No abstract

At 34 days of age, 376 crossbred rabbits of both sexes were housed in 16 open-top collective pens (1.68 m 2 ) according to a 2 × 2 × 2 factorial arrangement with two types of pen floor (plastic v. wooden slatted), two stocking densities (12 v. 16 animals/m 2 ) and two slaughter ages (76 v. 83 days). 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/m 2 ; P ⩽ 0.001), slaughter age (15.0% v. 22.0% at 76 v. 83 days; 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 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 v. 35.9 g/day; P ⩽ 0.05) and feed intake (140 v. 134 g/day; P ⩽ 0.01) during the second period (55 days to slaughter) and decreased slaughter weight (2725 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 muscleto-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 longissimus 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 owing to experimental factors deserve further investigation from the perspective of animal welfare issues.

In rabbit farms, quantitative feed restriction in the post-weaning period is widely used with the aim of reducing the impact of digestive diseases, whereas less information is available about feed restriction strategies based on the reduction of access time to feeders in different housing systems. This study compared morbidity, mortality, growth performance, carcass characteristics and meat quality of 368 crossbred rabbits fed ad libitum (L) or subjected to a time-based feed restriction programme (R) and housed from 31 to 73 days of age in cages or pens with different dimensions and group sizes, that is, eight conventional cages (0.33 m2, six rabbits/cage), eight small open-top pens (0.50 m2, eight rabbits/pen), eight medium open-top pens (1.00 m2, 16 rabbits/pen) and four large open-top pens (2.00 m2, 32 rabbits/pen). Feed restriction was attained by progressively reducing the access time to feeders in the 1st week from 14 to 8 h/day, maintaining 8 h in the 2nd week and then by increasing access time by 1 h/day during the 3rd and 4th week up to 24 h/day. In the first 2 weeks, R rabbits showed a lower (P ≤ 0.001) daily weight gain, feed intake and feed conversion as compared with L rabbits. During the 3rd and 4th weeks, R rabbits exhibited a greater daily weight gain and better feed conversion (P ≤ 0.001). In the last 2 weeks of trial, daily weight gain tended (P = 0.06) to be greater in the R than L rabbits. In the whole trial, R rabbits manifested a lower daily weight gain, feed intake and feed conversion, as well as lower final live weight and the carcass dressing percentage at slaughter (0.05 ≤ P ≤ 0.01). During feed restriction, R rabbits did not show digestive problems, which, however, appeared in the following 2 weeks of refeeding. Thus, R rabbits had a higher health risk index in the whole trial as compared with L rabbits (P ≤ 0.05). The housing system did not affect growth performance, characteristics at slaughter, and carcass and meat quality. Mortality tended to increase with group size (P = 0.06). In conclusion, the time-based feed restriction significantly improved feed efficiency of growing rabbits housed collectively but had somewhat negative effects on characteristics at slaughter and on morbidity and mortality rate.

No abstract

No abstract