Effects of Feed Restriction on Growth Performance, Nutrient Utilisation, Biochemical Parameters, and the Caecum Microbiota and Metabolites in Rabbits

The main objective of this research was to observe the effects of feed restriction on caecum microbiota and metabolites in rabbits. Forty-eight male 8-week-old rabbits with similar body weights (1872.11 ± 180.85 g) were randomly assigned to two treatments according to completely randomized design: (1) the control group received <i>ad libitum</i> access to feed (AL), and (2) the treatment received 80% of the feed consumed by the control (FR). The results showed that FR did not differ (<i>p</i> > 0.05) for average daily weight gain or feed conversion ratio between the two groups. FR treatment led to a significant increase (<i>p</i> < 0.05) in acid detergent fibre apparent faecal digestibility, nitrogen digestibility and retention, and gross energy digestibility and retention. The FR treatment showed significantly (<i>p</i> < 0.05) lower blood triglycerides, creatinine, high-density lipoprotein cholesterol, malondialdehyde, and hydroxyl free radicals but significantly (<i>p</i> < 0.05) greater total antioxidant capacity and superoxide dismutase. The FR group presented greater (<i>p</i> < 0.05) <i>Firmicutes</i> and <i>Ruminococcus</i> abundances but a lower (<i>p</i> < 0.05) <i>Akkermansiaceae</i> abundance in the caecal content. Moreover, 222 differentiated metabolites were identified, and beta-alanine metabolism was the top enriched pathway. Collectively, FR can improve nutrient utilisation, lipid metabolism, antioxidant activity, caecum microbiota, and metabolites in rabbits.