Progress 04/01/24 to 03/31/25
Outputs
Target Audience:?During this reporting period, our research focused on how heat stress impacts skeletal muscle and meat quality in beef cattle. This is an issue that affects many in the industry, from cattle producers trying to optimize animal performance to meat processors concerned about product quality. For beef producers, heat stress can lead to reduced feed intake, slower growth, and potential changes in meat quality. Our research helps understand the biological responses cattle experience under heat stress, which can guide better management decisions. It can include nutrition adjustments, genetic selection, or environmental modifications to keep cattle more productive. Meat processors and the beef industry can also benefit from these findings. Since heat stress can alter muscle composition, oxidative stability, and tenderness, understanding these changes at the cellular level helps improve processing techniques and maintain consistent meat quality. Beyond industry professionals, our research also reaches students in animal and food science. Our work has been discussed in lectures and coursework to help students connect fundamental muscle biology with real-world challenges in livestock production and meat quality. In the research community, this study is particularly relevant to scientists working in animal science, muscle biology, and meat science. Our findings contribute to ongoing discussions about how environmental stress affects muscle growth (the data lacking in beef cattle) and metabolism, and they provide a foundation for further studies on improving cattle resilience. Lastly, veterinarians and scientists in animal disease may find this research useful, as it provides insights into how heat stress affects muscle function. This knowledge can be applied to improve cattle health and welfare strategies during extreme weather conditions. Changes/Problems:The project has submitted a no-cost extension until March 31, 2026, as the analysis is taking longer than initially planned. This extension will allow sufficient time to complete the remaining analyses and finalize publication. What opportunities for training and professional development has the project provided?One PhD student was actively involved in the project and received training. The student successfully published a conference abstract at the ASAS-CSAS-WSASAS Annual Meeting and delivered an oral presentation at the conference. As the Principal Investigator, we have refined and improved the animal trial methodology, which is particularly challenging in large animals. This advancement lays the groundwork for conducting larger-scale animal trials with strong scientific relevance. How have the results been disseminated to communities of interest?Some of the findings were shared with the scientific community through presentations and abstracts at scientific conferences. Additionally, the Principal Investigatorincorporated a portion of the findings into ascientific talk, linking them to previous cell study results. Since the analysis is still ongoing, it is not yet the right time to fully share the findings from this project. A comprehensive interpretation and analysis must be completed before disseminating the results more broadly. What do you plan to do during the next reporting period to accomplish the goals?We have been analyzing the samples collected from the animal trial. The laboratory phase of transcriptomics analysis has been completed, and we are now focusing on data interpretation. Additionally, we are conducting protein analysis as planned. With all other analyses completed, once the remaining data analysis is finalized, we will begin preparing a manuscript for peer-reviewed publication. The findings will also be presented at international scientific conferences, including invited talks.
Impacts
What was accomplished under these goals?
We have completed the animal trial in year 1. During reporting period, we focus on sample analysis. (Aim 1)Heat-stressed cattle exhibited a reduction in dry matter intake by approximately 10 kg per pen, while their respiratory rate increased. However, rectal temperature did not differ between treatments. Longissimus muscle biopsies were conducted on days 0, 14, and 28 of the trial. By day 28, the heat-stressed (HS) group showed increased expression of heat shock proteins (HSPs) 20, 27, and 90, indicating that stress responses become more pronounced with prolonged exposure to heat stress. HSPs are chaperone proteins that play multiple protective roles at the cellular level, though their exact mechanisms remain unclear. Ongoing transcriptomic analyses are expected to provide further insights into these regulatory pathways. Additionally, myogenic regulatory factors (Myf5 and Pax7) and IGF-1 were overexpressed in the HS group by day 28, aligning with our previous in vitro findings. There is also evidence suggesting that heat stress shifts energy metabolism from glycolytic to oxidative pathways. In longissimus muscle biopsies, MHCI (a marker of oxidative muscle fibers) was elevated, supporting this metabolic transition. (Aim1 &2 )Cattle were tracked until harvest, and carcass characteristics were assessed. The HS group exhibited a reduction in hot carcass weight (347 kg vs. 335 kg), but other parameters--including backfat thickness, ribeye area, kidney-pelvic-heart (KPH) fat percentage, yield grade, and marbling score--remained unchanged. Although carcass weight decreased, fat accumulation was maintained, likely due to enhanced adipogenic/lipogenic regulation. In the longissimus muscle biopsy data, adipogenic genes such as PPARγ and CEBPα were upregulated, along with fatty acid synthase (FAS) and stearoyl-CoA desaturase (SCD). Similarly, in adipose tissue, PPARγ--a major regulator of adipogenic differentiation and lipogenesis--was elevated, along with FAS and SCD, further supporting increased lipogenic activity. (Aim 3) Samples from the 13th rib were analyzed for meat composition. Heat stress did not alter the moisture, protein, or fat content of the meat. However, cooking loss (%) was greater on day 3 of aging but showed no difference by day 21. Shear force measurements remained unchanged. Carcass color and pH levels were also unaffected. A portion of the longissimus muscle was shipped to Purdue University for further meat quality analyses. Heat stress did not affect Myofibrillar Fragmentation Index (MFI), troponin T, or desmin, which aligns with the shear force data. However, Thiobarbituric Acid Reactive Substances (TBARS) levels were elevated in HS cattle, indicating increased lipid oxidation in HS beef.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Eckhardt, E.P. and Kim, J., 2024. 78 Prolonged heat stress impact on molecular responses of skeletal muscle and growth performance in finishing beef steers. Journal of Animal Science, 102(Supplement_3), pp.223-224.
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Progress 04/01/23 to 03/31/24
Outputs
Target Audience:As proposed, we conducted an animal trial to assess how heat exposure affects meat production, utilizing 32 beef steers. During the summer, we prepared the animals and developed an IACUC-approved protocol. Subsequently, the trials were carried out over a 28-day period from October to November of 2023, where the animals were exposed to heat for 8 hours each day. We monitored their behavior, respiratory rate, and rectal temperature. Additionally, ten animals per treatment group were implanted with intramuscular temperature sensors to track temperature fluctuations. Biopsies of skeletal muscle and adipose tissue were performed every 14 days, and blood samples were drawn every 7 days to analyze the cellular response to heat stress. The cattle are scheduled for harvesting in March 2024, at which point we will evaluate carcass traits and meat quality. Changes/Problems:The initial plan was to remove the muscle temperature sensors after the heat trial; however, as the animals grew, the sensors became deeply embedded within the muscle tissue. Consequently, we will now be removing the temperature sensors in the MSU meat laboratory at the time of slaughter. What opportunities for training and professional development has the project provided?Throughout this project, a postdoctoral researcher and a PhD student have been actively involved, gaining experience in animal trial management and laboratory procedures. Additionally, two undergraduate students have joined the team to assist with the sampling process and are currently focusing on behavior video analysis as part of their sub-research project. The findings from this work will contribute to the PhD student's dissertation. How have the results been disseminated to communities of interest?The project has just begun, and we do not yet have data to share. What do you plan to do during the next reporting period to accomplish the goals?Sampling is scheduled to be completed by the end of March 2024. In the next reporting period, our focus will shift to analyzing the samples and generating data. We plan to share our findings at the ASAS meeting and work towards preparing publications.
Impacts
What was accomplished under these goals?
Aim 1, 2: We are currently in the process of gathering data related to Aims 1 and 2. Biopsies of skeletal muscle and adipose tissue have been collected, and their analysis through molecular techniques is underway. RNA sequencing is in progress following the completion of RNA and protein extractions. We anticipate that the data will be available in the third quarter of this year. Aim 3: Furthermore, we expect to achieve Aim 3 in the fourth quarter of this year. We plan to harvest the animals in March, after which the meat quality attributes will be assessed by our meat science laboratory and in collaboration with Dr. Brad Kim's group at Purdue University. To facilitate this process, we are conducting monthly meetings and regular phone calls.
Publications
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