ABSTRACT:The aim of this paper was to draw up a set of recommendations for applied nutrition and feeding trials with rabbits, in relation to certain aspects such as determining the nutritive value of raw materials or diets in growing or reproducing animals, studying digestive physiology and obtaining growth and reproduction parameters. We deal first with animals, size of the sample, housing conditions, diets, handling, measurements, and the data analyses relevant to the design of the experiment are described. Secondly, we give a list of recommended items and include some comments.
The aim of this work was to evaluate the ability of a line selected for reproductive longevity (LP) to confront productive challenges compared to a line selected during 31 generations for litter size at weaning (V). A total of 133 reproductive rabbit does were used (72 and 61 from LP and V lines, respectively). Within each line, three groups with different levels of productive effort were planned: PP9, inseminated at day 4 after the first partum and with nine kits during the second partum, and inseminated after first weaning (30 days) and with nine (PW9) or five kits (PW5) during the second partum. The reproductive performance, body condition (perirrenal fat thickness (PFT)) and lipolytic response were controlled. LP does showed greater mean live weight (LW; 1128 g; P , 0.05), PFT (10.47 mm; P , 0.05) and estimated body energy (EBE; 10.29 MJ/kg; P , 0.01) than V does at second partum. However, LP does that mated at first post partum did not significantly differ in EBE relative to V does at second partum. During the first week of lactation, dry matter (DM) intake was similar for both lines (94 and 95 g DM/kg LW 0.75 day for V and LP does, respectively). There was a significant difference in milk yield between both lines during the first week when litter size was nine (60 v. 54 g of milk/kg LW 0.75 day for LP and V does, respectively; P , 0.01), but no difference when litter size was five. Consequently, when litter size was nine, LP does showed a lower recovery of PFT (0.6 mm less; P , 0.05) than V does during the first 10 days of lactation. However, when litter size was five, LP does showed a higher LW (1210 g; P , 0.05) than V does at 10 days of lactation and a similar recovery of PFT. During the last 3 weeks of the lactation, LP does showed a higher feed intake (16 g DM/kg LW 0.75 day; P , 0.05) and milk yield (127 g/day; P , 0.001) than V does when litter size was nine, resulting in no significant differences in LW at 30 days of lactation. However, when litter size was five, both lines showed similar feed intake and milk yield, maintaining their differences in LW at 30 days of lactation (1206 g for LP does; P , 0.05). These results show that the rabbit line selected for reproductive longevity is more robust with respect to coping with productive challenges, than a line selected for reproductive intensity.
This article reviews how frequent feeding and selection programmes can affect resource allocation in rabbit does during reproduction. The consequences of these programmes and the central role of body condition for suitable female performance are analysed considering genetic level, health and welfare. Future reproductive potential of reproductive rabbit females is decided before first partum. There is 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 as the last of the 'pure' data on the animal, a sign of the animal soma that is probably related to its productive potential. An adequate feeding system during rearing and first pregnancy is relevant for the reproductive performance of rabbit females in the short and long term. The body condition of females changes during the reproductive cycle and throughout their reproductive life according to their genetically determined level. The problems arise when the animals are forced to diverge from this appropriate level, increasing susceptibility to disease, other stress factors and eventual failure. Negative energy balances detected during lactation do not seem to have the strength of those observed in late pregnancy. Genetic selection for litter size at weaning has increased prolificacy, but also the ability to obtain resources without compromising the survival of rabbit females. However, it could also have increased the susceptibility of animals to the environment, focusing more on the maternal investment in the future litter rather than on the current one under restricted conditions to maximise their fitness. Rabbit does selected for reproductive longevity have a greater soma, which enables them to better cope with the possible productive challenges. There is also evidence that they have greater plasticity in using their soma, making them more robust to overcome demanding situations. In addition, there is evidence of a possible improvement of immune system modulation in such robust animals.
A total of 190 rabbit females were used to evaluate five feeding programmes from 9 weeks of age to the first parturition: CAL, fed ad libitum with a control diet (C: 11.0 MJ digestible energy (DE) and 114 g digestible protein (DP)/kg dry matter (DM)) until first parturition; CR, fed ad libitum with C diet until 12 weeks of age and then C diet restricted (140 g/day) until first parturition; F, fed ad libitum with a low-energy, high-fibre diet (F: 8.7 MJ DE and 88 g DP/kg DM) until first parturition; FC, fed with F diet ad libitum until 16 weeks of age, and C diet ad libitum until first parturition; FCF, fed with F diet ad libitum until 16 weeks of age, then C diet ad libitum until 20 weeks and then F diet ad libitum until first parturition. The rabbits were artificially inseminated at 18 weeks of age. CAL group had a higher mortality rate compared with the other groups between 9 and 12 weeks of age (34% v. 3%; P , 0.05) and during the last 3 weeks of first pregnancy (14% v. 3%; P , 0.05). The CAL and FC females presented higher BW and perirenal fat thickness (PFT) than CR females at 11 days of pregnancy (10.41 kg and 10.6 mm; P , 0.05), with F females showing medium values. The type of feeding procedure did not affect the fertility rate of young females at first artificial insemination. Differences in BW disappeared at parturition, when only CAL females presented a greater PFT than CR and FC females (10.3 mm; P , 0.05). In comparison with FCF, CAL females had smaller and thinner live born litters (22.5 kits and 2139 g, respectively; P , 0.05), with CR, F and FC females showing medium values. The low number of kits born alive for CAL females was because of their lesser total number of kits born (21.7 kits; P , 0.05) and the greater mortality of their litters at birth (113.9%; P , 0.05) compared with FCF females. Non-esterified fatty acid was higher in the blood of females fed C diet (CAL and CR) than in others at partum day (on average 10.15 mmol/l; P , 0.05). In conclusion, the ad libitum use of diets for lactating rabbit does throughout the rearing period could lead young rabbit females to present a higher risk of early death and smaller litter size at first parturition. Feed restriction or earlier use of suitably fibrous diets led females to achieve the critical BW and fat mass at first mating to ensure reproduction.
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