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Weaning is a crucial period in the management of piglets. In modern piggeries economic interest make weaning age decrease more and more and the detrimental consequences of weaning have as much importance as earlier the weaning occurs. The risk of development of post-weaning diarrhea (PWD) in piglets is high and PWD is the cause of serious economic losses in pig herds. In the past the supplementation of the feed given after weaning with growth promoters antibiotics, in order to keep PWD under control, used to be a common practice, but their usage has been banned in EU since 2006. This measure led to the investigation of alternative suitable feed supplements that would be reasonably efficient in protecting and sustaining animal health and performance. Aim of this thesis was to evaluate the effect of some different alternatives to growth-promoters antibiotics on weaning piglets and to assess if some of them could be considered as valuables options to replace auxinic in animal feeding. The study is composed by four experimental trials. The first one aims to identify mechanisms involved in the auxinic effects of antibiotics in the diets; the following three evaluate the addition butyric acid, tryptophan, and nitrate as alternative to in-feed antimicrobials. Although some results are controversial, it appears from the data presented that the alternatives to in-feed antibiotics considered may exert positive effects on some zootechnical and health parameters on piglet in the post-weaning period. Anyway, the mechanism of action and the interaction with microbiota of such additives should be investigated inside out because many effects remains poorly understood.

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Weaning is an important and complex step involving many stresses that interfere deeply with feed intake, gastro-intestinal tract (GIT) development and adaptation to the weaning diet in young pigs. The health of the pig at weaning, its nutrition in the immediate post-weaning period, and the physical, microbiological and psychological environment are all factors that interact to determine food intake and subsequent growth. GIT disorders, infections and diarrhoea increase at the time of weaning, in fact pathogens such as enterotoxigenic Escherichia coli (ETEC) are major causes of mucosal damage in post-weaning disease contributing to diarrhoea in suckling and post-weaned pigs. The European ban in 2006 put on antibiotic growth promoters (AGP) has stimulated research on the mechanisms of GIT disorders and on nutritional approaches for preventing or reducing such disturbances avoiding AGPs. Concerning these aspects here are presented five studies based on the interplay among nutrition, genomic, immunity and physiology with the aim to clarify some of these problematic issues around weaning period in piglets. The first three evaluate the effects of diets threonine or tryptophan enriched on gut defence and health as possible alternatives to AGP in the gut. The fourth is focused on the possible immunological function related with the development of the stomach. The fifth is a pilot study on the gastric sensing and orexygenic signal given by fasting or re-feeding conditions. Although some results are controversial, it appears that both tryptophan and threonine supplementation in weaning diets have a preventive role in E.coli PWD and favorable effects in the gut especially in relation to ETEC susceptible genotype. While the stomach is believed as almost aseptic organ, it shows an immune activity related with the mucosal maturation. Moreover it shows an orexygenic role of both oxyntic mucosa and pyloric mucosa, and its possible relation with nutrient sensing stimuli.

Tra i componenti naturali biologicamente attivi, e con cui è possibile arricchire il latte, notevole importanza rivestono gli acidi grassi Omega3 e i CLA. I ruoli benefici svolti da questi particolari lipidi si manifestano soprattutto nella regolazione dei processi infiammatori, nella prevenzione del diabete e delle malattie cardiovascolari; è inoltre dimostrato come i CLA abbiano attività anticancerogena e ipocolesterolemica, stimolino il sistema immunitario e prevengano l’insorgenza del diabete e delle malattie croniche non trasmissibili. Lo scopo di questo lavoro è stato quello di individuare, in condizioni sperimentali controllate e nelle comuni realtà di allevamento, le possibili strategie alimentari atte ad aumentare le concentrazioni di Omega-3 e CLA del latte vaccino, senza penalizzare i titoli di grasso del latte. I lavori sperimentali effettuati possono essere distinti in 3 fasi: una prima fase in cui l’oggetto principale delle ricerche svolte è stato l’incremento in acidi grassi Omega3 del latte, una seconda fase in cui l’obiettivo si è allargato anche all’incremento delle concentrazioni in CLA, e una terza fase che ha avuto come scopo quello di incrementare i livelli di Omega3 e CLA del latte senza penalizzare i titoli di grasso. Le strategie alimentari più efficaci si sono basate sulla modificazione degli apporti lipidici della razione attraverso la supplementazione con seme di soia o relativo olio, semi di lino o relativo olio, olii di pesce e acido stearico. Le ricerche svolte hanno evidenziato come, attraverso opportune ed accurate modulazioni degli apporti lipidici delle razioni, sia di fatto possibile innalzare i contenuti di acidi grassi della serie Omega3 e CLA nel latte vaccino, senza penalizzare i titoli del grasso del latte. / Omega3 and CLA are among the most important active biologic components usually used as milk-enricheners. The main beneficial roles accomplished by these particular lipids are: the regulation of inflammatory processes and the prevention of diabetes and cardiovascular diseases. Furthermore, it is proven the CLA anticancer and hypocholesterolemic effect. Aim of this study was to identify the feed strategies to increase the Omega-3 and CLA concentration in milk, without affecting the titles of milk fat. Tests were carried out under controlled experimental conditions and in accomplishment with the common farming reality. The research was divided in three phases. Main object of the first phase was to find the best strategies to increase Omega-3 fatty acids of milk. The second phase collected the tests in which the goal was extended to include the increase also in CLA concentrations. The third phase aimed to enrich the levels of Omega-3 and CLA in milk without affecting the fat titles of milk. The researches were mostly conducted at the didactic-experimental farm of Bologna University; other tests were directed also in commercial farms, in order to respect the common operating conditions. The most effective dietary strategies based on the modification of lipid dietary intake. Supplementation of the ration was mainly based on soybean and relative oil, linseed and relative oil, fish oils and stearic acid. Results from this research show that operating an appropriate and accurate modulation of lipid intake of rations allows to raise the content of fatty acids Omega-3 and CLA in cow's milk, without penalizing the titles of milk fat.

In this thesis two approaches were applied to achieve a double general objective. The first chapter was dedicated to the study of the distribution of the expression of genes of several bitter and fat receptor in several gastrointestinal tracts. A set of 7 genes for bitter taste and for 3 genes for fat taste was amplified with real-time PCR from mRNA extracted from 5 gastrointestinal segments of weaned pigs. The presence of gene expression for several chemosensing receptors for bitter and fat taste in different compartments of the stomach confirms that this organ should be considered a player for the early detection of bolus composition. In the second chapter we investigated in young pigs the distribution of butyrate-sensing olfactory receptor (OR51E1) receptor along the GIT, its relation with some endocrine markers, its variation with age, and after interventions affecting the gut environment and intestinal microbiota in piglets and in different tissues. Our results indicate that OR51E1 is strictly related to the normal GIT enteroendocrine activity. In the third chapter we investigated the differential gene expression between oxyntic and pyloric mucosa in seven starter pigs. The obtained data indicate that there is significant differential gene exression between oxintic of the young pig and pyloric mucosa and further functional studies are needed to confirm their physiological importance. In the last chapter, thymol, that has been proposed as an oral alternative to antibiotics in the feed of pigs and broilers, was introduced directly into the stomach of 8 weaned pigs and sampled for gastric oxyntic and pyloric mucosa. The analysis of the whole transcript expression shoes that the stimulation of gastric proliferative activity and the control of digestive activity by thymol can influence positively gastric maturation and function in the weaned pigs.

Il microbiota intestinale riveste un ruolo importantissimo nell’influenzare la salute dell’ospite. È stato dimostrato come la composizione della dieta possa condizionare lo stato di benessere dell’animale, inducendo importanti cambiamenti tra le popolazioni batteriche che coabitano l’intestino; l’uso di prebiotici rappresenta una delle strategie maggiormente impiegate per modulare positivamente la composizione ed il metabolismo dell’ecosistema gastroenterico. Il presente progetto di dottorato si è proposto di indagare gli effetti sul microbiota intestinale del cane e del gatto di diete a diverso tenore proteico e contenenti proteine di diversa digeribilità in presenza o meno di sostanze prebiotiche. Inoltre, sono stati valutati gli effetti della presenza di un estratto di Yucca schidigera e di tannini sulla microflora intestinale del gatto. In ultima istanza, sono state valutate le conseguenze di dosi crescenti di lattosio sul benessere intestinale del cane. I risultati del presente studio hanno rilevato come le sostanze prebiotiche influiscono sulla composizione e sul metabolismo della microflora del cane e del gatto, e come l’impiego di diete ricche di proteine possa avere conseguenze negative sull’ambiente intestinale. Tuttavia, la presenza di oligosaccaridi non sembra contrastare gli effetti negativi che diete ad alto tenore proteico potrebbero avere sull’ecosistema intestinale dell’animale. Nella successiva prova è stato evidenziato come l’inclusione nella dieta di estratti di Yucca e tannini possa contribuire a mitigare l’emanazione di sostanze maleodoranti dalle deiezioni degli animali da compagnia. Nel corso dell’ultima prova, nonostante non siano state osservate differenze tra le popolazioni microbiche intestinali, la somministrazione di dosi crescenti di lattosio ha indotto una certa riduzione delle fermentazioni proteolitiche microbiche. Ulteriori studi sono necessari per stabilire in che misura la dieta e gli alimenti “funzionali” possano influire sul microbiota intestinale del cane e del gatto e come queste informazioni possono essere utilizzate per migliorare miratamente l’alimentazione e lo stato di salute degli animali da compagnia. / The microbiota of the large intestine plays a fundamental role in maintaining the state of health of the gastrointestinal tract and the host. Considerable evidence suggests that dietary macronutrients and prebiotic substances may affect microbial composition and activity. Knowledge about the modulation of canine and feline intestinal microbiota in response to macronutrients and prebiotic supplementation is limited. However, such information is necessary to investigate further the complex interplay between host and intestinal microbiota in response to changes of diet. The research for this PhD thesis focused upon the changes of the intestinal microbiota and bacterial metabolites of dogs and cats, in response to feeding diets differing in their protein content and digestibility, and containing or not a source of prebiotics. Additionally, the effects of tannins and Yucca schidigera extract on feline intestinal microbiota were evaluated. Furthermore, aim of the last trial was to evaluate the effect of increasing level of lactose on composition and metabolism of dog intestinal microbiota. The results from the present thesis show that different prebiotics exert different effects on the composition and activity of canine and feline intestinal microbiota and that high dietary protein levels can have negative effects on the animal intestinal environment. However, administration of oligosaccharides doesn’t seem to counteract the negative effects that can be observed when companion animals are fed high-protein diets. In the other study, Yucca extract and tannins does not affect feline fecal microbiota. Despite this, a reduction of odour components was observed due to fermentation of substrates. Finally, results from the final study showed no difference between treatments on canine microbial population. However, proteolytic compounds were decreased by lactose. Future studies must determine how diet composition and prebiotic supplementation affect the gut microbiota and how this information may be used to improve diets and the host’s health.

Questa tesi descrive lo stato delle conoscenze degli effetti tossici da micotossine su animali d allevamento, ed alcuni esperimenti condotti per valutare gli effetti indotti da esposizione cronica da micotossine sui ruminanti. Uno studio è stato condotto su 15 aziende specializzate in sistemi di produzione intensiva di carni bovine, situate nel Nord Italia (province di Verona e Mantova), con l'obiettivo di individuare i rischi d esposizione a contaminazione da micotossine. Alcuni metodi di laboratorio sono stati sviluppati: un metodo per la determinazione di ocratossina A (OTA) accumulata in tessuti e organi; Un metodo per valutare gli effetti delle fumonisine sulla biosintesi delle basi sfingoidi sfingosina (So) e sfinganina (Sa); Un metodo per rilevare l addotto AFB1-albumina. La razione totale mescolata (TMR) è risultata positiva alla AF e FB. Tra i singoli alimenti, il mais e la semola glutinata di mais sono stati i principali responsabili della contaminazione del TMR. Il livello di contaminazione è positivamente correlato al contenuto di umidità di mais. Il metodo per la determinazione dell OTA nei tessuti ed organi ha mostrato un buon recupero medio. L'analisi del rapporto Sa/So nel sangue non ha mostrato alcun effetto negativo delle fumonisine sulla biosintesi lipidica. L'addotto AFB1-albumina è risultato positivo per il 18% dei campioni totali di sangue. / The thesis describes the state of knowledge about toxic effects of mycotoxins on farm animals, and some experiments conducted to assess effects induced by chronic exposure to mycotoxins on ruminants. A field study for was carried out on 15 farms specialised for intensive beef production system, located in Northern Italy (provinces of Verona and Mantova), with the aim to identify risks of exposure to mycotoxins contamination. Some laboratory methods were performed: a method for the detection of ochratoxin A (OTA) concentration in tissues and organs; a method for evaluating the effects of fumonisin on biosynthesis of the two sphingoid bases sfingosine (So) and sphinganine (Sa); a method to detect the AFB1-albumin adduct. Total mixed rations (TMR) resulted positive for AF and FB contamination. Among single feedstuffs, corn and corn gluten feed were the main responsible for TMR contamination. Level of contamination was positively related to corn moisture content. The method for the determination of OTA in tissue and organ showed a good mean recovery. The analysis of ration Sa/So in blood did not show any negative effect by fumonisin on the lipidic biosynthesis. The AFB1-albumin adduct was positive on 18% of total blood samples.