Stato nutrizionale e produzione di citochine: effetti sulle performance produttive e riproduttive in specie animali di interesse zootecnico

Abstract

The nutritional and social stress are important factors that affect the neuro-endocrine and immune result in an increase in energy expenditure in animals by affecting the productive and reproductive performance. This thesis focused on certain aspects of this question, taking into consideration the porcine species, that is of great zootechnical interest, but also presents the various types of breeding, needs absolutely different. The common thread that unites this study is given by cytokines, a group of proteins secreted by various cell types which have a variety of functions. For a long time the term cytokine has been associated with immune cells; in the last twenty years, it has been discovered a new tissue seat active production of these factors, the adipose tissue. Adipose tissue has long been traditionally considered as a tissue dedicated to the storage of energy. However, already in the 50s Kennedy postulated the existence of a factor produced by adipocytes able to act centrally by inhibiting food intake and increasing energy expenditure, when the body weight exceeds the so-called threshold value. The discovery, in 1994, by Zhang (Zhang et al., 1994) of the ob gene and its gene product, leptin, has induced the study of the mechanism of homeostatic regulation of body weight and obesity. In fact, the axis leptin has proved much more complex than expected, and in the years studies on adipose tissue have multiplied leading to consider the adipose tissue as an endocrine organ. As a result of the increasing attention devoted to the study of adipose tissue in recent years, the current understanding of the biology of adipocytes and their role in physiology and pathology has greatly improved. In the veterinary field, the interest born around this tissue has a double feature. The first, along with human medicine, linked to the aspect of obesity that afflicts pets. The second concerns the physiology to understand how the adipose tissue and what is the role of the molecules it produces, to improve zootechnical productions. In fact, adipose tissue is involved in the regulation of the immune and endocrine systems and the factors expressed by adipocytes are related to the quality of animal products. The genetics of pork meat quality is the subject of research and its study is now essential to meet the demands of conscious consumer organoleptic quality of the products. The meat quality is influenced by a large number of factors and the adipose tissue is able to adjust the composition of the carcass. So, my work has focused on an important species, the swine. The first part of this thesis focused on the characterization of the adipose tissue of the pig "Nero di Parma" for the good qualities of some of his commercial cuts (lardo, culatello). I evaluated the characteristics of the adipose tissue, the fatty acid composition, comparing it with that coming from commercial breeds. I have analyzed the expression of some adipokines, such as leptin, adiponectin, inflammatory cytokines and not, receptors and transcription factors involved in the regulation of energy homeostasis and lipid metabolism. In a second step, I focused the research on other phases of the production cycle because, at least in an intensive farming, these factors related to the immune system, have a significant economic impact and health. While the pig “Nero di Parma” is raised in the wild and therefore in compliance with the social habits of the species, in intensive breeding animals are present in stressful situations. One of the greatest moments of social stress and nutrition is the period of weaning, with the shift from breast milk to the food dry that causes serious changes to morpho-functional of the gastrointestinal system. My study therefore investigated neuroendocrine and immune status in piglets during lactation and after weaning and evaluated supplementation with nucleotides can improve its ability to respond to stress. The last aspect that I faced in this species has been focused on sows in gestation. Unlike the pregnant females from other species, sows are subject to rationing and can not satisfy the hyperphagia typical gestation pregnancy as excessive adiposity at birth has adverse effects not only on the vitality of piglets but also on the feeding behavior of sows during the subsequent lactation. Moreover, if the production performance of the subjects is already determined in the womb, it is interesting to study the levels of leptin in these subjects and understand what could be the role of this hormone in these subjects.