal muscle proteins, and oxygen-binding proteins that facilitate the development of diving ability in late-fasting pups. Lastly, changes in the abundance of oxidative stress related proteins showed increased use of antioxidant proteins to control the production of reactive oxygen species in late-fasting pups. This study provides insight into cellular and physiological responses in marine mammals during ontogeny and their adaptive capacity during a key transition from a terrestrial to aquatic lifestyle.

O manejo de classificação por peso ao alojamento na fase de creche é amplamente praticado e supostamente melhora o desempenho zootécnico e gera, ao fim da fase, um grupo de leitões com peso mais uniforme O objetivo deste estudo foi avaliar se classificar os leitões desmamados por peso ao alojamento da creche, interfere no desempenho zootécnico e variação de peso final, bem como se este manejo altera o início de consumo de ração nas primeiras horas pós-desmame. Um total de 504 leitões machos inteiros e fêmeas (23.9 ± 0,6 dias e 7.0 ± 1,22 kg de peso corporal) foram ordenados por peso e cada 1/3 designado como Pequenos, Médios e Grandes. A partir disto, os leitões foram aleatoriamente distribuídos em baias mistas (mistas; 7 baias) compostas pelas três categorias e baias classificadas (classificadas; 21 baias) contendo apenas uma categoria de peso por baia. Nos três primeiros dias após alojamento, os leitões tiveram acesso a uma ração contendo um corante marcador vermelho (óxido de ferro a 1%) com o intuito de indicar quando um determinado animal iniciou o consumo através do uso de swabs retais as 30, 42, 54, 66 e 78 horas após o desmame. Semanalmente, o peso corporal e o consumo de ração era registrado. As pesagens do 7º, 21º e 42º dia pós-alojamento foram individuais visando aferir o CV das baias nestes momentos. Para o período total avaliado (0 a 42 d), não foram evidenciadas diferenças em GPD (P=0,94), CRMD (P=0,60) CA (P=0,39) entre baias mistas e classificadas. Ainda, não houve evidências de diferenças no peso final (P>0,05) entre mesmas categorias nos diferentes tratamentos, nem entre as baias classificadas e mistas (P=0,88). O CV médio do peso de cada foi diferente (P<0,0001) no início do experimento entre baias classificadas e mistas (17,5% ± 0,3 e 6,9% ± 1,8, respectivamente). Ao final do estudo a diferença persistiu, embora menor do que no início (15.6% ± 3,0 e 13,3% ± 2,5, P=0,03). O início do consumo apresentou uma interação entre categoria de peso e tratamento. Leitões grandes em baias classificadas retardaram o início do consumo em comparação com classificados pequenos e médios (P≤0,05). No entanto, para baias mistas, as três categorias não apresentaram evidências de diferença (P>0,05). Em conclusão, a variação de peso ao final da fase de creche foi levemente maior para baias mistas. Classificar ao alojamento pode gerar um atraso no início de consumo pós-desmame para leitões grandes além de não melhorar o desempenho zootécnico. / The sorting pigs by weight management in the nursery phase is a widely practiced and supposedly improve growth performance and produces more uniform pigs at the end of the nursery. The aim of this study was to evaluate if sorting weaned pigs by weight at nursery allotment alters growth performance and variation likewise if this management interferes the beginning of feed intake at the post weaning first’s hours. A total of 504 females and intact males (23.9 ± 0.6 of age and 7.0 ± 1.22 kg body weight) were categorized as: light, medium and heavy. From this, pigs were randomized distributed to unsorted pens (unsorted; 7 pens) with all three categories and sorted pens just with one weight category (sorted; 7 pens for each category for a total of 21 pens). In the first three days after allotment, pigs had access to a diet containing a red dye marker (1% iron oxide) aiming to indicate if such pig had already eaten through the use of rectal swabs at 30, 42, 54, 66 e 78 hours post weaning. Body weight and feed intake were recorded weekly. Pigs were weighted individually at 7, 21, and 42 days after weaning to obtain the within-pen weight variation. Overall (0 to 42 d), there was no evidence for differences (P=0.94) in ADG, ADFI (P=0.60), or F/G (P=0.39) between sorted and unsorted pigs. Additionally, there was no evidence for differences in final body weight among the same category in different treatments (P>0.05) nor between sorted and unsorted pens (P=0.88). The average of the within-pen weight variation was statistically different (P<.0001) at the beginning of the experiment among sorted and unsorted pens) (17.5% ± 0.3 and 6.9% ± 1.8, respectively). At the end of study the difference persists (P=0.03) but less than the start for sorted and unsorted pens (13.3% ± 2.5 and 15.6% ± 3.0, respectively)). The feed intake onset has shown an interaction between weight category and treatment. Heavy pigs in sorted pens started on feed later than light and medium sorted pens (P≤0.05). However, in unsorted pens the feed intake onset presented no differences (P>0.05) In conclusion, within-pen weight variation at the end of the nursery was slightly worsened when pigs were unsorted at placement. Sorting pigs at placement can create a lag of post weaning feed intake onset for heavy-weight pigs. Thus, sorting pigs by weight at placement did not improve nursery performance.

O manejo de classificação por peso ao alojamento na fase de creche é amplamente praticado e supostamente melhora o desempenho zootécnico e gera, ao fim da fase, um grupo de leitões com peso mais uniforme O objetivo deste estudo foi avaliar se classificar os leitões desmamados por peso ao alojamento da creche, interfere no desempenho zootécnico e variação de peso final, bem como se este manejo altera o início de consumo de ração nas primeiras horas pós-desmame. Um total de 504 leitões machos inteiros e fêmeas (23.9 ± 0,6 dias e 7.0 ± 1,22 kg de peso corporal) foram ordenados por peso e cada 1/3 designado como Pequenos, Médios e Grandes. A partir disto, os leitões foram aleatoriamente distribuídos em baias mistas (mistas; 7 baias) compostas pelas três categorias e baias classificadas (classificadas; 21 baias) contendo apenas uma categoria de peso por baia. Nos três primeiros dias após alojamento, os leitões tiveram acesso a uma ração contendo um corante marcador vermelho (óxido de ferro a 1%) com o intuito de indicar quando um determinado animal iniciou o consumo através do uso de swabs retais as 30, 42, 54, 66 e 78 horas após o desmame. Semanalmente, o peso corporal e o consumo de ração era registrado. As pesagens do 7º, 21º e 42º dia pós-alojamento foram individuais visando aferir o CV das baias nestes momentos. Para o período total avaliado (0 a 42 d), não foram evidenciadas diferenças em GPD (P=0,94), CRMD (P=0,60) CA (P=0,39) entre baias mistas e classificadas. Ainda, não houve evidências de diferenças no peso final (P>0,05) entre mesmas categorias nos diferentes tratamentos, nem entre as baias classificadas e mistas (P=0,88). O CV médio do peso de cada foi diferente (P<0,0001) no início do experimento entre baias classificadas e mistas (17,5% ± 0,3 e 6,9% ± 1,8, respectivamente). Ao final do estudo a diferença persistiu, embora menor do que no início (15.6% ± 3,0 e 13,3% ± 2,5, P=0,03). O início do consumo apresentou uma interação entre categoria de peso e tratamento. Leitões grandes em baias classificadas retardaram o início do consumo em comparação com classificados pequenos e médios (P≤0,05). No entanto, para baias mistas, as três categorias não apresentaram evidências de diferença (P>0,05). Em conclusão, a variação de peso ao final da fase de creche foi levemente maior para baias mistas. Classificar ao alojamento pode gerar um atraso no início de consumo pós-desmame para leitões grandes além de não melhorar o desempenho zootécnico. / The sorting pigs by weight management in the nursery phase is a widely practiced and supposedly improve growth performance and produces more uniform pigs at the end of the nursery. The aim of this study was to evaluate if sorting weaned pigs by weight at nursery allotment alters growth performance and variation likewise if this management interferes the beginning of feed intake at the post weaning first’s hours. A total of 504 females and intact males (23.9 ± 0.6 of age and 7.0 ± 1.22 kg body weight) were categorized as: light, medium and heavy. From this, pigs were randomized distributed to unsorted pens (unsorted; 7 pens) with all three categories and sorted pens just with one weight category (sorted; 7 pens for each category for a total of 21 pens). In the first three days after allotment, pigs had access to a diet containing a red dye marker (1% iron oxide) aiming to indicate if such pig had already eaten through the use of rectal swabs at 30, 42, 54, 66 e 78 hours post weaning. Body weight and feed intake were recorded weekly. Pigs were weighted individually at 7, 21, and 42 days after weaning to obtain the within-pen weight variation. Overall (0 to 42 d), there was no evidence for differences (P=0.94) in ADG, ADFI (P=0.60), or F/G (P=0.39) between sorted and unsorted pigs. Additionally, there was no evidence for differences in final body weight among the same category in different treatments (P>0.05) nor between sorted and unsorted pens (P=0.88). The average of the within-pen weight variation was statistically different (P<.0001) at the beginning of the experiment among sorted and unsorted pens) (17.5% ± 0.3 and 6.9% ± 1.8, respectively). At the end of study the difference persists (P=0.03) but less than the start for sorted and unsorted pens (13.3% ± 2.5 and 15.6% ± 3.0, respectively)). The feed intake onset has shown an interaction between weight category and treatment. Heavy pigs in sorted pens started on feed later than light and medium sorted pens (P≤0.05). However, in unsorted pens the feed intake onset presented no differences (P>0.05) In conclusion, within-pen weight variation at the end of the nursery was slightly worsened when pigs were unsorted at placement. Sorting pigs at placement can create a lag of post weaning feed intake onset for heavy-weight pigs. Thus, sorting pigs by weight at placement did not improve nursery performance.

O manejo de classificação por peso ao alojamento na fase de creche é amplamente praticado e supostamente melhora o desempenho zootécnico e gera, ao fim da fase, um grupo de leitões com peso mais uniforme O objetivo deste estudo foi avaliar se classificar os leitões desmamados por peso ao alojamento da creche, interfere no desempenho zootécnico e variação de peso final, bem como se este manejo altera o início de consumo de ração nas primeiras horas pós-desmame. Um total de 504 leitões machos inteiros e fêmeas (23.9 ± 0,6 dias e 7.0 ± 1,22 kg de peso corporal) foram ordenados por peso e cada 1/3 designado como Pequenos, Médios e Grandes. A partir disto, os leitões foram aleatoriamente distribuídos em baias mistas (mistas; 7 baias) compostas pelas três categorias e baias classificadas (classificadas; 21 baias) contendo apenas uma categoria de peso por baia. Nos três primeiros dias após alojamento, os leitões tiveram acesso a uma ração contendo um corante marcador vermelho (óxido de ferro a 1%) com o intuito de indicar quando um determinado animal iniciou o consumo através do uso de swabs retais as 30, 42, 54, 66 e 78 horas após o desmame. Semanalmente, o peso corporal e o consumo de ração era registrado. As pesagens do 7º, 21º e 42º dia pós-alojamento foram individuais visando aferir o CV das baias nestes momentos. Para o período total avaliado (0 a 42 d), não foram evidenciadas diferenças em GPD (P=0,94), CRMD (P=0,60) CA (P=0,39) entre baias mistas e classificadas. Ainda, não houve evidências de diferenças no peso final (P>0,05) entre mesmas categorias nos diferentes tratamentos, nem entre as baias classificadas e mistas (P=0,88). O CV médio do peso de cada foi diferente (P<0,0001) no início do experimento entre baias classificadas e mistas (17,5% ± 0,3 e 6,9% ± 1,8, respectivamente). Ao final do estudo a diferença persistiu, embora menor do que no início (15.6% ± 3,0 e 13,3% ± 2,5, P=0,03). O início do consumo apresentou uma interação entre categoria de peso e tratamento. Leitões grandes em baias classificadas retardaram o início do consumo em comparação com classificados pequenos e médios (P≤0,05). No entanto, para baias mistas, as três categorias não apresentaram evidências de diferença (P>0,05). Em conclusão, a variação de peso ao final da fase de creche foi levemente maior para baias mistas. Classificar ao alojamento pode gerar um atraso no início de consumo pós-desmame para leitões grandes além de não melhorar o desempenho zootécnico. / The sorting pigs by weight management in the nursery phase is a widely practiced and supposedly improve growth performance and produces more uniform pigs at the end of the nursery. The aim of this study was to evaluate if sorting weaned pigs by weight at nursery allotment alters growth performance and variation likewise if this management interferes the beginning of feed intake at the post weaning first’s hours. A total of 504 females and intact males (23.9 ± 0.6 of age and 7.0 ± 1.22 kg body weight) were categorized as: light, medium and heavy. From this, pigs were randomized distributed to unsorted pens (unsorted; 7 pens) with all three categories and sorted pens just with one weight category (sorted; 7 pens for each category for a total of 21 pens). In the first three days after allotment, pigs had access to a diet containing a red dye marker (1% iron oxide) aiming to indicate if such pig had already eaten through the use of rectal swabs at 30, 42, 54, 66 e 78 hours post weaning. Body weight and feed intake were recorded weekly. Pigs were weighted individually at 7, 21, and 42 days after weaning to obtain the within-pen weight variation. Overall (0 to 42 d), there was no evidence for differences (P=0.94) in ADG, ADFI (P=0.60), or F/G (P=0.39) between sorted and unsorted pigs. Additionally, there was no evidence for differences in final body weight among the same category in different treatments (P>0.05) nor between sorted and unsorted pens (P=0.88). The average of the within-pen weight variation was statistically different (P<.0001) at the beginning of the experiment among sorted and unsorted pens) (17.5% ± 0.3 and 6.9% ± 1.8, respectively). At the end of study the difference persists (P=0.03) but less than the start for sorted and unsorted pens (13.3% ± 2.5 and 15.6% ± 3.0, respectively)). The feed intake onset has shown an interaction between weight category and treatment. Heavy pigs in sorted pens started on feed later than light and medium sorted pens (P≤0.05). However, in unsorted pens the feed intake onset presented no differences (P>0.05) In conclusion, within-pen weight variation at the end of the nursery was slightly worsened when pigs were unsorted at placement. Sorting pigs at placement can create a lag of post weaning feed intake onset for heavy-weight pigs. Thus, sorting pigs by weight at placement did not improve nursery performance.

<p>The objective of this thesis was to investigate the effect of dietary enzymatically treated yeast (ETY) in weanling pigs and evaluate the effect of ETY in broiler chickens during a coccidia challenge. Two studies were carried out to investigate this objective.</p> <p>The first experiment examined the effect of ETY on the growth performance, nutrient digestibility, immune response, and gut health of weanling pigs. A total of 192 weanling pigs (6.0 ± 1.04 kg) were allocated to 4 corn, soybean-based diets with increasing concentrations of ETY (0, 1, 2, or 4 g/kg) for a 43-d trial. There were 8 replicate pens (4 replicate pens per sex) and 6 pigs per replicate for each dietary treatment. The experiment was set up as a randomized complete block design. Dietary ETY supplementation did not affect the growth performance of weanling pigs. The ATTD of neutral detergent fiber (NDF) linearly increased (P < 0.05) at d 28. The concentrations of serum antioxidant and antibody markers increased (P < 0.05) from d 14 to d 43; a linear increase (P < 0.05) in catalase was observed on d 14 with increasing ETY supplementation in the diets. The inclusion of ETY in the diet did not affect the mRNA abundance of anti-inflammatory markers in the ileal mucosa of pigs but increased (P < 0.01) glutathione peroxidase 4. Ileal villus height (VH) and villus height to crypt depth (VH:CD) ratio were greater (P < 0.05) in pigs fed ETY supplemented diets relative to control pigs. However, jejunal VH and the VH:CD ratio was not affected by ETY inclusion in the diet. Pigs fed diets with increasing ETY levels had higher (P < 0.05) ileal digesta butyrate concentration relative to control pigs, but not propionate or acetate. </p> <p>The second experiment examined the effect of ETY on the growth performance, nutrient digestibility, and intestinal health of broiler chickens during a coccidia challenge. From d 1 to 14 post hatching, 480 broiler chickens (49.9 ± 3.95 g) were allocated to 3 corn-soybean meal-based diets with increasing concentrations of ETY (0, 1, or 2 g/kg). There were 16 replicate cages and 10 birds per cage. The experiment was designed as a randomized complete block design with body weight (BW) used as a blocking factor. On d 14 post hatching, the birds were combined and re-randomized within each of the 0, 1, or 2 ETY g/kg experimental diets. Following this, the number of birds was reduced to 8 birds per cage with 8 replicate cages. Each of the 3 diet groups was split into a challenge or no-challenge group. This resulted in a 3 × 2 factorial arrangement of treatments with 3 experimental diets and 2 challenge states. The BW ratio before re-randomization was maintained across all treatments during the reallotment. On d 15 post hatching, the birds in the challenge group were orally gavaged with 1 mL solution containing 25,000, 25,000, and 125,000 oocysts of E. maxima, E. tenella, and E. acervulina, respectively. The birds belonging to the no-challenge group were orally gavaged with 1 mL phosphate buffered saline. Data were analyzed using the MIXED procedure of SAS, and polynomial contrasts were used to estimate the linear and quadratic effects of ETY. The coccidia challenge (CC) decreased (P < 0.01) the BW gain, feed intake, and G:F of broiler chickens from d 14 to 21. Increasing supplementation of dietary ETY improved (P < 0.05) the G:F of birds. Also, the CC reduced (P < 0.01) the apparent total tract utilization of dry matter (DM), nitrogen (N) and gross energy (GE). The CC reduced (P < 0.01) the apparent metabolizable energy (AME) and the nitrogen corrected apparent metabolizable energy (AMEn) of diets fed to broiler chickens. On d 21, dietary ETY linearly increased (P < 0.01) the apparent ileal digestibility of DM, N, and GE in broiler chickens. The CC increased (P < 0.01) the mRNA gene expression of TNFα, IL-1β, IL-10, and IL-6. There was a tendency (P < 0.1) for ETY to reduce IL-1β expression in broiler chickens on d 21. Additionally, ETY supplementation increased (P < 0.05) the gene expression of occludin in the ceca of broiler chickens but not claudin 1. Serum catalase increased (P < 0.05) with increasing supplementation of dietary ETY in broiler chickens on d 21. Dietary ETY linearly increased (P < 0.05) the ileal villus height to crypt depth ratio and ileal goblet cell count and density in broiler chickens. The ileal and excreta oocyst counts decreased (P < 0.01) with increasing supplementation of dietary ETY in coccidia-challenged broiler chickens on d 21. </p> <p>In summary, ETY inclusion in diets of weanling pigs partially reduced reactive oxygen species damage and enhanced intestinal health without negatively affecting growth performance. Hence, ETY could be favorable in attenuating some of the deleterious effects of post-weaning stress in weanling pigs. Dietary ETY also reduced oxidative damage, improved growth performance, enhanced nutrient utilization, and augmented intestinal development in broiler chickens. However, the inclusion of ETY did not mitigate the adverse effects of a coccidia challenge in broiler chickens. Therefore, further studies may be necessary to investigate the prospect of ETY as a dietary strategy for combating coccidiosis.</p> <p><br></p>

La diarrhée colibacillaire post-sevrage (DCPS) est une infection intestinale endémique dans les fermes porcines à l’échelle mondiale. Cette maladie est causée principalement par la présence et la multiplication au niveau de l’intestin des porcelets d’un pathotype d’Escherchia coli, nommé E. coli entérotoxinogène (ETEC) et en particulier celui qui exprime l’adhésine F4 (K88) (ETEC: F4). Le sérogroupe ETEC: O149 a été le plus isolé à partir des cas de DCPS à travers le monde. Plusieurs études ont rapporté un taux de résistance important des souches O149: F4 contre les antibiotiques qui sont classiquement utilisés pour traiter cette infection et en particulier les aminoglycosides. Ainsi, pour remédier aux échecs thérapeutiques observés dans les fermes porcines au Canada, les vétérinaires ont commencé à utiliser, sous leurs responsabilités, un antibiotique, la colistine sulfate (CS), qui n’est pas homologué en production animale au Canada. Cette étude avait pour buts d’étudier la pharmacocinétique de la CS in vitro et in vivo, de développer une technique sensible pour une quantification plasmatique de la CS, de déterminer son efficacité thérapeutique in vivo dans un modèle d’infection expérimentale de DCPS et de caractériser la résistance d’E. coli consécutive à l’utilisation thérapeutique de la CS chez le porc. Une simulation du liquide gastrique (SLG) a été préparée, et après l’ajout de la CS et de la pepsine à cette solution, les concentrations de la CS ont été mesurées par chromatographie liquide à haute performance couplée à la spectrométrie de masse en tandem (HPLC-MS/MS). Une dégradation rapide de CS a été constatée dans la SLG et a été accompagnée par la formation de produits de dégradation qui ont démontré une activité microbienne plus importante par comparaison avec la molécule mère (CS). Dans un volet in vivo, l’infection expérimentale des porcelets sevrés par une souche ETEC: F4 n’a pas augmenté l’absorption digestive de la CS dans un modèle subclinique de DCPS chez le porc. L’administration orale de la CS à la dose thérapeutique de 50,000 UI/kg à raison de 2 fois par jour pendant 5 jours pour traiter la DCPS dans des conditions expérimentales a entraîné une réduction significative de l’excrétion fécale de la souche infectieuse (ETEC : F4), de la population totale d’E. coli et des scores de diarrhée, uniquement pendant la période du traitement. Cependant, ces résultats ont été accompagnés par une légère augmentation dans l’excrétion fécale des E. coli résistants à la colistine, et le traitement n'a pas empêché la perte de poids des porcs infectés. En revanche, l’infection expérimentale des porcelets par ETEC: F4 a augmenté l’absorption digestive de la CS dans un modèle clinique de diarrhée colibacillaire chez le porc. Cette étude a permis de générer pour la première fois des données scientifiques concernant l’efficacité thérapeutique, la pharmacocinétique et la résistance à la colistine dans un modèle de DCPS chez le porc. Elle a également remis en doute la pertinence économique d’augmenter la dose de CS pour accélérer le rétablissement clinique des porcs. Finalement, elle a indiqué que des conditions d’élevage optimales, sans autres facteurs prédisposants, étaient aussi efficaces que la CS dans l’amélioration des symptômes cliniques de la DCPS. / Post-weaning diarrhea (PWD) caused by Escherichia coli is an endemic intestinal infection in pig farms worldwide. This disease is mostly the consequence of the presence and the multiplication in piglet’s gut of an Escherchia pathotype, named enterotoxigenic E. coli (ETEC) and in particular those that express the F4 (K88) fimbrial adhesin (ETEC: F4). The predominant serogroup of E. coli isolated from piglets with PWD worldwide is O149. Several studies have reported a significant resistance rate of O149 ETEC strains against commonly used antibiotics for the treatment of PWD, particularly, aminoglycosides. Thereby, to address therapeutic failures observed in pig farms during PWD treatment, veterinarians in Canada started using, under their responsibilities, the colistin sulfate (CS), an antibiotic not approved for farm animals in Canada. The objectives of this thesis were: to study the pharmacokinetics of CS in vitro and in vivo, to develop a sensitive method for the quantification of CS plasma concentrations in pigs, to determine the therapeutic efficacy of CS in an experimental model of PWD, and to characterize the resistance of E. coli to colistin consecutive to its therapeutic use in pigs. Simulated gastric fluid (SGF) was prepared, and after the addition of CS and pepsin to this solution, the concentrations of CS were followed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). A rapid degradation of CS in the SGF was observed, and the degradation products showed a greater antimicrobial activity compared to the native CS. On the other hand, the experimental challenge of piglets with an ETEC: F4 strain has not increased the CS intestinal absorption in a subclinical model of PWD in pigs. The oral administration of a therapeutic dose of CS at 50,000 IU/kg twice a day for 5 successive days to treat an experimental PWD in pigs, resulted in a significant reduction of fecal ETEC: F4 and total E. coli shedding, and in diarrhea scores but only during the treatment period. However, CS treatment resulted in a slight increase in fecal shedding of CS resistant E. coli and did not prevent weight loss in challenged pigs. In addition, challenge with ETEC: F4 resulted in an increase of CS intestinal absorption in a clinical model of PWD. This study has generated, for the first time, scientific data regarding CS therapeutic efficacy, its pharmacokinetic and the selection of E. coli colistin resistant in an experimental model of PWD in pigs. It also challenged the economic relevance of increasing CS oral doses to accelerate the clinical recovery of pigs. Finally, it indicated that optimal housing conditions were without other predisposing factors, effective as CS in improving clinical symptoms of experimental PWD in pigs.

Les E. coli entérotoxinogènes (ETEC) sont souvent la cause de diarrhée post-sevrage chez le porc. Deux types d’entérotoxines sont retrouvées chez les ETEC, soit les thermolabiles, comme la toxine LT, et les thermostables, comme EAST-1, STa et STb. Cette dernière est composée de 48 acides aminés et est impliquée dans la pathologie causée par les ETEC. Pour la première fois un variant de la toxine STb fut découvert dans une étude. Nous avons alors émis l’hypothèse qu’il y a présence de variants dans la population de souches ETEC du Québec. Dans les 100 souches STb+ analysées, 23 possédaient le gène de la toxine avec une variation dans la séquence génétique : l’asparagine était présente en position 12 remplaçant ainsi l’histidine. Une corrélation entre la présence du variant et la présence de facteurs de virulence retrouvés dans ces 100 souches ETEC étudiées a été effectuée. Ce variant semble fortement associé à la toxine STa puisque toutes les souches variantes ont hybridé avec le gène codant pour cette dernière. Étant donné sa présence répandue dans la population de souches ETEC du Québec, nous avons de plus émis l’hypothèse que ce variant a des caractéristiques biologiques altérées par rapport à la toxine sauvage. L’analyse par dichroïsme circulaire a montré que le variant et la toxine sauvage ont une structure secondaire ainsi qu’une stabilité similaires. Par la suite, l’attachement au récepteur de la toxine, le sulfatide, a été étudié par résonnance plasmonique de surface (biacore). Le variant a une affinité au sulfatide légèrement réduite comparativement à la toxine sauvage. Puisque l’internalisation de la toxine fut observée dans une étude précédente et qu’elle semble liée à la toxicité, nous avons comparé l’internalisation du variant et de la toxine sauvage à l’intérieur des cellules IPEC-J2. L’internalisation du variant dans les cellules est légèrement supérieure à l’internalisation de la toxine sauvage. Ces résultats suggèrent que le variant est biochimiquement et structurellement comparable à la toxine sauvage. / Enterotoxigenic Escherichia coli (ETEC) are a major cause of post-weaning diarrhea. STb is one of two heat-stable toxins produced by ETEC and is mostly associated with pathogenic porcine isolates. For the first time, a variant of the toxin was observed in a study in 2003. Our hypothesis is that STb variants are present in ETEC strains from Quebec. To screen for alterations at the gene level, a collection of 100 STb+ ETEC strains isolated from diseased pigs was randomly selected and analyzed. A total of 23 strains had a change from His12 to Asn. An association between the presence of the variant and virulence factors present in those strains was done. These strains were also positive for STa. Since this variant seems to be widely distributed in Quebec, we hypothesize that the variant has different biological properties compared to the wild-type STb. First, the secondary structure of the variant and wild-type toxin and their thermal stability was determined by circular dichroism. Both show similar structures and thermal stability. In addition, the binding affinity with the toxin receptor, the sulfatide, was determined by surface plasmon resonance. The affinity of the wild-type for the sulfatide is slightly superior to the variant. Finally, the internalization inside IPEC-J2 cells of the variant was compared to the wild-type. The variant is able to internalize more cells than the wild-type. Altogether, these results suggest that both the variant and the wild-type toxin are biochemically and structurally similar.

O espaço de comedouro por leitão deve ser suficiente para assegurar um acesso adequado ao alimento, sem prejudicar o consumo e o desempenho. No entanto a influência do espaço de comedouro no desempenho pós-desmame ainda não está bem estabelecida, principalmente para leitões sujeitos a uma alta densidade na fase de creche. O objetivo desse estudo foi verificar o efeito de quatro espaços de comedouro no início do consumo de alimento, consumo médio diário (CMD), ganho de peso diário (GPD), conversão alimentar (CA) e ocorrência de canibalismo em leitões submetidos a uma densidade de 0,23 m²/leitão, na fase de creche. Foram avaliados 630 leitões com peso médio de desmame 5,59 ± 0,9 kg e idade média de 20,5 ± 0,9 dias ao longo de um período de 6 semanas. Foram utilizadas 28 baias com sete repetições por tratamento, sendo a baia a unidade experimental. Os espaços de comedouro estudados foram 2,13 cm/leitão, 2,56 cm/leitão, 3,20 cm/leitão e 4,26 cm/leitão. A ração foi disponibilizada na forma ad libitum, com registro de consumo diário. Os leitões receberam, por um período de três dias pós-desmame, ração com corante de óxido de ferro a 1% e foram submetidos a swab retal nas 18, 24, 42, 50, 58 e 66 h pós-desmame para avaliar o início do hábito de consumo alimentar. Os leitões foram pesados nos dias 7, 14, 21, 28, 35 e 42 de alojamento, sendo observada e registrada, diariamente, a ocorrência de canibalismo de cauda e orelha. Houve redução no início do consumo alimentar (P<0,001) quanto maior foi o espaço de comedouro disponibilizado. Para o período de 0 a 14 dias pós-desmame, foi observado efeito linear significativo no CMD (P=0,015). Houve uma tendência linear de melhoria para o GPD quanto maior foi o espaço de comedouro disponível (P=0,062), mas não foram observados efeitos do espaço de comedouro nas variáveis CMD e CA (P>0,05), no período total (0 a 42 dias). A partir dos 21 dias pós-alojamento, foram observados quadros de canibalismo tanto de orelha como cauda. O tratamento de 4,26 cm/leitão foi o único a não apresentar canibalismo e diferiu de todos os outros tratamentos. O espaço de 2,13 cm/leitão foi o que apresentou os maiores percentuais de canibalismo, em comparação com os demais espaços. Em conclusão, maior espaço de comedouro reduz o tempo médio para início do consumo pós-desmame, tende a aumentar o GPD, além de melhorar o bem-estar, pela redução de canibalismo, em leitões alojados em uma alta densidade na fase de creche. / Feeder space per pig should be sufficient to ensure adequate access to feed, without impairing the consumption and performance of the animals. However, the influence of feeder space on growth performance of pigs is not well established for the nursery phase, mainly in scenarios of high stocking density. The aim of this study was to investigate the effect of four different feeder spaces on the beggining of feeding behavior, the average daily gain (ADG), average daily feed intake (ADFI), feeding efficiency and the occurrence of tail and ear biting in pigs under a stocking density of 0.23 m²/pig in nursery phase. A total of 630 weaned piglets weighing 5.59 ± 0.9 kg and ageing 20.5 ± 0.9 days were evaluated over a 6 weeks period. Seven replicates (28 pens) per treatment were used. The feeder spaces were 2.13 cm/pig, 2.56 cm/pig, 3.20 cm/pig and 4.26 cm/pig. The feed was offered ad libitum, with the feed intake being recorded daily. The pigs were fed for a three-days post-weaning period, with 1% iron oxide dye, and were submitted to rectal swab at 18, 24, 42, 50, 58 and 66 h post-weaning to determine the starting of the feeding behavior. The piglets were weighed at 7, 14, 21, 28, 35 and 42 days of housing. The appearance of tail and ear biting was daily recorded. There was a reduction in the period between weaning and first feed intake (P<0.001) as the feeder space available increased. For the period of 0 to 14 d post-weaning, feeder space linearly affected the increase of ADFI (P=0.015). There was a linear trend for increased GPD with higher feeder space available (P=0.062), but no statistical effect of feeder space was observed on ADFI and feeding efficiency (P>0.05), when considering the total nursery period (0-42 days). From day 21 post-weaning onward, tail and ear biting behavior were observed. Piglets submitted to 4.26 cm/pig were the only that did not present this behavior, differing (P<0.05) from all the other treatments. The space of 2.13 cm/pig presented the highest percentages (P<0.05) of total cannibalism in comparison with the others spaces. In conclusion, higher feeder space decreases the time for the beginning of feeding behavior, tends to increase the ADG, as well as improves the welfare by reducing cannibalism among piglets under high stocking density pens in the nursery phase.

Les E. coli entérotoxinogènes (ETEC) sont souvent la cause de diarrhée post-sevrage chez le porc. Deux types d’entérotoxines sont retrouvées chez les ETEC, soit les thermolabiles, comme la toxine LT, et les thermostables, comme EAST-1, STa et STb. Cette dernière est composée de 48 acides aminés et est impliquée dans la pathologie causée par les ETEC. Pour la première fois un variant de la toxine STb fut découvert dans une étude. Nous avons alors émis l’hypothèse qu’il y a présence de variants dans la population de souches ETEC du Québec. Dans les 100 souches STb+ analysées, 23 possédaient le gène de la toxine avec une variation dans la séquence génétique : l’asparagine était présente en position 12 remplaçant ainsi l’histidine. Une corrélation entre la présence du variant et la présence de facteurs de virulence retrouvés dans ces 100 souches ETEC étudiées a été effectuée. Ce variant semble fortement associé à la toxine STa puisque toutes les souches variantes ont hybridé avec le gène codant pour cette dernière. Étant donné sa présence répandue dans la population de souches ETEC du Québec, nous avons de plus émis l’hypothèse que ce variant a des caractéristiques biologiques altérées par rapport à la toxine sauvage. L’analyse par dichroïsme circulaire a montré que le variant et la toxine sauvage ont une structure secondaire ainsi qu’une stabilité similaires. Par la suite, l’attachement au récepteur de la toxine, le sulfatide, a été étudié par résonnance plasmonique de surface (biacore). Le variant a une affinité au sulfatide légèrement réduite comparativement à la toxine sauvage. Puisque l’internalisation de la toxine fut observée dans une étude précédente et qu’elle semble liée à la toxicité, nous avons comparé l’internalisation du variant et de la toxine sauvage à l’intérieur des cellules IPEC-J2. L’internalisation du variant dans les cellules est légèrement supérieure à l’internalisation de la toxine sauvage. Ces résultats suggèrent que le variant est biochimiquement et structurellement comparable à la toxine sauvage. / Enterotoxigenic Escherichia coli (ETEC) are a major cause of post-weaning diarrhea. STb is one of two heat-stable toxins produced by ETEC and is mostly associated with pathogenic porcine isolates. For the first time, a variant of the toxin was observed in a study in 2003. Our hypothesis is that STb variants are present in ETEC strains from Quebec. To screen for alterations at the gene level, a collection of 100 STb+ ETEC strains isolated from diseased pigs was randomly selected and analyzed. A total of 23 strains had a change from His12 to Asn. An association between the presence of the variant and virulence factors present in those strains was done. These strains were also positive for STa. Since this variant seems to be widely distributed in Quebec, we hypothesize that the variant has different biological properties compared to the wild-type STb. First, the secondary structure of the variant and wild-type toxin and their thermal stability was determined by circular dichroism. Both show similar structures and thermal stability. In addition, the binding affinity with the toxin receptor, the sulfatide, was determined by surface plasmon resonance. The affinity of the wild-type for the sulfatide is slightly superior to the variant. Finally, the internalization inside IPEC-J2 cells of the variant was compared to the wild-type. The variant is able to internalize more cells than the wild-type. Altogether, these results suggest that both the variant and the wild-type toxin are biochemically and structurally similar.

O espaço de comedouro por leitão deve ser suficiente para assegurar um acesso adequado ao alimento, sem prejudicar o consumo e o desempenho. No entanto a influência do espaço de comedouro no desempenho pós-desmame ainda não está bem estabelecida, principalmente para leitões sujeitos a uma alta densidade na fase de creche. O objetivo desse estudo foi verificar o efeito de quatro espaços de comedouro no início do consumo de alimento, consumo médio diário (CMD), ganho de peso diário (GPD), conversão alimentar (CA) e ocorrência de canibalismo em leitões submetidos a uma densidade de 0,23 m²/leitão, na fase de creche. Foram avaliados 630 leitões com peso médio de desmame 5,59 ± 0,9 kg e idade média de 20,5 ± 0,9 dias ao longo de um período de 6 semanas. Foram utilizadas 28 baias com sete repetições por tratamento, sendo a baia a unidade experimental. Os espaços de comedouro estudados foram 2,13 cm/leitão, 2,56 cm/leitão, 3,20 cm/leitão e 4,26 cm/leitão. A ração foi disponibilizada na forma ad libitum, com registro de consumo diário. Os leitões receberam, por um período de três dias pós-desmame, ração com corante de óxido de ferro a 1% e foram submetidos a swab retal nas 18, 24, 42, 50, 58 e 66 h pós-desmame para avaliar o início do hábito de consumo alimentar. Os leitões foram pesados nos dias 7, 14, 21, 28, 35 e 42 de alojamento, sendo observada e registrada, diariamente, a ocorrência de canibalismo de cauda e orelha. Houve redução no início do consumo alimentar (P<0,001) quanto maior foi o espaço de comedouro disponibilizado. Para o período de 0 a 14 dias pós-desmame, foi observado efeito linear significativo no CMD (P=0,015). Houve uma tendência linear de melhoria para o GPD quanto maior foi o espaço de comedouro disponível (P=0,062), mas não foram observados efeitos do espaço de comedouro nas variáveis CMD e CA (P>0,05), no período total (0 a 42 dias). A partir dos 21 dias pós-alojamento, foram observados quadros de canibalismo tanto de orelha como cauda. O tratamento de 4,26 cm/leitão foi o único a não apresentar canibalismo e diferiu de todos os outros tratamentos. O espaço de 2,13 cm/leitão foi o que apresentou os maiores percentuais de canibalismo, em comparação com os demais espaços. Em conclusão, maior espaço de comedouro reduz o tempo médio para início do consumo pós-desmame, tende a aumentar o GPD, além de melhorar o bem-estar, pela redução de canibalismo, em leitões alojados em uma alta densidade na fase de creche. / Feeder space per pig should be sufficient to ensure adequate access to feed, without impairing the consumption and performance of the animals. However, the influence of feeder space on growth performance of pigs is not well established for the nursery phase, mainly in scenarios of high stocking density. The aim of this study was to investigate the effect of four different feeder spaces on the beggining of feeding behavior, the average daily gain (ADG), average daily feed intake (ADFI), feeding efficiency and the occurrence of tail and ear biting in pigs under a stocking density of 0.23 m²/pig in nursery phase. A total of 630 weaned piglets weighing 5.59 ± 0.9 kg and ageing 20.5 ± 0.9 days were evaluated over a 6 weeks period. Seven replicates (28 pens) per treatment were used. The feeder spaces were 2.13 cm/pig, 2.56 cm/pig, 3.20 cm/pig and 4.26 cm/pig. The feed was offered ad libitum, with the feed intake being recorded daily. The pigs were fed for a three-days post-weaning period, with 1% iron oxide dye, and were submitted to rectal swab at 18, 24, 42, 50, 58 and 66 h post-weaning to determine the starting of the feeding behavior. The piglets were weighed at 7, 14, 21, 28, 35 and 42 days of housing. The appearance of tail and ear biting was daily recorded. There was a reduction in the period between weaning and first feed intake (P<0.001) as the feeder space available increased. For the period of 0 to 14 d post-weaning, feeder space linearly affected the increase of ADFI (P=0.015). There was a linear trend for increased GPD with higher feeder space available (P=0.062), but no statistical effect of feeder space was observed on ADFI and feeding efficiency (P>0.05), when considering the total nursery period (0-42 days). From day 21 post-weaning onward, tail and ear biting behavior were observed. Piglets submitted to 4.26 cm/pig were the only that did not present this behavior, differing (P<0.05) from all the other treatments. The space of 2.13 cm/pig presented the highest percentages (P<0.05) of total cannibalism in comparison with the others spaces. In conclusion, higher feeder space decreases the time for the beginning of feeding behavior, tends to increase the ADG, as well as improves the welfare by reducing cannibalism among piglets under high stocking density pens in the nursery phase.