Dietary strategies to minimize the detrimental impact of weaning on gut morphology, physiology and microbiota of piglets

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.

Biodegradable systems for the development of functional materials

This PhD work was aimed to design, develop, and characterize gelatin-based scaffolds, for the repair of defects in the muscle-skeletal system. Gelatin is a biopolymer widely used for pharmaceutical and medical applications, thanks to its biodegradability and biocompatibility. It is obtained from collagen via thermal denaturation or chemical-physical degradation. Despite its high potential as biomaterial, gelatin exhibits poor mechanical properties and a low resistance in aqueous environment. Crosslinking treatment and enrichment with reinforcement materials are thus required for biomedical applications. In this work, gelatin based scaffolds were prepared following three different strategies: films were prepared through the solvent casting method, electrospinning technique was applied for the preparation of porous mats, and 3D porous scaffolds were prepared through freeze-drying. The results obtained on films put into evidence the influence of pH, crosslinking and reinforcement with montmorillonite (MMT), on the structure, stability and mechanical properties of gelatin and MMT/gelatin composites. The information acquired on the effect of crosslinking in different conditions was utilized to optimize the preparation procedure of electrospun and freeze-dried scaffolds. A successful method was developed to prepare gelatin nanofibrous scaffolds electrospun from acetic acid/water solution and stabilized with a non-toxic crosslinking agent, genipin, able to preserve their original morphology after exposure to water. Moreover, the co-electrospinning technique was used to prepare nanofibrous scaffolds at variable content of gelatin and polylactic acid. Preliminary in vitro tests indicated that the scaffolds are suitable for cartilage tissue engineering, and that their potential applications can be extended to cartilage-bone interface tissue engineering. Finally, 3D porous gelatin scaffolds, enriched with calcium phosphate, were prepared with the freeze-drying method. The results indicated that the crystallinity of the inorganic phase influences porosity, interconnectivity and mechanical properties. Preliminary in vitro tests show good osteoblast response in terms of proliferation and adhesion on all the scaffolds.