Female Litter Research Articles

Mortality and milk yield of Burgundy Fawn, Flemish Giant and New Zealand White Rabbits and their Crosses

The aim of the study was to determine the effect of genotype on the rearing indices and milk yield of Burgundy Fawn (BF), Flemish Giant (FG) and New Zealand White (NZW) rabbits and their crosses. The experiment was performed according to the breeding program: FG FG = FG; NZW NZW = NZW; BF BF = BF, NZW FG = NZWFG; BF FG = BFFG; NZW BF = NZWBF. Litter size and litter weight were recorded from birth to weaning on the 35th day of life. The size of litter at birth was largest for purebred BF rabbits (9.20 kits), there were no significant differences in the size of the litter. The coefficient of milk yield of females remained on similar level for all genetic groups, and it ranged between 3.5 for purebred NZW females and 3.76 for the BF females crossed with Flemish Giant males. Rearing effectiveness was lowest for litters of purebred FG rabbits (79.12%), and highest for litters of BF females crossed with FG males (96.00%), however there were no significant differences between the groups. It was found that crossing of BF or NZW females with FG males results in a great effectiveness of rearing and high litter size, no significantly different from typical broiler breeds therefore, such crossing could be recommended for the production of rabbits.

Asymptomatic viral infection is associated with lower host reproductive output in wild mink populations

Many endemic viruses circulate in populations without hosts showing visible signs of disease, while still having the potential to alter host survival or reproduction. Aleutian Mink Disease Virus (AMDV) circulates in many American mink (Neogale vison) populations in its native and introduced ranges. In this study, we analysed how AMDV infection in female American mink affects the reproduction of a feral population. Females infected with AMDV delivered significantly smaller litters (5.8 pups) than uninfected females (6.3 pups), meaning their litter size was reduced by 8%. Larger females and yearling females had larger litters than smaller and older females. There were no significant differences in whole litter survival between infected and uninfected females; however, offspring survival until September or October within litters of infected females was 14% lower than that within those of uninfected females. This negative link between infection and reproductive output means that Aleutian disease could seriously affect the wild mink population. This study increases our understanding of the threats posed by the spread of viruses to wildlife from farm animals or humans, highlighting that viruses circulating in wildlife, even in the absence of clinical manifestation, can be important drivers of population dynamics in wildlife.

FHL2 deficiency impairs follicular development and fertility by attenuating EGF/EGFR/YAP signaling in ovarian granulosa cells

Female subfertility is an increasing reproductive issue worldwide, which is partially related to abnormal ovarian follicular development. Granulosa cells (GCs), by providing the necessary physical support and microenvironment for follicular development, play critical roles in maintaining female fertility. We previously showed that ectopic expression of four and a half LIM domains 2 (FHL2) promoted ovarian granulosa cell tumor progression. However, its function in follicular development and fertility remains unknown. Here, we confirmed that FHL2 is highly expressed in human and mouse ovaries. FHL2 immunosignals were predominantly expressed in ovarian GCs. A Fhl2 knockout (KO) mouse model was generated to examine its roles in follicular development and fertility. Compared with wildtype, knockout of Fhl2 significantly decreased female litter size and offspring number. Furthermore, Fhl2 deficiency reduced ovarian size and impaired follicular development. RNA-sequencing analysis of GCs isolated from either KO or WT mice revealed that, Fhl2 deletion impaired multiple biological functions and signaling pathways, such as Ovarian Putative Early Atresia Granulosa Cell, ErbB, Hippo/YAP, etc. In vitro studies confirmed that FHL2 silencing suppressed GCs growth and EGF-induced GCs proliferation, while its overexpression promoted GC proliferation and decreased apoptosis. Mechanistic studies indicated that FHL2, via forming complexes with transcriptional factors AP-1 or NF-κB, regulated Egf and Egfr expression, respectively. Besides, FHL2 depletion decreased YAP1 expression, especially the active form of YAP1 (nuclear YAP1) in GCs of growing follicles. EGF, serving as an autocrine/paracrine factor, not only induced FHL2 expression and nuclear accumulation, but also stimulated YAP1 expression and activation. Collectively, our study suggests that FHL2 interacts with EGFR and Hippo/YAP signaling to regulate follicular development and maintain fertility. This study illuminates a novel mechanism for follicular development and a potential therapeutic target to address subfertility.

New data on progesterone levels and the limits of the fertile period in dogs

Purpose: to clarify the possibility of pregnancy in dogs with blood progesterone levels above 20 ng/ml.Materials and methods. The study was conducted in the period from January 2018 to May 2022. The study involved 25 females of various breeds aged from 1.5 to 8 years. The progesterone level of peripheral blood was analyzed, taken into vacuum tubes using a butterfly needle with a size from 20G to 23G, the size of the needle section was selected depending on the thickness of the anterior subcutaneous vein of the forearm, from which samples were taken. Blood sampling for progesterone is performed immediately before insemination. Samples were sent to the veterinary laboratories of NVL Poisk (St. Petersburg) and Vetdiagnostic (St. Petersburg). The study was performed by immunochemiluminescence analysis (IHLA) on an IMMULITE 2000 XPi analyzer (Siemens Healthcare Diagnostics). The number of female litter was taken into account during insemination at a progesterone level of more than 20 ng/ml.Results. Four bitches out of 25 participating in the study were successfully inseminated once at a progesterone level in peripheral blood ≥ 21 ng/ml. 3 bitches out of 25 did not get pregnant for unknown reasons, 18 bitches were in the study area 15-20 ng/ml and did not fit the specified sample parameters. A multiple pregnancy was recorded in a four-year-old German Shepherd with a single insemination at a progesterone level of 45 ng/ml, which is one of the highest recorded results for today.Conclusion. When inseminating dogs at a progesterone level of 21-45 ng/ ml, multiple pregnancies may occur in dogs of various breeds aged from 1.5 to 8 years.

Regional variation in multiple paternity in the brown smooth‐hound shark Mustelus henlei from the northeastern Pacific

Multiple paternity (MP) in the brown smooth-hound shark (Mustelus henlei) was assessed in 15 litters (15 mothers and 97 embryos) collected in the northern Gulf of California of which 86.7% were sired by more than one male (i.e., from 2 to 4 sires). When taken together with results from previous studies, this record indicates that there is regional variation in MP in M. henlei in the northeastern Pacific. This pattern is associated with variations in the reproductive traits of each population (e.g., female size and litter size). In the Gulf of California, the results of a generalized linear model (GLZ) indicated that the litters of larger females had a higher probability of MP compared to those of smaller females.

Effects of lighting patterns in pubertal development and metabolism of female wistar rats

Modern lifestyle is characterized by constant exposure to artificial light, which is associated with alterations in biological rhythms, abnormalities to reproductive cycles and metabolic changes. In this study, we aimed to evaluate the effects of four different lighting patterns on puberty timing and on possible metabolic changes in female Wistar rats. Additionally, we developed a machine learning algorithm to automatically classify the stages of the estrous cycle. Adult Wistar rats mated during a week at a photoperiod station where they were exposed to combined red-green-blue lights (RGB) during the photoperiod that varied its spectral composition (i.e., variable color temperature) during the day (RGB-v; N = 14), RGB during the photoperiod with a fixed light color temperature (RGB-f; N = 13) during the whole photoperiod; constant darkness (DD; N = 13) and constant fixed light (LL; N = 15). Experiments were performed only on female litters from postnatal day (PND) 22 to 50. Body weight, puberty onset, estrous cyclicity and serum metabolic parameters were measured. We also collected pictures of vaginal smears to create a dataset of 15,936 images to construct an automatic classifier based on convolutional neural networks. No significant differences were found in the age of vaginal opening; however, the RGB-v group showed a significantly lower number of complete and consecutives cycles. Also, the RGB-f group showed the first complete estrous cycle significantly earlier than the RGB-v group. Female rats housed in LL condition presented significantly lower mean body weight from PND 33 to PDN 47 compared to the other groups. Furthermore, higher levels of plasma triglycerides were found in the DD group compared to RGB-f and RGB-v. HDL levels were significantly lower in RGB-v compared to RGB-f and LL groups. Total cholesterol was significantly lower in RGB-v compared to all groups. Visceral fat was significantly higher in RGB-f compared to the LL group. These results suggest that both changes in photoperiod and lighting quality affect pubertal development and alter lipid profiles and visceral fat accumulation.

Maternal effects on reproduction in the precocial European hare (Lepus europaeus).

In female mammals, reproduction, and in particular lactation, is the energetically most exigent life-history phase. Reproduction is strongly controlled by body reserves and food availability, so females with better body condition or food supply are believed to have higher reproductive output. Additionally, the growth and mortality of young mammals depends on their postnatal development. Therefore, the degree of precociality affects energetic demands for both mothers and young. To study the reproductive performance of the precocial European hare (Lepus europaeus), we analysed relationships between six predictor variables describing maternal and environmental effects and nine response variables relating to reproduction from 217 captive females. We compared the data with those of precocial and altricial mammal species from an extensive literature search. For hares, we found: (1) Heavier females had heavier litters at birth. (2) In summer and spring, total litter mass was larger than in winter. (3) At the end of lactation, the litters of multiparous females were heavier than those of primiparous females. (4) Both older females and females giving birth for the first time had relatively high leveret mortality during lactation. Comparing our results with the literature for other mammals revealed that the body condition (i.e., body mass) of females before birth is predictive of reproductive parameters in both precocial and altricial species. In the precocial hare, female body condition is no longer predictive of reproductive parameters at the end of lactation, whereas in altricial species, female body condition remains predictive of reproduction (litter mass at the end of lactation, offspring mortality) until the end of lactation. We conclude that these effects are caused by precocial offspring feeding on solid food soon after birth and, thus, being less dependent on the mother’s body condition during lactation than altricial offspring. In line with this, precociality might have evolved as a way of buffering offspring against maternal effects.

Breeding patterns of female prairie voles (Microtus ochrogaster) displaying alternative reproductive tactics.

Individuals of either sex may display alternative behaviors to obtain copulations, but few studies have examined the breeding patterns of females and males in populations where individuals of both sexes exhibit alternative reproductive tactics (ARTs). In prairie voles (Microtus ochrogaster), most adults are territorial, residing at a single nest site either as male-female pairs or as solitary individuals. However, some adults adopt nonterritorial, wandering tactics. During two field seasons monitoring prairie vole populations maintained in seminatural enclosures, we found evidence that females exhibiting different ARTs bred differentially with resident and wandering males. Females residing at a nest with a male bred significantly more often with a paired resident male, primarily their social partner, and significantly less often with male wanderers compared to single resident females or wandering females. These patterns were not due to chance, because paired resident females produced offspring with paired resident males significantly more than expected based on the relative abundance of these males in the population, whereas single resident females produced offspring with male wanderers significantly more than expected based on the proportion of male wanderers in the population. We did not find any evidence that multiple paternity was greater in the litters of single resident females and wanderer females even though these females lacked a male social partner to limit mating access by multiple males. This suggests that mate guarding by a female's male social partner was not the primary determinant of multiple paternity in the litters of females exhibiting different reproductive tactics. However, male ART did affect the likelihood of multiple paternity. Females that produced offspring with single resident or wanderer males had an increased likelihood of multiple paternity relative to females producing offspring with paired resident males. The results of this study show that female and male ARTs can affect breeding patterns.

Reproductive biology, morphology, and morphometry of ovaries and oviducts of Trachemys scripta elegans in Brazilian Cerrado

ABSTRACT: Although Trachemys scripta elegans is an exotic species popular as a pet in Brazil, studies on reproductive biology and capacity are non-existent in the Brazilian Cerrado. This study analyzed ovarian and oviduct characteristics and the egg production capacity of T. scripta elegans grown in this biome. The findings will associate with the size of the specimens and the sexual maturity, aiming at comparisons with native and exotic populations, as well as interspecific and contributing to the understanding of its impact on the invaded ecosystems and the establishment of eradication programs. Thus, 39 females had evaluated the body biometry and the morphology and morphometry of the ovaries and oviducts. G2 (N=20): with Class I (>5-10mm) follicles, with Class I and Class II (>10-fold) follicles, 25mm) and G3 (N=9) with Class I, Class II and Class III (>25mm) follicles. Analysis of variance, Scott-Knott’s test, and Pearson’s correlation analysis showed that there was no significant difference between the groups in body biometry; in the mean gonadosomatic index and gonadal morphometry, only the width of the oviducts in the right antimer and the mass and width in the left antimer were higher in G3, the only one that presented eggs. There was positive and harmonic development between body mass, carapace, and plastron, and gonadal growth occurred concomitantly with body growth, indicating a higher reproductive potential and a positive relationship between the size of the litter and the female litter. The gonadosomatic index proved to be an excellent reproductive indicator, and the ovarian evaluation was a better indicator of sexual maturity than the maximum carapace length. Ovaries were irregular structures, without delimitation between the cortical and medullary regions and filled with vitelogenic follicles of different diameters, atresic follicles, and corpora lutea, which reflected the ovarian complexity of the species and the presence of follicular hierarchy. In the scarce stroma, two germinative beds were observed per ovary and the presence of gaps very close to the follicles and associated with the blood vessels. Analysis of gonadal tissue revealed three types of oocytes according to cytoplasmic characteristics: homogeneous, vesicular or vesicular in the cortex with apparent granules. Oviducts were functional and separated, joining only in the final portion to form the cloaca and subdivided into infundibulum, tuba, isthmus, uterus, and vagina. The structure of the uterine tube was composed of serosa, muscular and mucous, which was full of glands. The presence of eggs in the oviducts indicated that the specimens can reproduce in the Brazilian Cerrado. This study provides necessary and relevant information on the reproductive biology and capacity of T. scripta elegans in the Brazilian Cerrado and can contribute to the understanding of its impact on the invaded ecosystems and the establishment of eradication programs. The extraction of females with capacity can reduce the annual reproductive yield of the species and decrease its effect on local biodiversity.

Implications from early life stress on the development of mouse ovarian follicles: Focus on oxidative stress.

The early life stress has significant long-term effects on the development of the offspring. This study was undertaken to verify if maternal separation as a stressor agent affects the oxidative status and developmental competence of mouse pre-antral follicles (PF) during in vitro culture period. Female litters of National Medical Research Institute mice were divided into two groups: maternally separated group (MS), separated from the mothers for 6 h per day from postnatal days 2-16; and the rest considered as the control group, which left undisturbed over the 14 days. The litters were sacrificed and the ovarian tissue was harvested to isolate the PF. The PF were in vitro cultured up to 12th day when ovulation was induced. The developmental parameters and oxidative status (i.e., total antioxidant capacity and Malondialdehyde levels, as well as the activities of superoxide dismutase, glutathione peroxidase and catalase) were assessed. The rates of survival, antrum formation, ovulation and oocyte maturation of PF derived from the MS group were significantly lower compared with those of the control group. Furthermore, the Malondialdehyde level of the MS group was significantly higher than that of the control group. By contrast, the total antioxidant capacity level was lower in the MS group with respect to the control group. Also, the activity of superoxide dismutase, glutathione peroxidase and catalase of PF, derived from the MS group, was significantly lower compared with those of the control group. Early life stress damages the developmental competence of mouse PF through induction of oxidative stress.

SAT-LB062 Adrenal Sexual Dimorphism Is Abolished by Tissue-Targeted Deletion of the Androgen Receptor

Introduction: Sex differences in mouse and human tissues can affect cancer risks, cardiovascular, kidney and liver diseases. Mouse adrenals have several sexually dimorphic traits, but their role in physiology remain poorly understood. Differences include larger adrenals in females and earlier regression of the X-zone (the mouse fetal adrenal) in males. The X-zone regresses at puberty in males and at pregnancy in females. There are also clear sex-differences in expression of adrenal mRNA and proteins. These include higher female levels of Dax-1 (Nr0b1), a nuclear receptor critically involved in adrenal development/steroidogenesis, whereas male adrenals exhibit higher levels of the androgen-metabolizing enzyme, 5α-reductase (Srd5a2). Determining the factors that drive adrenal sexual dimorphism may provide insight into the potential impact of these differences on adrenal physiology. One potential regulator of adrenal sexual dimorphism is exposure to sex steroids, particularly androgens and estrogens. Herein, we test the hypothesis that androgens, through the adrenal androgen receptor (AR), are responsible for sexually dimorphic traits of mouse adrenal glands. This hypothesis was tested through specific disruption of adrenal cortex Ar expression. Methods: Adrenal targeted deletion of Ar was accomplished in male mice by crossing heterozygous aldosterone synthase-Cre mice to floxed Ar mice (mAdARKO). Mice were sacrificed at 25 weeks of age and comparisons were made to wild type male (mWT) and female (fWT) litter mates. Adrenals were weighed, processed for histology (H&E), immunofluorescence (IF) for AR, and whole adrenal mRNA levels analyzed using quantitative RTPCR. Results: mAdARKO mice decreased adrenal Ar mRNA by 90% compared to mWT mice (p < 0.01) and AR protein was undetectable in the adrenal cortex using IF. mAdARKO adrenals were larger than adrenals of mWT mice (1.6-fold increase in weight, p < 0.01) but comparable to that of fWT animals. Nr0b1 transcripts in mAdARKO mice increased by 8-fold compared to mWT (p < 0.01) and were not significantly different from fWT adrenals. Adrenal Sdr5a2 expression was significantly downregulated in mAdARKO (0.16-fold compared to mWT; p < 0.01) and analogous to the levels seen in fWT mice. Histological analysis revealed the retention of an X-zone in post-pubertal mAdARKO which was not present in age-matched mWT animals. Moreover, mRNA for the X-zone marker, 20α-HSD (Akr1c18), increased by 140,000-fold (p < 0.01) in mAdARKO adrenals compared to mWT, and was 20 times that seen in fWT mice. Conclusion: The current study suggests that deleting adrenal Ar is sufficient to cause male adrenal phenotypic sex-reversal including retention of the X-zone. Finally, adrenal sexual dimorphism highlights the necessity to include both sexes in mouse adrenal studies and the mAdARKO model provides a novel model to determine the impact of sex on adrenal biology. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Consequences of rearing feeding programme on the performance of rabbit females from 1st to 2nd parturition

To evaluate how rearing programmes could affect resources allocation and reproductive performance of primiparous rabbit females, a total of 118 rabbit females were used to evaluate the effects of five rearing feeding programmes on their performance from 1st to 2nd parturition: CAL, fed ad libitum C diet (11.0 MJ digestible energy (DE), 114 g digestible protein (DP) and 358 g NDF/kg dry matter (DM) until 1st parturition; CR, fed ad libitum with C diet until 12 weeks of age and then C diet restricted (140 g/day) until 1st parturition; F, fed ad libitum with F diet (8.7 MJ DE, 88 g DP and 476 NDF/kg DM) until 1st parturition; FC, fed with F diet ad libitum until 16 weeks of age, and C diet ad libitum until 1st parturition; FCF, fed with F diet ad libitum until 16 weeks of age, then C diet ad libitum until 20 weeks and then F diet ad libitum until 1st parturition. From 1st parturition, C diet was ad libitum offered to all the experimental groups until 2nd parturition. CAL females presented lower feed intake than females of F, FC and FCF groups in the 1st week of lactation (on av. −16.6%; P<0.05). During 1st lactation, the perirenal fat thickness change in CAL females was not different from 0 (+0.02 mm), while in the other four groups it increased (on av. +0.44 mm; P<0.05). Plasma of females fed with F diet during rearing (F, FC and FCF) had lower non-esterified fatty acids content than those exclusively fed with C diet (–0.088 and –0.072 mmol/l compared to CAL and CR, respectively; P<0.05). FCF litters had higher weight than F litters at day 21 of lactation (+247 g; P<0.05), but FCF litter had significantly lower weight than FC litters at weaning (+170 g; P<0.05). CR females had the shortest average interval between the 1st and 2nd parturition (49 days) and FCF females the longest (+ 9 days compared to CR; P<0.05). At 2nd parturition, liveborn litters of F females were larger and heavier than litters of FCF females (+2.22 kits and +138 g; P<0.05), probably due to the lower mortality at birth of F litters (–16.5 percentage points; P<0.05). In conclusion, rearing females on fibrous diets seems to increase the ability of primiparous rabbit females to obtain resources, especially at the onset of lactation.

A vaccination trial with a precocious line of Eimeria magna in Algerian local rabbits Oryctolagus cuniculus

Coccidiosis is a major health problem in rabbits. A vaccine using Eimeria with perfect safety and effectiveness seems to be necessary to face this parasitosis. To assess the safety and the efficacy of a vaccine based on the Algerian precocious line of Eimeria magna against rabbit coccidiosis, twenty eight young rabbits from six litters of Coccidia free females were used to monitor oocystal excretion and body weights, they were distributed into four groups (vaccinated-challenged group, double challenged non vaccinated group, simple challenged non vaccinated group and control group). Three other Coccidia free rabbits served for the necropsy in order to compare the effect of the wild and the precocious strains of Eimeria magna at the histological level. Following the challenge inoculation, a statistically significant decrease of about 97% in the oocyst excretion was noticed in the vaccinated rabbits as a sign of a good immune response acquired by the vaccination associated to a good growth rate. Moreover, a statistically significant increase in oocyst output following the challenge in both double challenged non vaccinated group and simple challenged non vaccinated one was noticed: (1.2 × 108 and 1.5 × 108vs 4.6 × 106 oocysts/rabbit respectively). Taking the control group showing a steady growth as a reference, the vaccinated rabbits showed a good growth during the experiment (p < 0.05). Globally the challenged groups showed a normal growth compared with the control group except for a temporary decrease in weights. No case of diarrhea was recorded in the vaccinated – challenged group and the control one (neither vaccinated nor challenged) whereas more than 50% of the young rabbits from both simple and double challenged – non vaccinated groups presented diarrhea. Consequently, the Algerian precocious strain of Eimeria magna constitute a good candidate for anticoccidian vaccine in the future.

Female-biased sex ratios are associated with higher maternal testosterone levels in nutria (Myocastor coypus)

Under various ecological conditions, producing a biased sex ratio may be adaptive. However, the factors that translate specific ecological conditions into internal processes remain an enigma. A potential mediator is maternal testosterone, which may reflect physical, reproductive, and social conditions. The nutria (Myocastor coypus) is a polygynous rodent, invasive in many parts of the world, which shows fluctuating sex ratios. Using necropsies of 82 pregnant culled nutrias, we found that in early pregnancy, offspring sex ratios are more male-biased than in later pregnancy. Since sex ratios decrease with pregnancy age, male fetuses in our study population may be terminated. In 68% of the litters, the heaviest fetus was a male, suggesting that males are the “expensive” sex. We also found that while maternal weight was not associated with testosterone, heavier females and those with lower testosterone had male-biased sex ratios. Litters of high testosterone females had female-biased sex ratios. To the best of our knowledge, this study is the first to show a negative association between maternal testosterone and male-biased sex ratios. Testosterone, through its role in reproduction, might be mediating maternal internal and external conditions by adjusting intra-uterine sex ratio. For decades, the mechanisms behind offspring sex ratios have been of interest across disciplines. Maternal testosterone has been implicated in mediating maternal condition, thus influencing secondary sex ratios. Here, we investigated the reproductive parameters of a culled nutria and integrated it with maternal hair testosterone levels to test the association between long-term testosterone and sex ratios. Our most surprising result was that high maternal testosterone levels were related with female-biased sex ratios. This is contrary to previous studies in other species and counter-intuitive. Heavier females tended to have male-biased litters. We also found that the proportionate representation of males within litters declined over the course of pregnancy. Male fetuses were usually the heaviest fetus, suggesting that they are the more “expensive” sex. We believe that our study provides new insights in this long-debated issue and will contribute to understanding the reproductive costs involved with maternal testosterone across animal models.

Alloparental behaviour in Sinai spiny mice Acomys dimidiatus: a case of misdirected parental care?

Communal breeding, where reproducing females share a nest and the care of their pups, occurs in many animal species. According to kin selection theory, alloparental behaviour should occur predominantly among closely related conspecifics. However, familiarity between females, a prerequisite for reciprocal altruism, may also play a role. The aim of our study was to analyse the effect of kinship and familiarity on the occurrence of two types of alloparental care—nursing and the retrieval of pups wandering from the nest—in a communally breeding rodent, the Sinai spiny mice Acomys dimidiatus. In addition, the effects of other factors that may also have an impact on alloparental care were tested; these included age difference between litters, pup age, maternal experience, pup sex ratio, litter size, group age, and mother’s weight. We found that kinship and familiarity had no effect on alloparental care. The nursing of alien pups depended on the maternal reproductive experience measured as the number of weaned litters and also on the age difference between the litters of both females. Less experienced females nursed alien pups more often than experienced ones. With increasing age difference between litters, females preferentially nursed their own pups. Similarly, the retrieval of alien pups was affected by the age disparity between the litters; with increased age difference, the females more readily retrieved their own pups. These results indicate that the occurrence of alloparental care in the Sinai spiny mouse may be more related to misdirected parental care than to kin selection.

Effect of Dietary Energy on Productive and Reproductive Performance of Algerian Local Rabbit Does and Their Litters

Local rabbit reared in Algeria is well adapted to the climate of the country while being characterized by a variable phenotype and prolificacy. The present work was carried out to study the effects of dietary energy content on productive and reproductive performance of local does and their litters during their first two lactations. A total of 75 nulliparous rabbit does were separated in three equal groups and received isoproteinous diets (15% CP) differing in their digestible energy (DE) contents viz. 2300, 2450 and 2600 kcal DE/kg for dietary groups LE, ME and HE, respectively. Diets were supplied ad libitum between parturition and weaning which was performed at age 28 d. Dietary energy didn't show any effects on does live weight, weight gain and milk yield, but decreased significantly (P<0.001) feed intake during all weeks post partum. Total feed intake during 28 d post partum were than significantly higher (7635 g for LE vs. 6860 g for ME vs. 5872 g for HE) (P<0.001). We observed no significant difference between diets and parities for litter size and litter weight from birth to weaning. Milk production was on average 7.37% higher at the second parity (P<0.019). Litter weight was higher the two first weeks of live at the second parity (P<0.05). Does and their litters were more responsive to diet energy at the second parity. In the limit of this experiment, dietary energy has an influence on feed intake of local does but not on female weight and litter performance during the first two cycles of reproduction.

Paroxetine exposure skews litter sex ratios in mice suggesting a Trivers-Willard process.

While conducting a toxicity assessment of the antidepressant paroxetine (Paxil®), in wild-derived mice (Mus musculus), we observed that exposed dams (P0) produced female biased litters (32:68 M:F). Though numerous experimental manipulations have induced sex ratio bias in mice, none have assessed the fitness of the offspring from these litters relative to controls. Here, we retrospectively analyze experimentally derived fitness data gathered for the purpose of toxicological assessment in light of 2 leading hypothesis (Trivers-Willard hypothesis [TWH] and cost of reproduction hypothesis [CRH]), seeking to test if this facultative sex ratio adjustment fits into an adaptive framework. Control F1 males were heavier than F1 females, but no differences in mass were detected between exposed F1 males and females, suggesting that exposed dams did not save energy by producing fewer males, despite producing 29.2% lighter litters relative to controls. F1 offspring of both treatments were released into seminatural enclosures where fitness was quantified. In enclosures, the relative reproductive success of F1-exposed males (compared with controls) was reduced by ~20% compared with the relative reproductive success of F1-exposed females. Thus, exposed dams increased their fitness by adjusting litters toward females who were less negatively affected by the exposure than males. Collectively, these data provide less support that the observed sex ratio bias results in energetic savings (CRH), and more support for the TWH because fitness was increased by biasing litters toward female offspring. These mammalian data are unique in their ability to support the TWH through the use of relevant fitness data.

Female reproductive aging is master-planned at the level of ovary.

The ovary receives a finite pool of follicles during fetal life. Atresia remains the major form of follicular expenditure at all stages since development of ovary. The follicular reserve, however, declines at an exponential rate leading to accelerated rate of decay during the years preceding menopause. We examined if diminished follicle reserve that characterizes ovarian aging impacts the attrition rate. Premature ovarian aging was induced in rats by intra-embryonic injection of galactosyltransferase-antibody on embryonic day 10. On post-natal day 35 of the female litters, either a wedge of fat (sham control) or a wild type ovary collected from 25-day old control rats, was transplanted under the ovarian bursa in both sides. Follicular growth and atresia, and ovarian microenvironment were evaluated in the follicle-deficient host ovary and transplanted ovary by real time RT-PCR analysis of growth differentiation factor-9, bone morphogenetic protein 15, and kit ligand, biochemical evaluation of ovarian lipid peroxidation, superoxide dismutase (SOD) and catalase activity, and western blot analysis of ovarian pro- and anti-apoptotic factors including p53, bax, bcl2, and caspase 3. Results demonstrated that the rate of follicular atresia, which was highly preponderant in the follicle-deficient ovary of the sham-operated group, was significantly prevented in the presence of the transplanted ovary. As against the follicle-deficient ovary of the sham-operated group, the follicle-deficient host ovary as well as the transplanted ovary in the ovary-transplanted group exhibited stimulated follicle growth with increased expression of anti-apoptotic factors and down regulation of pro-apoptotic factors. Both the host and transplanted ovaries also had significantly lower rate of lipid peroxidation with increased SOD and catalase activity. We conclude that the declining follicular reserve is perhaps the immediate thrust that increases the rate of follicle depletion during the final phase of ovarian life when the follicle reserve wanes below certain threshold size.

Mating Systems, Reproductive Success, and Sexual Selection in Secretive Species: A Case Study of the Western Diamond-Backed Rattlesnake, Crotalus atrox

Long-term studies of individual animals in nature contribute disproportionately to our understanding of the principles of ecology and evolution. Such field studies can benefit greatly from integrating the methods of molecular genetics with traditional approaches. Even though molecular genetic tools are particularly valuable for species that are difficult to observe directly, they have not been widely adopted. Here, we used molecular genetic techniques in a 10-year radio-telemetric investigation of the western diamond-backed rattlesnake (Crotalus atrox) for an analysis of its mating system and to measure sexual selection. Specifically, we used microsatellite markers to genotype 299 individuals, including neonates from litters of focal females to ascertain parentage using full-pedigree likelihood methods. We detected high levels of multiple paternity within litters, yet found little concordance between paternity and observations of courtship and mating behavior. Larger males did not father significantly more offspring, but we found evidence for size-specific male-mating strategies, with larger males guarding females for longer periods in the mating seasons. Moreover, the spatial proximity of males to mothers was significantly associated with reproductive success. Overall, our field observations alone would have been insufficient to quantitatively measure the mating system of this population of C. atrox, and we thus urge more widespread adoption of molecular tools by field researchers studying the mating systems and sexual selection of snakes and other secretive taxa.

Birth timing for mountain lions (Puma concolor); testing the prey availability hypothesis.

We investigated potential advantages in birth timing for mountain lion (Puma concolor) cubs. We examined cub body mass, survival, and age of natal dispersal in relation to specific timing of birth. We also investigated the role of maternal age relative to timing of births. We captured mountain lion cubs while in the natal den to determine birth date, which allowed for precise estimates of the population birth pulse and age of natal dispersal. A birth pulse occurred during June–August. Body mass of cubs was related to litter size and timing of birth; heaviest cubs occurred in litters of 2, and those born after 1 July. Cubs born within pulse months exhibited similar survival to those born out of the pulse. We found that cubs born April–June dispersed at younger ages than those born after 1 July. There was less variation in birth timing for 1st litters of females than older females. We hypothesize that cubs born after the peak in births of neonate prey are advantaged by the abundance of vulnerable prey and those cubs and mothers realize an evolutionary advantage.