Genetic differences in yolk testosterone levels influence maternal hormone deposition in the second laying cycle in Japanese quails

Maternally-derived yolk androgens exhibit distinct among- and within-female variations but limited data refer to inter-seasonal changes of maternal hormones in the yolk. We investigated the deposition of yolk testosterone (T) across two laying cycles in Japanese quail. To test how genetically-determined differences influence between cycle variations in yolk androgens we compared females from low (LET) and high (HET) egg T lines at the end of the first and at the beginning of the second laying cycle after an induced moult. Line differences in yolk T levels exhibited high consistency exceeding two reproductive cycles. Yolk T concentrations increased in the second laying cycle in HET but not in LET females. Plasma T levels did not differ between cycles in both lines and no line differences were found either before or after the moult indicating the presence of mechanisms limiting the increase of T concentrations in the circulation. Differences in the yolk T levels were not accompanied by changes in the egg and yolk mass. The HET quail laid eggs with heavier eggshell than the LET quail. Our results demonstrate different abilities of mothers to deposit T in their eggs over two reproductive seasons with expected consequences on the development of their progeny.     

Experimental evidence for genetic heritability of maternal hormone transfer to offspring

In many animal species, embryos are exposed to maternal hormones that affect their development. Maternal hormone transfer varies with environmental conditions of the mother and is often interpreted as being shaped by natural selection to adjust the offspring to prevailing environmental conditions. Such hormone transfer requires genetic variability, which has not yet been experimentally demonstrated. Our study reports direct evidence for additive genetic variance of maternal androgens through a bidirectional selection on yolk testosterone (T) levels in Japanese quail. Lines selected for high egg T (HET) and low egg T (LET) concentration differed in yolk levels of this androgen, resulting in high realized heritability (h2 = 0.42)Correlated responses to selection on other gonadal hormones indicated that selection specifically targeted biologically active androgens. Eggs of HET quail contained higher androstenedione and lower estradiol concentrations than did those of LET quail, with no line differences in yolk progesterone concentration. Plasma T concentrations in adult females were not affected by selection, seriously challenging the hypothesis that transfer of maternal hormones to offspring is constrained by hormone levels in a mother's circulation. Our results suggest that transfer of maternal T represents an indirect genetic effect that has important consequences for the evolution of traits in offspring.     

Hatch weight selection: effect on post-hatch growth in the Japanese quail (Coturnix coturnix japonica)

The post-hatch growth of Japanese quail, weight selected at hatch, was investigated. The quail were grouped according to hatch weight as follows: Group I, 5.5-6.2 g; Group II, 6.3-7.0 g; and Group III, 7.1-7.6 g. Group III quail were 25 and 12% heavier at hatching than Group I and II quails, respectively, and reached a mature body weight which was 38 and 12% heavier than Group I and II quails, respectively. Gompertz growth parameters were not different in any of the groups. Feed and water consumption (g/kg body weight) rates were not significantly different among the three groups.     

Do different yolk androgens exert similar effects on the morphology or behaviour of Japanese quail hatchlings Coturnix japonica?

Avian eggs contain variable levels of several maternal androgens that may all be important in adjusting offspring phenotype at the individual or brood level. Most studies have focused on experimental manipulations of testosterone (T), and the other yolk androgens such as androstenedione (A₄) and 5‐alpha‐dihydrotestosterone (DHT) were so far neglected. However, in species where the amount of A₄ in the yolk much exceeds that of the other androgens, A₄ could represent the dominant agent of androgen‐mediated maternal effects, in which case manipulations of T would be misdirected. We conducted our study in a species with high yolk A₄ and relatively low T and DHT levels, the Japanese quail Coturnix japonica. We injected unincubated eggs with a physiological dose of either A₄, T, or DHT, and measured hatchling growth, as well as behaviour in an open field test. T treatment non‐significantly increased social reinstatement behaviour in the open field test, but it seemed to significantly suppress early skeletal growth and mass gain. The A₄ and DHT treatments, in contrast, significantly increased reinstatement behaviour, but did not affect mass and size growth. These results suggest that future investigations should view yolk androgens as integrated components of the complex yolk steroid environment.     

Japanese quail selected for high plasma corticosterone response deposit high levels of corticosterone in their eggs

Poor habitat quality or body condition often correlates with high responsiveness of the hypothalamo-pituitary-adrenal (HPA) axis rather than with elevated baseline levels of glucocorticoids. We hypothesized that, for egg-laying vertebrates, high responsiveness of the HPA axis would correspond to high concentrations of corticosterone in yolk. We tested the prediction that Japanese quail (Coturnix coturnix japonica) selected for high plasma corticosterone response to brief immobilization (HS quail) would lay eggs with higher yolk corticosterone concentrations than birds selected for low response (LS quail). Quail from both lines were left undisturbed, outside of the stressors associated with daily management, before a first round of egg collection. In a second experiment, quail of both lines were experimentally stressed during the week before egg collection. In both cases we found quail from the HS line to lay eggs with significantly higher yolk corticosterone concentrations than quail of the LS line. After exposure to added experimental stressors, the line difference was more pronounced (increasing from 62% to 96%). There was no line difference in concentrations of yolk testosterone. Our results suggest that (1) genetic differences underly differences in the transfer of maternal corticosterone to yolk and (2) females may be able to control deposition of corticosterone into yolk through a mechanism independent of baseline corticosterone titers.     

The postnatal demasculinization of sexual behavior in the Japanese quail (Coturnix coturnix japonica)

Three experiments were performed to analyze the time course of demasculinization in the Japanese quail and to test the activating and organizing effects of estradiol (E2) in adult sexually active birds. In Experiment 1, males and females were castrated at the age of 1 day or 1, 2, 4, and 6 weeks and treated as adults with testosterone (T). The age of castration had no effect on behavior and morphology in males. Plasma gonadotrophins (LH and FSH) were, however, higher in males castrated at or before than in those castrated after 2 weeks of age. This suggests that postnatal testicular secretions have organizing effects on the pituitary activity. Females which were castrated before 1 week of age were less sensitive to the activating effects of T than males, but were not fully demasculinized. The demasculinization of different reproductive characteristics such as male sexual behavior, cloacal gland size, and weight of the syringeal muscles is achieved in females at different times posthatching. In Experiment 2, castration of male and female quail at the ages of 4 days or 4 weeks confirmed that postnatal ovarian secretions contribute to the full behavioral and morphological demasculinization of females. It is easier to elicit mounting in T-treated females when they are tested in their home cage instead of a test arena. This difference was not observed in males. During Experiment 3, it was impossible to demasculinize sexually active adult males or females by treatment with Silastic implants of E2. E2 did not maintain sexual behavior in ovariectomized females showing male sexual behavior when treated with T but maintained the behavior in males.     

Effects of 2 G hypergravity exposure on Bobwhite (Colinus virginianus) and Japanese quail (Coturnix coturnix japonica)

We compared reproductive fitness and early postnatal growth of Bobwhite (Colinus virginianus) and Japanese (Coturnix coturnix japonica) quail incubated and hatched during 2 G centrifugation. Fertilized Bobwhite and Japanese quail eggs were placed in portable incubators on the 8-ft International Space Station Test Bed (ISSTB) Centrifuge at NASA Ames Research Center. The quail eggs were incubated throughout hatching and reared until Postnatal day (P)4 at either 1.0, 1.2 or 2.0 G. Two days before hatching, candling revealed significantly greater numbers of viable Bobwhite than Japanese quail eggs at all g-loads. Bobwhite quail exhibited significantly better hatching success at all g-loads than did Japanese quail. Bobwhite hatchlings were sensitive to gravitational loading as evidenced by reduced postnatal body mass and length of 2 G hatchlings relative to 1 G control hatchlings. In contrast, mass and length of Japanese quail hatchlings were unaffected by 1.2 or 2 G exposure. Together, our findings provide evidence for superior viability and hatching success in Bobwhite quail relative to Japanese quail, coupled with greater sensitivity of postnatal body growth and development to 2 G loading. Bobwhite quail may be better suited than Japanese quail for scientific studies on space biology platforms.     

Influence of different photoperiods on development of gonad, cloacal gland and circulating thyroid hormones in male Japanese quail Coturnix coturnix japonica.

One day old chicks of Japanese quail were exposed to different photoperiods (LD, 8:16, 13.5:10.5, 16:8 and LL) and observations (testes weight, cloacal gland size, body weight and circulating thyroxine and triiodothyronine) were taken at the age of 3, 5, 7, 9 and 16 weeks. Results indicate that immediate reproductive development occurred in birds exposed to long photoperiods (greater than 12 hr). Growth under LD 8:16, was not apparent till 7th week and by 16 weeks, degree of gonadal development was similar in all the birds, irrespective of photoperiodic treatment. Whereas body weight of the intermediate and long day (LD 13.5:10.5, 16:8 and LL) treated birds increased upto 5th week and remained constant thereafter. But the chicks maintained under short day length (LD 8:16), showed spontaneous increase till the end of the study and birds were much heavier compared to all other groups. Plasma T4 concentration increased with increasing age till 9th week and remained unaltered thereafter. On the other hand T3 level did not change till 7th week followed by a decline. It is suggested that the initiation and degree of gonadal growth in quail depends on the availability of daily photoperiod, until the achievement of full breeding condition. Peak level of T4 observed in 9 week old birds may be involved in the development of photorefractoriness at that age.     

No sex difference in yolk steroid concentrations of avian eggs at laying

Yolk steroids of maternal origin have been proposed to influence genetic sex determination in birds, based on sex differences in yolk steroid concentrations of peafowl eggs incubated for 10 days. More recent reports dispute this proposal, as yolk steroids in eggs incubated for 3 days do not show such sex differences. To date, research examining this phenomenon has only analysed incubated eggs, although sex in avian species is determined before incubation begins. This may be a serious methodological flaw because incubation probably affects yolk steroid concentrations. Therefore, we investigated sex differences in yolk steroid concentrations of unincubated avian eggs. We withdrew yolk for steroid analysis from fresh, unincubated Japanese quail (Coturnix japonica) eggs by biopsy, and then incubated those eggs for 10 days, after which we harvested the embryonic material for genetic sexing and the incubated yolk for further steroid analysis. We found no sex differences in fresh Japanese quail eggs; however, sex differences were apparent in yolk steroids by day 10 of incubation, when female eggs had significantly more oestrogen in relation to androgen than male eggs. Concentrations of all yolk androgens decreased dramatically between laying and day 10 of incubation, whereas oestradiol (E2) concentrations increased marginally. Thus, yolk concentrations of androgens and E2 do not appear critical for avian sex determination.     

Maternal dietary carotenoids mitigate detrimental effects of maternal GnRH on offspring immune function in Japanese quail Coturnix japonica

Maternal resources deposited in eggs can affect the development of several offspring phenotypic traits and result in trade‐offs among them. For example, maternal androgens in eggs may be beneficial to offspring growth and competitive ability, but detrimental to immunocompetence and oxidative stress. In contrast, maternal antioxidants in eggs may be beneficial if they mitigate oxidative stress and immunosuppressive effects of androgens. We investigated possible interactive effects of maternal steroids and carotenoids on aspects of offspring physiology and phenotype, by simultaneously manipulating levels of androgens (via gonadotropin‐releasing hormone, GnRH‐challenges) and carotenoids (via diet supplementation) in captive female Japanese quail Coturnix japonica during egg laying. Carotenoid supplementation of hens, which elevates yolk concentrations of carotenoid and vitamins A and E, enhanced egg hatching success, offspring survival to age 15 d, and size of the bursa of Fabricius in offspring. In contrast, repeated maternal GnRH challenges, which elevated yolk testosterone concentrations, enhanced offspring neonatal size, but negatively affected bursa size. However, interaction among the treatments suggests that the positive effect of maternal carotenoid supplementation on plasma bactericidal capacity was mediated by maternal GnRH challenges. Chicks originating from carotenoid‐supplemented hens were less immunosuppressed than those originating from carotenoid‐supplemented + GnRH‐challenged hens, which were less immunosuppressed than chicks from GnRH‐challenged females not supplemented with carotenoids. Females availability of carotenoid enriched diets allows them to enhance the development of offspring immune system via carotenoids and vitamins deposited in egg yolks and offset detrimental effects of androgens deposited by GnRH‐challenged females.     

Effect of long-term simulated microgravity on some sexual traits of male Japanese quail

The aim of this study was to investigate the effects of long-term stay of Japanese quail in simulated microgravity on some sexual features of males. As a model for simulating microgravity exposure of birds in laboratory conditions was used hypodynamia. The mean left testis weight in males reared under hypodynamia from day 3 up to 180 days of age was lower than that of control (P<0.05), but the right testis weight differences between both groups were not significant. Also the area, volume and foam production of cloacal gland was not significantly decreased in hypodynamia birds at the end of experiment. By contrast, the plasma testosterone concentration of males living in hypodynamia was reduced about 50 % at 90 and 180 days of age in comparison to control (P<0.05) suggesting some negative effects on sexual development. Our results demonstrated that male quail kept under simulated microgravity conditions were sexually competent although their sexual efficiency was reduced especially in terms of plasma testosterone.     

Weight variation by sex and nature of risk factors in high-risk infants: an evolutionary perspective

A retrospective cohort study was conducted to explore growth variation during the intrauterine and early postnatal period by sex and nature of high-risk factors (i.e. physiological and pathological) in 831 Korean infants at a University hospital. The results showed that infants with a physiological risk showed a more congruent intrauterine growth pattern compared to those with a pathological risk. Particularly with a physiological risk, female infants experienced more compatible intrauterine and postnatal growth than males, although male infants were heavier than female infants at a given gestational age. In conclusion bigger may not necessarily be better for prenatal growth in humans. A more confluent intrauterine growth in infants with physiological risk can be beneficial for early postnatal catch-up growth. From an evolutionary perspective, female infants with a physiological risk may keep their advantageous edge over male infants during the early postnatal period although such an advantage may not be present with a pathological condition.     

Effect of thermal stress on fertility and egg quality of Japanese quail

Heat stress is one of the major causes of a decreased performance of laying quail in tropical and subtropical countries. The aim of this study was to investigate the impact of temperature humidity index (THI) on fertility aspects, external and internal egg quality parameters in Japanese quail. One hundred and forty four (144) Japanese quail, 12 of weeks age, were used. Birds were divided randomly into three equal groups, control (at low THI, lower than 70), H₁ (at moderate THI, 70–75) and H₂ (at high THI, 76–80). Quail in the control and H₁ groups had significant greater fertility (p=0.021) and hatchability % (p=0.037), compared with H₂ group. Quail in the control group (at low THI) laid heavier egg weight with a higher external (egg weight (p=0.03), shell thickness, shell weight, eggshell ratio and eggshell density (p=0.001)) and internal egg quality score (albumin weight (p=0.026), yolk height (p=0.003), yolk index (p=0.039) and Haugh unit (p=0.001)). Otherwise, such quality traits were compromised in heat-stressed quail. At the high THI level, egg weight had a significant positive correlation with albumin weight (r=0.58, p<0.01), yolk weight (r=0.22, p<0.05), albumen ratio (r=0.17, p<0.05), yolk height (r=0.14, p<0.05) and yolk index (r=0.18, p<0.05), but was negatively correlated with yolk ratio (r=−0.15, p<0.05). Japanese quail exposed to heat stress (THI over 75) revealed drop in fertility indices and egg quality traits, indicating a detrimental policy of economic income.     

Phenotypic characterisation of extreme growth-selected mouse lines: An important prerequisite for future QTL analysis

A unique set of seven mouse lines, long-term selected for high growth, from different laboratories around the world has been comprehensively compared to evaluate these resources for future QTL and gene mapping for growth traits. The heaviest line (DUH) was 40% (males) to 44% (females) heavier than the smallest line (ROH) at birth, and 105% (males) to 114% (females) heavier at 98 d. Body conformation (body length and width, body areas), body composition (dry matter, fat, fatty acid composition, organ weights), and skeletal muscle cellularity also differed substantially. DUH was more than 20% longer (12.3 cm) compared to the shortest line ROH (9.7 cm). DAH (22.5%) had the highest percentage of gonadal fat and the leanest was BEH (7.7%). Line BEH (0.49 g) showed the highest weight for the left M. rectus femoris, which was 2.1 times higher, compared to ROH (0.23 g). These results suggest that different alleles, and possibly different physiological pathways, have contributed to the selection response in the different lines. Therefore these selection lines are an important tool with which to identify the genetic and physiological basis of growth as they may contain many, if not all, growth promoting alleles.     

Ovarian responses and serum LH levels after retraction or removal of the oviduct in Japanese quail

The effects of oviduct removal, oviduct displacement or sham-operation were studied in Japanese quail (Coturnix coturnix japonica). No significant differences were observed between the treatments for body weight, number of follicles larger than or equal to 6 mm diam., or number of ruptured follicles. Retraction or removal of the oviduct resulted in similar significant increases (P less than 0.05) in ovarian weight, diameter of the largest follicle, and serum LH levels when compared with the controls. Injection of yolk into normal hens did not cause any change. It is suggested that the oviduct normally exerts an inhibitory control on ovary growth without appreciable effect on ovulation rate.     

Relationship of cloacal gland with testes, testosterone and fertility in different lines of male Japanese quail

An attempt has been made to investigate the relationship of cloacal gland with testes, testosterone and fertility in different lines of Japanese quail (Coturnix coturnix japonica). For this study, three lines of healthy adult male Japanese quails (<12 weeks) viz., heavy body weight (HB), white breasted (WB), and white egg shell (WES) were taken. They were housed in individual cages under uniform husbandry conditions and were provided with normal quail breeder ration and water ad libitum, with 14 h light/day. The experimental birds were selected from each of these three lines and categorized into different groups (15 birds/group) based on the increasing order of the area of cloacal gland. At the end of this experiment (24 weeks) the data indicated that size of the cloacal gland was directly proportional to foam discharge, foam weight, testicular weight, fertility and testosterone concentration in plasma. From this study it may be concluded that area of cloacal gland in Japanese quail is positively correlated with testicular weight, level of testosterone in plasma and fertility. Visual examination of cloacal gland and cloacal foam may provide a valuable non-invasive tool for predicting the fertilizing ability of individual male bird.     

Juvenile body weight and gonad development in a diallel cross among lines of Japanese quail (Coturnix coturnix japonica)

Summary The influence of growth on the extent of heterosis for juvenile body weight and gonad development was studied in a diallel cross among two lines of Japanese quail differing in adult body size. A total of 1,096 birds (563 males and 533 females) was slaughtered between 25 and 49 days of age. Reciprocal cross differences were non-significant. Heterosis showed a curvilinear course with age peaking during early growth (body weight) and during sexual maturity (gonad percentage). Overall advanced physiological development of the crossbreds probably begins as early as during the embryonic stages and results in earlier sexual maturity. In females, heterosis for percentage gonads was biased strongly by the presence of a hard-shelled egg in the uterus.     

The effect of food restriction on morphological and metabolic development in two lines of growing Japanese quail chicks

To investigate whether there is a relationship between the inherent maximum growth rate of a chick and its degree of developmental plasticity, we studied the effects of food restriction on morphological and physiological development in P-line (selected for high growth rates) and C-line (nonselected) chicks of the Japanese quail between 2 and 64 d of age. In each line, three groups were created; one group in which the chicks were fed ad lib. and two other groups in which the chicks received 70% and 40% of the line-specific ad lib. feeding levels, respectively. In all three groups, chick survival rates were very high, and no relationship was detected between feeding level and chick mortality. The experimental feeding levels strongly affected the chicks' attainment of body mass at all ages. In addition, at most ages the growth of the structural components (wing, tarsus, and head) were also significantly affected by the feeding experiment but to a much smaller extent than the body mass. The feeding levels also affected the achievement of female sexual maturity such that, at the end of the experiment, most of the ad lib.-fed females and none of the females that received 40% of the ad lib. feeding level were laying eggs. In chicks of both lines that were fed ad lib., homeothermy was achieved at 7 d of age, but in chicks that received 40% of the line-specific ad lib. levels, homeothermy was achieved after 15-22 d of age. Poikilothermic chicks (P- and C-line) that were relatively heavy for their age exhibited relatively high resting metabolic rates (RMRs) and peak metabolic rates (PMRs) for their age. In addition, a positive relationship was found between the chicks' relative mass and RMR (based on mass-based predictive equations). No relationship was detected between the chicks' relative body mass and their relative PMR (relative to mass-based predictive equations). With respect to the metabolic scope (i.e., PMR-RMR), Japanese quail chicks exhibited remarkable developmental plasticity: chicks with body masses that were 50% lower than the normal growing chicks did exhibit a normal capacity of thermogenic heat production for their mass. Because no differences were found with respect to the level of plasticity of morphological and physiological development between the two strains, we conclude that the selection for high postnatal growth rates in P-strain chicks has not resulted in a in a higher vulnerability of these chicks to food restrictions.     

The effects of diet on plasma and yolk steroids in lizards (Anolis carolinensis)

Steroids present in egg yolk have been shown to vary as a resultof numerous social and environmental influences and to produceboth positive and negative phenotypic outcomes in offspring.In the present study, we examined how quality of the diet affectsplasma and yolk steroids in the green anole (Anolis carolinensis),a lizard species with genotypic sex determination. We documentedthe effects of body condition on plasma testosterone (T) andcorticosterone (CORT)—steroids with frequently opposingeffects—in breeding females and on the T and CORT contentof their eggs. We chose to manipulate body condition via dietbecause resource availability is a relevant, fluctuating variablein the environment to which females can be expected to respond.Field-collected females were housed in the laboratory and kepton either a reduced, standard, or enhanced diet (differing innutritional quality and/or quantity) for ten weeks. Althoughfemales did not differ in body condition at the beginning ofthe study, we found these diet regimes effective in producingfemales that differed in condition by the end of the study.Females on diets of enhanced quality were in better condition,produced more, but not heavier, eggs, and had higher plasmaT concentrations than did females on a standard diet or oneof reduced quality. There was also a significant positive relationshipbetween laying sequence of eggs and yolk T for females on dietsof enhanced quality, but not for the females on diets of standardor reduced quality. There were no effects of quality of dieton CORT in plasma or yolk, but yolk T and yolk CORT exhibiteda strong positive correlation irrespective of treatment. Femaleson diets of reduced quality did not differ from females on standarddiets either with respect to reproductive output or to endocrineprofiles, in spite of being in worse body condition. These resultsdemonstrate that females’ body condition, physiology,and reproductive output can be manipulated by quality of diet,and that changes in deposition of yolk steroids in responseto diet may be minimal.     

Reproductive performance and fetal growth in female mice from lines divergently selected on the basis of plasma IGF-1 concentrations

Reproductive performance, mammary gland weight and plasma concentrations of insulin-like growth factor-1 (IGF-1) were examined in 18-day-pregnant mice from lines divergently selected on the basis of plasma IGF-1 concentration. Females of the high IGF-1 (H) line were 14% heavier than those of the low IGF-1 (L) line at mating but did not differ in conception rate during a 15-day mating period. H-line females produced significantly larger litters by an average of 1.5 fetuses (19%), heavier fetuses (7%), greater total fetal weight (30%), heavier placental discs (15%), greater total placental weight (35%) and heavier mammary glands (18%). Plasma IGF-1 values were 12% greater in H-line than L-line females at Day 19 of gestation but the line difference was not significant. It is concluded that differences between the lines in litter size and mammary gland weight are most likely due to differences in maternal bodyweight (which are in turn a consequence of selection for plasma IGF-1 at puberty). Whether the difference in fetal weight is a function of fetal capacity to grow in utero or ability of the dam to provide nutrients for fetal growth is yet to be determined.