Effects of Dietary Inclusion of <i>Saccharina latissima</i> and <i>Ulva lactuca</i> on Growth Performance and Gut Health in Growing Rabbits

Rabbit meat production faces challenges due to the prevalence of gastrointestinal diseases in rabbits, exacerbated by restrictions on antibiotic use in European animal production. Marine macroalgae, rich in bioactive compounds such as soluble polysaccharides, represent promising solutions to this problem. However, research on the effects of macroalgae and the underlying mechanisms in rabbits is limited, especially in commercial settings. This study aimed to evaluate the impact of <i>Saccharina latissima</i> (dehydrated) and <i>Ulva lactuca</i> (dehydrated and hydrolyzed extract) on rabbit on growth performance and gut health in a commercial farm context. A total of 96 litters (8 rabbits/litter) of crossbred rabbits weaned at 33 days of age were randomly assigned to 4 experimental groups (control, <i>Saccharina latissima</i> dehydrated, <i>Ulva lactuca</i> dehydrated and <i>Ulva lactuca</i> hydrolyzed extract; 24 replicates/treatment) and monitored from weaning to slaughter at 61 days of age. The key indicators of gut health were assessed 14 days post-weaning by counting coccidia, isolating specific microflora and examining histological samples. Additionally, the relevant intestinal markers (microbiome composition, mucin content and gene expression related to immune response and tight junction proteins) were determined in order to elucidate the potential mechanisms involved. The inclusion of macroalgae in the diet did not influence growth performance of the animals. <i>S. latissima</i> had a positive effect in reducing coccidia counts (<i>p</i> = 0.10) and improving mucosal morphology (<i>p</i> < 0.001), which can possibly be attributed to modulation of the microbiota and improved mucosal functionality. <i>Ulva lactuca</i> had a favorable effect on gut tight junction proteins (<i>p</i> < 0.001), enhancing intestinal barrier function. These findings suggest the potential of macroalgae to modify the intestinal microbiome by reducing the presence of inflammatory bacteria. Further research is warranted to elucidate the mechanisms involved and optimize macroalgae supplementation in rabbit nutrition for enhanced gut health.