L'objectif de ce travail de thèse était d'évaluer l'intérêt de mettre en place des évaluations génomiques dans les programmes de sélection porcins. Des simulations stochastiques ont été réalisées dans le cas d'un programme de sélection d'une lignée mâle de grande taille contenant 1 050 femelles reproductrices et 50 verrats, sélectionnée pendant 10 ans pour améliorer un objectif de sélection combinant 2 caractères, respectivement mesurés sur 13 770 candidats par an (Car1) et sur 270 collatéraux par an (Car2) issus de 10% des portées. Dans la situation de référence, les valeurs génétiques étaient estimées selon la méthodologie du BLUP-Modèle Animal (BLUPMA). Dans une première étude, nous avons comparé le scénario BLUPMA à un scénario génomique dans lequel tous les candidats étaient génotypés. Les évaluations génomiques s'appuyaient sur deux populations de référence (PR) initialement constituées de 13 770 candidats pour Car1 et de 1 000 collatéraux pour Car2, et dont les tailles respectives augmentaient annuellement, en considérant les mêmes capacités de phénotypage que dans le scénario BLUPMA. Les résultats montrent que des évaluations génomiques améliorent nettement la précision d'estimation des valeurs génétiques des candidats pour les deux caractères et le progrès génétique réalisé annuellement sur l'objectif global de sélection (+27% à +33% selon les héritabilités considérées), tout en réduisant significativement l'augmentation de la consanguinité dans la population. Un second scénario génomique a été simulé, dans lequel les candidats n'étaient plus phénotypés et les évaluations génomiques s'appuyaient sur une PR uniquement constituée de collatéraux phénotypés pour Car1 et Car2. Dans ce cas, la précision des valeurs génomiques estimées et la réponse à la sélection pour Car1 sont nettement plus faibles que dans le scénario BLUPMA, montrant que la sélection génomique ne permet pas de mettre fin au phénotypage des animaux. La mise en place d'évaluations génomiques nécessitant de génotyper un grand nombre d'individus, elle entraîne un surcoût important par rapport au scénario BLUPMA. Dans une seconde étude, nous avons montré que ce surcoût peut être largement réduit en présélectionnant les candidats à génotyper sur la base de leur valeur génomique estimée sur ascendance. Il est ainsi possible de réduire de manière significative le nombre de candidats à génotyper tout en préservant une grande partie de l'avantage de la sélection génomique par rapport à la sélection conventionnelle BLUPMA. Ainsi, une diminution de 40% du nombre de candidats génotypés ne réduit que de 3 à 4% le progrès génétique annuel sur l'objectif global. Nous avons également montré qu'au-delà d'un certain seuil d'investissement, une dépense supplémentaire pour améliorer l'efficacité du programme de sélection est plus efficacement investie dans la mise en place d'évaluations génomiques que dans l'augmentation de la capacité de phénotypage des collatéraux dans le dispositif conventionnel. Ce seuil d'intérêt de mise en place d'un programme génomique est d'autant plus bas que le coût du génotypage est faible et que le coût de phénotypage des collatéraux est élevé. L'ensemble de nos résultats suggère qu'il serait intéressant de mettre en place des évaluations génomiques dans un programme de sélection d'une lignée porcine mâle de grande taille, notamment dans la population Piétrain collective française, dont la structure est proche de celle de la population simulée dans nos études. / The aim of this work was to evaluate the interest of implementing genomic evaluations in pig breeding schemes. Stochastic simulation was used. The simulated population was a pig sire line containing 1,050 breeding females and 50 boars. The line was selected for 10 years for a breeding goal including two uncorrelated traits, recorded on, respectively, 13,770 candidates per year (trait1) and 270 relatives per year born in 10% of the litters (trait2). In the reference breeding scheme (BLUPAM), the selection was based on pedigree-based BLUP estimated breeding values (EBVs). In a first study, we compared the BLUPAM scenario to an alternative genomic breeding scheme with the same phenotyping capacities, where all candidates for selection were genotyped. The genomic breeding values for trait1 and trait2 were estimated using two training populations (TP). The first one (TP1) was made up of selection candidates (phenotyped for trait1) and the second one (TP2) of relatives phenotyped for trait2. The size of TP1 and TP2 increased, respectively, from 13,770 to 55,080 and from 1,000 to 3,430 over time. Our results show that genomic evaluations significantly improve the accuracy of the EBVs of the candidates for both traits and therefore the annual genetic trends for the global breeding goal (+27% to +33% depending on trait heritability), while significantly reducing the inbreeding rate. A second genomic scenario was simulated, in which the candidates were no longer phenotyped for trait1, and the genomic breeding values were estimated with one single TP made up of relatives phenotyped for both traits. In that case, the accuracy of EBVs and the annual genetic trends for trait1 are significantly lower than in the reference (BLUPAM) scenario. This shows that a large TP is required to outperform the current schemes for traits recorded on the candidates. The implementation of genomic evaluations requires the genotyping of a large number of animals, and therefore generates additional costs compared to BLUPAM breeding schemes. In a second study, we showed that genotyping a subset of candidates that have been pre-selected according to their parental EBV allows to significantly reduce the extra costs of a genomic breeding scheme while preserving most of its superiority in terms of genetic trends and inbreeding over the BLUPAM breeding scheme. For instance, reducing the number of genotyped candidates by 40% only reduced by 3 to 4% the global annual genetic trend. We also showed that even a very marked increase in the number of relatives phenotyped for trait2 in a BLUPAM scenario does not allow to be as efficient as a genomic scenario when the number of genotyped candidates is large. Finally, we showed that the economic interest of genetic selection can be characterized by an additional cost threshold; below this threshold, it is preferable to maintain pedigree-based BLUP evaluations and increase the number of relatives, while implementing genomic evaluation is more efficient above this threshold. The value of this threshold depends on the cost of phenotyping additional relatives and on genotyping costs.Our results suggest that implementing genomic evaluations in a large size pig sire line can be a valuable strategy. This strategy could for instance easily be applied to the French Piétrain population, which resembles the nucleus population simulated in this study.

Doctor of Philosophy / Department of Animal Sciences and Industry / Robert D. Goodband / Two experiments evaluated effects of glycerol on pellet mill production and pig performance. In Exp. 1, increasing glycerol increased (quadratic; P < 0.01) pellet durability index through 9% added glycerol. Adding glycerol decreased (linear; P > 0.01) production energy (kWh/t). In Exp. 2, pigs were fed one of seven diets with no added soy oil or glycerol (control); the control diet with 3 or 6% added soy oil, 3 or 6% added glycerol, and 6 or 12% additions of a 50:50 soy oil/glycerol blend in a 26-d growth assay. Adding glycerol improved (P < 0.01) pellet durability compared to soy oil and the soy oil/glycerol blend treatments. Pigs fed glycerol had increased (linear, P < 0.03) ADG. Adding soy oil, glycerol, or the soy oil/glycerol blend resulted in similar final BW. Two experiments evaluated the effects of glycerol as a replacement for lactose on pellet mill production and nursery pig performance. In Exp. 1, pigs were fed one of ten treatments that included 0, 3.6, or 7.2% lactose or 0, 3.6, or 7.2 % glycerol and fed in either meal or pelleted form. Pellet durability index increased (linear; P < 0.01) with added lactose and glycerol. Glycerol decreased (linear; P < 0.01) production energy (kWh/t). There was a tendency (P < 0.06) for an inclusion level × diet form (meal or pellet) interaction observed for ADG. Pigs fed the pelleted diets containing the 7.2% glycerol inclusion had decreased ADG compared to all other treatments. In Exp. 2, pigs were fed one of fourteen diets that included 0, 3.6, 7.2, or 10.8% lactose or 0, 3.6, 7.2, or 10.8 % glycerol and fed in either meal or pelleted form. There was no effect (P < 0.27) of diet form, inclusion level, or source on ADG or ADFI. Eight experiments evaluated the effect of ingredients on the flow ability of ground corn. Flow ability of feed improved with added glycerol, especially when added to meal diets containing hammer mill ground corn. Specialty protein ingredients in powder form reduce flow ability, while fine lactose sources improved flow ability. Granulated ingredients improved flow ability.

No description available.

The state of diseases in South African domestic pigs drastically changed when Porcine reproductive and respiratory syndrome (PRRS) was introduced in the Western Cape Province during 2004 and was followed by an outbreak of Classical swine fever (CSF), primarily in the Eastern Cape, in 2005. These outbreaks occurred mostly in rural and backyard pig populations. Subsequent to an intensive culling operation, it became necessary to implement country-wide surveillance to substantiate that freedom from these two diseases had been achieved. Samples for a country-wide cross-sectional study were collected from commercial and non-commercial pig establishments in a combined effort between the South African Pig Producers Organisation (SAPPO) and the National and Provincial Departments of Agriculture, Veterinary Services. The survey targeted the high-risk sector of the pig population and included rural pig populations, pigs from “grey” herds (commercial farms with inadequate bio-security) and commercial establishments. Samples were also tested for Swine influenza (SI), Transmissible gastroenteritis (TGE), Aujeszky’s Disease (Aujeszky’s), Foot-and-mouth Disease (FMD) and African swine fever (ASF). The first objective of this study was to evaluate the validity of the survey design. The second objective was to evaluate the results and, thereafter, make valid inferences regarding the disease status of the domestic pig population. This also included the confidence level of the overall survey. The third objective was to qualify and quantify sample losses to enable improved future survey design and execution. The outcome of the survey indicated that the results were sufficient to conclude that the non-commercial pig population is free from CSF, PRRS and SI at the expected minimum prevalence of 1%. The calculations also indicated that the results were adequate to conclude that the commercial pig population is free from CSF, PRRS and SI at the expected minimum prevalence of 5%. The outcome of the calculations done on the second phase test results allows South Africa to conclude that the non-commercial pig sector is free from FMD, ASF, Aujeszky’s and TGE, at the expected minimum prevalence of 2%. The sample sizes for Aujeszky’s, TGE, ASF and FMD tests in the commercial sector were too small to allow for a decision to be made and, as a result, it was not possible to declare this sector free of disease. However, the non-commercial sector is much larger and the risk of disease introduction higher, therefore, if the non-commercial sector tested negative for the disease, it is highly likely that the commercial sector will be free of the disease as well. It is recommended that passive surveillance be augmented and that a national pig survey be conducted every 3 years to provide proof of disease freedom. It is important to conduct a risk analysis to qualify and quantify the risk of CSF and PRRS introduction. This could improve future surveys by providing a scientific basis for targeted surveillance. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Production Animal Studies / unrestricted

It is the aim of this work to study the role, if any, of C'4 in the immune response against Staphylococcus aureus infections.

<p>Carbohydrases have been used to improve fiber utilization in monogastric animals. However, their effects on animal performance and nutrient digestibility have been inconsistent in pigs. The efficacy of carbohydrases has been suggested to depend on enzyme activity and fiber composition, but recent evidence suggests other factors like environmental conditions may play significant role. The effect of heat stress (HS) on the efficacy of a multienzyme carbohydrase blend in growing pigs was investigated. It was hypothesized that HS alters the efficacy of carbohydrases. Ninety-six growing pigs (gilts:barrows; 1:1) (initial BW of 20.15±0.18 kg) were randomly assigned to 6 treatments, with 8 replicates of 2 pigs replicate pen in a 3×2 factorial arrangement: three levels of carbohydrase (0, 1X or 2X) and two room temperature conditions (20^oC constant or cyclical 28^oC night time and 35^oC daytime). The 1X is the recommended commercial dose of the enzyme (50g/tonne) and provides 1250 visco-units endo-β-1,4-xylanase, 4600 units α-L-arabinofuranosidase and 860 visco-units endo-1,3(4)-β-glucanase per kg of feed. The 2X dose was 100g/tonne. Pigs were fed ad libitum for 28 days and 1 pig per pen was sacrificed at d28. Heat stress increased the respiratory rate and skin temperature (P<0.001). There was no enzyme × temperature effect on response criteria. Enzyme treatment quadratically increased BW d28 (P=0.025), ADG (P=0.022) and average daily feed intake (ADFI) (P=0.032) with 1X being the highest. Heat stress reduced the BW at d14 (P=0.002) and d28 (P=0.006), average daily gain (ADG) (P=0.005) and ADFI (P<0.001). However, there was a trend of increased gain: feed ratio (G/F) (P=0.093) in the HS pigs compared to the thermoneutral (TN). Heat stress increased apparent jejunal digestibility (AJD) of energy (P=0.039) and apparent ileal digestibility (AID) of calcium (P=0.007). ADFI was positively correlated to ADG (r=0.57; P<0.001) but negatively correlated to G/F (r=-0.42; P=0.003). Enzyme supplementation increased in vitro viscosity at 3, 4 and 5 hours (P value). Heat stress reduced serum glucose concentration on d1 (P=0.0002) but increased serum non esterified fatty acid (NEFA) concentration (P=0.002). A similar trend to NEFA was observed in triacylglycride (TAG). In the jejunum, carbohydrases had trend for increased villi height (P=0.07) while HS reduced villi height (P=0.02). Heat stress increased the jejunal mRNA abundance of IL1β in the jejunum (P<0.001). There was a trend for a reduction in ileal MUC2 (P=0.092), occludin (P=0.091) due to HS, with the trend increasing in PEPT1 (P=0.064). There was no effect of HS on alpha diversity of fecal microbiome, but sampling day affected beta diversity. There was an increase in the abundance of pathogenic bacteria (like Clostridium) in the HS group. Heat stress did not alter the efficacy of carbohydrase but both carbohydrase and HS modulate pig performance independently.</p>

Unfertilized or parthenogenetically non-activated porcine oocytes matured in vitro conditions are subjected to a process known as aging. During such development, porcine oocytes undergo the complex of the structural and functional changes, which can result in spontaneous parthenogenetic activation, fragmentation or lysis. After three days of culture in our condition, 23% of oocytes remained at the stage of metaphase II, 48% of oocytes were spontaneously parthenogenetically activated, 26% of oocytes were subjected to fragmentation and 3% of oocytes were lysed. The complete suppression of porcine oocyte fragmentation during the process of aging occurred during oocytes cultured in medium with sulphide donor Na2S in concentrations 150 µM and 300 µM. Inhibition of enzymes catalyzing the synthesis of hydrogen sulfide in the oocytes during the process of aging (cystathionine-gamma-lyase and cystathionine beta-synthase), iniciates earlier onset of oocytes fragmentation. The effect of both inhibitors could be completely reversed by using sulphide donor Na2S. The process of aging in porcine oocytes significantly reduces the success of the activation processes. Parthenogenetic activation occurred in 94% of pig oocytes, which were not subjected to aging. The proportion of activated oocytes after exposure to 24...

<p><i>In utero </i>heat stress (<b>IUHS</b>) is a major concern for realizing full production potential in the swine industry. Postnatal phenotypes, such as growth performance, post-absorptive metabolism, and stress response, are negatively altered in pig offspring that have been exposed to IUHS. With current trends in global temperatures predicting a continuation of increased temperatures, it is necessary to further investigate mechanisms driving these altered postnatal phenotypes and to find mitigation strategies to combat the negative effects of IUHS. In a first study, postnatal consequences of IUHS in pigs were evaluated and a mitigation strategy was tested. A second study was conducted to investigate the HPA axis response to a stress challenge in IUHS pigs. The first study found decreased average daily gain in IUHS pigs, and that providing a nutrient-dense diet did not rescue this lost productivity due to a decrease in feed intake for this diet. These results show the importance of maintaining beneficial gestation environments to avoid IUHS and the need to continue looking for alternative strategies to mitigate negative effects of IUHS. In the second study, IUHS pigs had a decreased change in cortisol response (<b>Δ CORT</b>) from baseline when subjected to a corticotropin-releasing hormone (<b>CRH</b>) challenge at 10 wk of age, and 15 wk old pigs had a decreased Δ CORT response when subjected to a dexamethasone suppression test and a CRH challenge as well as decreased glucocorticoid receptor expression in both the hypothalamus and anterior pituitary when compared to 10 wk old pigs. These results show changes in HPA axis function as young pigs mature and that particular focus may need to be put on IUHS pigs at a young age when they might be more vulnerable to negative impacts of stress. Overall, these studies show that IUHS causes a variety of negative postnatal effects in offspring and that a better understanding of mechanisms driving these changes along with developing alternative strategies to combat the incidence of these negative postnatal effects remains of paramount importance for the swine industry.</p>

Effects of neurokinin A (NKA) and substance P (SP) on coronary resistance vessels were studied in isolated guinea pig hearts perfused with isotonic buffer containing 20 mM KCl. Injections of NKA and SP caused dose-dependent reductions in perfusion pressure with ED50 values of 14.0 and 0.326 pmol, respectively. Blockade of nitric oxide synthesis or removal of the endothelium inhibited vasodilator responses to neurokinins. Infusions of NKA or SP caused tachyphylaxis and cross-desensitization to the other neurokinin but not to acetylcholine. Injections of 2.5 nmol NKA increased perfusion pressure by 31 ± 8% when given after tachyphylaxis developed to infused SP (2.5 nmol/100 μl/min). It was concluded that 1) neurokinins cause an endothelium-dependent relaxation of coronary resistance vessels by stimulating NK-1 receptors on endothelial cells, and 2) desensitization of the receptor mediating vasodilation unmasks a vasoconstrictor response to NKA.

The dose-response ototoxic effects of cisplatin were studied in guinea pigs. Loss of Preyer reflex and suppression of the N1 amplitude occurred in cisplatin-treated animals and was described as dose-related. Drug-induced hair cell damage, as observed with scanning electron microscopy, occurred sporadically throughout the turns of the cochlea and the incidence increased with dose. Na, K-ATPase activity in the lateral wall tissues was not significantly different between treatment groups. The results reported here indicate that cisplatin ototoxicity was dose-dependent, but was not directly related to Na,K-ATPase activity in the lateral wall.