A balanced diet and intestinal microflora are essential to ensure a healty and well functioning gut. Nowadays, we know that a dog with a healty gut is a healty dog in general. Canine nutritional is very important to garantee this chain of events particularly manteining a good balance of the hindgut microbial flora.
Prebiotics, like Mannanoligosaccharides (MOS), can rule a significant part of this scenario and in this study we’ll can see how: prebiotics are defined as selectively fermented ingredients that allow specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host health.
In human is now well estabilished that MOS can positively influence the antioxydant indices and
also improve lipid profile by lowering serum concentrations of cholesterol, LDL-cholesterol, and
triglyceride.
Therefore, the aim of this study was to evaluate the effects of dietary MOS insertion on
nutrient digestibility, hindgut fermentation, immune response, lipid profile and antioxidant indices in dogs when fed on a home cooked diet.
Methods
The study was carried out in the kennel facility of Animal Nutrition Division, Indian Veterinary
Research Institute, Izatnagar, India.
Ten Spitz pups (age 4 months; average body weight 4.2 kg) were divided into two equal groups:
control (CON) and experimental (MOS), and fed a home-prepared diet for 150 days. The MOS group was supplemented with MOS powder (derived from the cell wall of Saccharomyces cerevisiae) at the rate of 15 g/kg of food. The dogs had access to drinking water throughout the day
and the total quantity of food required by individual dog was offered in clean feeding bowls in two equal portions, in morning (09:30) and evening (19:30).
Digestion trial and hindgut fermentation
A digestion trial of 4-days duration was conducted after 60 days of experimental feeding. A daily faecal score was recorded using a 1–5-point scale. Fresh fecal samples was obtained to estimate: nitrogen, pH, ammonia, short-chain fatty acid. Eventually a last aliquot was obtained from rest of the fresh faecal samples for determination of DM.
Other samples of faeces and food were dried at 60 °C in a forced-draft oven, ground through a 2- mm screen in a laboratory mill (SM100, Retsch GmbH, Haan, Germany) and used for further analysis.
Immune response
The cell-mediated immune (CMI) response was assessed at 110 day of the study by measuring the skin induration as delayed-type hypersensitivity (DTH) reaction to intradermal inoculation of phytohaemagglutinin-P (PHA-P). In addition blood samples were collected into chilled heparinized micro-centrifuge tubes to determinate immune-phenotyping of T-lymphocyte subpopulations by flow cytometry. The cell surface identified markers were T-cells CD3+, CD4+ and CD8+. The lymphocyte subsets were quantified by using dual-laser bench-top FACScan flow cytometer (FACSCalibur, Becton Dickinson, San Diego, CA, USA).
At 120 day of the study, humoral immune (HI) response of the dogs was assessed by measuring serum levels of immunoglobulin G (IgG) following subcutaneous inoculation of Leptospira antigen
(Intervet India Limited, Pune, India).
The blood samples were collected at 0, 7, 14 and 28 days post-inoculation. Serum levels of IgG were measured using single radial immuno-diffusion test kit.
Antioxidant indices and lipid profile
The blood samples were collected at 120-day of experimental feeding into sterilized microcentrifuge tubes containing acid citrate dextrose for analysis of antioxidants.
Blood samples were centrifuged at 3000 rpm for 20 min and sedimented cells were washed with 0.9% NaCl solution and re-centrifuged three times with phosphate buffer saline. The washed erythrocytes were then haemolysed with nine volumes of distilled water to prepare 10% erythrocytic haemolysate. Estimation of enzymatic- (superoxide dismutase: SOD and catalase) and non-enzymatic- (lipid peroxidation: LPO, reduced glutathione: GSH and total thiols ) antioxidant indices in the erythrocytic haemolysate were carried. The blood samples collected were analyzed in duplicate to determine serum concentrations of triglyceride, total cholesterol and high-density lipoprotein (HDL)-cholesterol using diagnostic kits.
Results and discussion
Nutrient digestibility and body weight changes
The palatability score, intake of dry matter (DM), crude protein (CP), fat, crude fiber (CF) and nitrogen-free extract (NFE) were comparable between the groups.
The CP digestibility, however, tended (P > 0.05) to be lower in MOS supplemented group as compared to CON group.
Some studies in dogs found that oligosaccharides supplementation decreased total tract digestibility of DM, OM, and CP. Prebiotics are added to the diet to facilitate changes in the microbial micro-climate of the hindgut, but most of digestion process is completed by the time the digesta reaches the colon of the dog. So, when poorly digestable proteins reach the colon get converted to ammonia by bacterial proteolisis. Adding MOS in this context, can improve fermentations, reducing ammonia production secondly to the higher production of bacterial proteins. This can result in a reduction of the CP digestibility, because the bacterial proteins are not absorbed by the colon. We can also say that in this study, that have fed dogs with 15 g MOS/ kg of food, didn’t influence body weight.
Hindgut fermentation
The faecal score, weight of faeces voided and faecal dry matter were without any significant (P > 0.05) difference between the two groups. In addition, MOS supplementation did not affect (P > 0.05) faecal pH, faecal concentrations of ammonia and lactate. Faecal concentrations of acetate, propionate, butyrate and total SCFAs were comparable (P > 0.05) in both the groups.
However other authors came to different results, using different oligosaccarides at different doses.
Immune response
The MOS and the immune system interaction was expected as mannans and glucans found in cell walls of S.cerevisiae have been shown to induce an antigenic response [31], and modulate immunity due to the direct influence of the MOS on immune system and/or improved intestinal absorption of some nutrients, such as zinc, copper, selenium.
The delayed type hypersensitivity (DTH) reaction is a good indicator of events occurring at the effector phase of the CMI response in vivo.
The DTH response in MOS supplemented group is significantly higher and this is particularly evident looking at the values of lymphocyte subpopulation CD4+ and in the CD4+/CD8+ ratio.
The significant increase in population of CD4+ T-lymphocytes in the present study may therefore indicate positive influence of MOS on the immune system.
Dietary MOS supplementation also tended to increase (P = 0.084) the serum levels of IgG in MOS (1956 ± 67.1 mg/dL) group of dogs in comparison to the CON (1731 ± 84.1 mg/dL) group. This, when interpreted in conjunction with the observed increase in CD4+ population, indicates that dietary MOS supplementation might have had a stimulating influence on the humoral immune response of the dogs.
Antioxidant indices and lipid profile
No influence of MOS was evident on the measured antioxidants in the present study.
However supplementation of MOS in diet of dogs significantly (P < 0.05) reduced serum total- (125.4 vs. 139.8 mg/dL) and LDL- cholesterol It has been suggested that the products of bacterial fermentation, specifically SCFAs, may inhibit cholesterol synthesis in the liver and/or cause the mobilization of plasma cholesterol to the liver.
Conclusions
The supplementation of MOS in dog diet didn’t have any influence on the digestibility of nutrients, hindgut fermentation and antioxidant indices.
However, it improved the immune status and lipid profile of treated dogs.