Effect of group size, environmental enrichment, and temperature on growth performance and meat quality of rabbits

The present study aimed at evaluating how group size, environmental enrichment and room temperature can affect performance, carcass yield, and meat quality of growing rabbits. To this purpose, 512 rabbits (854 ± 124 g live weight; 33 days of age; mixed sex) were housed in elevated pens in two rooms maintained at different thermal conditions until slaughtering (71 d). The rabbits were randomly divided into eight experimental groups according to a three-factorial arrangement with 2 group sizes (8 vs. 32 rabbits per pen), 2 environmental conditions (18-20 °C vs. 25-26 °C), and provision or not of environmental enrichment (wooden sticks). During the trial, the rabbits were fed ad libitum. At 71 days of age, all animals were slaughtered in a commercial slaughterhouse and 128 carcasses were randomly selected to evaluate carcass traits, muscle pH and colour indices. Overall, the rate of dead and excluded animals (live weight < 2.2 kg) was 16.6% without differences among treatments. Group size and environmental enrichment did not influence daily growth rate (44.9 g/d on average) and feed intake (139 g/d on average) during the trial. However, rabbits housed in groups of 8 per pen showed a higher final live weight compared with rabbits in groups of 32 per pen (2541 g vs. 2494 g; P<0.05). Rabbits housed at higher temperature showed a lower feed intake (131 g/d vs. 146 g/d; P<0.01), daily weight gain (43.5 vs. 46.3 g/d; P<0.01), and final live weight (2475 vs. 2560 g; P<0.001), compared with those reared at neutro-thermal conditions, whereas feed conversion ratio did not differ (3.09 on average). Dressing out percentage changed only according to room temperature, i.e. it was higher (+2%; P<0.01) in rabbits submitted to the thermal stress. Meat quality was affected only by group size, where rabbits kept in groups of 32 showed a lower muscle-to-bone ratio (–7%; P<0.05) and higher L* index of longissimus lumborum and biceps femoris (+2% and +3%, respectively; P<0.05) compared to rabbits kept in groups of 8. In conclusion, at high environmental temperature (25-26°C), growth performances impaired as for final live weight, whereas slaughter dressing percentage increased. On the other hand, group size and environmental enrichment played a minor role on rabbit growth performance and meat quality. Research supported by Project RABBINOUT (PRIN2022) “No cage system for rabbits: indoor and outdoor scenarios” - PNRR M4C2 Investimento 1.1 Progetto di Ricerca di Rilevante Interesse Nazionale (PRIN) - 2022JAX4TZ.