Impact of feed restriction and of the hygiene of housing on rabbit performances and health

Introduction: Limiting the post-weaning intake of the young rabbit is now known to improve its resistance to digestive troubles (Gidenne et al. 2012), while the feed conversion is improved. In contrast a poor hygiene of housing is supposed to have a negative impact on performances and health, as demonstrated in the piglet (Le Floc'h et al., 2010). However, these two factors may interact in determining performances and health as recently showed in pig (Pastorelli et al., 2012). We thus aimed to determine the effect of a moderate post-weaning feed restriction in the rabbit to cope with a poor housing hygiene, in terms of growth and health. Methods: Restriction and housing hygiene were studied according to a 2 X 2 factorial design: free intake "F" or restricted "R" at 70% of F, and high vs low hygiene of housing (H and L), and thus corresponded to four groups of 105 rabbits: HF, HR, LF, LR. Rabbits (INRA hybrid line) were fed the same pelleted experimental diet (crude protein 17.4%, ADF=18.4% as fed) and housed in collective cages (5 rab./cage), in two independent breeding rooms (high or low hygiene), from weaning (28d) to slaughter (63d). The intake of the R groups was adjusted three times per week to reach 70% of the intake of F groups within each room. The poor hygiene of housing was obtained by avoiding cleaning one breeding room before and during the experiment. Mortality was checked daily, while morbidity (rabbits having clinical signs of diarrhoea or a very low growth) was checked weekly as for the intake and live weight control Results: No significant interactions were found between the restriction and hygiene, for performances or health status. From 28 to 63d old the mortality rate was relatively low (meanly 11%) suggesting a good health status. Although the number of rabbits was insufficient to reach substantial conclusions about the health impact, we observed that mortality from digestive troubles started one week after weaning (figure 1) and levelled after 7 weeks of age. We detected a significant positive impact of the feed restriction on the mortality rate during the post-weaning period (28-40d old): 1.9 vs 6.2% (P=0.046). For the whole growth period, restriction or low hygiene did not affect significantly the mortality rate, although we recorded the highest mortality for the rabbits fed freely in poor hygiene housing (15/105). In parallel, the morbidity rate was not affected by the restriction strategy, but was surprisingly lower in low hygiene of housing (table 1) during the post weaning period. With a 30% reduced intake the weight gain was meanly reduced by 16% (49.9 vs 41.7 g/d from 28 to 63d old, P<0.001, table 2). Accordingly, the feed conversion was sharply improved for restricted rabbit groups by 16% (2.47 vs 2.11 from 28 to 63d old, P<0.001), as found previously (Gidenne et al., 2012). The level of housing hygiene did not greatly affect the growth, although the post weaning daily gain tended to be lower during the two weeks after weaning (42.6 vs 41.3 g/d, P=0.09). The feed conversion was surprisingly better for rabbit housed in poor hygiene conditions (2.30 vs 2.25 from 28 to 63d old, P=0.03), sourcing from a slightly lower intake (107.0 vs 103.2 g/d, P=0.02). In conclusion, our strategy of feed restriction improved sharply the feed conversion, from 2 weeks after weaning, and was beneficial for the health of the rabbit during the post-weaning period. Our model of hygiene degradation seemed insufficiently stressful to affect the health of the rabbit, and should be further investigated.