STIMULATION OF THE HEALTH AND PRODUCTIVITY OF NURSING AND WEANED PIGLETS.

Summary: Worldwide the swine industries are under pressure to reduce the use of antibiotics while maintaining animal health and performance. In 2006 all the AGP (antibiotic growth promoters) and some feed additives with growth promoting activities were banned (Cu, Zn). Since the first restrictive measures were taken, and due to the beginning of the negative consequences of the ban, numerous efforts have been done to find alternatives or replacement strategies to maintain pig growth performance and controlling enteric bacterial diseases. Therefore, the following studies aimed to find ways to control additive efficacy with due consideration to animal welfare and consumers requirements. The main objective of this thesis was to improve our knowledge on the properties of new additives as feeding strategy and oral vaccination to improve general and gut health in young pigs with the aim to substitute antibiotics growth promoters. To achieve these objectives, three different trials were designed to study different strategies to improve the gut health of the post-weaning piglets. I) Evaluation of the immune response against ovalbumin (OVA) in pigs orally vaccinated with OVA in tablets containing carboxymethyl high amylose starch (CM-HAS), flagellin and sow’s milk. This trial was designed with the aim to determine the effects of a new delivery system designed for oral vaccination or delivery of bioactive molecule in the gut. The trial was also designed to evaluate the potential of the sow’s milk to modulate the systemic as well as local immune response against the antigen ovalbumin incorporated in the vaccine. Sixteen piglets of 28 days (d) of age were divided into 4 groups of 4 animals each. The first group was vaccinated with compressed tablets containing only ovalbumin (OVA); the second group was immunized with tablets containing ovalbumin and the B subunit of the flagellin from Salmonella enterica Typhimurium (OVA-FLA); the 3rd and 4th groups were immunized with tablets containing ovalbumin pre-incubated in sow milk with or without flagellin, respectively (OVA-LT or OVA-LT-FLA). The oral vaccination was performed in two periods of three days; the 1st period being from day 28 to day 30 of age (D1-D3 of the trial) and the 2nd from 42 d to 45 d of age ( D14-D16). Blood samples were collected at days 1, 14, 21, 28 and 42 of the trial to determine, by ELISA, serum antibody titre against OVA. Feces samples were also collected before the first immunization and intestinal content from the ileum was collected at slaughtering to evaluate level of IgA anti-OVA by ELISA. All the animals were euthanized 42 days post-immunization to collect blood, mesenteric lymph nodes (MLN) and ileum content. The immune cells were isolated from the MLN and from blood and cultured with OVA to evaluate the lymphocyte proliferative response by flow cytometry (CFSE cell proliferation kit) and production of the main cytokine produced in adaptative immune response such as Interleukine-2 (IL-2) , IL-4, IL-10 and interferon-gamma (IFN-γ). Experimental animal studies have indicated that oral administration of antigens targets the systemic T cell compartment, diminishes cell-mediated immune responses, and induces tolerance. This phenomenon might lead to the induction of cytokines such as Transforming Growth Factor beta (TGF–β) and IL-10, and consequently enhance antigen-specific antibodies such as IgA and IgG. While the humoral immune response is critical in the control of some mucosal pathogens, those effects might be inappropriate on other mucosal pathogens where cell mediated immune responses may play a larger role. II) Milk rice in piglet nutrition: benefits or not? Rice milk has been shown to contain a high sugar level and antioxidants such as Ɣ-Oryzanol. For this reason the effects on growth performance and health status of piglets have been studied on 36 litters from (Landrace x LargeWhite) x Penerland sows. At 10 days after birth 18 litters were supplemented with rice milk (T) until weaning while the others 18 received creep feed (C). At 21 days a total of 288 piglets were weaned. Half from each group (72 piglets) were randomly assigned to either control (C) or treated (T), so there were four experimental piglet groups: C-C, C-T, T-C and T-T. All the animals received a pre-starter (0-14 d post weaning) and a starter (14-42 d pw) diets. Piglets from C-T and T-T groups were also supplemented with rice milk from weaning to 14 days pw. Piglets of T-C group had significantly higher weight at 42 d pw (P<0.01), an higher average daily gain (ADG) and dry matter feed intake (DMFI) (P< 0.01). Rice milk supplementation had no influence in glucose, urea, total protein and lysozyme. Reactive oxygen metabolites (ROMs) levels resulted lower in T-T piglets than C-C and C-T groups at 14 d-post w. (P<0.05). Total antioxidant capacity was higher in C-C and C-T than TC piglets at 14 d after weaning (P<0.05). The data from this trial suggest that rice milk was associated with greater post weaning growth and health status when supplementation was given only during the nursing period. III) Effects of plant polyphenols and mannan oligosaccharide on growth performance, antioxidant defense system and gut health in Escherichia coli Challenged piglets Objective of the current study was to evaluate the effects of plant polyphenols (PP) and/or, mannan oligosaccharide (MOS) on growth performance, plasma antioxidant capacity and health in E. Coli-challenged weaned piglets. Ninety-six piglets (7.43 + 0.89 kg L.W., 21 d age) were randomly allotted into 4 dietary treatments: control (basal diet), 0.1% PP, 0.1 % MOS or PP+MOS in a 5 weeks study. At 21 and 25 d on trial half piglets of each group were orally inoculated with 4 ml of E.coli (1×109 cfu/ml) and half with the same amount of saline water. No difference was observed in growth. Plasma urea was markedly increased in PP+MOS group compared to PP group (P< 0.05), and lysozyme content was significantly decreased in PP+MOS group compared to groups on d 7 (P< 0.05). PP+MOS dietary supplementation decreased intestinal lipase and trypsin compared to PP on d 21 (P< 0.05). Plasma malondialdehyde content (MAD) increased, while plasma total antioxidant capacity (TAOC) and catalase (CAT) activities decreased in piglets 6 days after infection. Challenged piglets fed PP and those fed MOS showed higher TAOC than challenged piglets fed PP in combination with MOS. CAT activity resulted higher in challenged piglets fed diet supplemented with PP or PP+MOS than control or MOS at d 13 after infection (P< 0.05). The results showed that dietary PP or MOS had the potential to improve enhance systemic antioxidant capacity. However no synergic effect was observed when PP and MOS were combined. General conclusions During the weaning period, several factors affecting the welfare and health of piglets with a consequently effect on the productive performance of the animals. One of the key factors for high growth performance is the maintenance of a healthy gut. The presence of a balanced enteric microflora which may protect the piglets from weaning common bacterial infections, has a general beneficial effect on the health of the animal. What we tried to demonstrate with this thesis is that we are running the correct way to find alternatives substances to protect the gut health of our piglets, but more research will be needed to understand different techniques such the oral vaccination of the animals.