Sexual Maturity Rating Research Articles

Tanner Stages and Pubertal Development

Abstract Puberty typically follows a predictable pattern that can be assessed using the Tanner stages or Sexual Maturity Rating scale. Clinicians can use this tool to evaluate and monitor progress in female and male puberty. The timing and sequence of puberty are important indicators of the growth and development of pediatric patients. Stages of puberty and normal findings must be known before variations can be identified. Pubertal changes that fall outside the normal timeline or trajectory are considered abnormal and must be investigated. Treatments for abnormal variations are based on pathologic versus idiopathic causes. Nurses, as members of the interprofessional collaborative team, serve an important role by obtaining data, monitoring progress, providing health education, performing ongoing assessment/evaluation, and ensuring continuity of care when needed.

Polycyclic aromatic hydrocarbons are associated with later puberty in girls: A longitudinal study

The objective of this study is to explore associations between PAH exposures and puberty timing in girls. Beginning in May 2014, 734 girls age 7.2–11.8 years in Chongqing, China, were enrolled in a prospective cohort study. They were followed up every 6 months from enrollment through June 2021, at which point participants were ages 13.6–18.3 years. Metabolite concentrations of four PAHs (1-hydroxypyrene [1-OHPyr], 2-hydroxynaphthalene [2-OHNap], 2-hydroxyfluorine [2-OHFlu], and 9-hydroxyphenanthrene [9-OHPhe]) were measured in urine samples at baseline. At each follow up visit, the Tanner's Sexual Maturity Rating scale was administered. Cox proportional hazards models were used to estimate associations between four urinary PAH metabolite concentrations and four markers of puberty: menarche, breast development, pubic hair development, and axillary hair development. Geometric mean concentrations of 1-OHPyr, 2-OHNap, 2-OHFlu and 9-OHPhe in urine were 0.47 μg/L, 3.31 μg/L, 1.49 μg/L, 3.75 μg/L, respectively. There were statistically significant associations between several urinary PAH metabolite concentrations and puberty outcomes. PAH metabolite concentrations were grouped as Low (<25th percentile, referent group), Moderate (25th–75th percentile) or High (>75th). Girls with moderate levels of 1-OHPyr were at higher risk of delayed pubic hair development (hazard ratio [HR]: 0.82, 95 % confidence interval [CI]: 0.68–0.99). Delayed breast development (HR: 0.77, 95 % CI: 0.60–0.99) and pubic hair development (HR: 0.76, 95 % CI: 0.60–0.95) were associated with high 2-OHNap. High c 2-OHFlu was associated with delayed pubic hair development (HR: 0.77, 95 % CI: 0.61–0.96). Delayed breast (HR: 0.79, 95 % CI: 0.64–0.97), pubic hair (HR: 0.79, 95 % CI: 0.65–0.96) and axillary hair development (HR: 0.80, 95 % CI: 0.65–0.99) was associated with moderate 9-OHPhe. In conclusion, PAH exposure may delay puberty onset in girls.

Comparative characteristics of the sensitivity of the bird to aspergillosis pathogens

It has been established that the most common mycoses among poultry are aspergillosis and mucormycosis, which are observed in sporadic cases under conditions of violation of egg incubation technologies, zoohygienic conditions for poultry keeping, and feed storage. Aspergillosis (pneumomycosis, brood pneumonia, mycosis) is an infectious disease that most often affects the respiratory system and, less often, the serous membranes of other organs, namely the liver, intestines, spleen, kidneys, central nervous system, and air cavities of the tubular bones. Aspergillosis affects all species of poultry and wild birds. The disease is more common in young animals in the first days of life. In the studied poultry farms, aspergillosis has a different intensity. The disease can kill 30 to 50 % of all young animals and, in some cases, only a few. This is due to the infection of the fungus in the environment, its pathogenicity, the bird's age, and its resistance. The material for the research was carcasses and aspergillosis-sick birds from Poltava HPE LLC, Poltava Poultry Factory JSC, Poltava Incubator Agricultural Complex, and Poltava district private farms. Statistical indicators from the surveyed farms and micro-sections. It has been established that the causative agent of aspergillosis in chickens and young guinea fowl is mainly the fungus Aspergillus fiimigatus, less often Aspergillus flavus. Sources of infection in the surveyed farms are infected hatching eggs infected with fungal spores and moldy litter. Determining factors contributing to the infection are unsatisfactory conditions for keeping young birds: high humidity and faulty ventilation system. Chickens are more sensitive to aspergillosis than young guinea fowl because, for chickens, the number of detected pathologies in various organs and systems is much higher. The disease in chickens is superacute, acute, and chronic; in young guinea fowl, it is in a mild form (without chronic forms). Clinical signs of avian aspergillosis are not typical, which complicates the lifelong diagnosis of the disease. The results show that raising guinea fowl is a more profitable business because the rate of loss of young is much lower than that of chickens and the rate of sexual maturity for guinea fowl is also higher. Aspergillosis in one-three-day-old chickens is characterized by serous tracheitis, bronchitis, aerosacculitis, and serous fungal pneumonia. Histological examination of the lungs showed swelling of endothelial and alveolar cells, the presence of fungal spores in blood vessels, necrosis, and desquamation of the respiratory epithelium.

The effect of age and sexual maturation on thermal preferences of honey bee drones.

The thermal preferences of Apis mellifera carnica drones (male individuals) are poorly understood, though their reproductive quality affects the quality of the inseminated queen and the whole honey bee colony. Therefore, the aim of this study was to determine the thermal preferences of individual drones according to their age and sexual maturity. Drones at the ages of 1, 5, 10, 15, 20 and 25 days were tested. The drones were placed on a platform in a temperature gradient in the range 20 °C and 46 °C. The thermal preferences of the drones were measured with the use of a thermal-imaging camera. Drones significantly differed with their choice of a preferred temperature. The one-day-old and the 25-day-old drones preferred the lowest temperatures. A slightly higher temperature was preferred by the 5-day-old drones, and the highest temperature was chosen by the drones at the ages of 10, 15, and 20 days. The changes in the thermal preferences of drones correspond to physiological changes occurring with age and connected with the rate of sexual maturation.

Associations between infant growth and pubertal onset timing in a multiethnic prospective cohort of girls

BackgroundEarly puberty increases risk of adverse health conditions throughout the life course. US girls are experiencing earlier puberty without clear reasons. Studies suggest early life factors, such as infant growth, may influence pubertal timing. We assessed the associations between infant growth and onset of breast development (thelarche), pubic hair development (pubarche), and menarche in girls.MethodsA prospective cohort of girls born at a Kaiser Permanente Northern California medical facility in 2005–11 was used. Weight-for-age z-scores were calculated at birth and 24 months. Difference in z-scores greater than 0.67 represent rapid “catch-up” growth, less than -0.67 represent delayed “catch-down” growth, and between -0.67 and 0.67 represent “normal” growth. Pubertal onset was measured using clinician-assessed sexual maturity ratings (SMRs) and defined as the age at transition from SMR 1 to SMR 2 + for both thelarche and pubarche. SMR data was collected through June 2020. Menarche was analyzed as a secondary outcome. Weibull and modified Poisson regression models were used. Models were adjusted for potential confounders.ResultsThere were 15,196 girls included in the study. Approximately 30.2% experienced catch-up growth, 25.8% experienced catch-down growth, and 44% had normal growth. Girls with catch-up growth had increased risk of earlier thelarche (hazard ratio = 1.26, 95% confidence interval (CI): 1.18, 1.35), pubarche (1.38, 95% CI: 1.28, 1.48), and menarche (< 12y, relative risk = 1.52, 95% CI: 1.36, 1.69) compared to those with normal growth, after adjusting for covariates. These associations were partially mediated by childhood body mass index. Catch-down growth was associated with later pubertal onset.ConclusionsGirls who experience infant catch-up growth have higher risk of earlier pubertal development compared to girls with normal growth and the associations are partially explained by childhood obesity. This information may help clinicians to monitor girls who are at high risk of developing earlier.

Abstract 97: Lipoid congenital adrenal hyperplasia in a boy with primary adrenal insufficiency with normal male external genitalia

Background: Lipoid congenital adrenal hyperplasia (CAH) commonly manifests as atypical genitalia or apparent female external genitalia in 46, XY whereas rarely, it may present with normal male external genitalia. Hence, we report the first Indian case of lipoid CAH with normal male external genitalia.Case Presentation: A 8-year-old boy born of a third-degree consanguineous marriage, presented in 2018 with generalized hyper-pigmentation. Serum 8:00 am cortisol was 2.78 μg/dl and plasma 8:00 am ACTH was 1260 pg/ml. He was diagnosed to have primary adrenal insufficiency and started on oral hydrocortisone 12 mg/m2/d and fludrocortisone (100 μg/d). He had developed hypokalemia on 100 μg/d and also, on 50 μg/d susequently. Hence, his fludrocortisone had been stopped. On review visit after 3 years (at present), his height and weight were appropriate for age and Tanner's sexual maturity rating was P3, SPL-7 cm and TV-15 cc bilateral. His ACTH-stimulated steroid profile showed low serum cortisol (0.15 μg/dL) and aldosterone (3.48 ng/dL) whereas direct renin concentration was elevated (167.5 μIU/mL). Subsequent genetic analysis revealed homozygous pathogenic variant c.574C>T (p.Arg192Cys) in STAR. The patient was restarted on fludrocortisone 25 μg/d.Conclusion: We report the first genetically-proven case of lipoid CAH in a boy with normal male external genitalia in India presenting with primary adrenal insufficiency. The case emphasizes that the diagnostic possibility of lipoid CAH can not be excluded in 46,XY primary adrenal insufficiency with normal male external genitalia.

Abstract 101: A case of CYP11A1 enzyme deficiency with unambiguity

We hereby present a 20 years old boy who presented at 14 years of age with generalized hyperpigmentation, bilateral breast enlargement, loose stools and fever. He was born out of second-degree consanguinity with uneventful birth and childhood history. On examination he had generalized hyperpigmentation, gynecomastia, no genital ambiguity with normal sexual maturity ratings. Blood biochemistry was suggestive of primary adrenal insufficiency and primary testicular failure. The computerized tomography imaging showed normal adrenal glands. With involvement of both adrenal glands and gonads, differential diagnosis including autoimmune polyglandular syndrome, NR5A1 and NR0B1 mutations were considered. Clinical exome sequencing was done which showed a novel homozygous missense variation in exon 4 of the CYP11A1 gene (chr15:g.74343895G>C). A diagnosis of side chain cleavage enzyme (CYP11A1) deficiency unusually presenting with genital unambiguity was made.

Consequences of hybridization on life history and growth in postmetamorphic Triturus macedonicus

Abstract The Macedonian crested newt T. macedonicus forms a complex hybrid zone with the Balkan crested newt T. ivanbureschi in the central part of the Balkan Peninsula. In this study, we compared life history parameters (sex ratio, survival rate and age of sexual maturation) and growth parameters (body length and mass) of T. macedonicus and T. macedonicus × T. ivanbureschi hybrids over the first three postmetamorphic years. Survival rates were high and similar for both genotypes. Sexual dimorphism in body size (length and mass) was evident at the beginning of the third postmetamorphic year, after the first breeding year, for both T. macedonicus and hybrids. We did not find clear and consistent difference in any of the analysed traits suggesting that hybridization with T. ivabureschi does not affect postmetamorphic growth and survival of T. macedonicus.

Evaluation of Hyperandrogenism in Children with Autism Spectrum Disorder.

This study evaluated 32 children (mean age: 8.5 y) with autism spectrum disorder (ASD) and 23 healthy controls (similar age, sex, and Tanner stage) for hyperandrogenism. These children underwent sexual maturity rating (Tanner staging), ASD severity assessment (Childhood Autism Rating Scale), and quantitative estimation for plasma testosterone, dehydroepiandrosterone sulfate (DHEAS), and androstenedione. There was no significant difference in androgen levels in the two groups. Elevated (> 95 centiles) testosterone, DHEAS, and androstenedione levels were seen in 12.3%, 6.2%, and 9% children with ASD, and 7/9 of these children (78%) with hyperandrogenism had severe ASD. However, there was no significant correlation between ASD severity and androgen levels.

Growth and Pubertal Development Among HIV Infected and Uninfected Adolescent Girls in Lagos, Nigeria: A Comparative Cross-Sectional Study.

This study aimed to compare growth and pubertal developmental parameters among HIV-infected and uninfected adolescent girls (11-19 years) in Lagos using a cross-sectional approach. Height, weight, BMI Z-scores, sexual maturity rating by Tanner stages and age at menarche, were compared in the 2 groups. The mean age was similar in both groups (13.2 [±2.3] years and 13.6 [±1.6] years for HIV positive and negative respectively [P = .13]). Majority (66.2%) were in Junior Secondary classes and the mean socioeconomic class was 2.5 (±0.9). HIV-infected girls had significantly lower height, weight, and BMI Z scores compared to their uninfected counterparts. The proportion that had attained Tanner stages 3 to 5 were significantly lower among the HIV-positive participants. The study identified lower growth parameters and pubertal delay among HIV-infected adolescent females compared to HIV uninfected girls. Growth and sexual maturation assessment should form part of routine care of adolescents living with HIV.

Prevalence of metabolic syndrome and predictors of metabolic risk in Indian children, adolescents and youth with type 1 diabetes mellitus.

Children with type 1 diabetes (T1D) are at the same risk of developing metabolic syndrome (MS) as the general population. Several environmental factors such as lifestyle, exogenous insulin therapy (over-insulinization) and genetic/familial factors are thought to underlie the phenotype of 'double diabetes' (co-existence of MS components in patients with T1D). To determine the prevalence of overweight/obesity and MS and to identify its predictors in Indian children, adolescents and young adults with T1D. This cross-sectional study included 355 children and youth aged 6-23 years with T1D. Demographic data were obtained from patients using questionnaires. Anthropometry, blood pressure, sexual maturity rating, biochemical measurements and body composition measurements were performed using standard protocols. Insulin resistance (IR) was calculated using estimated glucose disposal rate (eGDR) and MS was diagnosed using the international diabetes federation (IDF) consensus definition 2017. The prevalence of overweight/obesity and MS in our study was 15.5% and 4.5%, respectively. Abnormal HDL-cholesterol was the most common component of MS (55.6%) among children with T1D. Age, gender, body mass index (BMI) and eGDR were identified as significant predictors of the likelihood of MS. We found a similar prevalence of MS in children with T1D as compared to other healthy children, which emphasises the need for monitoring of eGDR to determine IR in these children.

Clinician practices assessing hypothalamic-pituitary-gonadal axis suppression in adolescents with an eating disorder.

Although extensive literature exists on hypothalamic-pituitary-gonadal (HPG) axis suppression in females with an eating disorder, there are few studies in males. Our study aimed to determine clinician practices for the assessment of HPG axis suppression and to identify differences in practice based on the sex of the patient. Our 31-item survey queried clinicians about confidence level and practices for assessing HPG suppression in male compared to female patients. Findings showed that clinicians (n=104) were less likely to evaluate HPG suppression in males compared to females, including assessment of sexual maturity rating (p < .050), screening of decreased libido compared to amenorrhea (p < .001) and lab assessment (luteinizing hormone and follicular-stimulating hormone: p < .001; estradiol/testosterone: p < .010; TSH: p < .050). Participants also felt less confident evaluating male patients (p < .001) and requested better screening tools for males (p < .001). Our data suggest that clinician practices differ based on patient sex and that clinicians request tools for HPG suppression assessment in males. This is the first study examining specific practices and comfort levels of clinicians when assessing HPG axis suppression. Findings suggest that more guidance on the management of male patients may be needed to standardize care and to prevent short and long-term sequela of malnutrition.

Atypical genotype in a typical phenotype

Introduction: Usually, onset of thelarche heralds puberty. Delayed puberty is worrisome and needs medical attention. Our patient in her late adolescence presented with primary amenorrhea, whose evaluation left us surprised. Case report: An eighteen-year-old scholastically backward girl, presented with complaints of not attaining menarche. Physical examination included a height of 156 cm(10th-25thcentile),weight 51 kg(50th centile), wide carrying angle, multiple nevi and a broad chest, however no other Turner stigmata was noted. Her sexual maturity rating (SMR) was A2P2B1 Laboratory investigations revealed increased gonadotropins (FSH:77mIU/ml; LH:25.4mIU/ml), low estradiol (14 pg/ml) and vitamin-D deficiency (21ng/ml). Ultrasonography of abdomen-pelvis showed small infantile uterus with streak ovaries. Karyotype (50 metaphases) demonstrated mosaicism [47,XXX (29)/45,X(19)/46,XX(2)]. Hormone replacement therapy and vitamin D replacement was initiated. Conclusion: 30-40% of the Turner syndrome are mosaics, the most common being 45,X/46,XX. Mosaicism is the presence of 2 or more cell lines with different chromosomal constitutions. The cell lines are derived due mostly to postzygotic mitotic nondisjunction. X/XX/XXX can present with or without classical turner stigmata. Trisomy X has a spectrum of presentation from normal menses and fertility to recurrent abortions and primary/secondary amenorrhea (primary ovarian insufficiency). Varied clinical phenotype due to three cell lines in a Turner mosaic makes this case unique.

Adolescent Gynecology in the Office Setting.

Ensuring open communication, partnership with patient and parent, and clarification of confidentiality during an adolescent gynecologic visit helps establish an environment in which a history and physical examination can be performed safely and with a focus on prevention, recognition of disease, and treatment as necessary. The history should include the menstrual status and gynecologic review of systems. The examination should document Tanner staging (sexual maturity rating) and be otherwise symptom guided. Similarly, testing in the office is largely risk and symptom related. Contraceptive counseling is an important component of the office visit, as well. Long and short curricula for teaching pediatric and adolescent gynecology have been developed by the North American Society for Pediatric and Adolescent Gynecology and are readily available for use. (1)(2) Although state-based variation in consent and confidentiality exists, pediatric practices should aim to protect patient confidentiality and transition to more independent health-care decision making.

Atypical genotype in a typical phenotype

Introduction: Usually, onset of thelarche heralds puberty. Delayed puberty is worrisome and needs medical attention. Our patient in her late adolescence presented with primary amenorrhea, whose evaluation left us surprised. Case report: An eighteen-year-old scholastically backward girl, presented with complaints of not attaining menarche. Physical examination included a height of 156 cm(10th-25thcentile),weight 51 kg(50th centile), wide carrying angle, multiple nevi and a broad chest, however no other Turner stigmata was noted. Her sexual maturity rating (SMR) was A2P2B1 Laboratory investigations revealed increased gonadotropins (FSH:77mIU/ml; LH:25.4mIU/ml), low estradiol (14 pg/ml) and vitamin-D deficiency (21ng/ml). Ultrasonography of abdomen-pelvis showed small infantile uterus with streak ovaries. Karyotype (50 metaphases) demonstrated mosaicism [47,XXX (29)/45,X(19)/46,XX(2)]. Hormone replacement therapy and vitamin D replacement was initiated. Conclusion: 30-40% of the Turner syndrome are mosaics, the most common being 45,X/46,XX. Mosaicism is the presence of 2 or more cell lines with different chromosomal constitutions. The cell lines are derived due mostly to postzygotic mitotic nondisjunction. X/XX/XXX can present with or without classical turner stigmata. Trisomy X has a spectrum of presentation from normal menses and fertility to recurrent abortions and primary/secondary amenorrhea (primary ovarian insufficiency). Varied clinical phenotype due to three cell lines in a Turner mosaic makes this case unique.

Short-term efficacy of 1-month and 3-month gonadotropin-releasing hormone agonist depots in girls with central precocious puberty.

PurposeGonadotropin-releasing hormone agonist (GnRHa) has been the mainstay of central precocious puberty (CPP) treatment for decades, but few reports have compared the efficacy of 1-month and 3-month depot GnRHa formulations. This study investigates the short-term efficacy of 1-month and 3-month GnRHa depots in girls with CPP.MethodsOverall, 150 girls with CPP were included in a retrospective review of medical records. Subjects in group 1 (n=105) were treated with 1-month GnRHa depots for ≥12 months, and those in group 2 (n=45) were treated with 1-month GnRHa depots for 6 months followed by 3-month GnRHa depots for ≥6 months. Anthropometric and biochemical data were compared between the groups at 3-time points (after 0, 6, and 12 months of GnRHa treatment).ResultsDemographic and clinical characteristics did not differ between the groups at baseline or after 6 months of GnRHa treatment. After 12 months of GnRHa treatment, patients in the both groups showed no difference in bone age (BA), chronological age (CA), BA–CA difference, height standard deviation score (SDS) for CA and BA, or body mass index SDS for CA and BA. The sexual maturity rate of the breast was prepubertal at 12 months in most of subjects. GnRH-stimulated luteinizing hormone (LH) level was suppressed during GnRHa treatment in both groups at 6 and 12 months, although the LH level in group 2 was higher than that in group 1.ConclusionsTreating CPP with a 3-month GnRHa depot showed short-term efficacy comparable to that with a 1-month depot in anthropometric parameters and pubertal suppression.

Sexual maturity assessment in Indian children-a study from western India.

Pubertal assessment is crucial as puberty is the transition from childhood to adulthood. Pubertal assessment, growth, and secular trend in puberty need to be explored further in India. The objectives were to assess Sexual Maturity Rating (SMR) among children and establish normative data of puberty from western India. We also compared age of attainment of various stages of puberty with BMI and secular trend in menarche. A cross-sectional observational study was undertaken at a tertiary care pediatric center. The study population were healthy girls and boys between 6 and 18years. Demographic data was noted. Anthropometry and SMR assessment (Tanner staging) were performed. The age of menarche was noted among the girls and their mothers. Data were analyzed using SPSS 21. In girls, median age of thelarche, pubarche, and menarche was 9.37 (8.5-10.2), 10.18 (9.87-10.49), and 12.55years (12.41-12.75) respectively. There was an early appearance of thelarche but menarche was delayed in overweight-obese girls (statistically not significant). Age of menarche showed a shift to left in girls as compared to their mothers (p=0.036). In boys, median age of testicular stage 2 and pubarche was 10.7 (9.9-11.8) and 11.6years (11.1-12.1) respectively. In overweight-obese boys the pubertal milestones were achieved earlier (statistically not significant). Normative data on pubertal assessment from western India is presented. Age of menarche shows a shift to left in girls as compared to their mothers. Pubertal milestones were observed at a younger age in overweight obese children which was not significant.

Lead contamination in tissues of large avian scavengers in south-central Europe.

Lead poisoning from spent ammunition is known to affect many avian species. Birds of prey ingest lead when feeding on game shot with lead gunshot or bullets. Raptors with scavenging habits are particularly vulnerable to ingesting lead in areas with intensive hunting and are good indicators of the risk of poisoning from lead ammunition. To assess how much facultative and obligate avian scavengers suffer lead contamination in south-central Europe, between 2005 and 2019 we collected and analysed 595 tissue samples from 252 carcasses of 4 species (golden eagle, bearded vulture, griffon vulture, cinereous vulture). Lead concentrations in organs showed a similar pattern across species with long and small bones revealing the highest median values (5.56 and 6.8mg/kg w.w., respectively), the brain the lowest (0.12), and the liver and kidney the intermediate (0.47 and 0.284). Overall, 111 individuals (44.0%) had lead concentrations above background thresholds in at least one tissue (i.e. >2mg/kg w.w. in soft tissues, >8.33 in bone) and 66 (26.2%) had values indicating clinical poisoning (>6mg/kg w.w. in liver, >4 in kidney, >16.6 in bone). Tissue lead concentrations and incidence of clinical and sub-clinical poisoning were higher in golden eagles and griffon vultures than in bearded and cinereous vultures, likely due to different feeding habits. In all species we found a rapid increase in lead values with age, but differences between age classes were significant only in the golden eagle. Birds with lead fragments in their digestive tract, as detected by X-rays, had higher median lead concentrations, suggesting that hunting ammunition is the main source of lead poisoning. Our results imply that lead impacts the demography of these long-lived species with delayed sexual maturity and low reproduction rate. A rapid transition towards lead-free bullets and gunshot is therefore required across Europe.

EVALUATION OF FOUR NONLINEAR MODELS DESCRIBING EGG PRODUCTION CURVE OF FAYOUMI LAYERS

Egg production data used in this work were obtained from records of Fayoumi chickens flock belongs to El-Takamoly poultry project at Al-Azab, Fayoum Governorate. Egg production records over a 52-wk egg laying period related to 1900 hens. All data was summarized on a weekly basis as eggs per hen per week on hen-day (survivor) basis. Regarding Wood and McNally models, (a) stands for initial egg production, (a) parameter value was very low (0.001) for both models. The increasing rate to the egg production peak (parameter b) was 2.90 for the Wood model and 2.19 for the McNally model. Similarly, parameter c, the decreasing rate of egg production from the peak, was estimated to be 0.08 for the Wood model and 0.06 for the McNally model. Depending on compartmental function m, n, p and q represent scale parameter, measure of persistency of egg production, sexual maturity rate, and age at first egg, respectively and estimated values for these parameters were 86.47, 0.01, 0.23 and 21.61 wks of age, respectively, Concerning the modified compartmental model the parameters A, B, C and D represent a scale parameter, the rate of decrease in laying ability, the reciprocal indicator of the variation in sexual maturity and the mean age of sexual maturity of the hens, respectively. In this work the estimated values of the abovementioned parameters were 75.26, 0.006, 1.14 wks and 24.96 wks of age for A, B, C and D respectively. According to goodness of fit criteria, modified compartmental model was the best model for describing the egg-laying pattern of Fayoumi layers which had the lowest Akaike information criterion and Bayesian information criterion values and the highest coefficient of determination. Moreover, the modified compartmental model showed correspondence with the actual hen day of egg production (age and percentage at peak were 29.44 weeks of age and 64.16%, respectively).

Reproduction Ecology of the Bank Vole Myodes (Clethrionomys) glareolus Schreb. at the Northern Periphery of the Range: Communication 2. Sexual Maturation and Fertility of Adults and Juveniles

Over many years of field studies (1958–2017), we determined that, under the conditions of the northern periphery of the range, the rate of sexual maturation of bank vole juveniles depends on the calendar date of birth more than on the absolute age. It was noted that individuals can reproduce as early as 25–30 days after birth. The earlier the animals are born, the faster they grow and develop and the earlier they mature and begin to reproduce. It was established that males and females born later than June do not generally mature in the year of birth and reproduce only the next spring, after wintering, and although among them there are mature individuals (mainly July broods), their number does not exceed 21%. It was found that the rapidly developing underyearlings of early broods, almost without exception participating in reproduction in the year of birth, provide population growth by the fall of the current year, and those born in the second half of summer serve as a population reserve for the next breeding season. We registered the age-related differences in the quality of the population and a clear “distribution of responsibilities” between individual generations, which are quite labile and serve as one of the most important mechanisms of population regulation. It was also noted that the fertility of adult and breeding new females depends not only on the environmental conditions, but also on their numbers in spring.