Modulation of gut health in monogastric animals through nutritional additives

There is a wide interest in developing management and feeding strategies to stimulate gut development and health in monogastric animals. The ultimate aim of these strategies is to improve productivity, while minimizing the use of antibiotics and rather expensive feed ingredients: indeed, under practical conditions, animals don’t achieve the maximum of their growth performance potential. Large amounts of research have been conducted evaluating the impact of a wide range of feed ingredients and feed additives on various aspects of gut health and development in monogastric animals. The main objective of this thesis was to improve our knowledge on the properties of new additives as feeding strategy, in order to increase general health in piglets around weaning and poultry, with the aim to substitute antibiotics growth promoters. Three different trials were designed to study different strategies. In the first study proposed, the effects of plant extract administered through drinking water on post-weaning gut health of piglets were investigated. Phytogenic feed additives are plant-derived products used in animal feeding to improve the performance of agricultural livestock. The objective of the present work was to evaluate the effects of a novel plant extract derived from common food plants on performance and health of weaned piglets fed mixed diet. At weaning (24 d), a total of 144 piglets were allocated in two post-weaning rooms, using a 2x2 factorial arrangement; treatments were Plant Extracts, 0 (Control group) or 8 μl daily/piglet (PE group) and Feeding Regimen, Ad Libitum or Restricted (piglets fed from 8 AM to 8 PM). Plant Extracts were a liquid mixture administered through drinking water. Piglets were housed in pens of three; each pen represented one treatment replicate, with six pens per treatment per room. On day 9 of the trial, after an adaptation period, each piglet of room 2 was orally injected with 4 ml of a solution containing 109 cfu of the virulent E. coli 0149: F4(K88)-positive strain. Animals were weighed and growth performance were recorded weekly; fecal score was evaluated at the same time as the weighing. At 0, 14 and 35 days, fecal samples were collected for microbiological analysis, while at day 0, 6, 19 and 35, blood samples were obtained from one pig per pen. At the end of the trial (35 d), 24 animals (12 from Control groups and 12 from Plant Extract groups) among Restricted feeding piglets were selected according to their body weight and slaughtered; immediately after slaughtering, the gastro-intestinal tract was removed from each animal: the distal ileum was collected and examined to assess the ileum micro-anatomical structure, perform histometry and immunohistochemistry and determine intestinal inflammatory parameters. PE supplementation enhanced ADG during the last week of the trial (P=0.007) and reduced FCR during the second (P=0.009) and the last weeks (P=0.04), and considering the overall period (P=0.01); a lower fecal score was observed in PE piglets (P<0.01). On day 35, lower fecal E.Coli (P=0.02) and Entrobacteriaceae (P=0.009) concentrations were determined in PE animals compared to control ones. Ileum crypts from PE piglets were deeper in challenged animals in comparison with not-challenged ones (P<0.05); number of mucosal macrophages was higher in Control challenged animals (P<0.05): in particular, number of mucosal macrophages in PE challenged piglets was similar to that one identified in not challenged Controls. PE supplementation also increased GSH-Px plasma concentration at d 6 (P=0.02) and tended to lower value of MDA at day 6 (P=0.07) and to increase value of T-AOC at the end of the trial (P=0.07). Hence, our results confirmed the possible protective functional role of the plant extracts mixture after the bacterial challenge: we can postulate that the use of plant extracts may be useful in the prevention of post-weaning diarrhea with an associated improvement in performance. The aim of the second trial was to evaluate the effect of the administration of mannanooligosaccharides (MOS) on growth performance, microbial population in feces and cecum and potential alteration of intestinal histomorphometric and gene expression of some intestinal inflammatory parameters of piglets fed a low digestible diet. Forty-eight weaned piglets (6.72 ± 0.32 kg of BW, 24 d of age) were used in a 35-d experiment and randomly allotted to 2 dietary treatments: basal diet (Control) and basal diet + 0.2 % MOS. Growth performance were recorded weekly, fecal samples were collected at 0, 14 and 35 d. At the end of trial, 10 piglets from each group were slaughtered and intestinal samples were collected. Data were analysed by a General Linear Model (GLM) procedure of SAS. BW, ADG, ADFI were not influenced by MOS supplementation; FCR was lower in treated animals in the last 2 weeks (P<0.05). Mean fecal score was improved in MOS piglets (P<0.01). At the end of trial treated piglets had higher Lactobacilli fecal count (P<0.05). No difference was detected among groups for Coliforms, while lower Clostridia occurred on day 14 in MOS piglets (P<0.05). Intestinal villi height in the duodenum was higher in MOS than Control (P<0.05). MOS supplementation also led to significant increase of NO production in ileal mucosa (P<0.05); finally, MOS suppressed mRNA relative expression of pro-inflammatory genes for IL-1α, IL-1β, IL-6 and TLR2 (P<0.05), for TLR4 (P<0.01) and for TNF (P<0.001), while there was no effect on IL-10 and PPARγ expression. Results indicate that MOS supplementation improved feed efficiency and intestinal morphometry of piglets fed low digestible diet. The third study was carried out to determine the effects of a probiotic mixture containing two strains of Lactobacillus on growth performance, carcass composition, blood lipids, digestive enzyme activity and intestinal microbiota in broiler chickens. Two dietary treatments, consisting of basal diet (control) and basal diet supplemented with combination of L. farciminis and L. rhamnosus were fed to 392 one day-old Ross 708 broiler chicks for 7 weeks. Each treatment had 28 replicates of 7 broilers. The results showed that body weight gain was improved in broilers fed probiotics diet compared to controls during 0-42 d (P<0.001) but not 43-49 d of age. Probiotic fed chicks had transitorily higher serum total cholesterol (P=0.02) and high-density lipoprotein cholesterol (P<0.008) at 28 d of age. Serum total protein was higher at 28 d of age (P=0.02) and lower at 49 d of age (P=0.001) in probiotics fed chicks compared to controls. Probiotics tended to increase abdominal fat percentage at 49 d of age (P<0.10). No difference in enzyme activity of small intestine digesta was observed. Dietary probiotics markedly increased Lactobacilli (P=0.01) and total Anaerobes (P≤0.01) counts and decreased Coliform (P=0.01) and total Aerobe counts (P≤0.01) in small intestine and caecum. The overall results demonstrated that dietary inclusion of a mixture of L. farciminis and L. rhamnosus could promote the growth and positively modulate intestinal microbiota in broiler chickens.