Progress 04/01/24 to 03/31/25
Outputs
Target Audience:The target audience for this work over the past year included the scientific community, swine industry stakeholders and the general public. Communication with the scientific community occured in the form of poster and oral presentations across three meetings including ASAS-CSAS-WSASAS Annual Meeting in Calgary (international meeting), 57th Annual Meeting of the Society for the Study of Reproduction in Dublin Ireland (International), and the Swine in Biomedical Research Conference in Wisconsin (national). Two manuscripts were also published in scientific journals describing the porcine response to hypothyroidism. Results from this project were also presented at a meeting of the Indiana Pork Board, allowing us to disseminate the results of our work to swine producers and related stakeholders. Finally undergraduate student projects made possible through this work were presented at three local research symposium, disseminating information on to the general public. Changes/Problems:Despite our best efforts ongoing disease challenges within the Purdue university swine herd including porcine reproductive and respiratory virus (PRRSV), Porcine circoviruses 2 and 3 (PCV2 & PCV3) and Mycoplasma hyopneumoniae continue to disrupt our efforts to complete the animal trials. We are currently investigating other facilities and animal sources to complete the remaining work. What opportunities for training and professional development has the project provided?This project has provided training for 3 MSc students and 6 undergraduate students. Graduate student training has covered a wide range of skills essential for a career in animal science, including in-depth knowledge of swine physiology, molecular biology, and data analysis. One graduate student has already completed the master's program and accepted a position as a swine extension educator. The 6 undergraduate students involved in this project have completed independent research projects, during which they learned to read and interpret scientific literature and conduct industry-relevant experiments. Additionally, each of the undergraduate students has presented their findings at local research symposiums, gaining valuable experience in communicating their research to a general audience. How have the results been disseminated to communities of interest?This past year we published two peer reviewed manuscripts, with the primary audience being swine veterinarians and researchers. An additional 7 abstracts were shared in the form of oral presentations or posters at 2 international conferences, 1 national conference. Five additional abstracts and posters were presented by undergraduate students at local conferences/symposiums. Our results were further shared with producers and industry stakeholders at a meeting of the Indiana State Pork Board. What do you plan to do during the next reporting period to accomplish the goals?To better understand the mechanism underlying stressed induced hypothyroidism we will utilize samples collected during the weaning and transport study to evaluate gene expression in the hypothalamic-pituitary-thyroid/adrenal axis. In order to better our understanding of the role of thyroid hormone in fetal development we will conduct further experiments with our fetal model of induced hypothyroidism. We will also conduct additional analysis of IUGR phenotypic parameters and endocrine function in and effort to determine the underlying cause of preweaning mortality and poor growth performance. We will also assess endocrine activity in the IUGR population at later time points to determine if IUGR is altering the programming of the hypothalamic-pituitary-thyroid/adrenal axis, resulting in long term effects.
Impacts
What was accomplished under these goals?
Our prior work has demonstrated that swine are particularly vulnerable to endocrine disruption due to infectious diseases, suggesting that non-pathogenic stressors might induce similar effects. More importantly, our research shows that the suppression of thyroid hormones in response to these stressors correlates strongly with reduced performance, ultimately affecting profitability within the American swine industry. To develop effective farm counter measures, an improved understanding of this effect is required. Thus, this project aims to directly characterize the endocrine response to non-pathogenic stressors relevant to the industry and explore the cause-and-effect relationship between thyroid hormone levels and fetal/postnatal growth and development in pigs. Within the U.S. swine industry, it is standard practice to wean pigs at 21 days of age, a process that introduces significant physiological and psychological stress. Pigs must rapidly transition from a liquid to solid diet, while also adjusting to new social hierarchies and novel environments. Moreover, piglets are often transported long distances after weaning. Transport at this stage is necessary to get piglets from states such as North Carolina with an abundance of farrowing/nursery facilities in to grow-finish operations in corn producing states such as Iowa. To better understand how this combined stress affects endocrine function and growth performance, we conducted two transport studies. In the first study, average-weight, healthy pigs were subjected to weaning alone, weaning with nine-hour transport, or weaning with and equivalent nine-hour feed restriction. Compared to piglets that stayed with their sow, all weaned groups exhibited a significant acute decrease in circulating thyroid hormones. We collected tissue samples from the hypothalamus, pituitary, thyroid, and adrenal glands to assess the mechanisms behind this endocrine disruption. Growth performance was tracked through to market, and no additive effects of concurrent transport or feed restriction were observed. To confirm these results, we conducted a second trial with pigs categorized by low, average, and high body weight. Regardless of weight, transported pigs lost more weight as a percentage of their body weight compared to those weaned alone. However, contrary to some prior work, transport did not have an additive effect on growth performance through to market. Further analysis revealed no significant difference in performance between average and high-weaning-weight pigs, though low-weaning-weight pigs showed reduced average daily gain throughout the grow/finish period. The lack of compensatory growth in these low-weaning-weight animals indicates the need for improved management strategies targeted at improving performance in this specific population. To investigate the cause-and-effect relationship between thyroid function and postnatal performance, we completed an analysis using a postnatal model of induced hypothyroidism. Histological analysis confirmed central hypothyroidism, but circulating hormone levels indicated significant compensatory action within the hypothalamic-pituitary-thyroid axis. We found a significant reduction in growth performance, coinciding with decreased feed intake, resulting in equivalent feed-to-gain ratios. Given that hypothyroidism in other species is often linked to constipation, we used indigestible markers to assess gut transit rate. The results showed no increase in transit time, suggesting that the decreased feed intake may be due to hypothyroid induced appetite suppression. These findings suggest that while thyroid suppression in pigs does not negatively impact feed efficiency, it does reduce production by increasing days to market. Our previous work with in utero porcine reproductive and respiratory virus infection indicates that the fetal pig is exquisitely sensitive to hypothyroidism during mid to late gestation. We conducted an animal study involving induced fetal hypothyroidism at different gestational time points using the antithyroid medication methimazole (MMI). Histological assessments of fetal thyroids revealed severe central hypothyroidism at all gestational ages. In contrast to our postnatal model, circulating hormone concentrations confirmed complete suppression of fetal thyroid hormone production in the MMI-treated pigs, with limited compensatory capacity. Intensive phenotyping showed that short periods of hypothyroidism did not negatively impact fetal or organ mass accumulation. However, radiographs taken of the fore- and hind-limb bones of 96 fetuses showed that hypothyroidism between days 65 and 86 of gestation significantly shortened the long bones. Intensive selection for increased litter size in swine has resulted in larger embryonic and fetal populations, exceeding uterine capacity and limiting nutrient availability for fetal growth. This leads to widespread intrauterine growth retardation (IUGR), manifesting as low birth weight, high preweaning mortality, and poor lifetime growth performance. IUGR has thus become a major reproductive issue affecting efficiency in the U.S. swine industry. Using samples from fetuses at day 95 of gestation, we previously identified that IUGR is associated with reduced circulating thyroid hormone. To verify these findings, we conducted a trial involving 80 litters of pigs and phenotyped 1,061 piglets immediately after birth. Among these, we identified 92 IUGR piglets and an equivalent number of healthy, non-IUGR counterparts. The IUGR piglets showed significantly lower average daily gain during the first and second weeks of life, confirming their compromised growth. More critically, pre-suckle blood samples showed significantly lower circulating T4 in the IUGR piglets compared to non-IUGR pigs. Further analysis revealed that IUGR pigs had lower circulating glucose at birth, and their rectal temperatures at 2 and 48 hours after birth were significantly lower, indicating an inability to thermoregulate in the postnatal environment. Since thyroid hormones play a crucial role in basal metabolic function and thermoregulation, these results suggest that IUGR pigs suffer from reduced thyroid function, which impairs their ability to adapt to the external environment.
Publications
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2024
Citation:
Smith, A.A., Vesey, A., Helfrich, C. et al. Late gestation fetal hypothyroidism alters cell cycle regulation across multiple organ systems. BMC Vet Res 20, 268 (2024). https://doi.org/10.1186/s12917-024-04102-y
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2024
Citation:
Fazioli JC, Mulligan MK, Ison EK, Pasternak JA. Impact of methimazole-induced hypothyroidism on postnatal swine. Physiol Rep. 2024 Apr;12(8):e16007. doi: 10.14814/phy2.16007. PMID: 38658325; PMCID: PMC11043046.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Alyssa A Smith, Kaylyn Rudy, J Alex Pasternak, 105 Fetal hypothyroidism dysregulates local hepatic and renal renin-angiotensin systems in a temporal manner, Journal of Animal Science, Volume 102, Issue Supplement_3, September 2024, Pages 272273, https://doi.org/10.1093/jas/skae234.314
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Isabel Turner, Alyssa A Smith, Kaylyn Rudy, Dayeon Jeon, Brian T Richert, J Alex A Pasternak, PSI-24 Acute and chronic stress response following weaning and transportation in the average piglet, Journal of Animal Science, Volume 102, Issue Supplement_3, September 2024, Pages 477478, https://doi.org/10.1093/jas/skae234.542
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Kaylyn Rudy, Alyssa A Smith, Bea Cabot, J Alex A Pasternak, PSI-21 Limited impact of hypothyroidism on porcine fetal growth during mid to late gestation, Journal of Animal Science, Volume 102, Issue Supplement_3, September 2024, Pages 476477, https://doi.org/10.1093/jas/skae234.541
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Alyssa A Smith, Kaylyn Rudy, J Alex A Pasternak, PSIII-22 Downregulations in the expression of insulin-like growth factor binding proteins in a temporal model of in utero hypothyroidism, Journal of Animal Science, Volume 102, Issue Supplement_3, September 2024, Pages 501502, https://doi.org/10.1093/jas/skae234.567
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Innis S, Pasternak JA, Cabot R. Epigenetic profiling in late gestation porcine placenta reveals placental responsiveness to fetal endocrine status. 57th Annual Meeting of the Society for the Study of Reproduction (SSR). July 1519, 2024. Dublin Ireland.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Innis S, Pasternak JA, Cabot R. Unlocking Epigenetic Insights in a Porcine Model of Fetal Endocrine Disruption Using CUT&RUN, Swine in Biomedical Research 2024, June 14-18 2024, Madison WI.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Smith AA, Rudy K, Pasternak JA. Modulation of the Renin-Angiotensin and Insulin-Like Growth Factor Systems in a Porcine Model of Fetal Hypothyroidism. Swine in Biomedical Research 2024, June 14-18 2024, Madison WI
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Progress 04/01/23 to 03/31/24
Outputs
Target Audience:The target audience for this work over the past year has primarily been the scientific community. Abstracts on this work have been submitted to ASAS-CSAS-WSASAS Annual Meeting in Calgary (international meeting) and the Swine in Biomedical Research Conference (national). These meeting will allow us to disseminate our initial findings to other researchers working on swine production and physiology respectively. Changes/Problems:A number of disease challenges within the university swine herd including porcine reproductive and respiratory virus (PRRSV), Porcine circoviruses 2 and 3 (PCV2 & PCV3) and Mycoplasma hyopneumoniae have hampered our ability to complete animal trials. We are currently working to complete the planned experiments while minimizing the influence of these additional variables. What opportunities for training and professional development has the project provided?Thus far this project has been directly associated with the training of 3 MSc student and 4 undergraduate students. The three graduate students are pursuing degrees in animal science and this project will form the basis of their dissertation work. In addition, it will provide an opportunity to develop a broad range of skills required for a career in animal science including experimental design and logistics, anatomy and physiology, molecular biology, as well as data analysis and interpretation. The three undergraduate students associated with this project have gained an in-depth understanding of the scientific method and valuable experience in animal and laboratory methodology. Three of these undergraduate students have also participated in a pair of undergraduate research symposiums, gaining valuable experience communicating their findings to a general audience. How have the results been disseminated to communities of interest?Three abstracts for preliminary results on the impact of hypothyroidism on development of the intestine, placenta and brain have been presented an undergraduate research symposium. In addition, 4 abstracts have been submitted to the ASAS-CSAS-WSASAS Annual Meeting in Calgary, and 1 abstract to the Swine in Biomedical Research Conference. What do you plan to do during the next reporting period to accomplish the goals?To further our investigations into the effect of weaning stress on thyroid physiology and post weaning performance we will conduct a follow up transport stress study using average weight pigs as well as the top and bottom 15% of the weaning weight distribution. To understand the causal impact of postnatal hypothyroidism on apparent total tract digestibility and gut transit rate we will complete analysis of fecal samples from two completed metabolism crate studies. In order to better our understanding of the role of thyroid hormone on in utero development we will complete analysis of phenotypic data from our fetal hypothyroidism study. In addition, we will complete analysis of the impact of fetal hypothyroidism on other critical endocrine systems. Finally, in order to elucidate the role of thyroid hormone in the negative outcomes of IUGR we will complete an ongoing animal trial using head shape to identify IUGR in a large population of neonatal pigs.
Impacts
What was accomplished under these goals?
The overarching goal of this project is to improve our understanding of the cause-and-effect relationship between thyroid hormone and fetal/postnatal growth and development in pigs. Prior work in this area has shown that swine are particularly susceptible to thyroid suppression in response to disease challenge and that this response is strongly correlated with reduced growth performance. However, the impact of non-disease stressors such as weaning or intrauterine growth restriction have not been established. Similarly, the functional the impact of hypothyroidism in the absence of pathogenic disease has not been established. The lack of information in this area has hampered the development on farm measures to offset or minimize the negative impacts associated with otherwise unavoidable stressors Current standard practice within the American swine industry is to wean pigs at 21 days of age, which is a physiologically stressful event involving rapid transition from a liquid to solid diet and psychological stress associated with establishing a new social hierarchy in a novel environment. As a result of the geographic distribution of the various components within the swine production system, weaning is often coincident with long distance transport from nursery facilities to grow-finish operations adding addition stress. To better understand the individual and collective effects of these stressors we conducted a controlled weaning transport study using average, objectively healthy pigs. Our results indicate a transient decrease in circulating thyroid hormone associated with weaning. We did not however find any indication that this thyroid suppression post weaning is exacerbated by the additional stress associated with transport or temporary post weaning feed restriction. Samples were collected to investigate where in the hypothalamic-pituitary-thyroid axis this disruption is being created. Interestingly, we found no evidence that 10 hours of transport at weaning had any effect on subsequent growth performance as has been previously reported by other groups. We hypothesize that this incongruity may be associated with our use of average objectively healthy pigs, and will conduct a follow up experiment to investigate the response in the bottom and top 15% of the weaning weight distribution. To better understand the cause-and-effect relationship between thyroid status and growth performance and nutrient utilization we have recently conducted two repetitions of a trial using a postnatal model of induced hypothyroidism. Preliminary analysis of data from the first iteration suggests that 21 days of hypothyroidism produces a near significant effect on growth, and a substantial decrease in feed intake suggesting that hypothyroidism alters feed utilization. However recent data from the second iteration will need to be incorporated to verify this outcome. In addition, Fecal samples from both trials will be analyzed to determine the impact of hypothyroidism on gut transit and apparent total tract digestibility. Our prior work has demonstrated that the fetal pig is particularly susceptible to in utero hypothyroidism following viral infection, however we do not fully understand the consequences of this thyroid suppression. As proposed, we have carried out an animal study involving induced fetal hypothyroidism at various time points though gestation. We have deeply phenotyped the resulting fetal population and are in the process of evaluating the impact of this hypothyroid state on other endocrine systems. Intrauterine growth retardation (IUGR) is becoming an increasingly detrimental issues in the swine industry as a result of ongoing intensive selection for larger litter size which has increased ovulation rate well above uterine capacity. IUGR results in undesirable phenotype at birth, as there is a well-established relationship with increased preweaning mortality and reduced lifetime growth performance. However, the physiological mechanisms underlying the short and long term effects of IUGR have not been identified. Using samples from fetuses at day 95 of gestation we have now shown that an IUGR phenotype is associated with reduced circulating thyroid hormone. We have now developed an image analysis pipeline to produce non-invasive quantitative measures of head shape to identify IUGR piglets, and using this is an ongoing study to better understand the relationship between IUGR, thyroid hormone levels at birth and postnatal performance
Publications
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