Performing Department
(N/A)
Non Technical Summary
Global warming poses a significant threat to the livestock industry as high environmental temperatures become more frequent and intense thereby leading to extreme cases of heat stress. Poultry, a major source of animal protein in the United States, are highly susceptible to heat stress due to their elevated body temperature, insulating feathers, and the lack of sweat glands for cooling. Heat stress not only has an immediate impact on animal production, but it may also impact multiple generations produced by the heat-stressed parents, thereby leading to substantial economic losses and potential food security and safety risks. The effects of heat stress across multiple generations are mediated by epigenetic (DNA) modifications that are poorly understood in poultry species. The main objective of this project is to investigate the epigenetic processes that drive heat stress responses in birds using Pekin ducks as a model. Our study will employ an integrative approach through analyses of phenotypic traits related to physiology, production, behavior, and welfare, and the examination of transgenerational DNA changes in response to heat stress. This project will enable us to provide evidence-based recommendations to the United States poultry industry, consumers and policy makers regarding the most effective indicator traits and breeding strategies to enhance heat tolerance in ducks. Further, we aim to formulate guidelines that outline the optimal utilization of management and breeding strategies to improve heat tolerance in poultry. This is an integrative approach that offers a potential long-term solution to the effect of climate change on poultry production globally.
Animal Health Component
100%
Research Effort Categories
Basic
60%
Applied
40%
Developmental
(N/A)
Goals / Objectives
The main objective of this project is to investigate the epigenetic processes that drive heat stress responses in birds using Pekin ducks as a model. Our study will employ an integrative approach, encompassing the analysis of phenotypic traits related to physiological responses and welfare, and the examination of transgenerational epigenomic changes.SA1: To evaluate the effects of in ovo glucocorticoids and norepinephrine on the epigenomics of the Hypothalamic-Pituitary-Adrenal (HPA) axis and post-hatch performance. The effect of in ovo stress hormones, including glucocorticoids, norepinephrine, combination of glucocorticoids and norepinephrine, or vehicle administration will be investigated on meat-type Pekin ducks. Post hatching, we will collect bodyweight, feed conversion ratio, and weekly body condition scores. We will also evaluate how these ducks respond to stress by first giving a subset of birds an Adrenocorticotropic Hormone (ACTH) challenge (Tetel et al., 2022a). After the ACTH challenge, the remaining ducks will be exposed to heat stress for 7 days. At the end of the heat stress, the diencephalon, pituitary, and adrenal gland will be used for analyses of whole-genome DNA methylation -- a marker of epigenetics. These studies will provide a holistic understanding of the role of GC and norepinephrine on the post hatch performance, ability to cope with stressors and their role in DNA methylation of HPA genes.SA2: To quantify the direct and transgenerational effects of heat stress in breeder ducks based on the integration of DNA methylation and comprehensive phenotyping of key traits. We will utilize grand-parent adult breeder male and female Pekin ducks for this experiment (SA2a). Ducks will be exposed to heat stress or thermoneutral temperature for the duration of 3 weeks. We will collect data on production, reproduction, welfare and physiological traits. Diencephalon, pituitary, and adrenal glands will be collected as described in SA1 for epigenomics analyses. This will enable the identification of epigenetic biomarkers and phenotypic traits for heat tolerance in Pekin ducks. Glucocorticoid concentration in eggs will be analyzed, and eggs will also be incubated from both control and heat treatment groups. Compelling evidence suggests that epigenetics modification is heritable with significant impact on immunity, heat tolerance, behavior, and overall performance. Our hypothesis is centered around the idea that parental stress plays a critical role in inducing phenotypic changes in offspring after hatching, specifically by altering DNA methylation patterns of crucial regulatory pathways associated with heat tolerance and other biological functions within the HPA axis. The F1 progeny from the grandparents will be raised as breeder ducks and will be subjected to ACTH stimulation to validate their stress response (SA2b). We will collect the same data and utilize the same method for SA2b as in SA2a. Eggs will be collected and incubated from F1 hens, and we will raise the F2 generation as meat-type ducks. The F2 will also be exposed to the same ACTH stimulation test experienced by their parents and to an additional heat stress event (SA2c). We will collect the same data and utilize the same method for SA2c as in SA1. This will allow us to investigate whether epigenomic changes are transmitted to the F1 and F2 generations, shedding light on the multigenerational effects of DNA methylation. This will further validate the role of glucocorticoids in direct and transgenerational epigenetic modification as hypothesized in SA1.
Project Methods
For the first part of the study, we will obtain fertilized duck eggs and treat them with stress hormones or control treatments in order to determine if these hormones elicit effects on the hatchlings as does heat stress previously reported by our lab. After hatching, we will perform a series of tests to determine how the stress hormones impact their physiology, behavior, and welfare. These tests will include:Stress test: a well-established ACTH-stimulation test will be done to evaluate how the ducks will react to a simulated stressor in terms of stress hormone release and immunological function. Stress hormone and immune function data will be analyzed statistically and any significant deviations from control ducks will suggest an in ovo genetic alteration of these systems by the stress hormones applied.Production and Welfare tests: weekly body weights, feed intake, feed conversion ratio, and body condition scores will be collected and analyzed statistically. Also weekly, we will perform a novel object test (NOT) to determine the birds' fear responses. All of these variables will be analyzed statistically and any significant deviations of production, welfare or behavior variables of treated ducks compared to control ducks will suggest an in ovo genetic alteration of these systems by the stress hormones applied.We will also perform a heat stress test. In order to evaluate an actual heat stress, we will apply a heat stress to these ducks as described by our lab previously. We will again evaluate production, welfare, behavioral and physiological variables as described above.We will also assess molecular changes associated with these stress hormone treatments compared to controls by evaluating DNA methylation that is indicative of epigenetic changes. Any such differences in DNA methylation in treated compared to control birds will suggest that these hormones that are deposited into eggs during chronic stressors, such as heat stress, are involved in epigenetic changes to prepare offspring for a changed environment.In the second part of the experiment, we will obtain breeder ducks who have never been exposed to a heat stress. We will then expose half of the birds to a 3-week heat stress period and the other half to thermoneutral conditions. Prior to and during the heat stress we will evaluate production, welfare, behavior, physiological, and molecular measures as described above. In addition, we will also measure egg quality and egg biochemistry for stress hormone deposition using mass spectrometry. During the last 3 days of the heat stress, eggs will be collected and incubated to raise the offspring (F1 generation).The F1 generation will be raised as breeder ducks and undergo the same analyses as explained above for part 1. Once these ducks have reached peak production, we will evaluate production, welfare, behavior, physiological, and molecular measures as described above. After which, eggs will be collected and analyzed for egg quality and biochemistry, then an additional set of eggs collected for incubation in order to hatch the second generation (F2).The F2 generation will be grown as grow-out (meat type) ducks and will have same production, welfare, behavior, physiological, and molecular measures as described above.We expect that the original breeder heat stress exposure will elicit deficits in production and welfare as is well described. We also predict that the heat stress will increase the deposition of a specific stress hormone, cortisol, in the eggs as we have previously described. We expect this cortisol to lead to DNA methylation that is related to behavioral and physiological, but not production, measures of the F1. We further expect these physiological, behavioral and DNA methylation changes will last through to the F2 generation indicating epigenetic changes due to the original heat stress two generations earlier.Our efforts to disseminate our findings and outcomes will include scientific presentations and publications in journals such as Poultry Science and Genetics. We will further disseminate our findings to growers, producers, and industry stakeholders through personal meetings and presentations at trade shows such as IPPE and PEAK. We will also inform the public and policy makers of the impact of heat stress through press releases and interviews.