Pasture availability and genotype effects in rabbits: 2. Development of gastro-intestinal tract and immune function of the vermiphorm appendix.

The aim of this trial was to investigate the effect of pasture availability on gastro-intestinal tract and lymphoid follicle development from the vermiphorm appendix (VA) of weaned rabbits of the Leprino of Viterbo and New Zealand White (NZW) breeds. Weaned Leprino of Viterbo and NZW weaned rabbits, (30 days old; 40 animals/breed) were divided into two groups, placed into bicellular cages (17 rabbits/m) or wired pens (10 rabbits/m) and provided with an external grass pasture (1 rabbit/20 m). Rabbits were slaughtered at 90 days of age and body weights were recorded. The gastro-intestinal tracts were excised and weighed. Length, diameter and weight of VA were recorded as well as the number and area of the lymphoid follicles. Differences in pasture availability and locomotive activity were associated with different slaughter weights. Rabbits reared with pasture available exhibited a higher gastro-intestinal tract weight (P<0.05), in particular NZW rabbits which showed the greatest pasture intake. As expected, the highest weight of full gastro-intestinal tract (P<0.05) was observed in the two breeds with pasture availability. A slight increase in the number of lymphoid follicles in the VA from animals reared with pasture could explain a better health condition, even taking into account that this structure represents only a part of the total lymphoid tissue associated with the gut.

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