OPTIMIZING MONOGASTRICS AND RUMINANTS GUT HEALTH TO FACE WEANING TRANSITION CHALLENGES

The weaning transition represents one of the most critical phases of the cycle of production, in which monogastrics and ruminants are susceptible to environmental, social, and nutritional stressors that may favor the outburst of multifactorial diseases. Among them, gastroenteric pathologies represent a major cause of economic loss and antimicrobials usage. Feed additives represent a key tool to shape the gut health of monogastrics and ruminants during weaning transition. As depicted by current European legislation, antimicrobials and pharmacological dosages of zinc and copper for growth-promoting purposes are no longer allowed due to public health and environmental issues which brought lower limits of inclusion in feeds, especially concerning zinc and copper. Continuous research of different solutions able to guarantee an effective modulation of gut health is strongly needed. Weaning changes in the gut environment involves a dynamic interplay between the gut barrier and the microbiota. Nevertheless, the balance among microbial niches and the enteric environment can be perturbed during weaning. The purpose of the present thesis was to evaluate different nutritional strategies based on feed additives and verify their effects on gut health and microbiota of piglets and dairy calves during weaning. In chapter 6 is described an in vitro characterization of a blend of carvacrol, tannic acid and medium chain fatty acids (MCFAs) supplemented in weanling piglets. Published results showed the potential of the blend in ameliorating gut barrier integrity and morphological characteristics, having notable reflexes in terms of salivary cortisol as biomarker of intestinal health, fecal score and gut microbiota composition. After the ban on pharmacological dosages of zinc and copper, the need to deeply investigate their relationship in dietary interventions was particularly evident. In chapter 7, the administration of different ratios of zinc and copper administered via specialty oxide sources in weanling piglets was evaluated. The unbalanced administration of Zn and Cu can be detrimental to intestinal permeability and immune parameters during early post-weaning phases, as confirmed also by evident microbiota variations in terms of compositional distances and taxa. The dietary supplementation of Bacillus spp. strains has not been extensively investigated in calves during weaning. A third study (chapter 8) was focused on the administration of Weizmannia faecalis strain DSM32016 in Italian female Holstein calves’ diet. Results highlighted the effectiveness of the treatment in conditioning the circulating immunoglobulins level, the antioxidant status and the fecal microbiota features, ameliorating growth performance and fecal score. The possibility to evaluate further alternative strategies to counterattack diarrheal disorders in piglets was explored during a 6-month secondment at the Department of Animal and Veterinary Sciences of Aarhus University (Denmark). In particular, an immunostimulant parenteral vaccine targeting secretory IgA production was tested to prevent E. coli induced post weaning diarrhea. As this project is on-going, a brief report of this experience is reported in chapter 9. As discussed in chapter 10, the tested solutions outlined their validity as a preventive tool to enhance gut health and animals’ performance during weaning also by establishing a balanced microbiota, possibly promoting the reduction of antimicrobial-based treatments and decreasing the manifestation of gastroenteric disorders.