Abstract
Ninety lactating rabbit does of 3 different genetic types [2 from a line differentiating 20 generations by selection for litter size at weaning (V16 and V36) and 1 from a line founded under reproductive longevity criteria and then selected by litter size at weaning (LP)] were subjected to 3 environmental conditions: NC, females housed under normal conditions (14 to 20°C) and fed with a control diet [333 g neutral detergent fibre (NDF)/kg dry matter (DM)]; HC, females housed under heat conditions (25 to 35°C) and fed with the control diet; or NF, females housed under normal conditions and fed with a fibrous diet (443 g NDF/kg DM).
The apparent digestible coefficients of dry matter (DMd), organic matter, crude protein (CPd), gross energy, NDF (NDFd) and acid detergent fibre, as well as the daily intake of DM, digestible protein and digestible energy (DE), were determined (14 to 18 d post-partum). The environment affected all variables analysed. In general, heat conditions reduced the daily DM intake (around 30%; P<0.05) and increased main apparent digestible coefficients (+4.5 percentage points for DMd). In contrast, the use of a fibrous diet led to reduce DE intake (217 kJ/d; P<0.05) and main apparent digestibility coefficients (13.5 percentage points for DMd). Females from line V, regardless of generation, showed lower daily DM intake (19.2 g/d; P<0.05) and NDFd (1.5 percentage points; P<0.05) than line LP. Interactions between genetic type and environment were found for daily DM intake, NDFd and CPd. When receiving fibrous diet, LP females showed a higher increment in daily DM intake (+65.6 g/d; P<0.05) than V36 females, compared to control. Under heat conditions, NDFd obtained for LP females were higher to those in normal conditions (+3.14 percentage points), while V females showed similar NDFd. In addition, the increase in CPd observed under heat conditions was higher for LP (+9.87 percentage points) and V36 (+8.74 percentage points) than V16 females (+3.84 percentage points). In conclusion, rabbit females from a line founded for reproductive longevity seem to show a higher flexibility in their digestive capacity under constrained conditions.
