Oestrus induction in primiparous lactating rabbits by a 48 hours mother-litter separation: endocrine and behavioural responses

[EN] Primiparous does express low mating acceptance during lactation and different oestrus induction methods are employed to improve sexual receptivity. The aim of this work was to study the effect of a biostimulation, a 48 h doe-litter separation (DLS), in primiparous lactating rabbits on mating acceptance, external characteristics of the vulva and plasma concentrations of estradiol, testosterone, progesterone and cortisol. Seventy primiparous does from local population were divided on day 1 after kindling into 2 equal groups: control (C, n=35), where does always had free access to the nest-box, and DLS (n=35), where free suckling was adopted, except from day 9 to day 11 post-partum (PP). Litter size was equalised to 6-7 kits. Before mating, blood samples were obtained from 10 does per group on 9th and 11th d post-partum (dpp). The results showed that the DLS treatment improved the mating acceptance on 11th dpp (88.5 vs. 54.2%; P<0.01) and the frequency of red or pink and turgid vulva (54.3 vs. 20%; P<0.01). The sexual receptivity of DLS does depended on the time for which the female was presented to the male: 60% refused mating before opening the nest-box, while 80.9% of them accepted the male after the nursing episode. Plasma levels of estradiol, testosterone and progesterone in DLS group rose from 9th to 11th dpp (+44.4; +59.2 and +82%, respectively; P<0.01) compared to C group (+6.7; -3.9 and +33.4%, respectively; P>0.05). In contrast, cortisol plasma levels were not affected by the DLS treatment (-12.4 and -14.4% for control and DLS group; P>0.05). At day 11 PP, higher plasma E2 and P4 levels were described in DLS in comparison to C, although no significant difference was found, while plasma testosterone concentrations tended to be higher in DLS (165.5±27.1 vs. 114.9±31.9 pg/mL, for DLS and C, respectively; P=0.075). In summary, the 48 h doe-litter-separation acted as an efficient oestrus inductor in primiparous lactating rabbits. Insemination of biostimulated