Different resource allocation strategies result from selection for litter size at weaning in rabbit does

Abstract

This study examined the effect of long-term selection of a maternal rabbit line, solely for a reproductive criterion, on the ability of female rabbits to deal with constrained environmental conditions. Female rabbits from generations 16 and 36 (n = 72 and 79, respectively) of a line founded and selected to increase litter size at weaning were compared simultaneously. Female rabbits were subjected to normal (NC), nutritional (NF) or heat (HC) challenging conditions from 1st to 3rd parturition. Animals in NC and NF were housed at normal room temperatures (18°C to 25°C) and respectively fed with control (11.6 MJ digestible energy (DE)/kg dry matter (DM), 126 g digestible protein (DP)/kg DM, and 168 g of ADF/kg DM) or low-energy fibrous diets (9.1 MJ DE/kg DM, 104 g DP/kg DM and 266 g ADF/kg DM), whereas those housed in HC were subjected to high room temperatures (25°C to 35°C) and the control diet. The litter size was lower for female rabbits housed in both NF and HC environments, but the extent and timing where this reduction took place differed between generations. In challenging conditions (NF and HC), the average reduction in the reproductive performance of female rabbits from generation 16, compared with NC, was −2.26 (P < 0.05) and −0.51 kits born alive at 2nd and 3rd parturition, respectively. However, under these challenging conditions, the reproductive performance of female rabbits from generation 36 was less affected at 2nd parturition (−1.25 kits born alive), but showed a greater reduction at the 3rd parturition (−3.53 kits born alive; P < 0.05) compared with NC. The results also showed differences between generations in digestible energy intake, milk yield and accretion, and use of body reserves throughout lactation in NC, HC and NF, which together indicate that there were different resource allocation strategies in the animals from the different generations. Selection to increase litter size at weaning led to increased reproductive robustness at the onset of an environmental constraint, but failure to sustain the reproductive liability when the challenge was maintained in the long term. This response could be directly related to the shortterm environmental fluctuations (less severe) that frequently occur in the environment where this line has been selected.

Within-litter variation in birth weight: impact of nutritional status in the sow

“…Therefore, this criterion has been extended for use in the Danish Landrace and Yorkshire breeding program since 2004 (Nielsen et al, 2013). At the same time, a maternal line selected on litter size at weaning in rabbits for 21 generations improved the number of progeny born alive and litter size at weaning, compared with selection on litter size at birth (García and Baselga, 2002), suggesting that it is effective in both promoting litter size at birth and survival rate during lactation (Savietto et al, 2014). Additionally, it is feasible to select for within-litter uniformity in birth weight (Damgaard et al, 2003;Kapell et al, 2011) to improve piglet survival (Canario et al, 2010).…”

Lactating performance, water and feed consumption of rabbit does reared under a Mediterranean summer circadian cycle of temperature v. comfort temperature conditions

“…Similarly, smaller litter sizes were seen in does of a line selected by litter size at weaning, housed in high temperature environment. Moreover, this reduction differed between generations of selection, indicating that selection to increase litter size at weaning led to increased female reproductive robustness, possibly due to a change in resource allocation strategies (Savietto et al, 2014).…”

“…However, it was not estimated from the data of contemporary animals but from data obtained of the same group of animals, collected in different seasons and in different reproductive periods (Maertens and De Groote, 1990). Only Savietto et al (2012Savietto et al ( , 2013Savietto et al ( and 2014 have estimated the effect of a heat pattern, similar to that from a hot-climate country, on doe and kit performance using animals in the same season. This was carried out by comparing animals housed under heat conditions to others in comfort conditions, but this comparison was carried out avoiding any possibility of adaptation to the environment.…”

Milk yield prediction at late lactation in reproductive rabbit does

“…Set 2: Consisting of 140 primiparous rabbit does from different genetic types of UPV reporting different lactation curves (Savietto et al, , 2014: 53 from LP line (GT1); 42 from generation 16 of line V (GT2); and 45 from generation 36 of line V (GT3). One half was fed a commercial diet (D1; 11.6 MJ DE/kg DM, 175 g CP/kg DM) and the other half was fed with a low energy fibrous diet (D2; 9.1 MJ DE/kg DM, 162 g CP/kg DM).…”