NEW PERSPECTIVES IN LIVESTOCK NUTRITION TO IMPROVE HEALTH AND PERFORMANCE

In the last years the livestock and poultry farming are dealing with important changing, characterized by an increase in animal product demand, which must be associated with greater sustainability of animal production sector. In these light different measures are under investigation, involving biosecurity, genetics, health care, farm management, animal welfare and nutrition, to prevent diseases and promote animal health. The main objectives of this thesis were to investigate 1) the effects of yeasts (Chapter 3, 4 and 5) and nucleotides (Chapter 6) supplementation as feed additives to improve animals’ performance and gut health, and 2) the in vivo and in vitro efficacy of an essential oil-based compound (EOC) to inhibit sporulation and thus to prevent oocysts from becoming infectious in Holstein dairy calves (Chapter 7). Therefore, the beneficial effects of yeasts and yeast derived products in horse nutrition have been firstly reviewed (Chapter 3). Then an in vivo trial (Chapter 4) was performed to investigate the effects of Saccharomyces cerevisiae supplementation in mature horses’ diet, in a crossover experimental design, considering changes in body weight and feed consumption of treated animals together with a focus on the apparent digestibility of dietary fibrous fractions using Acid Insoluble Ash as marker in the faeces. The obtained results outlined no significant changes in body weight and feed intake in yeast-fed horses, while apparent digestibility was improved for dry and organic matter, neutral detergent fibre, acid detergent fibre, hemicellulose, and cellulose in treated animals. The administration of live yeast to mature horses showed positive effects of the digestibility of the fibrous fractions of a high frorage:concentrate ratio diet. A second study (Chapter 5) was aimed to investigate the effects of a combination of three different yeasts strain supplementation to weaning piglets, on animal performance and gut health. The obtained results did not show a significant improvement of growing performance, but differences in faecal consistency depending on the experimental week. Yeast-fed piglets showed improved ileum morphological and histochemical parameters, as 16S rRNA sequencing for faecal microbial community outlined decreased abundance of potential pathogens bacteria and increased presence of beneficial bacteria. The administration of a compound containing a combination of three yeasts in weaned piglet showed to improve the gut health on treated animals. In the third study (Chapter 6) nucleotides’ administration in broiler was tested when provided in drinking water during critical phases of the production cycle. Growth and slaughter performance, and the incidence of footpad lesions were investigated in a 42-days trial. No significant effect of nucleotides supplementation on broilers’ performance and footpad lesions were evidenced during the trial. The observed lack of effectiveness for nucleotides supplementation can be partially attributed to the mitigation effect of the optimal rearing conditions provided in the experimental farm during the trial. The last study (Chapter 7) was aimed to assess whether the administration of an essential oil-based compound was able to reduce the excretion of oocysts of Eimeria spp., in vitro and in vivo with the aim to improve animal health and performance. The in vitro study showed no effectiveness of the product to inhibit the Eimeria oocysts sporulation, stating that the product was unable to prevent the acquisition of infection. The in vivo study performed on Holstein dairy calves between the 21st and the 120th day of life did not evidenced significant differences on growing performance and faecal score and the supplementation of the essential oil-based compound did not affect the number of oocysts eliminated in the feces, although a significant reduction in the number of oocysts per gram of feces (OPG) emitted over time in both groups was observed. Overall, these results contributed to the investigation of nutritional strategies to improve the animal health and growth performance. Nevertheless, further investigations are suggested to improve our knowledge about the gaps that have been observed.