Convergent changes in the maternal emission and pup reception of the rabbit mammary pheromone

Abstract

Lactating rabbit females emit volatile odour cues that trigger specialized motor actions leading to sucking. But the activity of these cues may change with advancing lactation. Here, we tested this possibility in three experiments. In Exp. 1, we assessed whether 2-day-old pups respond differently to the odour of milk from females in early (day 2) as compared to late (day 23) lactation. In Exp. 2, a compound bearing pheromonal properties, the Mammary Pheromone (MP), was dosed in these milks to assess whether its concentration is correlated with behavioural activity. In Exp. 3, the responsiveness to a constant level of MP was compared in d2 versus d23-pups. Run on 240 pups, the assays showed that a) the milk activity declines between d2 and d23 of lactation; b) during this same period, the concentration of the MP decreases in milk; c) the MP itself becomes less active to elicit oral grasping in pre-weaning pups than in newborns. These results indicate that the MP is active during the period when pups are exclusively dependent on milk. The convergent changes in emission and reception of this pheromone may sequentially warrant that pups are first attracted to the mammae, and then that they progressively disinvest the mother as they begin to eat solid food and to be attracted by other conspecific

The reactivity of neonatal rabbits to the mammary pheromone as a probe for viability

“…This high level of response corroborates previous observations on the strong releasing potency of this compound (Coureaud et al, , 2004(Coureaud et al, and 2006aSchaal et al, 2003;Montigny et al, 2006). In the same time, the behavioural assay using the mammary pheromone permitted to target pups that are unresponsive to the pheromone on days 1 and 3.…”

“…The behavioural assay (e.g. Coureaud et al, 2003 and2006a;Schaal et al, 2003) consisted in holding a pup in one gloved hand with its head left free to move. When the pup came to rest, the tip of the glass-stick carrying the mammary pheromone was positioned 0.5 cm in front of its muzzle, avoiding any contact.…”

“…The mammary pheromone belongs to this latter category. It is carried in rabbit milk and is an extremely potent activator of typical orocephalic movements that pups generally display to find the nipples under the nursing female (Coureaud, 2001;Coureaud et al, 2003 and2006a;Schaal et al, 2003).…”

Configural processing of odor mixture: Does the learning of elements prevent the perception of configuration in the newborn rabbit?

“…In rabbit neonates, the elemental ability to respond to peculiar odor cues contained in complex mixtures emitted by the maternal body is certainly a way to rapidly detect the entry of the mother into the nest and to start searching immediately for the nipples [41][42][43]. This is typically the case of the response to the mammary pheromone, which is perceived among a huge diversity of odorants in rabbit milk from early lactation [44][45][46][47]. However, perceiving configurations in addition to elemental features may also promote the detection of stimuli that are critical in terms of benefits.…”

The responsiveness of young rabbits to the mammary pheromone: developmental course in domestic and wild pups

“…Moreover, it has been only intermittently followed along the pup postnatal development Coureaud et al 2006;Montigny et al 2006). Thus, the main goals of the present investigation are: 1) to run a detailed screening of the MP behavioural activity from birth to weaning, related to the maturity of the pup sensory systems, the rate of mother-young interactions, the context in which nursing take place, and the diet of pups, and 2) to compare it with the related developmental curve of wildtype pups.…”