Abstract
Among plant products, tannins exhibited a strong antioxidant activity and their employment was studied as food or feed addictive with positive effects. Nevertheless, their health-enhancing properties remain to be completely clarified, particularly in rabbits. The aim of the present study was to investigate the influence of a mix of chestnut and quebracho tannins as supplementation in rabbit diet on intestinal morphology, as well as bacterial loads and Eimeria spp coccidial oocyst excretion and humoral immune response after vaccination. Rabbits were fed four different diets: basal diet (negative control, group CN), basal diet with anticoccidial supplementation (positive control, group CP) and basal diet with tannins mix 0.3% (group T0.3) or 0.6% (group T0.6). Samples of intestine, liver, spleen thymus, mesenteric lymph nodes, kidney and heart were submitted to histopathologic investigations. Morphometric analyses were performed on portion of duodenum, jejunum and ileum. Intestinal contents were analyzed by flotation test for Eimeria spp. oocysts excretion and by microbiological assays for Clostridium perfringens and Escherichia coli. Rabbits belonging to the four experimental groups were vaccinated by means of a live attenuated myxomatosis virus and sera were collected individually at three time points to determine antibody response.The obtained results demonstratedthe absence of toxic effects of the tannin mix on examined organs, particularly on liver and kidney and any negative influence on the growth performance. A relevant anti-inflammatory effect on the intestinal tract, a reduction of Eimeria spp. oocysts excretion and a positive immunomodulatory and antibacterial effects were also observed. Diets supplemented with the tannins mix affected also the morphology of examined intestinal tracts, particularly duodenum and ileum.
Highlights
Rabbit meat is an important Mediterranean product and it is consumed in Central America and Asia (FAO, 2018)
The aims of our study were to evaluate the effects on growth performance of two dietary doses of a mix of chestnut and quebracho tannins, never been tested before as supplementation in rabbit diet and to investigate the influence of tannins supplementation on intestinal morphology, as weel as bacterial loads and Eimeria spp. oocyst counts and on the humoral immune response after vaccination
A basal diet which consisted in a commercial pellet was used as negative control diet (CN) and as base to formulate the other three diets
Summary
Rabbit meat is an important Mediterranean product and it is consumed in Central America and Asia (FAO, 2018). The most important qualities of rabbit meat are colour, texture and flavour (Dalle Zotte, 2002), so lipid oxidation, due to high content of polyunsaturated fatty acids, represents the major problem leading to reduced shelf life, because of rancidity and colour deterioration (Liu et al, 2009). Tannins exhibited a strong antioxidant activity and their employment was studied as food or feed addictive (Chung et al, 1998). Consumption of tannin high doses can have several negative effects including hepatotoxicity, toxic nephrosis, feed intake depression and growth reduction, due to the reduction of protein digestibility and digestive enzymes activity and the damage of intestinal mucosa (Mueller-Harvey, 2006). Tannins in various plant extracts act preventing the colonization of intestinal bacteria, protozoa and viruses (Min and Hart, 2003; Biagi et al, 2010, Fraquelli et al, 2015) and for this reason are widely used in traditional medicine to counter the incidence of diarrhoea and dysentery (Lewis, 2003)
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