IMPACT OF FUNCTIONAL FOODS ON GUT HEALTH OF POST-WEANING PIGLETS

Post-weaning is the most crucial period in pig management. Associated with weaning are marked changes to the histology and biochemistry of the gut which cause decreased digestive and absorptive capacity and contribute to post-weaning diarrhoea. In last years, the interest in developing management and feeding strategies to stimulate gut development and health in newly-weaned pigs was increasing. In order to increase general health in post-weaning piglets and be alternative to in-feeding antibiotic, three trials were created in this thesis to determine the utilizations of some functional foods which have been widely used to improve growth performance while minimizing the use of antibiotics and rather expensive feed ingredients in weaned piglets. We utilized essential oils (Thymol and Cinnamaldehyde, EO) and/or enzymes (Xylanase and β-glucanase, XB) in the first 2 trials. The first trial mainly focused on the effects of those additives on general parameters such as performance and digestibility of weaned piglets. To investigate the possible protective effects of EO and/or XB on health status in weaned piglets, we created a model of challenge using Escherichia coli in the second trial. After first two investigations, we intended to enlarge the categories of functional foods and determine the effects on regulation of systemic inflammatory reaction and, in addition, we supposed that initial body weight might also influence the regulation. Therefore, the third trial was desined to determine the effects of dietary cocktail (bovine colostrums, cranberry extract, encapsulated essential oil, yeast-derived products, the probiotic Pediococcus acidilactici MA18/5M, vitamins A, D, E and B complex, seleno-methionine) and body weight on inflammatory cytokines and time responses under Lipopolysaccharides challenge in early weaned piglets. In the first trial, a total of 192 weaned piglets (Stambo HBI Dalland 40, 24 d) with an average initial body weight of 8.10 kg were allocated according to body weight into 4 experimental treatments (12 replicates per treatment with 4 piglets per replicate). Each group was fed the basal diet alone or supplemented with either essential oils or enzymes, or their combination. There was no effect of essential oils and/or enzymes supplementation on the growth performance of piglets. However, the combination of essential oils and enzymes decreased feed conversion ratio during the last week. Although the fecal digestibilities of all the piglets were increased from d 21 to 35 (P < 0.001), no effect of essential oils or enzymes or the combination on the fecal digestibility was observed. All the additives significantly decreased counts of Coliforms at 42 days of the trial (P < 0.001). Dietary enzymes improved gut morphology by decreasing crypt depth, increasing villus:crypt ratio and reducing the number of macrophages (P < 0.001). Supplementation of essential oils and the combination with enzymes also improved gut morphology by decreasing crypt depth (P = 0.065; P < 0.001), and decreasing the number of lymphatic follicles (P = 0.002; P < 0.001) and macrophages (P < 0.001). No effect of additives on mRNA expression of inflammatory cytokines was observed in ileal mucosa. Results showed that diet supplementation with EO and/or XB had positive effects on intestinal bacterial counts and gut morphology, although there was no significant diet effect on grow performance or digestibility. In the second trial, 192 weaned piglets (Stambo HBI Dalland 40, 8.64 kg) were allocated according to body weight into eight experimental treatments (6 replicates per treatment with 4 piglets per replicate). The treatments were in a factorial arrangement: 1) dietary treatments [a weaned piglet control diet (CTR), CTR + 0.05 g/kg essential oils (EO), CTR + 0.1 g/kg enzymes (XB), and CTR + 0.05 g/kg EO + 0.1 g/kg XB] and 2) with or without an E. coli challenge. On d 8, half of piglets in each dietary group were challenged with E. coli. E. coli challenge significantly impaired growth performance, induced severe diarrhea, increased populations of E. coli, Clostridia and Coliforms, depressed antioxidant activities, damaged gut morphology and promoted TLR-4 and TNF-α mRNA expression in ileal mucosa (P < 0.05). In the E. coli challenge group, dietary enzymes or combinated with essential oils improved feed efficiency compared with control treatment during the last week (P = 0.025; P = 0.020). The Coliforms populations in the cecum of challenged piglets fed combination of essential oils and enzymes were lower than control treatment (P < 0.001). In the E. coli challenge group, supplemented essential oils and/or enzymes improved gut morphology by increasing villus height and villus:crypt ratio and decreasing crypt depth (P < 0.001). The positive effects on intestinal bacterial counts and gut morphology suggests that supplementation of EO and/or XB might improve the protective capacity against pathogenic bacteria when piglets were submitted to a bacterial challenge. In the third study, a total of 256 Yorkshire × Landrace weaned piglets (20 ± 1 d) were allocated into eight experimental treatments (8 replicates per treatment with 4 piglets per replicate). The treatments were in a factorial arrangement: 1) dietary treatments: a basal weaning diet added [spray-dried plasma protein (PP) (CTR), PP + antibiotic (ATB), PP + dietary cocktail (DC), or bovine colostrum + the dietary cocktail (BC+DC)] and 2) low weight (LW) or high weight (HW). At 37 d of age, 2 piglets in each pen were injected with LPS. Stimulations of LPS and PMA in PBMCs of piglets significantly induced TNF-α, IL-8 and IL-10 (P < 0.05). There was no diet effect on the concentrations of TNF-α, IL-8 and IL-10 in PBMCs of piglets (P > 0.05). Piglets had low weight tended to increase the concentration of IL-8 (P = 0.106) and IL-10 (P = 0.098) in the PBMCs stimulated by LPS 0.5µg/ml LPS and the concentration of IL-10 (P = 0.097) in PMA stimulated PMBC compared with high weight animals. Infection with LPS increased (P < 0.001) serum concentrations of all the cytokines four hours post inoculation, and animals recovered to basal levels at 18 h after challenge. No significant diet effect was found in the serum concentrations of cytokines (P > 0.05). At 4 h after challenge, low weight piglets had partially greater serum concentrations of TNF-α (P = 0.046), IL-6 (P = 0.158), IL-8 (P = 0.179) and IL-10 (P = 0.185) than high weight animals. Dietary cocktail or combined with bovine colostrum may replace plasma protein and antibiotics and weight difference may influence the production of inflammatory cytokines after infected by LPS. In conclusion, we observed that supplementation of functional foods as essential oils and enzymes might strengthen protective capacity of weaned piglets against pathogenic bacteria by decreasing negative intestinal bacterial counts and improving gut morphology. Dietary cocktail or combined with bovine colostrums, at the amount used in this work, may replace plasma protein and antibiotics. Besides, weight difference may influence the production of inflammatory cytokines after infected by LPS.