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Research Question: What is the impact of radiation exposure on oocyte quality and female fertility?, Design: Prepubertal mice underwent whole-body irradiation with a single dose (0.02, 0.1, 0.5, 2, 8 Gy) of gamma- or X-rays. Oocytes were quantified in irradiated (n = 36) and sham-treated (n = 8) mice. After a single exposure to 2 Gy, formation of DNA double-strand breaks (n = 10), activation of checkpoint kinase (Chk2) (n = 10) and dynamics of follicular growth (n = 18) were analysed. Fertility assessment was performed in adult irradiated mice and controls from the number of pups per mouse (n = 28) and the fetal abortion rate (n = 24). Ploidy of mature oocytes (n = 20) was analysed after CREST immunostaining, and uterine sections were examined., Results: Radiation exposure induced a massive loss of primordial follicles with LD 50 below 50 mGy for both gamma and X-rays. Growing follicles survived doses up to 8 Gy. This difference in radiosensitivity was not due to a different amount of radio-induced DNA damage, and Chk2 was activated in all oocytes. Exposure to a 2 Gy dose abolished the long-term fertility of females due to depletion of the ovarian reserve. Detailed analysis indicates that surviving oocytes were able to complete folliculogenesis and could be fertilized. This transient fertility allowed irradiated females to produce a single litter albeit with a high rate of fetal abortion (23%, P = 0.0096), related to altered ploidy in the surviving oocytes (25.5%, P = 0.0035)., Conclusions: The effects of radiation on surviving oocyte quality question natural conception as a first-line approach in cancer survivors. Together, the data emphasize the need for fertility preservation before radiation exposure and call for reassessment of the use of cryopreserved oocytes., (Copyright © 2021 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.)

The objective of this study was to determine the effect of age at photostimulation on sexual maturity and performance of layer breeders. A total of 192 fourteen-wk-old White Leghorn (WL) breeder hens were randomly allocated to 4 treatments of 48 birds each, with 2 replicates per treatment. The birds were photostimulated at 16 (PS16), 18 (PS18), 20 (PS20), and 22 (PS22) wk of age. Four birds per treatment were randomly selected to evaluate sexual organ development at 1 D before photostimulation and 2, 4, and 6 wk after photostimulation. The ovary weight, large yellow follicles number (LYF), oviduct weight, and oviduct length of PS18 increased sharply after photostimulation. Conversely, the increase in PS16 was not observed until 2 wk after photostimulation. There was no difference in age at sexual maturity between treatments (P > 0.05). The PS16 had the longest interval (28 D) from photostimulation to 5% egg production, while PS22 reached 5% egg production 7 D before photostimulation. The PS22 had lower peak production (P = 0.02) and less egg production (P = 0.02) than other treatments. The PS16 had more broken and abnormal eggs (P = 0.01) and lower hatchability (P = 0.04) than other treatments. In conclusion, photostimulation at 16 and 22 wk of age decreases hatchability and egg production, respectively, and photostimulation at 18 wk is appreciated for the WL breeder hens., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

As broiler breeders face increased reproductive challenges specifically related to overfeeding, a clear understanding of the physiological effects of BW and rearing photoperiod on reproductive development is needed. The objective was to use mathematical models to compare plasma estradiol-17β (E2) concentration to characterize the effect of BW and rearing photoperiod on E2 levels. A 2 × 3 factorial arrangement of treatments was used. Hens (n = 180) were fed with a precision feeding system to allocate feed individually to achieve the breeder-recommended BW curve (Standard) or to a BW curve reaching the 21 wk target at 18 wk (High). Hens were on 8L:16D, 10L:14D, or 12L:12D photoschedules during rearing and were photostimulated at 21 wk. Age at first egg (AFE) was recorded. Plasma E2 levels were determined weekly between week 20 and 28. Two modified Gompertz models described E2 level as a function of (a) chronological or (b) physiological (relative to AFE) age. Timing of E2-inflection point was compared between models and treatments. Differences were reported as significant at P ≤ 0.05. The chronological age model inferred that High BW reduced the duration between the E2-inflection point and AFE, whereas the physiological age model inferred that High BW only reduced the duration between photostimulation and the E2-inflection point. Hens on the Standard BW treatment had a longer period between photostimulation and the E2-inflection point compared to hens on the High-BW treatment (11.03 vs. 1.50 wk, respectively, based on physiological age). Hens on the 12L:12D photoschedule had a longer period between photostimulation and the E2-inflection point compared to hens on the 8L:16D or 10L:14D photoschedule, both in the Standard and High BW (28.91 vs. 1.78 and 2.40 wk, 2.65 vs. 0.93 and 0.94 wk, respectively, based on physiological age). The described methodology and results provide quantitative insight into E2 dynamics and serves as a model for future endocrinological studies in poultry reproduction., (© The Author(s) 2019. Published by Oxford University Press on behalf of Poultry Science Association.)

This work studied the effect of age at photostimulation on reproductive performance of Beijing-You Chicken (BYC) breeders. A total of 384 fourteen-week-old BYC breeder hens were randomly allocated to 4 treatments of 96 birds each, with 2 replicates per treatment. The treatments represent photostimulation at 16, 18, 20, and 22 wk of age, respectively (PS16, PS18, PS20, and PS22) by incrementally increasing day length from 8L:16D to 14L:10D and by increasing lighting intensity from 10 to 80 lx. Egg production was recorded for each replicate until 51 wk. Four birds randomly selected from each treatment were sacrificed to characterize sexual organ development at 4 time points: 1 D before photostimulation and 2, 4, and 6 wk after photostimulation. Eggshell quality at peak laying was measured. The results showed that the changes in ovary and oviduct weight in PS22 were 8.68- and 4.27-fold higher than in PS16 at 6 wk after photostimulation. PS16 had an earlier age at 5% egg production than PS20 and PS22 (P = 0.003). The interval from photostimulation to age at 5% egg production in PS20 and PS22 was shorter than in other treatments (P = 0.005). Later peak egg production was seen in PS20 (211.0 D) and PS22 (218.0 D) than in PS16 (183.0 D) and PS18 (190.0 D, P = 0.020), but the laying rate of PS20 decreased slowly after peak laying. PS20 and PS22 had higher egg weights than PS16 and PS18 at peak laying (P = 0.018). Age at photostimulation had no effect on egg number, defective egg number, or hatchability (P > 0.05). In summary, the onset of lay can be advanced by photostimulation at early ages, but there is no difference on egg production until 51 wk. Photostimulation at 20 wk improves peak of laying and laying uniformity., (© 2019 Poultry Science Association Inc.)

We evaluated the effect of photoperiod on ovarian morphology, reproductive hormone secretion, and hormone receptor mRNA expression in layer ducks during the pullet phase. A total of 480 71-d-old Jinding layer ducks were randomly divided into 5 groups that received 6L (hours of light):18D (hours of darkness), 8L:16D, 10L:14D, 12L:12D, or 14L:10D, respectively. Each group had 6 replicates with 16 birds each. The photoperiod feeding trial lasted 80 d until 150 d of age. The age at first egg (AFE), the total number, and weight of eggs increased linearly with increasing photoperiods (P < 0.05); lower values of AFE occurred with photoperiods ≥8 h, whereas a higher total number and weight of eggs occurred with photoperiods ≥10 h, compared with 6L:18D (P > 0.05). Oviduct weight, ovary percentage, and initial and bare stroma (weight and percentage) increased quadratically with increasing photoperiods (P < 0.05), and 10.24, 10.01, and 10.10 h were the optimal photoperiods for oviduct weight, bare stroma (follicles ≥2 mm in diameter removed) weight, and bare stroma percentage, respectively, as calculated from reliable regression equations (R2 ≥ 0.5791). Compared with 6L:18D, 10L:14D had a higher total large white follicle weight, small yellow follicle number, and weight (P < 0.05). In addition, higher serum levels of follicle-stimulating hormone, luteinizing hormone, and progesterone were observed with ≥10-h photoperiods (P < 0.05), as were levels of hormone receptor mRNA expression in ovarian follicles (P < 0.05), with the highest values for both measures at 10L:14D. In the hypothalamus, mRNA expression of gonadotropin-releasing hormone increased in ≥8-h photoperiods, with the highest value at 10L:14D. In contrast, gonadotropin-inhibitory hormone increased in photoperiods ≥12 h (P < 0.05). In conclusion, an appropriate photoperiod led to early sexual maturity and improved the development of reproductive organs and ovarian follicles through effects on reproductive hormones and their receptors; 10 to 10.24 h is an adequate photoperiod for layer ducks during the pullet phase., (© 2019 Poultry Science Association Inc.)

Reproductive tract development during puberty is critical to reproductive performance, and the light is crucial in this process in birds. However, in male quail, there is little information on the effects of types of lamps, more specifically the wavelength emitted. Thus, the objective was to evaluate the effects of types of lamps on the reproductive performance of male Japanese quail (Coturnix coturnix japonica). Two hundred and forty male quail were exposed to six different types of lamp (incandescent, white fluorescent, or blue, white, red or green LED). The experimental design was completely randomized with six treatments and five replicates of one quail. Quail were slaughtered on days 35, 47, 57, 71 and 123 to evaluate the development of testes. On day 117, semen samples were analyzed and fertilized eggs were incubated. Body weight of the quails was influenced (P < 0.01) by lamps only until the 47 days of age. Higher body weight until this age were observed with incandescent, blue and green LED bulbs. Fluorescent and red LED bulbs propitiated (P < 0.05) early testicular development of quails but, at 57 days of age, higher testicular development was obtained (P < 0.01) whit white LED bulbs. Lower testicular development was observed (P < 0.01) at 123 days of age with the red LED. No influence of different types of lamps was observed (P > 0.05) on the quality of semen nor on the fertility rates of quail. It is concluded that lamps can influence the histological reproductive characteristics of male quails, but without influencing the semen quality. Fluorescent bulbs and red LED seem to anticipate the sexual maturity, but the white LED results in higher testicular development at 57 days of age., (Copyright © 2017 Elsevier Inc. All rights reserved.)

We determined the molecular mechanism underlying the environmental (photoperiodic) regulation of sexual maturation in fish, we examined the expression of sexual maturation-related hormones and vertebrate ancient long opsin (VAL-opsin) in goldfish (Carassius auratus) exposed to different light spectra (red and green light-emitting diodes). We further evaluated the effect of exogenous gonadotropin hormone (GTH) on the expression of VAL-opsin under different light conditions. Our results demonstrated that the expression of GTHs was higher in the fish exposed to green light, and VAL-opsin levels were increased in the fish receiving GTH injection. Therefore, we have uncovered a molecular mechanism underlying the environmental (light)-induced trigger for sexual maturation: VAL-opsin is activated by green light and GTH, which promotes the expression of sexual maturation genes., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Genetic selection programs in broiler stocks have contributed to changes in the responsiveness of the broiler breeder female to nutritional factors. A study was conducted to investigate the effect of photostimulation (PS) age on sexual maturity traits in current broiler breeder pullets. Seven hundred twenty Ross 308 pullets with full access to feed to 1 or 3 wk of age were divided among 8 environmental rooms to 16 wk of age. At this time, 128 pullets (64 per initial feeding treatment) were randomly assigned to individual cages in 8 rooms with 16 pullets per room. Pullets were PS at 17 (PS17), 19 (PS19), 21 (PS21), or 23 (PS23) wk of age by increasing the day length from 8L:16D to 16L:8D (multiple steps). Each hen was dissected on the morning after first oviposition (sexual maturity). Data were analyzed by 2-way ANOVA with additional analysis of covariance analysis done using sexual maturity on BW as a covariate. Sexual maturation occurred later with later PS ages. Rate of sexual maturation was accelerated at later PS ages, although age at PS did not affect variation in age at sexual maturity. Despite a 42 d difference in PS age between the PS17 and PS23 groups, only a 25 d difference existed in mean age at sexual maturity among these groups. Initial egg weight, breast muscle weight, frame size, and abdominal fat pad weight at sexual maturity increased in birds with later PS ages. Covariate analysis indicated that these effects were influenced primarily by increased age and BW at sexual maturity in later PS birds. Pullets PS at 17 wk of age had 11.0 large white ovarian follicles, compared with 14.9 in PS23 birds. Comparison to previous studies demonstrates that the years of genetic selection for growth traits have not changed the interval between PS and sexual maturation. Previous research published on this theme likely had a confounding effect of mean BW on estimates of variation at various PS ages. Photostimulating later presented advantages with regard to development of the reproductive tract; these effects were BW dependent.

Bone strength in layers is a concern for economic reasons and animal welfare concerns. Bone characteristics were investigated in 3 strains of hens: Babcock B-300, a small-bodied commercial white-egg layer; ISA-Brown, a commercial brown-egg layer; and an unselected Brown Leghorn line (BL). After being reared together in a single pen with 8 h of light per day, hens were caged with 14 h of light per day. Half of the hens were caged at 18 wk of age and the other half at 20 wk of age, resulting in a 2-wk difference in the age at photostimulation. Body weights, egg production, feed efficiency, and egg quality were measured throughout production. At 15, 25, 50, and 74 wk of age, hens were euthanized for sampling of the radius and the humerus. Breaking strength of the radius and humerus was measured, and the area and density of trabecular (largely medullary bone) and cortical bone were measured using quantitative computed tomography. Egg production and feed conversion of ISA-Brown hens was as good as or better than that of Babcock B-300 hens, and both commercial strains had higher production than the BL. Photostimulation late delayed sexual maturity and improved albumen and shell characteristics but had only minor effects on egg production and did not affect the yolk weight. The delayed photostimulation resulting from caging 2 wk later affected the radius by increasing the area of the trabecular space at 50 wk of age and the density of the bone in the trabecular space at 74 wk of age. Breaking strength of the humerus at 25 wk of age was greater for the birds that were photostimulated late but was not different later in the trial. The humerus, but not the radius, of the BL had a greater breaking strength than that of the commercial strains, suggesting that selection has decreased humeral breaking strength.

The effects of strain, age at photostimulation, and dietary CP intake during the early lay period on sexual maturation and egg production parameters in broiler breeder hens were determined. Three Arbor Acres strains, Classic, Feather Sexable Yield (FSY), and an experimental line (EXP), were reared in floor pens. At 19 wk of age, pullets were moved into individual cages. At 20 wk of age one-half of the birds were photostimulated by increasing the day length from 8L:16D to 15L:9D. The remaining birds were photostimulated at 23 wk of age. The birds were fed 16 or 18% CP diets from 19 to 32 wk of age. The Classic hens achieved sexual maturity 4 d before the EXP hens. Delaying photostimulation to 23 wk of age delayed sexual maturity but the rate of sexual maturation was accelerated after photostimulation occurred. Egg weight at sexual maturity was higher for the later photostimulated birds. The FSY and EXP hens, selected for more white-meat yield than the Classic hens, were heavier in BW but had lower settable egg production than the latter. Feeding 18% CP resulted in a higher BW throughout the trial, as compared to the 16% CP diet. There was a response to dietary CP and photostimulation age on initial egg weight and the number of double-yolked eggs. Early photostimulation was not advantageous because egg production parameters were not affected. Both Classic and FSY strains performed well when fed 18% CP; however, EXP hens benefited from 16% CP intake.