The maintenance and termination of maternal behavior in rabbits: Involvement of suckling and progesterone
Publication Type: |
Journal Article |
Year of Publication: |
2014 |
Authors: |
Gabriela González-Mariscal, José Antonio Gallegos |
Publication/Journal: |
Physiology & Behavior |
Keywords: |
lactation, mammary gland, oxytocin, prolactin, uterus, weaning |
ISBN: |
0031-9384 |
Abstract:
Rabbits mated at postpartum estrus become concurrently pregnant and lactating. They wean the first litter shortly before delivering the second one. Lactating-only rabbits do not spontaneously wean their young. These differences suggest that: a) suckling contributes to the long-term maintenance of maternal responsiveness and b) pregnancy-associated factors are essential to promote weaning. To explore if suckling stimulation interacts with the pregnancy condition we compared the behavior of intact and thelectomized (thelx; nipple-removed) rabbits, mated or not at postpartum estrus (Experiment 1). All lactating-only rabbits still showed nursing behavior by postpartum day 44; only 71% of thelx not pregnant does displayed maternal responsiveness for 31 days and none by postpartum day 44. If mated at postpartum estrus maternal responsiveness was observed only in 25% of pregnant–lactating does on postpartum day 29 and in 8% of thelx-pregnant rabbits on postpartum day 26. As in pregnant–lactating does progesterone (P) is present across ca. 3 weeks and then declines, but it is absent in lactating-only rabbits, in Experiment 2 we explored the effect of injecting P to lactating-only animals on their maternal responsiveness and milk output. P injections (20 mg/day) were given across lactation days 1–30 or 1–23. Neither treatment modified maternal behavior: nearly all females entered the nest box, crouched over the litter and suckled it for ca. 3 min, as did oil-injected nursing rabbits. In contrast, both P treatments accentuated the decline in milk output, with respect to oil-treated does. Results suggest that suckling promotes the long-term maintenance of maternal behavior while pregnancy-associated factors (not P) are essential to trigger weaning.