Maternal Nest Building Research Articles

Pituitary involvement in maternal-nest building in the rabbit

A change in the ratio of estrogen-progesterone is essential for maternal-nest building behavior in the rabbit. The present study suggests that the pituitary gland is also necessary for nest building in addition to the ovarian steroids. Hypophysectomy of 10 rabbits during the last third of gestation completely abolished maternal-nest building normally seen at parturition; whereas, maternal-nest building occurred in 75% ( 3 4 ) of the sham-hypophysectomized females ( P < .05). Ovariectomy during the last third of gestation induced abortion followed by maternal-nest construction in 100% ( 4 4 ) of the control females and in 80% ( 4 5 ) of the sham-hypophysectomized females; whereas, none of five females that were hypophysectomized and ovariectomized built maternal nests ( P < .01). Treatment with estradiol and progesterone induced maternal-nest building in 87% ( 7 8 ) nonpregnant, ovariectomized, sham-hypophysectomized females while none of 12 nonpregnant, hypophysectomized, ovariectomized females built maternal nests ( P < .01).

Maternal behavior in the rabbit: Effects of androgen treatment during gestation upon the nest-building behavior of the mother and her offspring

Female New Zealand White rabbits mated to Purdue-Dutch belted males were treated with testosterone propionate from Day 17–29 of gestation. While there was no apparent effect on gestation and maternal behaviors of injected mothers, the hybrid offspring showed anatomical and behavioral masculinization. Adult hybrid offspring were gonadectomized and treated with estradiol and progesterone to induce nest-building behavior. Ninety per cent of the control females built maternal nests as compared to only 11% of the female offspring of mothers treated with high levels of testosterone during gestation. None of the control males built maternal nests. Testosterone propionate apparently influences the organization of CNS structures mediating maternal-nest building in the adult rabbit. The similarity of these results to the findings concerned with the role of the androgen in the development of sexual behavior are discussed.

Strain differences in the endocrine basis of maternal nest-building in the rabbit.

Summary. The Dutch-belted and grey chinchilla strains of rabbits, Oryctolagus cuniculus, were compared for incidence of maternal nestbuilding after normal pregnancy, pseudo-pregnancy induced by human chorionic gonadotrophin (hcg), castration during pregnancy, oestradiol treatment during pregnancy and treatment of the castrated doe with oestradiol and progesterone. In both strains all does built nests at the end of normal pregnancy, but only 85% of the Dutch-belted does and 31% of the grey chinchilla does at the end of pseudo-pregnancy. All other treatments induced maternal nest-building in both strains; but the grey chinchilla rabbits required longer treatment for the induction of nestbuilding after castration and more oestradiol for the induction of nestbuilding during pregnancy. The critical period for the induction of maternal nest-building after castration in the pregnant rabbit is before Day 20 of gestation in the Dutch-belted and about Day 25 for the grey chinchilla strain.

MATERNAL BEHAVIOUR IN THE RABBIT: ENDOCRINE CONTROL OF MATERNAL NEST BUILDING.

Summary. Experiments have been conducted on maternal-nest building and factors affecting its occurrence in the rabbit. Females deprived of nesting material built a nest out of their own body hair and were as successful in rearing young as does which used both body hair and straw; females deprived of body hair (by shaving) and nesting material showed defective maternal behaviour. Interrupting pregnancy by spaying or foetectomy resulted in maternal-nest building. Nest building was induced in spayed females by the withdrawal of progesterone after injections of progesterone and oestradiol for several weeks. Similar regimes did not induce nest building by castrated males. Further experiments strongly suggest that the onset of nest building is governed by the change in the ratio of progesterone to oestrogen.

Maternal behavior in the rabbit: critical period for nest building following castration during pregnancy.

SummaryA critical period of exposure to certain hormones appears to be necessary for maternal-nest building since no nest building occurs in animals castrated before day 14 of gestation. It appears that ovarian steroids must act for a period of 16 or 17 days for the occurrence of maternal-nest building.

Maternal behaviour in the rabbit: evidence for an endocrine basis of maternalnest building and additional data on maternal-nest building in the Dutch-belted race.

Summary. Two types of nest building are found in the rabbit. One type of nest is made of straw or similar elements available to the animal, and a second type of nest is composed of straw into which hair is incorporated after being plucked from the body. The second type of nest is called a maternal nest and is considered to be part of the maternal behaviour complex. Maternal-nest building was induced in 209 out of 250 (84 %) rabbits following complete removal of the entire conceptus mass on Days 20 to 27 of gestation, as compared with a 96 % maternal-nest-building rate in 941 control rabbits from the same colony. The maternal-nest-building behaviour was also induced in twelve out of sixteen (75 %) rabbits following ovariectomy on Days 20 to 24 of gestation and in five out of eleven rabbits made pseudopregnant with human chorionic gonadotrophin (hcg). Comparable results were obtained in a separate study that used the Dutch-belted rabbit, although a higher percentage of animals in this race built maternal nests following pseudopregnancy or ovariectomy during gestation. Treatment with stilboestrol, progesterone and prolactin induced maternal-nest building in four out of seventeen rabbits and lactation in all the animals. Possible endocrine mechanisms involved are discussed.