| Summary: | Today’s pet food industry is growing rapidly, with pet owners demanding high-quality
diets for their pets. The primary role of diet is to provide enough nutrients to meet metabolic
requirements, while giving the consumer a feeling of well-being. Diet nutrient composition
and digestibility are of crucial importance for health and well being of animals. A recent
strategy to improve the quality of food is the use of “nutraceuticals” or “Functional foods”.
At the moment, probiotics and prebiotics are among the most studied and frequently used
functional food compounds in pet foods.
The present thesis reported results from three different studies.
The first study aimed to develop a simple laboratory method to predict pet foods
digestibility. The developed method was based on the two-step multi-enzymatic incubation
assay described by Vervaeke et al. (1989), with some modification in order to better
represent the digestive physiology of dogs. A trial was then conducted to compare in vivo
digestibility of pet-foods and in vitro digestibility using the newly developed method.
Correlation coefficients showed a close correlation between digestibility data of total dry
matter and crude protein obtained with in vivo and in vitro methods (0.9976 and 0.9957,
respectively). Ether extract presented a lower correlation coefficient, although close to 1
(0.9098). Based on the present results, the new method could be considered as an alternative
system of evaluation of dog foods digestibility, reducing the need for using experimental
animals in digestibility trials.
The second parte of the study aimed to isolate from dog faeces a Lactobacillus strain
capable of exert a probiotic effect on dog intestinal microflora. A L. animalis strain was
isolated from the faeces of 17 adult healthy dogs..The isolated strain was first studied in
vitro when it was added to a canine faecal inoculum (at a final concentration of 6 Log
CFU/mL) that was incubated in anaerobic serum bottles and syringes which simulated the
large intestine of dogs. Samples of fermentation fluid were collected at 0, 4, 8, and 24 hours
for analysis (ammonia, SCFA, pH, lactobacilli, enterococci, coliforms, clostridia).
Consequently, the L. animalis strain was fed to nine dogs having lactobacilli counts lower
than 4.5 Log CFU per g of faeces. The study indicated that the L animalis strain was able to
survive gastrointestinal passage and transitorily colonize the dog intestine. Both in vitro and
in vivo results showed that the L. animalis strain positively influenced composition and
metabolism of the intestinal microflora of dogs.
The third trail investigated in vitro the effects of several non-digestible
oligosaccharides (NDO) on dog intestinal microflora composition and metabolism.
Substrates were fermented using a canine faecal inoculum that was incubated in anaerobic
serum bottles and syringes. Substrates were added at the final concentration of 1g/L (inulin,
FOS, pectin, lactitol, gluconic acid) or 4g/L (chicory). Samples of fermentation fluid were
collected at 0, 6, and 24 hours for analysis (ammonia, SCFA, pH, lactobacilli, enterococci,
coliforms). Gas production was measured throughout the 24 h of the study. Among the
tested NDO lactitol showed the best prebiotic properties. In fact, it reduced coliforms and
increased lactobacilli counts, enhanced microbial fermentation and promoted the production
of SCFA while decreasing BCFA. All the substrates that were investigated showed one or
more positive effects on dog faecal microflora metabolism or composition. Further studies
(in particular in vivo studies with dogs) will be needed to confirm the prebiotic properties of
lactitol and evaluate its optimal level of inclusion in the diet.
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