Source: University of Maryland Eastern Shore submitted to NRP
HEAT STRESS MITIGATION AND NUTRITIONAL STRATEGIES TO IMPROVE THE HEALTH AND WELFARE OF PASTURED POULTRY
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
ACTIVE
Funding Source
Reporting Frequency
Annual
Accession No.
1030286
Grant No.
2023-38821-39583
Cumulative Award Amt.
$565,991.00
Proposal No.
2022-10017
Multistate No.
(N/A)
Project Start Date
May 1, 2023
Project End Date
Apr 30, 2026
Grant Year
2023
Program Code
[EQ]- Research Project
Recipient Organization
University of Maryland Eastern Shore
11868 College Backborne Road
Princess Anne,MD 21853
Performing Department
(N/A)
Non Technical Summary
In the United States, conventional raised broiler chickens dominates the poultry industry as it is a very efficient and safe method of poultry production. Despite the safe and economical poultry products that are produced by U.S. poultry companies, consumer demand for meat that is produced through alternative methods (pasture, free range, and organic) continues to increase. In 2019, sales of organic chicken were $1.115 billion, and the value of the U.S. broiler chicken industry in 2021 was about $31.5 billion. Studies evaluating early age thermal conditioning, diet manipulation on heat stressed pastured poultry are limited. The objectives of this project are to 1. Evaluate the performance effects, stress response parameters, and bird behavior indicators of early age thermal conditioning, and feeding tryptophan and pre and probiotic supplemented diets, to mitigate the effects of heat stress on different breeds of chickens raised on pasture; 2. Evaluate carcass microbial levels and fecal microbiome from different breeds of chickens raised on pasture fed tryptophan and pre and probiotic supplemented diets; and 3. Establish a pasture poultry extension program at University of Maryland Eastern Shore (UMES) to assist poultry growers in the region. The ultimate goal of this project is to establish a research foundation at UMES to develop research projects to address challenges surrounding pasture raised poultry, and educate high-skilled graduates who are needed in the region and nation. This projectmeets the follwing CBG priority areas: food safety, rural communities for the 21st century and sustainable agriculture.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3073220101050%
3063220310050%
Goals / Objectives
The goal of this projectis to evaluate early age thermal conditioning and nutritional strategies to improve the health and welfare of chickens raised on pasture. Theobjectives of this project are:i. Evaluate the performance effects, stress response parameters, and bird behavior indicators of early age thermal conditioning, and feeding tryptophan(Trp) and pre and probiotic supplemented diets, to mitigate the effects of acute heat stress on two breeds of chickens (fast growing commercial broilers (FGB) and crossbred slow-growing broiler breed, (SGB)raised on pasture. ii. Evaluate carcass microbial levels and fecal microbiome from two breeds of chickens (FGB and SGB) raised on pasture fed Trp and pre and probiotic supplemented diets.iii. Establish a pasture poultry extension program at UMES to assist poultry growers in the region.
Project Methods
Project Methods1) Study 1 (Trp and heat stress effect): This will be a randomized complete block (RCB) design as a 2x2 factorial arrangement of treatments with 4 treatments and 8 replicates per treatment. The birds will be fed diets with and without Trp supplementation and will be exposed to either an acute heat stress environment (41? temperature for 6 hours at 20 d of age and 35? for 6 hours at 41 d of age, or a control (thermo-neutral temperature regime (25.5? for 6 hours at 20 d of age and 19? for 6 hours at 41 d of age). At the end of the 42 d study, performance parameters will be measured. In addition, behavior indicatorswill be measured. Blood corticosterone levels, and bursa and spleen weights will be measured for stress response indicators. Also soil samples for nutrient analysis will be collected prior to placing birds on pasture and at the end of the trial to determine the impact of raising birds on pasture on the soil nutrient content.Treatments: 1) 0% added Trp diet and thermo-neutral temperature regime (25.5? for 6 hours at 20 d of age and 19? for 6 hours at 41 d of age), 2) 0% added Trp diet and acute heat stress regime (41? temperature for 6 hours at 20 d of age and 35? for 6 hours at 41 d of age), 3) 0.4% added Trp diet and thermo-neutral temperature regime (25.5? for 6 hours at 20 d of age and 19? for 6 hours at 41 d of age), and 4) 0.4% added Trp diet and acute heat stress regime (41? temperature for 6 hours at 20 d of age and 35? for 6 hours at 41 d of age).For the heat stress treatments (d 20 and 41), birds will be moved by pen to temperature controlled rooms. Room temperature and relative humidity will be monitored during the heat stress treatments. Recording cameras will be installed to measure behavior indicatorswill be measured during the heat stress treatments, and when birds are outside on pasture. At the end of the 6 hour heat stress period birds will be moved back to their respective pens on pasture. At the end of the trial (d 42), two birds per pen will be selected for processing. Blood will be collected from each bird to measure corticosterone levels immediately upon handling.Additionally bursa and spleen weights will be collected from each bird. Fecal samples for microbiome will be analyzed using 16S rRNA sequencing. Carcass samples will also be tested for the presence of Salmonella using the whole carcass enrichment methods.This trial will be conducted two times. The first trial will use FGB (Cornish x White Plymouth Rock cross) and the second trial will use SGB.2) Study 2 (thermal conditioning and heat stress effect): This will be a RCB design as a 2x2 factorial arrangement of treatments with 4 treatments and 8 replicates per treatment. The factors for this study include thermal conditioning (unexposed control group, 31? or chicks exposed to 36? and 70-80% relative humidity at 5 d of age for 24 hours x grow-out temperature (thermo-neutral control or heat stress). At hatch, 12 male broiler chickens (experimental unit) will be group weighed and brooded in pens inside the UMES research house. At 5 d of age, the thermal conditioned treatment (36? and 70-80% relative humidity for 24 hours) will be applied to chicks. All chickswill be moved to pensoutside on the UMES farm when they have obtained sufficient plumage (approximately 14 days of age). The birds will be exposed to either an acute heat stress environment (41? for 6 hours at 20 d of age and 35? for 6 hours at 41 d of age,) or a control (thermo-neutral temperature regime (25.5? for 6 hours at 20 d of age and 19? for 6 hours at 41 d of age). At the end of the 42 d study, performance parameters will be measured (body weight gain, feed efficiency, feed consumption, mortality, and carcass yield). In addition, behavior indicators such as number of birds observed panting, wing spreading, eating, and drinking during heat stress exposure period (20 and 41 d of age) will be measured. Blood corticosterone levels, and bursa and spleen weights will be measured for stress response indicators.Treatments: 1) Unexposed thermal conditioning and thermo-neutral temperature regime, 2) Unexposed thermal conditioning and acute heat stress regime, 3) Thermal conditioned and thermo-neutral temperature regime, and 4) Thermal conditioned and acute heat stress regime.For the heat stress treatments (d 20 and 41), birds will be moved by pen to temperature controlled rooms. Room temperature and relative humidity will be monitored during the heat stress treatments. Recording cameras will be installed to evaluate behavior indicators during the heat stress treatments, and when birds are outside on pasture. At the end of the 6 hour heat stress period birds will be moved back to their respective pens on pasture. At the end of the trial (d 42), two birds per pen will be selected for processing. Each bird will be wing tagged and a live weight will be recorded. Blood will be collected from each bird to measure corticosterone levels. UMES's SOP will be followed to humanely process the birds for carcass yield determination. Additionally bursa and spleen weights will be collected from each bird. Fecal samples for microbiome will be analyzed using 16S rRNA sequencing. Carcass samples will also be tested for the presence of Salmonella using the whole carcass enrichment methods.This trial will be conducted two times. The first trial will use FGB and the second trial will use SGB. Genotype selection will be the same as described in Study 1.3) Study 3 (probiotic/prebiotic and heat stress effect): Two flocks (Ross 708) will be raised during the summer in Mississippi (June-August) using a RCB design with a 2 X 4 factorial arrangement of treatments i.e. thermoneutral-control or heat stress and four dietary treatments consisting of. 1) corn/SBM diet (control diet), 2) the control diet plus probiotic , 3) control diet plus prebiotic , or 4) control diet with a combination of prebiotic and probiotic. Each treatment will be made up of 5 replicates with 15 birds/replicate.Thermal conditioned chicks will be exposed to 36? and 70-80% relative humidity at 5 d of age for 24 hours.After thermal conditioning and brooding period (d 15) chicks will be transferred to well-established pasture. Portable pens with open bottoms will be used to house the birds at a stocking density of 3 ft2 per bird. Pens will be moved once or twice a day depending on pasture conditions, diets and water will be offered ad libitum. Broiler performance will be evaluated weekly. Blood samples will be collected before and after heat stress and analyzed for pH, pO2, pCO2, HCO3, glucose, Na+, and K+ using a VetScan i-Stat analyzer and EC81 cartridges (Abaxis, Union City, CA) in addition, circulating levels of triiodothyronine (T3), thyroxine (T4), and corticosterone (CORT) in plasma will determined using commercial kits4) Study 4. Effects of dietary probiotic and prebiotic on broiler exposed to heat stress in commercial house setting.A similar experiment design as the one described in Study 3 will be used to conducted research using floor pens in a commercial broiler house. However, all birds (thermos-conditioned and non-conditioned birds) will be exposed to constant heat stress (32oC) for 6 hours per d for a duration of last two weeks before processing.Meat Quality parameters: After processing, chicken breast and thigh meat will be analyzed for lipid oxidation using 2 -thiobarbituric acid reactive substance (Min and Ahn, 2009). Protein oxidation and antioxidant capacity using oxygen radical absorbance capacity will also be determined (Lund et al., 2008; Min et al., 2017) respectively. Shear force and texture profile of cooked meat will be determined using a texture analyzer.

Progress 05/01/24 to 04/30/25

Outputs
Target Audience:UMES faculty and staff, and the University of Arkansas principal investigators and interested researchers. UMES graduate and undergraduate students and technical (research) support for learning opportunities and research experiences in pasture poultry management. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Two graduate students worked on this project. One graduate student attended the International Poultry Exposition and Southern Poultry Science Association meeting in January. The second student is being trained in the UMES Food Science lab to determine Salmonella levels on carcasses and is also being trained in DNA extraction for the microbiome analysis. How have the results been disseminated to communities of interest?The results of trial 1 were presented in a poster presentation at the Southern Poultry Science Association meeting in January. What do you plan to do during the next reporting period to accomplish the goals?Two more pasture studies are planned for the next reporting period. These two studies will evaluate the performance effects, stress response parameters, and bird behavior indicators of early age thermal conditioningto mitigate the effects of acute heat stress on two breeds of chickens (fast growing commercial broilers (FGB) and crossbred slow-growing broiler breed, (SGB)raised on pasture. In addition, the Salmonella results and microbiome results for trials 1 and 2 will be completed and summarized.

Impacts
What was accomplished under these goals? Pasture-raised broiler chickens face temperature extremes that can threaten welfare. In the first trial, we evaluated whether a 0.26 % tryptophan-supplemented diet (T) improved heat stress (HS) resilience in Ross-708 broilers raised on pasture. At D14, birds began the T or remained on the control diet and were moved outdoors. On D20 and 41, half of each group underwent six-hour HS; the remainder stayed under thermoneutral conditions. Weekly body weight, feed intake on D20 and D41, and fear via tonic immobility were measured. Neither diet nor HS affected body weight. However, T birds had similar body weights and higher feed conversion ratios (FCR) in Week 6 and cumulatively from D14 to 42 compared to C, suggesting reduced feed efficiency. On D20 and 41, HS significantly reduced feed intake during HS, regardless of diet. At both ages, HS did not significantly affect fear behavior, though HS birds tended to remain immobile longer on D22, suggesting increased fearfulness. On D15, T birds showed shorter latency to first leg movement and more leg movements, indicating heightened vigilance under stress; these effects did not persist under HS on D22. Under HS, birds spent more time sitting, panting, and wing spreading, and less time standing and eating. Within HS pens, T birds exhibited more simultaneous panting and wing spreading (PAWS) than controls, implying greater thermal stress. Age effects were observed during HS, where older birds on D41 relied more on panting and stationary behaviors, whereas younger birds on D20 were more active and utilized convective cooling (walking, wing spreading, PAWS), indicating developmental shifts in behavioral strategies for thermoregulation. Overall, tryptophan supplementation did not affect growth performance or reduce fear before or after HS; instead, T-diet had higher FCRs and subtle effects on vigilance and thermoregulatory behavior. HS reduced eating and altered behavior, confirming that hyperthermia remains a primary welfare and performance concern for outdoor poultry systems. To determine if tryptophan supplementation is an effective HS mitigation strategy, since 0.26 % tryptophan did not greatly affect performance or thermoregulatory behavior, future studies should include indoor-housed controls, additional supplementation levels, and physiological metrics (e.g., body temperature, corticosterone). The secondstudy evaluated the efficacy of supplemental Trp to mitigate the impact of heat stress on slow growing male broilers (SGB) raised on pasture to 63 d of age.The factors for this study include added dietary Trp (0% Trp or 0.26% Trp x heat stress (HS) conditions (non-heat stress, NHS or HS). Chicks were placed in (0.914 m x 1.83 m) outside on established pasture at 21 d of age. Birds were fed diets with and without Trp supplementation and were exposed to either an acute heat stress environment (33.8ºC temperature for 6 hours at 28 d of age and 31.6ºC for 6 hours at 57 d of age, or a control (NHS temperature regime (23.8ºC for 6 hours at 28 d of age and 20ºCfor 6 hours at 57 d of age). The dependent variables measured were weekly body weight gain (BWG), weekly feed conversion ratio (FCR), feed intake (FI), mortality, and percent carcass weight. No significant interactions were detected for d 63 BWG and FCR therefore only main effects will be presented. No significant effect of Trp (2.35 kg and 2.41 kg; 0%Trp and 0.26% Trp, respectively) or HS on 63d BWG was detected (2.4 kg and 2.36 kg; NHS and HS, respectively). Similar results were found for the effect of Trp on FCR. However, the HS treated birds had a higher (P < 0.05) FCR (2.2) compared to the FCR of NHS treated birds (2.14). Additionally, FI during the d57 HS exposure was lower (P < 0.01) in the HS treated birds (7.20 g/bird) compared to the NHS treated birds (13.5 g/bird). Mortality and carcass weight was not affected by the TRT. In conclusion, supplemental Trp did not mitigate the effect of HS for pasture raised SGB. However, exposing SGB to HS had a negative impact on their final FCR.

Publications


    Progress 05/01/23 to 04/30/24

    Outputs
    Target Audience:UMES faculty and staff, Unviersity of Arkansas, and Alcorn Stateprinciple investigators and interested researchers. UMES undergraduate students and technical (research) support for learing opportunities and research experiences in pasture poultry management. Changes/Problems:A graduate student was scheduled to begin working on this project September 2023. However, due to health issues the student was not able to work on this project. As a result there was delay in finding a graduate student to work on this project. Another graduate student is scheduled to begin work on this project September 2024. What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Two of the pasture studies (Trp study) with fast growing and slowing breeds will be conducted. The PIs on the project will meet to discuss poultry behavior/welfare portion of the project (to determine camera placement and stress parameters to measure). The data will be analyzed and presentation is planned at the Southern Poultry Science meeting in January 2025. In addition, a graduate student is scheduled to begin work on this project September 2024.

    Impacts
    What was accomplished under these goals? This report of work covers the time period between May 2023 to April 2024. During this reporting period, PI Timmons worked with the poultry research technician to determine a design for the pasture pens. Once a design was established, a template pen was built. This pen was used to raise broilers for the Poultry Management lab course. This allowed the research team to evaluate any flaws that may be encountered with the pens. The design flaws were corrected as a result. The materials for the pasture pens were purchased and the remaining pens were built during this reporting period. In addition, the pasture was planted September 2023 and is well established. The research team met virtually to discuss the pen design and determine the start date for the first trial. The first trial is scheduled to begin May 2024.

    Publications