Resources allocation in reproductive rabbit does: a review of feeding and genetic strategies for suitable performance

Abstract

In the present work is analysed how frequent feeding and selection programmes could be affecting resources allocation in reproductive rabbit does, and the possible consequences resulted from these changes, as well as the central role of body condition for a suitable female performance considering genetic level, health and welfare.  Resources allocation between functions, and consequently body condition, must be genetically driven.  Traditional view of body reserves mobilisation in reproductive rabbit does as a response of feed intake must be moved to an animal view, where feed intake must be considered more as an “output” consequence of the resources allocation in the female to ensure current and future litter viability.  To a great extent, future reproductive potential of reproductive rabbit females is decided before first partum.  There seems to be enough evidence of a possible threshold for the rabbit female birth weight to reach the beginning of reproductive life in a suitable body condition to maximise their future reproductive potential.  The moment of first mating could be identified the last ‘pure’ data of the animal, sign of the animal soma and probably related to their productive potential.  The choice of an adequate feeding system during rearing and first pregnancy also seems to be relevant in the reproductive performance of rabbit females in the short and long term. This should allow young females to reach first mating and late pregnancy with a good maturity level, but over-fattening must be avoided to reduce the risk of pregnancy toxaemia and reduced reproduction.  The body condition of the females changes during the reproductive cycle and throughout their reproductive life according to their genetically determined level.  The problems appear when the animals are forced to differ from this adequate level, increasing susceptibility to disease, other stress factors and eventual failure.  The body condition of young rabbit females reaches the peak 10 days before kindling.  From this moment to kindling, reproductive rabbit does seem to suffer the highest mobilisation of body reserves, with the body condition showing the lowest level at partum.  Negative energy balances detected during lactation do not seem to have the strength of those observed in late pregnancy.  Genetic selection in rabbit by litter size at weaning has increased prolificacy but also the ability to obtain resources (more feed intake at the onset of lactation, better energy utilisation during pregnancy), without compromising the survival of rabbit females.  However, it could also have increased the sensibility of animals to the environment, addressing more the maternal investment to the future litter respect to the actual under restricted conditions to maximize their selection success “the number”. Rabbit does selected for reproductive longevity have a greater soma (body weight and body condition), which enables them to better cope with the possible productive challenges that they may meet in the course of their productive life.  There is also evidence that they have greater plasticity in using their soma, making them more robust to overcome demanding situations. In fact, the response to environment restriction of females coming from a line founded for reproductive longevity criteria was flatter than those obtained for females selected for litter size at weaning in all the traits controlled, highlighting their differences on robustness.  In addition, it seems to be evidence of a possible improvement of the immune system modulation in robust animals (lower sensitivity to immunological challenges), although further research effort must be done in the future to confirm this matter.