[en] This Thesis was designed with the main objective of evaluating the potential of some prebiotic, probiotic and synbiotic strategies to control digestive disorders of piglets around weaning. To achieve this purpose, three experiments were designed. In Trial 1 we first investigated the potential of lactulose, a probiotic strain of Lactobacillus plantarum, or its synbiotic combination on the gastrointestinal environment and the performance of piglets after weaning. Animals were randomly divided into four groups and fed either: a control diet, the same diet supplemented with a daily culture of L. plantarum (109 CFU/ml sprayed on top; 20 ml/pig); a diet with 1% w/v lactulose or its synbiotic combination. The experiment lasted 14 days after which 8 piglets from each group were euthanized. Digesta from proximal colon was collected and pH, short-chain fatty acids (SCFA), microbiota composition were analyzed. Furthermore, blood urea nitrogen (BUN) and acute-phase proteins (Pig-MAP) were measured. The trial 2 with a similar design to trial 1 attempted to evaluate whether lactulose, Lactobacillus plantarum, or its synbiotic combination could reduce the diarrhoea incidence and modulate the intestinal microbiota after an experimental challenge with enterotoxigenic Escherichia coli (ETEC) K88. For this, 72 weaning piglets were randomly assigned to one of the 4 treatments in the same way as trial 1. The pigs were orally challenged after receiving the supplemented diets for 7 days. Body weight, feed intake and diarrhoea incidence were measured. Six pigs per treatment were euthanized on days 6 and 10 post challenge (PC) and samples digesta of ileum and colon were collected for the analysis of lactic and SCFA and the quantification of different microbial groups. Ileal mucosa was also sampled for the analysis of adhered enterobacteria and E. coli. Ileal tissue and serum samples were also taken for histological studies and TNF-α and Pig-MAP determination. Finally in the Trial 3 it was evaluated the prebiotic potential of a carob seed product to enhance the piglet gut health and performance after an experimental infection with ETEC K88. A total of seventy two 28 day-old commercial piglets were used in a 15 days experiment. The treatments consisted of a control diet, the same diet to which 5 g/Kg of a product from carob seed was added, and a third diet with 3 g/Kg of ZnO as positive control. Body weight, feed intake and diarrhoea incidence were measured. Four and 8 days PC 8 pigs per treatment were euthanized and different samples taken similarly to trial 2. Lactulose as prebiotic for weaned piglet Results showed that addition of lactulose improved the feed intake, increased the lactic acid bacteria in ileum and at the same time reduced enterobacteria:lactobacilli ratio in colon. The colonic fermentation turned on more butyrogenic and less proteolytic with reductions on the BCFA and blood urea nitrogen. All these changes were also observed under challenging conditions. Moreover we detected other benefits on intestinal health indicators including: increases of ileum villous height or reductions on Pig-MAP concentration. All these benefits could be behind the improved weigh gain observed in the piglets during the post-challenge period. Role of Lactobacillus plantarum on preventing and/or controlling of ETEC K88 infection. Regarding supplementation of Lactobacillus plantarum the results demonstrated its ability to survive and colonize the distal part of gastrointestinal tract of weaned piglet even under ETEC K88 infection. The probiotic promoted a shift in the number and diversity of lactobacilli, with a decrease on the enterobacteria:lactobacilli ratio and on the percentage of branched fatty acids suggesting a reduction in the proteolytic microbial activity. The inclusion of the probiotic showed to diminish the incidence of diarrhoea (P 0.05), although we were not able to detect reductions in the E. coli K88 counts. Together to a possible control of enterobacteria, beneficial effects of L. plantarum could also be due to others mechanisms such as: (i) a promotion of a more healthy fermentation profile (mainly observed in colon with a lower ammonia concentration and increases in total SCFA and in the percentages of butyrate), (ii) an improved barrier function (increased villous height and goblet cells), or (iii) a modulation in the inflammatory response, (reduction in plasmatic TNF and in IEL in ileum). Synbiotic combination Positive results obtained with both lactulose and L. plantarum were added in the synbiotic combination; despite that lactulose was not able to promote any additional increase in the numbers of L. plantarum. Therefore it was concluded that this combination could act as complementary synbiotic, adding the beneficial effects of each additive, but not as a synergic combination. Efficacy of carob seed product on improving the health status of piglets after weaning. The supplementation with the carob seed product reduced the diarrhoea incidence and the numbers of enterobacteria and E. coli in the hindgut and attached to ileal mucus. These results were associated: with increases in total SCFA and lactic acid in colon and a faster recovery of acute inflammatory response in similar manner to ZnO treatment (reducing IEL and serum Pig-MAP concentrations). These effects could be due to an indirect effect through reinforcement of the indigenous microbiota of piglets and also to a possible direct action interfering with the pathogen adhesion mechanisms to the intestinal epithelium, considering the high content of galactomannans of carob seed. The results exposed in this thesis have highlighted that the use of prebiotic and probiotic may be a way to improve the adaptation of piglets around early weaning. These benefits are associated with the ability showed by L. plantarum to increase the population and activity of lactobacilli in order to prevent and/or controlling the incidence of digestive disorders. Lactulose demonstrated prebiotic effects with increases on lactobacilli, and promotion of a fermentation profile more butyrogenic and less proteolitic, increasing the ileal villous height. Dietary intervention with the carob seed product reduce the enterobacteria and E. coli population in the hindgut and show improvements in the fermentation profile and reductions in the inflammatory response associated to an ETEC K88 challenge.

[es] El principal objetivo de la presente memoria de tesis fue evaluación del potencial de algunas estrategias prebióticos, probióticos y simbiótica para prevenir y/o controlar los trastornos digestivos de los lechones alrededor del destete. Para lograr este propósito, se diseñaron tres experimentos. El Experimento 1 se diseñó con el ánimo de evaluar el potencial de una combinación simbiótica de lactulosa y Lactobacillus plantarum, sobre el ambiente intestinal y el rendimiento de lechones tras el destete. Los animales de distribuyeron por grupos y se asignaron 4 dietas, una dieta control, otra con L. plantarum (2 x 109 UFC/ lechón/d); otra con lactulosa (1%) y su combinación. El experimento duró 15 días y al finalizar el mismo se sacrificaron 8 lechones por tratamiento y se obtuvieron muestras de digesta de colon proximal para pH, análisis de ácidos grasos de cadena corta (AGCC) y para el estudio de la microbiota. También se tomaron muestras de sangre para la medición de nitrógeno de urea (BUN) y proteínas de fase aguda. En el Experimento 2 se evaluó la eficacia de la lactulosa, Lactobacillus plantarum y su combinación simbiótica para reducir la incidencia de diarrea y modular la microbiota intestinal en lechones infectados con Escherichia coli enterotoxigénica (ETEC) K88. El estudio se realizó con 72 lechones que fueron distribuidos en 4 grupos y se le asignaron los mismos tratamientos evaluados en el Experimento 1. Los cerdos fueron desafiados oralmente con una cepa de ETEC K88 (6 x 109 UFC) después de 7 días de adaptación a las dietas. Diariamente se realizó el examen clínico de los animales y se registró la incidencia de diarrea. Los días 6 y 10 post inoculación se sacrificaron 6 cerdos/tratamiento y se obtuvieron muestras de sangre para la medición de TNF-α y proteínas de fase aguda (Pig-MAP) y de digesta de íleon y de colon proximal para determinación de pH, NH3, ácido láctico y AGCC y para cuantificar los diferentes grupos microbianos. Fueron tomadas además, muestras de de tejido del íleon para estudios histológicos y para el análisis de enterobacterias y E. coli adheridas. Finalmente, en el Experimento 3 se evaluó el potencial prebiótico de un producto de semilla de garrofa para mejorar la salud intestinal y el rendimiento de los lechones después de una infección experimental con ETEC K88. El estudio se realizó durante 15 días con 72 lechones de 28 días de edad. Los animales fueron asignados a una de entre 3 dietas experimentales: una dieta control, la misma dieta a la que se le añadió 5 g/kg de un derivado de semilla de garrofa decorticada, desgerminada y micronizada y otra con alta dosis de ZnO (3g/kg), como control positivo (ZnO). Diariamente se evaluó la incidencia de diarrea y los días 7, 11 y 15 se registraron el peso y el consumo de pienso de los animales. Los días 4 y 8 post-infección se sacrificaron 8 cerdos/tratamiento y se tomaron las mismas muestras que en el Experimento 2. Los resultados expuestos en esta tesis han puesto de manifiesto la eficacia del uso prebióticos y probióticos para mejorar la adaptación de los lechones en torno a un destete temprano. Estos beneficios se relacionan con la capacidad mostrada por el L. plantarum para aumentar la población y la actividad de los lactobacilos, con el fin de prevenir y/o controlar la incidencia de trastornos digestivos. Se demostró además la capacidad prebiótica de la lactulosa, promoviendo el aumento en los lactobacilos y estimulando un perfil de fermentación más butirogénico y menos proteolítico. Finalmente la adición a la dieta de un derivado de semilla de algarroba, reduce la población de enterobacterias y E. coli, mejora el perfil de fermentación y modula positivamente la respuesta inflamatoria, en lechones infectados con ETEC K88.