Time-based feed restriction and group composition in growing rabbits: Effects on feed intake pattern, growth performance, carcass traits and meat quality

This study aimed to evaluate the effects of the feeding system (AL: ad libitum, R: feed restriction) and group composition (X: only females, Y: only males, XY: mixed sex) on the feed intake pattern, growth, and slaughter results in growing rabbits. A total of 288 crossbred rabbits were housed in 18 pens (16 animals per pen) from weaning to slaughter (33 to 75 d of age). At the beginning of the trial, R rabbits had access to the feeders for 10 h/d, afterwards, feeding time increased by 1 h every 3-4 d in the first three weeks until 16 h/d was reached, and by 1 h per day until 24-h access to feeders was reached in the 4th week; thereafter, all animals were fed ad libitum. On average, the feed intake pattern of AL rabbits was characterized by small and frequent meals throughout the day, with minimum intakes (about 2-3 g/h) occurring in the morning and maximum intakes (7-10 g/h) in the evening. During the restriction period, R rabbits showed a lower daily feed intake (-6 g/d; P < 0.01), better feed conversion (2.29 vs. 2.42; P < 0.001), and a higher hourly feed intake compared to the AL rabbits, reaching peaks of 18, 15, and 14 g/h when the feeding time was 11, 13, and 16 h/d, respectively (P < 0.001). In the second period, once the rabbits were fed freely, R rabbits achieved the same intake as AL rabbits but with a higher feed conversion (4.10 vs. 3.89; P < 0.001). In this study, the feeding system did not affect growth performance, health (mortality 1.4% on average), carcass traits, and meat quality. In terms of group composition, the daily growth and feed conversion were worse in the Y groups than in the X and XY groups in the second period (P ≤ 0.01), with no other differences observed throughout the whole trial. Dressing out percentage was significantly different among the three groups (61.8%, 61.0% and 60.2% in group Y, group XY and group X, respectively; P < 0.001). In conclusion, time-based feed restriction during the first three weeks (based on an access to the feeders increasing from 10 h/d at the beginning until 16 h/d) reduced the feed intake to 95% of ad libitum, without compromising growth performance and slaughter results, but modified the rabbit feed intake pattern during the restriction phase. In terms of gender composition, the separate housing of male and female rabbits was not justified by our results.