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

## TL;DR

This study shows that feed restriction in rabbits improves nutrient use, lipid metabolism, and gut health without affecting growth.

## Contribution

The study reveals how feed restriction alters caecum microbiota and metabolites in rabbits, offering insights for healthier feeding practices.

## Key findings

- Feed restriction increased nutrient digestibility and retention in rabbits.
- FR improved antioxidant activity and altered gut microbiota composition.
- Beta-alanine metabolism was the top enriched pathway in the caecum of restricted-fed rabbits.

## Abstract

Feeding restriction refers to artificially controlling the amount of feed consumed by animals so that the quality of the nutrients consumed is lower than the animal’s demand level, which can effectively improve the body’s immune function and disease resistance. Feed restriction has been used to improve body health in growing rabbits. In addition, meat rabbits are monogastric herbivores with developed caeca and a strong ability to decompose and digest nutrients. However, the effects of feed restriction on the caecum microbiota and metabolites in rabbits remain unclear. Thus, in the present study, we investigated the effects of feed restriction on the growth performance, nutrient utilisation, lipid metabolism, antioxidant activity, caecal microbiota, and metabolites of rabbits. Our research results provide a theoretical reference for the development of healthy feeding restriction standards for meat 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 ad libitum 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 (p > 0.05) for average daily weight gain or feed conversion ratio between the two groups. FR treatment led to a significant increase (p < 0.05) in acid detergent fibre apparent faecal digestibility, nitrogen digestibility and retention, and gross energy digestibility and retention. The FR treatment showed significantly (p < 0.05) lower blood triglycerides, creatinine, high-density lipoprotein cholesterol, malondialdehyde, and hydroxyl free radicals but significantly (p < 0.05) greater total antioxidant capacity and superoxide dismutase. The FR group presented greater (p < 0.05) Firmicutes and Ruminococcus abundances but a lower (p < 0.05) Akkermansiaceae 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.