Time-based restriction and refeeding programmes in growing rabbits: Effects on feeding behaviour, feed efficiency, nutrient digestibility, and caecal fermentative activity

The present study evaluated the effect of five feeding programmes (AL, ad libitum feeding; DF, daylight access to feed followed by fast full refeeding; NF, nightly access to feed and fast full refeeding; NS, nightly access to feed and slow full refeeding; NI, night access to feed until the end of the trial) on growth, nutrient digestibility, caecal fermentative activity, and carcass and meat quality of 400 crossbred rabbits housed in 40 open-top pens (10 rabbits/pen) from weaning to slaughter (28–70 days of age). In all feed-restricted rabbits, feeding time decreased from 14 to 9 h/day during the 1st week, it stood at 8 h/day during the 2nd week, and it increased from the beginning of the 3rd week according to three refeeding systems: i) fast until ad libitum (+4 h/day until 24 h/day) for the DF and NF groups; ii) slow until ad libitum (+1 h/day until 24 h/day) for the NS group; and iii) very slow and until 12-h-restriction (+30 min/day until 12 h/day) for the NI group. During the restriction period, DF and NF programmes compared with the AL programme, improved the coefficient of total tract apparent digestibility (CTTAD) for crude protein (+4.6%) and ether extract (+2.7%) (P < 0.001); NF programmes increased caecal volatile fatty acids (VFA) (79.7 vs 67.7 mmol/L; P = 0.034) and decreased pH (5.32 vs 5.46; P = 0.013) compared with AL. During the refeeding period, the NI programme increased the CTTAD of dry matter (+2.9%; P = 0.001), crude protein (+3.9%; P = 0.003), and gross energy (+2.6%; P = 0.001) compared with the DF and NF groups. The AL, DF, and NF treatments decreased caecal VFA compared with NS and NI (81.0 mmol/L vs. 95.4 mmol/L; P < 0.001). In the whole trial, the NI programme decreased feed intake (−7.5%; P < 0.001) and feed conversion (−6.7%; P = 0.002) compared with the AL programme, without differences in growth, final live weight, and slaughter traits among groups. Compared to AL feeding, feed restriction increased the mortality rate due to digestive disorders (9.0 vs 1.6%; P = 0.036), without affecting morbidity and health risk index. Slaughter weight (on average: 2608 g), carcass yield (60.2 g/100 g live weight at slaughter), and carcass and meat quality traits were not affected. In conclusion, the NI programme improved feed efficiency without impairing growth, slaughter, and carcass traits.