Avian Reproduction Research Articles

A New Interpretation of Avian and Mammalian Reproduction Toxicity Test Data in Ecological Risk Assessment

The long-term risks of pesticides to wildlife in the EU currently are assessed by comparing the lowest no-observed-effect concentration (NOEC) determined from the suite of endpoints measured in existing avian and mammalian laboratory reproduction tests with estimated exposure concentrations by calculating Toxicity to Exposure Ratios (TERs). Regulatory authorities experience difficulties when assessing long-term risks because of the lack of accepted methods to improve the ecological realism of exposure and toxicity estimates and understand risks at a population level. This paper describes an approach for interpreting existing avian and mammalian toxicity test data that divides breeding cycles into several discrete phases and identifies specific test endpoints as indicators of direct pesticide effects possible at each phase. Based on the distribution of breeding initiation dates for a species of concern and the dates of pesticide applications, this approach compares the phase-specific toxicity endpoint with the expected pesticide exposure levels during each of the breeding phases. The fate of each breeding attempt is determined through a series of decision points. The cumulative reproductive response of individuals in a breeding population based on this decision framework provides a means of examining the estimated risks over the course of the breeding season and deriving an overall metric of the impact of the pesticide on reproduction. Research needed to further improve the approach is discussed.

Molecular cloning of an oxytocin-like receptor expressed in the chicken shell gland

The avian homologs of arginine vasopressin (AVP) and oxytocin (OT) are arginine vasotocin (AVT) and mesotocin (MT), respectively. In birds, AVT shares many of the functions of AVP including regulation of fluid balance, blood pressure regulation and the stress response. AVT also plays an oxytocin-like reproductive role in birds by stimulating uterine (shell gland) contraction during oviposition. The role of MT in avian reproduction is not clear. Here, we report the cloning of a third neuropeptide receptor in the chicken ( Gallus gallus). Parsimony analysis reveals that the new receptor has highest homology to mammalian OT receptors and the MT receptors of non-mammalian vertebrates. Moreover, the receptor bears far less homology to the two avian VT receptors that have been cloned. Reverse transcription-polymerase chain reaction and in in situ hybridization analyses reveal the receptor is expressed in both the endometrium and myometrium of the shell gland. The expression pattern and high homology to OT receptors suggest that the receptor may stimulate myometrial contraction and therefore play a critical role in oviposition.

Vitellogenin detection and chick pathology are useful endpoints to evaluate endocrine‐disrupting effects in avian one‐generation reproduction study

To investigate additional endpoints for screening of endocrine disruptors in birds, effects of 17beta-estradiol (E2) on one-generation reproduction in the Japanese quail (Coturnix japonica) were assessed. Pairs of the 10-week-old Japanese quail were fed a low-phytoestrogen diet containing E2 at 0 (control), 10, 100, and 1,000 ppm for six weeks. In the E2 100- and 1,000-ppm groups, the parental quail represented marked toxic changes including high mortality, decreased food consumption, decreased gonad weights, gross and histologic toxic changes in the reproductive and other organs, and inhibition of the reproduction. However, no adverse effects were observed in the parental quail from the E2 10-ppm group. In the parental males, serum vitellogenin (VTG) concentrations were increased significantly in the E2 10-ppm group, disclosing that serum VTG concentration is one of the highly sensitive endpoints for evaluating estrogenic endocrine activities. In the E2 10-ppm group, number of eggs laid, number of eggs with abnormalities, eggshell strength and thickness, fertility, early and late viabilities of embryos, normal hatchling rate, and clinical signs, mortality, viability, and body weight of chicks at 14 d of age were not affected. However, histopathology of the chicks in the E2 10-ppm group revealed meaningful morphological changes in the reproductive organs, such as cystic dilatation of seminiferous tubules, increased interstitial cells in the testis, and decreased theca cells in the ovary. The present study suggests that serum VTG concentration in the parental quail and histopathology of reproductive organs in the offspring are sensitive endpoints and are useful as additional endpoints in the avian one-generation reproduction test using the Japanese quail for evaluating estrogenic endocrine-disrupting effects.

Introduction to the European Science Foundation Technical Meeting: Analysis of Hormones in Droppings and Egg Yolk of Birds

In 2002, a workshop entitled “Adaptations and Constraints in Avian Reproduction: Integrating Ecology and Endocrinology” took place in Wageningen, the Netherlands. The aim of the workshop was to build a network between scientists of different disciplines to exchange their knowledge and methods. This initiative resulted in the formation of the E-Bird network with the same name: “Adaptation and Constraints in Avian Reproduction: Integrating Ecology and Endocrinology.” Within this E-Bird framework we organized this technical meeting on the analysis of hormones from bird droppings and egg yolk, supported both by the European Science Foundation and the U.S.-based National Science Foundation (ESF and NSF). Starting in the late 1970s and early 1980s with pioneering studies in birds 1,2 and mammals, 3 noninvasive methods to measure steroid hormone levels in feces have been developed for an increasing number of species. 4 In birds, the term “fecal analysis” is a bit problematic, because feces and urine are excreted together in the form of droppings and in general, a complete separation of the fecal and urine fraction is not possible. 5 Hence, it may be more appropriate to speak of excreta or droppings. Increasing interest in noninvasive methods to monitor hormonal profiles in birds and other vertebrates, combined with common misconceptions about the ease of applying such methods, triggered the idea to organize this technical meeting. The intention was to discuss this method among a small group of experts and come up with some guidelines for its proper application. 6 During the organizational phase of the meeting it became clear that the analysis of hormones from egg yolk is accompanied by very similar methodological issues. Hence, we decided to extend the scope of the meeting and include the analysis of hormones from egg yolk. Although this meeting was held with a focus on birds, most contributions are of equal importance for studies in mammals and other vertebrates. Noninvasive methods to measure hormones from droppings have the major advantage that samples can be collected repeatedly with no handling stress. Hence, re

Endocrine disruption in avian reproduction: the histological analysis

Endocrine disruption in avian reproduction: the histological analysis

Reassessment of ecotoxicities of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane in Japanese quail under the OECD draft new avian one-generation reproduction test guideline

Ecotoxicological hazards of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane ( p, p′-DDT) were investigated by a one-generation reproduction study using Japanese quail ( Coturnix coturnix japonica) under an Organization for Economic Co-operation and Development (OECD) draft new test guideline 206 following acute and subchronic toxicity studies. In the subchronic feeding toxicity study, tremors, convulsions, and deaths were observed with a clear sex difference, males being more susceptible than females. The estimated total number of sperm tended to decrease in a dose-dependent manner at the end of 6-week treatment. In the one-generation reproduction study conducted at dose levels of 0, 6, 30, and 150 ppm, the estimated total number of sperm tended to decrease in a dose-dependent manner with a significant difference at 150 ppm. Tremors were observed in the majority of hatchlings in the 150 ppm group and at lower incidences in the 30 ppm group. Significantly high mortality rate in chicks persisted from treatment week 3–6 in the 150 ppm group and at treatment weeks 4 and 5 in the 30 ppm group. Despite of these severe adverse effects of p, p′-DDT on hatchlings and chicks, fertilization, egg laying, eggshell thickness or embryonic development was hardly impaired by p, p′-DDT or its metabolites. From these results, it appears that the OECD draft new avian one-generation reproduction test guideline is effective for ecological hazard assessment of chemicals.

Exposure and effects of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in tree swallows (Tachycineta bicolor) nesting along the Woonasquatucket River, Rhode Island, USA

Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in tree swallows (Tachycineta bicolor) nesting along the Woonasquatucket River northwest of Providence (RI, USA) in 2000 and 2001 were some of the highest ever reported in avian tissues. Mean concentrations in eggs ranged from 300 to >1,000 pg/g wet weight at the two most contaminated ponds, Allendale and Lyman. Mean egg concentrations at Greystone, the upstream reference pond, were 12 and 29 pg/g. Positive accumulation rates and concentrations in diet samples from 12-day-old nestlings indicated that the contamination was accumulated locally. Concentrations in diet of between 71 and 219 pg/g wet weight were more than 6 and 18 times higher than concentrations considered safe for birds (10-12 pg/g). Hatching success was negatively associated with concentration of TCDD in eggs. Only about half the eggs hatched at Allendale compared with >77% at Greystone. The national average for hatching success in successful nests is 85%. No other contaminants, such as polychlorinated biphenyls and mercury, were present in any sample at concentrations known to affect avian reproduction. Three bioindicators, half-peak coefficient of geometric variation, ethoxyresorufin-O-dealkylase activity, and brain asymmetry were assessed relative to TCDD contamination.

INDIVIDUAL CRYOPRESERVATION WITH DIMETHYL SULFOXIDE AND POLYVINYLPYRROLIDONE OF EJACULATES AND POOLED SEMEN OF THREE AVIAN SPECIES

Artificial insemination (AI) has been used for avian reproduction due to the discovery of cryoprotectants extending its usefulness both in production of domestic fowl and conservation of wild species. The goal of this study was to assess the effect on domestic and wild fowl pooled semen and individual ejaculate cryopreservation with dimethyl sulfoxide (DMSO) and polyvinylpyrrolidone (PVP). Twenty ejaculates and twenty samples of pooled semen of roosters, pheasants and hawks were frozen in media containing DMSO or PVP. DMSO and PVP cryopreservation are equally effective both for ejaculates and pooled semen. Even PVP is a good alternative since no significant difference was found when compared to DMSO. The fertilizing capacity of fresh and cryopreserved pooled semen was analyzed through AI of hens and female pheasants. Similar fertility rates using DMSO, PVP or frozen-thawed samples demonstrated that reproduction is possible through the use of cryopreserved semen. In the case of female pheasants, the same values were obtained with both cryopreserved and fresh semen.

Calcium Availability Limits Reproductive Output of Tree Swallows (Tachycineta Bicolor) in a Nonacidified Landscape

AbstractBreeding birds require high levels of energy and certain nutrients, such as calcium. The extent to which calcium limits reproduction in wild birds is unclear. We performed a supplementation experiment to determine whether calcium limits the reproductive output of free-ranging insectivorous Tree Swallows (Tachycineta bicolor), a species whose usual diet contains little calcium. Providing supplemental calcium in the form of crushed oyster shell did not affect clutch initiation date, but it caused birds that had not started constructing a nest when we first detected them on the study area to begin laying sooner, which suggests that calcium reduced the length of the prelaying period. Supplemented females produced larger eggs, and that effect was most pronounced among females in good body condition. There was a trend for supplemented birds to produce larger clutches, and their clutches had significantly greater total mass than those of control birds. Supplemented birds, in particular those breeding late in the season, also hatched significantly more eggs. Our results suggest that calcium availability may limit some aspects of avian reproduction, even in nonacidified landscapes like our study area, where levels of calcium in the soil are high.La Disponibilidad de Calcio Limita el Rendimiento Reproductivo de Tachycineta bicolor en un Paisaje no Acidificado

Calcium availability affects bone growth in nestlings of free‐living great tits (Parus major), as detected by plasma alkaline phosphatase

AbstractRecent studies have revealed that calcium limitation of avian reproduction may be a widespread phenomenon, affecting both egg properties and chick development. The effect of calcium shortage on the final body size of fledglings is usually rather weak, possibly owing to compensatory growth. Achieving full skeletal size is not, however, a reliable indication of complete ossification and it is possible that chicks with similar tarsus lengths are in different stages of skeletal development. We hypothesized that measuring plasma activity of the bone alkaline phosphatase (ALP), a highly specific marker for bone calcification, may reveal subtle developmental differences in full‐grown fledglings, having experienced different levels of calcium availability during growth. In two seasons, a number of pairs of great tit Parus major were provided with calcium‐rich material during the nestling period, while others were not supplemented (controls). While no significant differences in size of fledglings were detected between groups, bone‐ALP activity at the pre‐fledging stage was lower in the calcium‐provided nestlings than in the control nestlings. This may indicate that supplemented chicks had completed the rapid phase of bone formation, but this process was delayed in controls. Measuring ALP as a marker of skeletal development expands our knowledge of how delayed skeletal development of chicks can result in protraction of the nestling period, thereby reducing the breeding success of adult birds.

Calcium supplementation of breeding birds: directions for future research

Calcium is an essential nutrient for avian reproduction. Calcium‐rich foods are consumed by breeding birds for production of eggshells and for provisioning chicks that are mineralizing skeletal tissues. A number of studies have documented calcium‐limited reproduction, and calcium supplementation has been employed over the last decade to demonstrate degrees, causes and consequences of calcium limitation. However, supplementation studies have produced equivocal findings resulting from an absence of calcium limitation in the study species, a poorly designed supplementation procedure or both. Prior to effective calcium supplementation, many factors need to be considered. Calcium‐limited breeding in birds can only be detected by monitoring breeding attempts for more than one year and by ensuring that the measured breeding parameters are sensitive to calcium availability. Natural calcium availability needs to be estimated, and daily calcium budgets for the appropriate reproductive stages determined for the study species. Most crucially, if calcium limitation of breeding is caused by secondary calcium limitation (e.g. through heavy metal toxicity), calcium supplementation will probably be ineffective. Effective calcium supplementation will then be achieved through careful planning – a study over several years using appropriate supplements (i.e. naturally occurring ones used by breeding birds), applied at the appropriate time of year (i.e. prelaying and/or chick‐rearing phases) and using a response variable that is highly sensitive to calcium availability. If properly planned and performed, calcium supplementation is a cost‐effective and potent tool for the study of bird breeding biology.

Flushing, Capture, and Bleeding do not Affect Return Rate of Female Wood Thrushes (Hylocichla Mustelina) in Delaware

Abstract Theoretical questions and conservation concerns have prompted numerous, intensive studies of songbird nesting ecology. Such studies use several techniques (flushing, capture, and blood sampling) that have the potential to negatively affect reproduction, survival, and site fidelity. Although studies have examined the effects of those techniques on avian reproduction and survival, the effect on the return rate of breeding songbirds has not been researched. We used data from a 28-year demographic study to investigate the possible effect of those three common research practices on the return rate of female Wood Thrushes (Hylocichla mustelina). We also tested reproductive success and age as predictors of return because they have been shown to influence site fidelity. Number of successful nests in a breeding season was the variable that best predicted return the following year. None of the research practices negatively affected return rate. That pattern held even among yearlings with zero production, a group that should be the most easily disturbed. We also show that using all years of return for site-faithful birds as observations (i.e. repeated sampling) inflates the estimated return rate.

FLUSHING, CAPTURE, AND BLEEDING DO NOT AFFECT RETURN RATE OF FEMALE WOOD THRUSHES (HYLOCICHLA MUSTELINA) IN DELAWARE

Abstract Theoretical questions and conservation concerns have prompted numerous, intensive studies of songbird nesting ecology. Such studies use several techniques (flushing, capture, and blood sampling) that have the potential to negatively affect reproduction, survival, and site fidelity. Although studies have examined the effects of those techniques on avian reproduction and survival, the effect on the return rate of breeding songbirds has not been researched. We used data from a 28-year demographic study to investigate the possible effect of those three common research practices on the return rate of female Wood Thrushes (Hylocichla mustelina). We also tested reproductive success and age as predictors of return because they have been shown to influence site fidelity. Number of successful nests in a breeding season was the variable that best predicted return the following year. None of the research practices negatively affected return rate. That pattern held even among yearlings with zero production, a...

Environmental risk assessment scheme for plant protection products

Environmental risk assessment scheme for plant protection products

Breeding Birds as a Commodity

Understanding of the physiology, molecular genetics and developmental biology of avian reproduction is essential for advances in the efficient breeding of birds for commercial gain. 2. Reproduction is controlled at the central nervous level by gonadotrophin releasing hormone-I (GnRH-I) and prolactin. 3. The activity of GnRH-I neurones can be manipulated photoperiodically, through understanding of the physiology of photorefractoriness, to prevent premature onset, or to enhance persistency of reproductive function. 4. Active immunisation against prolactin releasing hormone, vasoactive intestinal peptide, delays the development of photorefractoriness and enhances persistency of reproductive function. 5. The creation of molecular maps of the chicken genome makes it possible to identify quantitative trait loci for repro- ductive traits, which will be used to identify DNA sequences for marker assisted selection. Polymorphisms in alleles of physiological candidate genes for reproductive efficiency might also be useful for marker assisted selection. 6. New understanding of the developmental biology of the chicken opens up the prospect of developing methods to control sex ratios, and to make transgenic birds. Transgenic technology will be used to introduce genes for disease resis- tance, and to make proteins for biomedical applications. 7. Nuclear transfer technology might be applied to save endangered species from extinction.

Is prolactin responsible for avian, saurian, and mammalian relapse and periodicity of fever in malarial infections?

P.C.C. Garnham came to Toronto nearly 35 years ago to see if he, and the laboratory of A.M. Fallis, could unravel the enigma of "relapsing" malaria-like infections in migrating ducks (to Algonquin Park, Ontario). At the time, not enough was known about the endocrinology of avian migration and reproduction. Now a growing body of indirect evidence seems to point to a role for prolactin in many of the uniquely pathologic phenomena witnessed in malarial infections. Arguments in favour of the involvement of prolactin, as both a developmental hormone and a proinflammatory cytokine, in the pathology of relapse, fever, anaemia, and maternal malaria are presented in the hope that experiments to test such involvement will be designed.

Leptin is involved in the regulation of ovarian activity in fasted hens (Gallus domesticus)

In mammals leptin plays a key role in regulating the whole-body energy homeostasis and is important for for normal reproduction Much evidence indicates that leptin mediates the undernutrition-induced alterations of the reproductive axis (Ahima and Flier, 2000). In birds leptin gene was cloned in chickens (Taouis et al., 1998) and recombinant chicken leptin (chLep) was prepared in our laboratory (Raver et al., 1998). Unlike mammals, leptin is expressed not only in the adipose tissue but also in liver and leptin plasma level is lower in fasted than in fed hens (Dridi et al., 2000). However, the importance of leptin in avian reproduction is not known. Therefore, the aim of the present study was to examine whether in chickens leptin affects events occuring in the ovary during fasting.

Specific Anti-peptide Antibody to β Subunit of Chicken Thyrotropin: Production and Characterization

The unavailability of homologous antibodies to avian thyrotropin (TSH) has been a major hindrance in the study of avian reproduction and metabolism. Here we report the production and characterization of an anti-peptide antibody specific to chicken TSH β subunit. According to the cDNA sequence of chicken TSH β subunit, a synthetic peptide corresponding to the amino acid residues 35-50 (Tb3550; Asp-Ser-Asn-Gly-Lys-Lys-Leu-Leu-Leu-Lys-Ser-Ala-Leu-Ser-Gln-Asn) was prepared to produce polyclonal antibody in rabbits. This peptide sequence is highly specific to avian TSH β and was designed for the antibody to show no cross-reaction to pituitary and other chicken proteins with known amino acid sequences. Anti-Tb3550 recognized a 18.2-kDa band on immunoblot of the cephalic lobe homogenate, but not of the caudal lobe homogenate, of chicken anterior pituitary gland. Positive immunohistochemical staining with anti-Tb3550 was restricted to the cephalic lobe, whereas the cells positive to anti-chicken luteinizing hormone were scattered throughout the anterior pituitary. Anti-Tb3550 did not bind either to purified chicken luteinizing hormone or to follicle stimulating hormone preparation. These results indicate that this antibody specifically recognizes chicken TSH β subunit. This antibody should be useful for immunochemical study of avian TSH and for tracing TSH activity during the purification of the hormone.

The Prudent Parent: Energetic Adjustments in Avian Breeding1)

1. Energetics of reproduction in birds is reviewed with the question in mind how the parent adjusts its effort in relation to prevailing environmental conditions in order to maximize the output of young in its lifetime. Emphasis is on proximate controls, rather than ultimate factors measurable in terms of adult survival and recruitment of young. 2. The decision to breed or not to breed is clearly related to body condition of the female, presumably because of the implications this has for survival. 3. Laying date and clutch size are likewise under the influence of female condition and can hence be modified by experiments involving supplementary feeding. Natural variation in these features may often be related to territory quality. 4. How the bird decides whether or not to commence a second brood is not clear, but in the Great Tit the habitat-related difference in incidence of second broods is functionally understandable when survival probabilities of birds at different times are considered. 5. A distinction is made between a capital and income model for translatting rates of change of female body condition into appropriate decisions on laying date and clutch size and experiments are suggested that discriminate between the two. 6. Lack's view that brood size is in an evolutionary sense adjusted in order to balance food requirement and foraging capacity of the parents is accepted, and growth rates in nidicolous birds are analysed to ascertain if a finer adjustment exists superimposed on the integer steps of brood adjustment. Critical for this analysis are groups of birds where broods of one are common, since only in these circumstances is growth adjustment the only strategy open to the parents. In common with other animals, growth rate is related to mature body size but within a category of adult weight clear examples can be found for retardation of growth rate in pelecaniform and charadriiform species with singleton broods. 7. Since daily energy requirement is related to nestling size and growth rate, retardation of growth is explicable as a strategy only in terms of reducing the daily commitment of the parents, not reducing the total cost of producing a nestling. 8. An additional economy in growth is to reduce the contribution of fat to the nestling body. 9. Implied in Lack's view of brood size is a limitation of parental foraging capacity, and the last section of the paper is devoted to exploration of the proximate factors delimiting what Royama terms the optimal working capacity of parents feeding young. Observations of parent starlings confronted with manipulated brood size suggest a limit on the time that can be devoted to energetically extravagant flight activity, rather than a shortage of absolute time. Beyond the limit to which stressed parents can be made to fly, body weight declines. 10. Preliminary data on energy metabolized daily by parents confronted with large broods conforms to the simplified view that parental effort on a sustained basis equates to energy mobilization equivalent to 4 B.M.R. units and it is suggested that this level of energy expenditure represents a proximal decision substrate for determining the optimal working capacity of the parent. 11. The paper ends with a plea for more research on the proximate controls of avian reproduction, and calls attention to the central importance of the protein bank to parental body condition.

Avian Incubation: Behaviour, Environment, and Evolution

This is the first scientific review of all factors affecting incubation in avian nests. These range from nest construction, egg characteristics and patterns of embryonic development. There is an extensive section describing incubation behaviour of parents and embryos, and there are chapters reviewing brood patch physiology and the various factors determining the incubation environment, including nest microbiology. Another section provides chapters giving detailed descriptions of examples of unusual aspects of avian incubation, whilst the final section provides consideration of the ecological, energetic and fitness cost of incubation. Written by authorities in their respective fields from around the world, this provides a comprehensive review of this critical aspect of avian reproduction. Much of the data included has not been previously published, and so Avian Incubation is not only an extensive reference text but is also a valuable contribution to our basic understanding of incubation