Differences in productive robustness in rabbits selected for reproductive longevity or litter size

Abstract

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.

Digestive efficiency in rabbit does according to environment and genetic type

“…Moreover, the NDFd was higher (1.4%; P<0.05) for LP than for V36 animals (+1.8%, P<0.05). As observed by Pascual et al (2008) and Theilgaard et al (2009), females from LP line showed a higher feed intake (19.21 g DM/d) during lactation period than the V line. However, the difference between V16 and V36 (-14.0 g DM/d) was not statistically significant.…”

“…high temperatures and feed restriction). They delayed reproductive senescence (Theilgaard et al, 2007) and improved their lifespan (Theilgaard et al, 2006;Sanchez et al, 2008), resulting in more robust animals (Theilgaard et al, 2009). All of these findings could be related to a better use of the energy resources available to cope with the reproduction effort, as hypothesised by Pascual et al (2008).…”

Environmental sensitivity differs between rabbit lines selected for reproductive intensity and longevity

“…Line V, in contrast, seemed to adjust the DE intake and milk yield to ensure a higher PFT at weaning. The effort of V does to accrete more PFT than LP does was also observed by Theilgaard et al (2009), but cannot be clearly elucidated from Theilgaard et al (2007). However, Theilgaard et al (2007) observed a tendency of V WP is the weaning to partum interval.…”

“…A likely reason for this difference between studies is the difference in the reproductive rhythm adopted in each one. When the reproductive rhythm was less intense (insemination at 25 or 30 dpp), the initial live weight differences between lines were maintained (Theilgaard et al, 2007 and, whereas when it was more intense (insemination at 4 or 11 dpp) the live weight differences disappeared (Theilgaard et al, 2009). …”

“…Does from line LP were characterised by having an extended lifespan (Sánchez et al, 2008), a later reproductive senescence (Theilgaard et al, 2007) and a greater adaptability to maintain the productive level in the face of nutritional constraints (Theilgaard et al, 2009), compared with a maternal line exclusively founded and subsequently selected for reproductive intensity (line V; Estany et al, 1989). The advantages of LP does were dependent on specific conditions (environmental restriction or high reproductive effort) and seem to be related to the use of their greater soma (i.e.…”