Effects of dietary fiber and starch levels on the non-specific immune response of growing rabbits

Inclusion of Soybean Hulls (Glycine max) and Pupunha Peach Palm (Bactris gasipaes) Nanofibers in the Diet of Growing Rabbits: Effects on Zootechnical Performance and Intestinal Health

This study evaluated the inclusion of nanofibers from soybean hulls and pupunha peach palm heart sheaths in the diet of growing rabbits. Twenty-four New Zealand White rabbits (male and female) were allocated in three experimental groups: control, fed a basal diet; Nanosoy, fed a diet containing 7% soybean-hull nanofibers; and Nanopupunha, fed a diet containing 7% pupunha palm heart-sheath nanofibers. The Nanosoy-group rabbits showed poorer final weight, daily feed intake, and daily weight gain than those in other groups. In the duodenum, villus height, total mucosal thickness, and villus width were higher in rabbits that received nanofiber-supplemented diets than in the controls. Higher villus density and wall thickness were observed in Nanopupunha-fed rabbits than in the controls. In the jejunum, although the crypt depth was higher in Nanosoy-fed rabbits, the villus height:crypt depth ratio was higher in the Nanopupunha-fed group. Nanosoy-fed animals exhibited increased count Enterobacteriaceae populations. Rabbits in both nanofiber-fed groups exhibited higher lactic-acid bacterial counts than those in the control-diet group. Therefore, although the inclusion of 7% Nanopupunha in the diet of rabbits did not alter the performance, it improved intestinal health and increased the lactic-acid bacterial count in the cecum of growing rabbits.

mTOR and ERK1/2 signaling participate in the process of acetate regulating lipid metabolism and HSL expression

Objective

Acetate plays an important role in host lipid metabolism. However, the network of acetate-regulated lipid metabolism remains unclear. Previous studies show that mitogen-activated protein kinases (MAPKs) and mechanistic target of rapamycin (mTOR) play a crucial role in lipid metabolism. We hypothesize that acetate could affect MAPKs and/or mTOR signaling and then regulate lipid metabolism. The present study investigated whether any cross talk occurs among MAPKs, mTOR and acetate in regulating lipid metabolism.

Methods

The ceramide C6 (an extracellular signaling-regulated kinases 1 and 2 [ERK1/2] activator) and MHY1485 (a mTOR activator) were used to treat rabbit adipose-derived stem cells (ADSCs) with or without acetate, respectively.

Results

It indicated that acetate (9 mM) treatment for 48 h decreased the lipid deposition in rabbit ADSCs. Acetate treatment decreased significantly phosphorylated protein levels of ERK1/2 and mTOR but significantly increased mRNA level of hormone-sensitive lipase (HSL). Acetate treatment did not significantly alter the phosphorylated protein level of p38 MAPK and c-Jun aminoterminal kinase (JNK). Activation of ERK1/2 and mTOR by respective addition in media with ceramide C6 and MHY1485 significantly attenuated decreased lipid deposition and increased HSL expression caused by acetate.

Conclusion

Our results suggest that ERK1/2 and mTOR signaling pathways are associated with acetate regulated HSL gene expression and lipid deposition.

Nutritional ecology and ecological immunology in degus: Does early nutrition affect the postnatal development of the immune function?

Environmental conditions experienced by developing animals have an impact on the development and maturity of the immune system. Specifically, the diet experienced during early development influences the maintenance and function of the immune system in young and adult animals. It is well known that exposure to low-protein diets during early development are related to an attenuation of immunocompetence in adulthood. While this functional linkage has been widely studied in altricial models' mammals, it has been little explored how the nutritional history modulates the immune function in precocial animals. We evaluated the effect of dietary protein consumed during early development on the immune function and the oxidative costs in the precocial Caviomorph rodent Octodon degus, or degu. We evaluated components of the acute phase response (APR) and oxidative parameters before and after immune challenge. We found that after the immune challenge, the juveniles on the low-protein dietary treatment exhibited an attenuation of body temperature but showed higher levels of lipid peroxidation than juvenile degus on the high-protein diet. We did not find a significant effect of the interaction between diet and immune challenge on body mass, levels of inflammatory proteins, nor in the total antioxidant capacity. Our results suggest that some components of the immune function and the oxidative status in the degu can be modulated by diet during development. However, the modulation would depend on the immune variables analyzed, and the characteristics of the immune system of precocial rodents.

The Effects of Deoxynivalenol on the Ultrastructure of the Sacculus Rotundus and Vermiform Appendix, as Well as the Intestinal Microbiota of Weaned Rabbits

Deoxynivalenol (DON) is a mycotoxin found in grains that poses a potential threat to human and animal health, and the gastrointestinal tract is the primary target organ. There are few studies focused on the toxicology of DON to rabbits, especially on the relation among DON, microbiota, and the gut-associated lymphoid tissue. A total of 30 weaned rabbits (35 d) were evenly divided into the control group and DON group (1.5 mg/kg bodyweight (BW)) based on their body weight. After a 24-day trial, the ultrastructures of the sacculus rotundus and vermiform appendix were observed using a scanning electron microscope and transmission electron microscopy. The morphology and microflora in the ileum, caecum, and colon were also examined. The results proved that the ultrastructure of the sacculus rotundus and vermiform appendix, as well as the integrity of the intestinal barrier (especially for the ileum), were impaired after DON was administrated to the rabbits. Compared to the control group, the relative abundance and diversity of the microflora decreased in all three intestinal segments in the DON group, particularly in the ileum and caecum. In conclusion, the toxic effect of DON on weaned rabbits may be performed by destroying the structure of the sacculus rotundus and vermiform appendix, as well as affecting the structure and diversity of the intestinal flora.

Effects of dietary-fiber levels on RANK/RANKL/OPG expression in the appendix of weanling rabbits

BACKGROUND/PURPOSE

The dietary fiber can regulate the intestinal mucosal immunity, and the M cell is the portal for initiating mucosal immunity. We investigated the effects of dietary fiber on the transport of Escherichia coli to assess the function of microfold (M) cells in the appendix.

METHOD

A total of 150 New Zealand rabbits were fed three diets (high fiber (HF): 31.72%; control: 37.36%; low dietary fiber (LF): 41.84%; neutral detergent fiber (NDF). An infection model was established in vivo using E. coli containing green fluorescent protein as the indicator in appendix loops. Samples were collected before and after inoculation with indicator for 10, 30, or 60 min. The M cells number, differentiation-related genes and proteins were monitored by respectively using immunofluorescence, Q-PCR and Western-blot.

RESULTS

The number of M cells in HF group was significantly higher than that of LF group before and at 10 min, 30 min post injection with E.coli (P < 0.01), which has an opposite at 60 min. The number of fluorescent E. coli transported across the appendix was significantly increased in the HF group (P < 0.01) compared with the LF group at 30 min (P < 0.001); expression of RANKL gene and protein levels were no difference between HF and LF group. The variation tendency of RANK, OPG genes and proteins were consistent with the change of M cell transport indicator number in different time points.

CONCLUSION

Our study showed that a high-fiber diet can increase number of M cells and speed up antigen transfer under regulation of ANKL/OPG/RANK system.

Diet induced changes in the microbiota and cell composition of rabbit gut associated lymphoid tissue (GALT)

The gut associated lymphoid tissue (GALT) is the largest immune organ of the body. Although the gut transient and mucosa-associated microbiota have been largely studied, the microbiota that colonizes the GALT has received less attention. The gut microbiome plays an important role in competitive exclusion of pathogens and in development and maturation of immunity. Diet is a key factor affecting the microbiota composition in the digestive tract. To investigate the relation between diet, microbiota and GALT, microbial and cell composition of vermiform appendix (VA) and sacculus rotundus (SR) were studied in two groups of New Zealand white rabbits on different diets. Diet shifted the lymphoid tissue microbiota affecting the presence and/or absence of certain taxa and their abundances. Immunohistochemistry revealed that a higher fibre content diet resulted in M cell hyperplasia and an increase of recently recruited macrophages, whereas T-cell levels remained unaltered in animals on both high fibre and standard diets. These findings indicate that diet has an impact on the microbiota and cell composition of the GALT, which could act as an important microbial recognition site where interactions with beneficial bacteria can take place favouring microbiota replacement after digestive dysregulations.

Impact of dietary fiber/starch ratio in shaping caecal microbiota in rabbits

The objective of this experiment was to determine whether changing the dietary neutral detergent fiber (NDF)/starch ratio affected caecal microbiota when 4 different diets (diet A: 2.3 NDF/starch, diet B: 1.9, diet C: 1.4, diet D: 1.0) were formulated. A total of 200 weaned rabbits (35 days old, 50 per group) were used for the experiment, which started after an adaptation period of 7 days (i.e., day 42). Caecal contents were obtained from rabbits fed different NDF/starch diets at 52, 62, 72, and 82 days of life. The bacterial community structure was characterized by high-throughput 16S rRNA sequencing. Firmicutes, Actinobacteria, Synergistetes, and Tenericutes did not significantly change with diet or age. However, Bacteroidetes (P < 0.05), Proteobacteria (P < 0.01), and Verrucomicrobia (P < 0.05) reads were significantly affected by diet, and Proteobacteria (P < 0.01) and Verrucomicrobia (P < 0.05) reads were significantly influenced by age. At the genus level, Escherichia/Shigella (P < 0.01) was overrepresented in diet A (high fiber) relative to diet D (high starch) in 52- and 62-day-old rabbits. Venn diagrams and heat map plot analyses revealed that the number of gut species shared between animals with different diet treatments increased with age. These results suggest that dietary fiber per starch ratios and age significantly alter the composition of caecal microbiota in growing rabbits.

Quantitative feed restriction rather than caloric restriction modulates the immune response of growing rabbits

BACKGROUND

Short-term feed restriction strategies are used in rabbits to reduce postweaning digestive disorders, but little is known about the involvement of the immune system in these beneficial effects.

OBJECTIVE

In the present study, the consequences of feed and energy restriction on immune response were investigated.

METHODS

At weaning, 320 male and female rabbits were assigned to 4 groups differing in dietary digestible energy (DE) concentrations and intake levels: a low-energy ad libitum-feed (LE100) group, a low-energy restricted-feed (LE75) group, a high-energy ad libitum-feed (HE100) group, and a high-energy restricted-feed (HE75) group. The high-energy groups consumed 10.13 MJ DE/kg of feed, whereas the low-energy groups consumed 9.08 MJ DE/kg (formulated values). Intake amounts for the restricted groups were 75% those of the ad libitum groups. Rabbits consumed these diets until age 63 d, after which they consumed feed ad libitum for 9 d. Ten rabbits per group and per age were killed at ages 42, 50, 63, and 72 d. Spleens and appendixes were weighed; Peyer's patch surface area was determined by image analysis; plasma total immunoglobulin (Ig) G and anti-ovalbumin IgG; and fecal and plasma IgA concentrations were determined by ELISA; and ileal expressions of cytokines were measured by quantitative reverse transcriptase-polymerase chain reaction at ages 50 and 63 d.

RESULTS

The relative weight and size of the lymphoid organs were not affected by treatments. Concentrations of plasma total IgA (-41% at 63 d and -29% at 72 d), IgG (-22% at 72 d), and anti-ovalbumin IgG (-41% at 63 d) were lower with feed restriction. Fecal IgA concentrations were lower with quantitative restriction (-40%, -52%, and -65% at age 42, 50, and 63 d, respectively) and energy restriction (-56%, -46%, and -73% at ages 50, 63, and 72 d, respectively). Feed-restricted rabbits tended to have greater expressions of interleukin (IL) 1β and IL-2 and lower expressions of tumor necrosis factor α (P < 0.1).

CONCLUSION

These results demonstrated that, in rabbits, restriction and, to a lesser extent, dietary energy concentration modulate gut immunity.