Effects of restricted feeding during rearing, combined with a delayed first insemination, on reproductive activity of rabbit does.

The experiment was performed to verify the effects of restricted feeding during rearing, combined with a 3-week delay in first artificial insemination (AI), on body development and reproductive traits of young rabbit does, with the aim of improving their productivity and life-span. At 11 weeks of age, 82 New Zealand White(NZW) females were divided into two groups and assigned to different treatments: ad libitum feeding and first AI at 16.5 weeks of age (AL-16.5); feed restriction to 75% until 10 days before first AI, performed at 19.5 weeks of age (R-19.5). Five days after AI, 10 females per treatment were slaughtered to determine body composition and count of corpora lutea (CL) and embryos. The career of the 62 does was checked for 160 days, during which a 42-day reproduction rhythm was followed. From 11 weeks to first AI, the R-19.5 had lower growth rate than AL-16.5 (23.1 vs 35.4 g/d; P<0.0001) but showed higher body weight at AI (3571 vs 3427 g; P=0.002). All of the slaughtered females had CL, but the embryo recovery was higher in the R-19.5 than in AL-16.5 (75.6 vs 57.6%; P=0.34). The empty body of R-19.5 was higher in both water (+104 g; P=0.005) and protein (+39 g; P=0.13), and lower in fat (-31 g; P=0.30). At the first AI, the treatment did not affect the kindling rate, but the litter size at birth was higher by 0.7 kits in the R-19.5. After 160 days, although the culled rate of R-19.5 was lower by only 6.4% than the AL-16.5 (48.4 vs 54.8%), the final value was attained more slowly, so that the average duration of activity of R-19.5 tended to be higher (121 vs 105; P=0.14). During the 160-day period, the R19.5 showed a tendency towards higher productivity in terms of number (+2.7; P=0.16) and weight (+1.8 kg; P=0.14) of weaned rabbits. When lactating, an improvement in kindling rate was observed in R-19.5 (83.0 vs 69.5%; P=0.15). The body weight of lactating R-19.5 was constantly greater from AI to litter weaning (day 31). The restricted feeding, applied from the age of 11 weeks, meant obtaining young rabbit does that, inseminated 3 weeks later, weighed more, without any increase in body fat deposition. The better body development of females favoured an improvement in reproductive efficiency at first AI, productivity during the subsequent activity, and a tendency towards a longer life-span.