This study investigated intestinal physiology of piglets at weaning. Piglets (n = 60) weaned at 21 d were food deprived for 2 d and then tube-fed using 2 different diets (a conventional diet vs. a wheat-enriched diet). They were slaughtered at d 0, 2, 5, 8, or 15 postweaning. Jejunum, ileum, and colon were mounted in Ussing chambers. In addition, segments of the proximal jejunum of 4 growing pigs were studied 35 d after weaning. Secretory function was assessed by basal short-circuit current (Isc) and secretagogue-stimulated Isc. Glucose absorption was measured by the increase in Isc after the addition of glucose. Epithelial barrier function was measured by transmucosal resistance (R) and horseradish peroxidase (HRP) fluxes across the epithelium. There were no significant differences between the pigs fed the 2 diets for any of the parameters studied. As already reported, a transient villous atrophy was observed. At the same time, we observed an increased basal Isc in jejunum and colon, increased glucose absorption and a dramatic drop of R in jejunum. These parameters had returned to preweaning values by d 5. Weaning was also followed by long-lasting modifications. In jejunum, responses to the secretagogues and glucose absorption were decreased at wk 2 after weaning and were not different between d 15 and 35. Ileal transmucosal resistance increased on d 5 and was stable thereafter. HRP flux in jejunum declined on d 2 and stayed at this low level throughout the experiment. We conclude that weaning induces transient dramatic changes in intestinal physiology but is also a period of maturation of the intestine.

We studied the effects of amounts of colostrum consumed on intestinal morphology and proliferation and digestive enzyme activities in neonatal calves. Group GrCmax calves were fed colostrum from the first milking undiluted on d 1-3 and diluted with 25, 50, 75 and 75 parts of a milk replacer on d 4-7. Group GrC1-3 calves were fed colostrum from milkings 1-6 up to d 3 and then a milk replacer up to d 7. Group GrF1-3 calves were fed a milk-based formula (containing only traces of growth factors and hormones) up to d 3 and then a milk replacer up to d 7. Calves were killed on d 8. Differences in feeding affected villus sizes and villus height/crypt depth ratios in the duodenum (GrCmax > GrC1-3), villus areas and villus height/crypt depth ratios in the jejunum (GrC1-3 > GrF1-3) and crypt depths in the colon (GrF1-3 > GrC1-3). Furthermore, different feeding protocols affected the proliferation rates of epithelial cells in the duodenum (GrC1-3 > GrCmax; GrC1-3 > GrF1-3) and the jejunum (GrF1-3 > GrC1-3; based on Ki-67 labeling). Lipase activities in the pancreas were influenced by colostrum feeding (GrC(max) > GrC(1-3)). Colostrum intake differentially affected intestinal epithelial surface and proliferation and enzyme activities. Feeding high amounts of first colostrum seemed to enhance the survival of mature mucosal epithelial cells in selected parts of the small intestine, whereas the lack of colostrum seemed to decrease epithelial growth.

Reducing the CP content and increasing the fermentable carbohydrates (FC) content of the diet may counteract the negative effects of protein fermentation in newly weaned piglets fed high-CP diets. To study the synergistic effects of CP and FC on gut health and its consequences for growth performance, 272 newly weaned piglets (26 d of age, 8.7 kg of BW) were allotted to 1 of 4 dietary treatments in a 2 x 2 factorial arrangement, with low and high CP and low and high FC content as the factors. Eight piglets from each dietary treatment were killed on d 7 postweaning. Feces and digesta from ileum and colon were collected to determine nutrient digestibility, fermentation products, and microbial counts. In addition, jejunum tissues samples were collected for intestinal morphology and enzyme activity determination. During the entire 4-wk period, interactions between the dietary CP and FC contents were found for ADFI (P = 0.022), ADG (P = 0.001), and G:F (P = 0.033). The high-FC content reduced ADFI, ADG, and G:F in the low-CP diet, whereas the FC content did not affect growth performance in the high-CP diet. Lowering the CP content of the low-FC diet improved ADFI and ADG, whereas lowering the CP content of the high-FC diet did not influence growth performance. The low-CP diets resulted in a lower concentration of ammonia in the small intestine (P = 0.003), indicating reduced protein fermentation. In the small intestine, the high FC content increased the number of lactobacilli (P = 0.047), tended to decrease the number of coliforms (P = 0.063), tended to increase the lactic acid content (P = 0.080), and reduced the concentration of ammonia (P = 0.049). In the colon, the high-FC diets increased the concentration of total VFA (P = 0.009), acetic acid (P = 0.003), and butyric acid (P = 0.018), and tended to decrease the ammonia concentration (P = 0.076). Intestinal morphology and activity of brush border enzymes were not affected by the diet, although maltase activity tended to decrease with increasing dietary FC (P = 0.061). We concluded that an increase in the dietary FC content, and to a lesser extent a decrease in the CP content, reduced ammonia concentrations and altered the microflora and fermentation patterns in the gastrointestinal tract of weaned piglets. However, these effects were not necessarily reflected by an increased growth performance of the piglets.

Glucagon-like peptide 2 (GLP-2) may mediate in part the rapid growth effects of luminal nutrients in the small intestine of newborns. The objectives of this study were to determine plasma GLP-2 concentrations and small intestinal GLP-2 receptor (GLP-2R) mRNA abundance (measured by reverse transcription polymerase chain reaction) during pre- and postnatal development and the relationship between these variables and small intestinal growth in enterally and parenterally fed fetal and newborn pigs (premature and term-delivered, 92 and 100% gestation, respectively). Plasma GLP-2 concentrations increased before birth, peaked in suckling 1-d-old pigs (87 +/- 14 pmol/L, P < 0.05), decreased with weaning-related anorexia (34 +/- 5 pmol/L, P < 0.05) and increased when normal food intake resumed (81 +/- 9 pmol/L, P < 0.05). Plasma GLP-2 concentrations were increased 1 d after enteral infusion of colostrum in fetal pigs at 92% gestation compared with untreated controls (59 +/- 11 vs. 7 +/- 2 pmol/L, P < 0.05). In newborn pigs, plasma GLP-2 was increased 2-6 d after the enteral administration of a milk diet, compared with the parenteral infusion of elemental nutrients, but the time course of the response was delayed in premature newborn pigs. Small intestinal GLP-2R mRNA abundance was highest at birth and decreased with enteral food intake in fetal, suckling and weaned pigs (P < 0.05). In contrast, enteral feeding increased (P < 0.05) relative small intestinal weight and/or villous heights in these pigs. We conclude that the introduction of enteral feeding transiently increases plasma GLP-2 concentrations and decreases small intestinal GLP-2R mRNA levels during pig development. GLP-2 may play a role in the growth of the small intestine around birth and weaning via a response to enteral nutrition.

-Two trials involving a total of 56 pigs were conducted to examine the effects of weaning at 7 d of age (trial 1) and of energy intake level and length of post-weaning underfeeding period (trial 2) on small intestinal (SI) development and morphometry. At 3 d after weaning, weight of the SI and mucosa (g/kg body weight) and villous height along SI were reduced by 20, 36 and 41%, respectively, compared to the day of weaning. Intestinal morphometrical changes are dependent on SI site and days post-weaning. Villous atrophy on d 3 and recovery on d 14 post-weaning were greater and occurred earlier in the proximal than in the medial and distal SI. Villous height was dependent on the level of energy intake which explains 56% of the variations in proximal SI villous height in weaned pigs and 73% when data of the sow-reared pigs were included in the analysis. Moreover, after 4 d of refeeding, underfed piglets showed similar villous characteristics to piglets fed a continuously high feeding level after weaning stressing that capacities of intestinal restoration were not affected by the length of the post-weaning underfeeding period. Overall, the present results suggest a spatial and temporal effect of weaning on villous atrophy and recovery, and that the level of energy intake is a major factor accounting for the post-weaning villous height.weaning / level of food intake / small intestine / morphometry / piglet Reprod. Nutr. Dev. 42 (2002) [339][340][341][342][343][344][345][346][347][348][349][350][351][352][353][354] 339

No abstract

-The impact of dietary factors on the gut morphological maturation is poorly documented in rabbits. The weights of the digestive segments as well as the morphology of villi and crypts along the small intestine were analysed weekly from day 14 till day 49, in two rabbit groups weaned at either 21 (W21 group, n = 12 litters) or 35 days (W35 group, n = 12 litters) of age. From 21 till 35 days, the W21 group ate 57% more solid feed than the W35 group (P < 0.01), and presented slighter body weights from day 28 till day 49 (-9%, P < 0.05). Tissue weights of the empty digestive segments, as expressed relative to the body weights, were higher in the W21 than in the W35 group from day 28 till day 49 (P < 0.001), whereas absolute tissue weights appeared similar (except for the proximal colon). From day 28 to day 49, small intestinal villi grew in height and surface area (P < 0.05) whereas the crypts deepened. Villous height followed a proximo-distal decreasing gradient from the duodenum to the ileum (P < 0.05) from day 28 onward. The villous height to width ratio changed with the beginning of significant solid feed intake: from a thin shape until day 21, villi became wider from day 28 on. The effect of weaning age on mucosal morphology was insignificant, except for the jejunal crypts whose surface area and depth were higher in the W21 group. The present results showed that morphological changes in the digestive tract of young rabbits were weakly influenced by an early stimulation of solid feed intake. gut maturation / rabbit / weaning / intestinal morphology / digestive mucosa

Summary This review summarizes recent advances on blood plasma patterns, receptors, secondary messengers and metabolism of gut regulatory peptides (i.e. gastrin, secretin, somatostatin, cholecystokinin, vasoactive intestinal polypeptide, pancreatic polypeptide, gastric inhibitory polypeptide, motilin), in young ruminants during fetal and perinatal stages, during the preruminant stage and at weaning. It also deals with their role in the digestive tract function and postabsorptive changes. Some pathological situations in young ruminants are considered. Recent molecular aspects of digestive enzyme synthesis are also reported.