Placentophagia in weanling female laboratory rats

Abstract

Placentophagia is common in parturient mammals and offers physiological and behavioral advantages for mothers. In natural environments, weanlings are often present during the birth of younger siblings, but it is unknown if weanling rats are placentophagic or prefer placenta over other substances. To examine this, primiparous rats were remated during the postpartum estrus and weanling females remained in the nest during their mother’s next parturition. Continuous observation revealed that 58% of weanlings were placentophagic. To determine if this placentophagia occurs away from parturient mothers, weanling females still living in their natal nest were offered placenta, liver, or cake frosting in a novel chamber. They ingested more placenta and liver than frosting. Thus, many weanling female laboratory rats are placentophagic during birth of younger siblings but do not selectively prefer placenta when tested outside their natal nest. Consequences of placentophagia by weanlings are unknown, but it may promote their alloparenting or postpartum mothering.

Consumption of Maternal Placenta in Humans and Nonhuman Mammals: Beneficial and Adverse Effects

“…Similar findings were found by Melo and González-Mariscal [ 12 ]: they offered rabbits ( Oryctolagus cuniculus ) liver and placenta during parturition and observed that the behavior of ingesting placenta increased in this state up to practically a 100% frequency. In contrast, liver consumption was only 10%, compared to another physiological state [ 11 ].…”

“…Placentophagia has been thoroughly studied, primarily in mice ( Peromyscus californicus ) [ 9 ], hamsters ( Phodopus campbelli ) [ 10 ], rats ( Mus musculus ) [ 11 ], rabbits ( Oryctolagus cuniculus ) [ 12 , 13 ], ungulates [ 14 , 15 ], and carnivores [ 16 ], and regularly occurs in all nonhuman primate species [ 17 , 18 , 19 ]. In contrast, it is assumed that traditionally, women did not carry out this practice for socio-cultural reasons.…”

“…On the other hand, in some animals, the appetite for placental materials depends on the female’s reproductive stage, increasing during the peripartum period [ 12 ]. However, placentophagia is not exclusive to females, as some bi-parental and monogamous male rodents (mice, rats, and hamsters) also practice it [ 9 , 10 , 11 , 23 ]. Placentophagia is considered to have advantages not only for females but also for their offspring, such as increased mother–offspring interaction, potentiation of the action of brain opioids that promote caring behavior towards the young, aiding neonatal respiration by removing membranes from the nostrils, and providing analgesia enhancement in the parturient female [ 5 ].…”

Extensive juvenile “babysitting” facilitates later adult maternal responsiveness, decreases anxiety, and increases dorsal raphe tryptophan hydroxylase‐2 expression in female laboratory rats

“…These data are very consistent with those of Uriarte et al (). They also extend upon them by suggesting that the reduction in anxiety is not due to other events experienced by older pups raised in overlapping litters, such as the endocrine consequences of suckling on a pregnant dam (Koldovsky & Thornberg, ; Melo, ), sharing in placentophagia with their mothers during the second parturition (Harding & Lonstein, ), or the continued interaction with the mother past typical laboratory weaning age (Wu et al, ). Our results also show that the juvenile alloparental experience can be as short as three days and still reduce aspects of females’ later anxiety behavior.…”

Affective changes during the postpartum period: Influences of genetic and experiential factors

“…These manipulations of the early postnatal environment involve additional maternal stimulation of the pups, which may underlie the later changes in postpartum anxiety during adulthood. In addition, because most juvenile females in overlapping litters would naturally join their mother in ingesting the placenta of the younger litter while she gives birth to them (Harding and Lonstein, 2014), there might be hormonal or other factors ingested by the periweanlings that can influence their adult postpartum affective behaviors.…”