Progress 05/15/17 to 05/14/21
Outputs
Target Audience:The target audience for this project is anyone concerned with or working toward increasing food production to feed the growing world population. Specific target audiences include other scientists in academia and industry working with poultry and the poultry companies. Changes/Problems:We encountered several problems during the funding period. First, our animal research facilty was shut down for renovation of the air conditioning system for 18 months. Second, all of our research laboratories were closed for an additional 3 months due to the COVID epidemic, and then social distancing restrictions hampered our ability to work together for an additional 6 months. These two events seriously impared our ability to complete the proposed research. The third problem that occurred was that thermoconditioning proved to be an unreliable method to reduce mortality from heat stress. We had proposed to perform RNAseq on hypothalamic samples from control and thermoconditioned birds. However, this analysis was scrapped, because no effects of thermoconditioning on mRNA levels for specifc genes were found in the hypothalamus or any other tissue. In the end, we found no consistent effect of thermoconditioning on any parameter measured during heat stress conditions. What opportunities for training and professional development has the project provided?Two postdoctoral researchers, one laboratory technicians, one graduate student, one international visiting graduate student, and three undergraduate students participated in this project. They gained training and experience in experimental design, molecular and cellular techniques such as total RNA isolation, reverse transcription, quantitative PCR, cell culture, cell transfection, and luciferase reporter assays, and data analysis. How have the results been disseminated to communities of interest?Results from this project have been presented at two national poultry science meetings. Abstracts for these presentations were published. Results were also published in one manuscript, and an additional manuscript based on our results will be submitted for publication in the coming year. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective 1. Define the minimal duration of thermal conditioning required for reducing heat stress and morbidity. Three trials of the experiments described under this objective were performed. Thermoconditioning occurred on day 3 after hatch. The temperature in the brooder pens was increased from 33ºC/92oF to 37.8ºC/100oF for four durations, 0, 6, 12 and 24h. No mortality as a result of thermoconditioning was observed in any of the trials or for any duration. However, plasma corticosterone levels were increased in response to the thermoconditioning, indicating that the thermoconditioning was stressful to the chicks. At 28 days of age, birds from each pen were transferred to grower batteries. The "heat stress" challenge occurred on day 31, when the temperature of the heat stress rooms was increased to 95oF. Two battery rooms were maintained at "normal" industry target conditions (72oF/22.2ºC). Mortality as a result of heat stress ranged from 25% to 50% across the three trials. Plasma corticosterone and glucose levels and blood pH were increased in heat stressed birds in all trials, indicating physiological changes in response to heat stress. In contrast with our preliminary results and previously published reports from other laboratories, thermoconditioning for any of the durations tested, including 24 hours, failed to reduce mortality as a result of heat stress. In total, thermoconditioning at 100oF for 24 hours beginning on day 3 after hatch reduced mortality in response to heat stress on day 31 in only 1 of the 4 experiments. At this point, we do not recommend thermoconditioning as a method to decrease mortality in broiler chickens during a heat stress event. Objective 2. Characterize mechanisms involved in alleviation of heat stress by thermal conditioning. Blood and tissue samples were collected from the trials conducted for the experiments descibed above under objective 1. Blood samples were assayed for levels of CO2, K, glucose, HCO3, pH, T3, T4, and corticosterone. RNA was extracted from tissue samples, and mRNA levels for genes were quantified by RT-qPCR. The following genes were evaluated in the hypothalamus: POMC, CRH, TRH, DIO2, TRB, TRA, NPY, GHRH, and SST. The following genes were evaluated in the pituitary gland: POMC, DIO2, TSHB, TRHR, CRH1, CRH2, TRA, GR, TRB, GHRHR, and GH. The following genes were evaluated for the thyroid: TPO, TG, TRHR, and TSHR. The following genes were evaluated for the adrenal gland: CYP11A1, HSD3B2, MC2R, and STAR. The following genes were evaluated for adipose: ADIPOQ, HSL, PPARA, and TRHR. The following genes were evaluated for liver: THRHSPA, DIO1, FASN, DGK, and ALDOB. The following were evaluated for breast and thigh muscle: HSP70, MTFA, NFR-1, PGC1A, and aUCP. The following genes were evaluated for heart: HIF1A, PGC1A, MTFA , NFR-1, and aUCP. Heat stress decreased (P<0.05) blood levels of HCO3, K, CO2, and T3, while heat stress increased mortality, glucose, pH, plasma T4, and corticosterone. Heat stress increased levels of TRH and DIO2 and decreased levels of CRH in the hypothalamus. Within the pituitary gland, expression of CRHR1, and GHRH were decreased, while CRHR2, TRHR, TRA, TRB, TSHB and GH mRNA levels were higher. Heat stress increased mRNA levels for TG and decreased leves of TRHR in the thyroid and CYP11A1, MC2R, and STAR in the adrenal. No effects of heat stress on mRNA levels in adipose were found. Within the liver, heat stress decreased mRNA levels for THRHSPA, DIO1, FASN, and DGK. Heat stress increased levels of mRNA for HSP70 and PGC1A in thigh muscle, while in breast muscle levels for HSP70, PGC1A, and aUCP were increased and levels for MTFA were decreased. No effects of thermoconditioning on mRNA levels for any gene in any tissue were found. In the end, we found no consistent effect of thermoconditioning on any parameter measured during heat stress conditions. We had proposed to perform RNAseq on hypothalamic samples from control and thermoconditioned birds. However, this analysis was scrapped, because no effects of thermoconditioning on mRNA levels for specific genes were found in the hypothalamus or any other tissue. Objective 3. Evaluate effects of thermal conditioning on performance under production conditions. Two trials were performed at the Applied Poultry Research Laboratory (APRL) in Upper Marlboro, MD, which is operated by the Maryland Agricultural Experiment Station, to evaluate the effects of thermoconditioning and heat stress on broiler performance under production conditions. In each trial, 1,440 1-d old chicks were placed in 12 floor pens for thermoconditioning. On day 3 half of the birds were subjected to thermoconditioning for 24 hours. At 4 days, chicks were distributed into 60 pens in the broiler house. On day 31, all the birds were subjected to heat stress for 8 hours. Body weights and feed intake were measured, and blood samples were collected. In one of the two trials, thermoconditioning reduced mortality in response to heat stress from 41% to 26%. In the second trial, no effect of prior thermoconditioning on mortality in response to heat stress was observed (50%). There were no significant differences in body weight, feed intake, nor feed-to-gain ratio between thermoconditioned and non-thermoconditioned birds. Plasma T3, T4, and corticosterone levels measured post heat stress were not significantly different between thermoconditioned and non-thermoconditioned treatments. Thermal conditioning had no adverse effects on chick health and performance. However, thermoconditioning failed to consistently reduce mortality in response to heat stress under production conditions.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Beckford RC, Ellestad LE, Proszkowiec-Weglarz M, Farley L, Brady K, Angel R, Liu HC, Porter TE (2020) Effects of heat stress on performance, blood chemistry and hypothalamic and pituitary mRNA expression in broiler chickens. Poult Sci 99:6317-6325
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Beckford RC, Farley L, Ellestad LE, Proszkowiec-Weglarz M, Brady K, Porter TE (2018) Effects of heat stress on hypothalamic and pituitary mRNA expression in broilers. Program 2018 Annual Meeting of the Poultry Science Association.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Beckford RC, Ellestad LE, Proszkowiec-Weglarz M, Farley L, Brady K, Angel RA, Liu HC, Porter TE (2019) Early-life thermal conditioning alleviates effects of heat stress in broilers. International Poultry Scientific Forum.
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Progress 05/15/19 to 05/14/20
Outputs
Target Audience:Results were reported at National Meeting on Poultry Health, Processing and Live Production in Ocean City, MD, and at theInternational Poultry Scientific Forum in Atlanta, GA.. Changes/Problems:Our facilities at the University of Maryland continue to cause problems. A new HVAC system was installed, but it continues to be unstable. The coronavirus shutdown is delaying all research. What opportunities for training and professional development has the project provided?One postdoc, one technician, and two undergraduate students assisted with this project in the past year. They gained experience in poultry husbandry, tissue collection, hormone assays, mRNA quantification, and data analysis. How have the results been disseminated to communities of interest?Results were shared with producers at the National Meeting on Poultry Health, Processing and Live Production held in Ocean City, MD, and at theInternational Poultry Scientific Forum held in Atlanta, GA. What do you plan to do during the next reporting period to accomplish the goals?We will complete the analysis of all experiments and submit two manuscripts for publication.
Impacts
What was accomplished under these goals?
Objective 3 of this proposal was conducted in our production facility. Birds were thermally conditioned for 24 hours, a duration selected based on previous studies. The heat stress occurred on day 31. There was no mortality among the control birds. Birds that were thermally conditioned and heat stressed had a lower mortality than those that were not thermally conditioned. Overall, there were noperformance differences between the thermally conditioned birds and the non-thermally conditioned birds. Birds that were thermally conditioned showed an increase in circulating glucose.However, no differences wereseen in the other blood parameters measured. To further understand the molecular changes that are occurring during heat stress, samples were collected from the hypothalamus, pituitary, heart, liver, thyroid, breast, thigh, and adrenal. Levels of mRNA for 31 previously selected genes that are thought to be involved in stress responses, thermoregulation, and metabolism were evaluated using real time qPCR. These results are being analyzed and prepared for publication.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Beckford RC, Ellestad LE, Proszkowiec-Weglarz M, Farley L, Brady K, Angel RA, Liu HC, Porter TE (2019) Early-life thermal conditioning alleviates effects of heat stress in broilers. International Poultry Scientific Forum.
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