Rabbit dietary supplementation with bovine colostrum: impact on gut and liver integrity

Italy is the second largest producer of rabbit meat in the world, after China, and the first one in Europe (1). Infections of the gastroenteric and reproductive system are among the main causes that limit the profitability of rabbit breeding and welfare (2). Recent studies showed that bovine colostrum (BC) may have beneficial effects on the individual health, and in preventing and treating several animal diseases (3). The aim of this study was to evaluate the effects of supplementing the diet of rabbit with BC, in terms of productive performance and integrity and health of the gastroenteric system and liver. After weaning (35 days), rabbits were fed three types of diets until slaughtering (105 days): CTR (control, fed a commercial feed); BC1and BC2 (colostrum fed 2.5% and 5% BC, respectively). Body weight (BW) was registered on a weekly basis throughout the experiment. At slaughtering, samples of stomach body (fundic mucosa), and liver of 5 animals for each experimental group were collected for histological and histochemical analyses: sections of the gut were stained with Hematoxylin–Eosin (HE) in order to establish structural details, while sections of the liver were stained with Periodic Acid Schiff (PAS), which reveals neutral glycoconjugates (purple stain) and Azan for demonstrating collagen fibres (blue staining). This study was approved by the Ethic Committee of the University of Milan (OPBA_42_2021). At weaning, the BC2 showed the lowest BW (438±90 g; p<0.01), but, after weaning, it was higher than the BC1 BW (1294±17 g; p=0.049). Finally, no differences were found in carcass weight. The fundic mucosa of the stomach was regularly organized in all groups, but in the BC1 and BC2 it was possible to observe haemorrhagic infiltrates in the lamina propria towards the lumen, while the basal side revealed to be morphologically normal. Intestinal samples revealed normal morphological organization. PAS staining revealed the presence of intrahepatic glucogen, evident in all groups and Azan staining showed an increasing degree of collagen fibre staining from CTR to BC2. Overall, samples presented a normal structural organization of the gut with no damage of the epithelium. The changes observed in the lamina propria of the stomach and the presence of glucogen and collagen fibres in the liver, apparently had no negative effect on the productive performance taking into account that at slaughtering there were no significant differences between treatments as well as in health and welfare of the animals.