Effects of floor type, stocking density, slaughter age and gender on productive and qualitative traits of rabbits reared in collective pens

At 34 d of age, 376 crossbred rabbits of both sexes were housed in 16 open-top collective pens (1.68 m2) according to a 2×2×2 factorial arrangement with two types of pen floor (wooden v. plastic slatted), two stocking densities (12 v. 16 animals/m2), and two slaughter ages (76 v. 83 d). The rabbits were examined for growth performance, slaughter results, and meat quality. The effect of gender was also examined. The percentage of rabbits with wounds due to aggression varied with stocking density (8.2% v. 26.2% for 12 v. 16 animals/m2; P ≤ 0.001), slaughter age (15.0% v. 22.0% at 76 v. 83 d; P ≤ 0.10), and gender (11.3% v. 25.8% for females v. males; P ≤ 0.001). Rearing rabbits on a plastic rather than a wooden slatted floor promoted slaughter weight (2795 g v. 2567 g; P ≤ 0.001), dressing percentage (61.4% v. 60.9%; P ≤ 0.01), dissectible fat (2.4% v. 2.0%; P ≤ 0.01), and hind leg muscle-to-bone ratio (5.81 v. 5.35; P ≤ 0.001). Increased stocking density impaired daily growth (38.5 g/d v. 35.9 g/d; P ≤ 0.05) and feed intake (140 g/d v. 134 g/d; P ≤ 0.01) during the second period (55 d to slaughter) and decreased slaughter weight (2725 g v. 2637 g; P ≤ 0.01). At the older slaughter age, the feed conversion ratio was impaired (2.98 v. 3.18; P ≤ 0.001); the slaughter weight (2574 g v. 2788 g; P ≤ 0.001), dissectible fat (2.0% v. 2.4%; P ≤ 0.01), and hind leg muscle to bone ratio (5.41 v. 5.75; P ≤ 0.01) increased; meat thawing losses, cooking losses, and shear force decreased (P ≤ 0.05). The main differences between the females and males were found in the slaughter for transport losses (2.6% v. 2.2%; P ≤ 0.01) and l. lumborum proportions (13.0% v. 12.4%; P ≤ 0.01). In conclusion, the growth performance of pen-housed rabbits was largely determined by the type of floor and less affected by stocking density. The meat quality depended on ontogenetic factors, such as slaughter age and gender, and not on housing conditions. The differences in the percentages of wounded animals due to experimental factors deserve further investigation from the perspective of animal welfare issues.