Long-term under-masculinization in male rabbits due to maternal stress is reversed by prenatal administration of testosterone

Effects of intrauterine position during gestation on specific endocrine and behavioral parameters that impact reproduction in domestic rabbits

Prior studies from others, performed in a different breed, reported that doe rabbits developing between two male siblings (2 M) during gestation display characteristics indicative of masculinization: larger anogenital distance (AGD), larger submandibular glands, and higher chinning frequency than females with zero (0 M) or one (1 M) contiguous brothers. Similar effects are provoked by injecting androgens to the pregnant doe suggesting that prenatal androgen exposure masculinizes female embryos. To further understand the scope of such masculinization we compared 0 M, 1 M, and 2 M females regarding behavioral, neuroendocrine, and somatic parameters, related or not to reproduction. IUP did not impact: body weight, sexual receptivity, mating-induced LH secretion, maternal nest-building, litter size, or milk output. At puberty: a) chinning frequency was: 0 M and males>1 M and 2 M; b) ambulation in open field was lowest in 1 M females and males. IUP effects on AGD were significant only on postnatal day 1: 0 M, 1 M, and males>2 M, in contrast to earlier study. Willingness to nurse at delivery was less frequent in 2 M than in 1 M and 0 M does and correlated with nursing occurrence across lactation. Does that did not nurse at parturition delivered fewer kits/min than those that nursed then, regardless of IUP. The duration of nursing bouts across lactation was significantly longer in the1 M and 2 M does that showed this behavior on postpartum days 1-20. Our findings indicate that IUP is associated with alterations in specific aspects of postpartum maternal behavior.

Induced Stress and Tactile Stimulation Applied to Primiparous does and their Consequences on Maternal Behavior, Human-Animal Relationships, and Future Offspring's Sexual Disorders

The aim of this study was to investigate whether tactile stimulation in rabbits during the gestation phase improve the maternal behavior and human-animal relationships as well as the effects on reproductive behavior of male kits when reached maturity compared to induced stress. A total of 33 primiparous New Zealand does were selected after pregnancy confirmation and allocated in a randomized complete block design. The treatments applied were as follows: (C) animals not stimulated during the experimental period; (TS) animals that received tactile stimulation; and (SS) does which were immobilized. The nest building behavior as well as the weight, sexual behavior, mortality, and semen analysis of the offspring was recorded. In addition, the novel object, flight distance, social isolation, and human-approach tests were conducted. Under the conditions of the present trial, TS animals showed more trust in the unfamiliar observer when compared to the other two treatments. The treatments applied to the females (TS and SS) were sufficient to confirm that the control group presented better values for the number of stillbirths and the proportion of deaths in the first week. Finally, the handling of does reduce the males' ejaculation and sperm presence but not inhibited sexual behavior or impaired semen quality. It is possible to conclude that TS did not impair does welfare or maternal behavior and it improved the human-animal relationship, however there was a negative impact on the litter. More studies that directly assess impact on the future reproductive capacity of the offspring are necessary.