Department of Animal Science

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The Department of Animal Science originally concerned itself with teaching the selection, breeding, feeding and care of livestock. Today it continues this study of the symbiotic relationship between animals and humans, with practical focuses on agribusiness, science, and animal management.

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The Department of Animal Husbandry was established in 1898. The name of the department was changed to the Department of Animal Science in 1962. The Department of Poultry Science was merged into the department in 1971.

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https://dr.lib.iastate.edu/handle/20.500.12876/98939
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Thesis

Variation in early postmortem pH of fresh pork loin affects quality attributes and degradation of key proteins

2024-12 , Jess, Cydne' , Huff-Lonergan, Elisabeth , Lonergan, Steven M , Hansen, Stephanie L , Department of Animal Science

Inconsistency in fresh pork quality is a persistent challenge faced by the United States pork industry. In order to maintain the demand for pork products globally, the mechanisms responsible for quality development must be investigated further to improve meat quality and consumer acceptance. The discovery of reliable molecular markers that can be measured non-destructively shortly postmortem to predict quality traits could aid in enhancing the consistency and value of fresh pork products. Therefore, this project aimed to contribute to the search for markers of quality by advancing the understanding of how early postmortem pH variation affects the quality, sensory, and biochemical attributes of fresh pork loin. Desmin was chosen as the target protein of interest in this study as the postmortem degradation of desmin, or lack thereof, has been shown in previous studies to influence important meat quality traits such as tenderness and water-holding capacity. To achieve the objective, fresh pork loins (N=62) were selected from the production line of a commercial facility at 1-day postmortem. Loins were selected based on the following pH criteria to ensure a population that was diverse in quality (pH ≤ 5.70; pH ≥ 5.90). Loins were then vacuum packaged and immediately transported on ice to the Iowa State University Meats Laboratory. The product was then sorted into distinct groups by 1-day postmortem pH: low/normal (n=25, 5.59-5.71, x̄= 5.67) and high/normal (n=25, 5.90-6.46, x̄=6.09), resulting in a refined population of (N=50) on which all analyses were performed. All loins were cut into 2.54cm or 0.635cm thick chops and trimmed of external fat and connective tissue. Subjective color score, marbling score, and Hunter L, a, and b values were determined on chops the same day as collection. Drip loss of chops at 1-day postmortem was measured over 24 hours. The remaining loin chops not utilized in these initial measurements were individually vacuum packaged per aging time, aged for a total of 1, 7, or 14 days (4°C), and frozen until analysis. Two chops from each loin at each time point were used for sensory analysis and to determine cook loss. Palatability characteristics consisting of off-flavor, pork flavor, juiciness, tenderness, and chewiness were evaluated by a trained panel of (n=3) on a 10-point categorical scale. Instrumental tenderness was performed on a pair of cooked 1, 7, and 14-day aged chops using an Instron fitted with a star probe attachment. Intramuscular lipid and moisture content were determined on frozen, homogenized longissimus thoracis (LT). Desmin degradation was analyzed using low ionic strength extracts from the LD from each aging period. The abundance of desmin degradation products within the soluble protein fraction was determined using western blotting analyses. Chops from the High/Normal pH group had approximately 79% less drip loss at day 1 and approximately 19% less cook loss than Low/Normal pH chops at all aging times. High/normal chops exhibited higher color scores than Low/Normal chops on day 1 (P<0.001) and day 14 (P<0.0001). Moreover, High/Normal chops exhibited a lower Hunter L value at day 1 (P<0.0001) and 14 (P<0.0001) compared to Low/Normal chops. Intramuscular lipid content was not different between the pH groups (P=0.36). Intramuscular moisture content was greater in High/Normal chops than in Low/Normal chops (74.11% vs. 73.53%) (P<0.05). High/Normal chops had significantly lower star probe values than Low/Normal chops at 1 (5.11kg vs. 5.88 kg), 7 (4.90 kg vs. 6.14), and 14 days of aging (4.07 kg vs. 5.18 kg). The trained panel rated 14- day aged High/Normal chops to be more juicy (P<0.001), tender (P<0.0001), and less chewy (P<0.05) while having greater pork flavor (P<0.0001) and less off-flavor (P<0.0001). The abundance of soluble desmin degradation products was significantly greater in low ionic strength extracts from High/Normal chops at 1, 7, and 14 days postmortem (P<0.0001). Variation in 1-day postmortem pH significantly impacted the quality, sensory, and biochemical attributes of fresh and aged pork loin. Higher pH at 1-day postmortem resulted in conditions that likely generated more proteolysis of desmin, which is proposed to result in improved quality of fresh pork. Furthermore, desmin degradation products were detected within the soluble protein fraction of postmortem muscle in this study, which have been identified by previous literature as a reliable indicator of aged pork tenderness; observations of the current study confirm this. Results from this study are also the first to detect the appearance of soluble desmin degradation products as early as 1 day postmortem and that differences in the abundance of soluble desmin persisted throughout 14 days of aging. Data from this study suggest that 1-day postmortem pH could be indicative of quality development in aged pork and that soluble desmin fragments could potentially be utilized as a viable predictor of value within fresh pork products.

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Dissertation

Immunometabolism, energetics, and intestinal barrier health during immune activation

2024-12 , Rodriguez Jimenez, Sonia , Baumgard, Lance H. , Jayasooriya, Ranga Appuhamy , Gorden, Patrick J. , Kohut, Marian L. , Ross, Jason W. , Department of Animal Science

Livestock encounter a multitude of physiological, psychological, nutritional, and environmental stressors that frequently lead to exacerbated immune activation or inflammation, which compromises animal health, production efficiency, and thus, animal agriculture sustainability. Two of the most critical immune activating events/factors affecting dairy farms’ profitability are the transition period and environmentally-induced hyperthermia or heat stress (HS). Animals utilize physiological, metabolic, inflammatory, and endocrine adjustments to homeorhetically survive these insult(s). While inflammation can originate from various sources (i.e., uterus, mammary gland, lungs), intestinal barrier hyperpermeability appears to play a critical role in the etiology of immune activation during the transition period and HS. Regardless of the origin, immune activation burdens animal welfare, and it undoubtedly plays a crucial part in some undesirable production outcomes (i.e., reduced appetite, low milk yield, impaired reproduction). Gastrointestinal tract (GIT) epithelial barrier dysfunction allows bacteria components and pathogen translocation into circulation, which induces local, compartmentalized, and potentially systemic inflammation. Immune activation and inflammation are energetically and amino acid expensive, and nutrients are repartitioned to fuel the immune system to the detriment of production (i.e., growth, reproduction, and lactation). The increased energetic demands of immune activation coincide with a concomitant reduction in feed intake and, subsequently, reduced nutrient absorption. Therefore, the main objectives of this dissertation were to improve our understanding of 1) the etiology of transition cow chronic inflammation, fatty liver, and ketone metabolism, 2) the effects of HS on intestinal physiology and immunometabolism, and 3) dietary strategies that potentially alleviate the negative consequences of HS on intestinal physiology, immunometabolism, and production in lactating dairy cows. In studies 1 and 2 (Chapters 2 and 3) we created a chronic inflammation and mild liver steatosis model, respectively, resembling immunometabolism alterations occurring during the transition period. Overall, immune activation markedly influenced endocrine and metabolic homeostasis, and these alterations closely resembled changes observed in poorly transitioning dairy cows. In study 3 (Chapter 4), we evaluated the effects of a mycotoxin deactivator (MD) dietary supplement on performance, metabolism, inflammation, and intestinal health during acute and chronic HS. In study 4 (Chapter 5) we evaluated the effects of dietary zinc hydroxychloride (HYD) on performance, metabolism, inflammation and GIT integrity during acute and chronic HS and following HS recovery. As anticipated, HS markedly decreased feed intake and milk production. Moreover, HS altered endocrine, metabolic, and inflammatory biomarkers relative to thermoneutral conditions, and although supplementing MD did not have a large impact during HS, HYD reduced GIT barrier permeability during acute HS and increased feed intake during HS recovery. In summary, immune activation impacts a wide range of phenotypical, endocrine, and metabolic parameters. Moreover, inflammation stems from a multitude of stressors (i.e., feed restriction, HS) causing intestinal barrier integrity disruption and subsequent luminal content translocation. This intestinal hyperpermeability may also contribute to metabolic disorders (i.e., ketosis, fatty liver) during the peripartum period, and lead to compromised health and performance. Further investigation is necessary to better understand how immune activation induces metabolic and endocrine alterations and nutrient partitioning observed during the transition period and HS. This would be the requisite for developing strategies to alleviate the negative impact of different stressors on animal health and production and ultimately improve farm profitability and sustainability.

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Preprint

miRNA-microbiome interplay is related to Bos indicus feed efficiency

2024-08-09 , De Oliveira, Priscila Silva Neubern , Andrade, Bruno Gabriel Nascimento , Cardoso, Tainã Ferreira , Conteville, Liliane Costa , Pena, Gabriel Alexander Colmenarez , Malago-Jr, Wilson , Bruscadin, Jennifer Jéssica , Pascoal, Juliana Jorge , Almeida, Lauro Fraga , Josahkian, Luiz Antônio , Ventura, Henrique Torres , Maciel, Giovana Alcantara , Mourão, Gerson Barreto , Coutinho, Luiz Lhemann , Reecy, James , Almeida Regitano, Luciana Correia de , Department of Animal Science

The fecal microbiome is emerging as an essential component of the gut microbiota and host metabolism, whereas in cattle, fecal microbiome characterization is still needed. Recent evidence indicates that small RNAs, such as miRNAs, may be isolated from feces and involved in host–microbe interactions. In this study, fecal samples were collected from the rectal ampulla of Nelore bulls phenotypic divergent for residual feed intake (RFI). miRNA sequencing and 16S rRNA gene (V3-V4 region) were performed to reveal the associations between host miRNAs and microbiome composition and their relationships with the feed efficiency phenotype. Among the 162 identified fecal miRNAs, seven were more expressed in the inefficient group: bta-miR-27b, bta-miR-30a, bta-miR-126, bta-miR-143, bta-miR-155, bta-miR-205 and bta-miR-196a. Using metabarcoding sequencing, we identified 5,005 bacterial ASVs, and after filtering, we used 357 ASVs in subsequent analyzes. Weighted gene coexpression network analysis (WGCNA) was used to identify miRNA and microbiome interactions. We observed significant correlations between fecal miRNA expression and microbiota composition. The differentially expressed fecal miRNAs were correlated with some taxa as Prevotella, Anaerorhabdus furcosa, Bifidobacterium, Bacillales, Succinispira mobilis, Peptostreptococcaceae and Coriobacteriaceae, suggesting that they may play a role in the expression of feed efficiency-related miRNAs. Our results provide a new perspective for exploring host-microbiome interactions that affect FE traits. Taken together, these results point to miRNAs and taxa identified here as potential regulators of feed efficiency, which may provide the knowledge needed to develop future strategies to manipulate the microbiome.

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Thesis

The individual and interactive effects of rumen modifiers on feed efficiency in lactating dairy cows

2024-08 , Rigert, Sydney , Appuhamy Jayasooriya, Ranga , Baumgard, Lance H , Carpenter, Gail , Koltes, James E , Department of Animal Science

The Food and Agriculture Organization 2023 publications highlight that increasing the productivity of global livestock systems through improved feeding, genetics, and husbandry practices is essential to make them sustainable. This goal is, however, not new to the US dairy industry, given the tremendous productivity improvements achieved through continuous advancements in genetics, nutrition, and management practices over the last century. The US dairy industry continues to become more sustainable through nutritional advancement. Improving the feed efficiency of lactating cows (e.g., fluid milk volume per unit feed weight) garners the utmost priority, given the increasing feed prices and the carbon footprint associated with feed crop production. Being a ruminant animal, the feed efficiency of dairy cows largely depends on rumen microbiota and their functions, such as carbohydrate fermentation and the efficiency of microbial protein synthesis. Ionophores, predominantly monensin, are widely used in US dairy operations to enhance the feed efficiency of cows, in addition to other purposes, such as bloat and ketosis prevention. Ionophores are classified under a special feed additive category termed rumen modifiers because they modulate rumen microbiota composition and thus shift the fermentation, leading to increased feed efficiency attributed to increased milk yields, decreased feed intake, or both. However, feeding monensin can elicit milk fat depression and elevated milk urea nitrogen, depending on feeding conditions. The European Union has restricted monensin use in dairy cows, prompting a need to develop other strategies to improve feed efficiency. In that regard, feed additives with a “natural” outlook, for instance, direct-fed microorganisms or their fermentation extracts and secondary plant metabolites, have been proposed. The preliminary findings, predominantly from in vitro investigations, demonstrate these novel feed additives may modulate the rumen function through both non-competitive and competitive mechanisms to that of monensin. Given that most dairy cows are given monensin, and monensin can considerably increase the income over feed cost ($0.29 to 0.42 per cow/d) in US dairy operations, it is crucial to evaluate these novel rumen modifiers for their ability to modulate cow productivity and feed efficiency against monensin. Chapter 2 of this thesis covers an experiment designed to evaluate the individual and interaction effects of a fermentation extract derived from Bacillus licheniformis (BLFE) and monensin (Rumensin®; R) on production performance and feed efficiency of lactating dairy cows fed a corn silage-based TMR. This 90-d study utilized 20 primiparous and 40 multiparous Holstein cows at 108 ± 35 DIM when the study began. Cows were assigned randomly to two monensin [0 and 420 mg/cow/day] and two BLFE [0 and 2.4 g/cow/day] doses in a 2 × 2 factorial arrangement. The study consisted of four consecutive periods starting with training (13 d) and baseline measurement (14 d) periods, where cows received the basal TMR containing monensin, followed by treatment adaptation (21 d) and response measurement (42 d) periods, where cows received the treatment doses of monensin and BLFE top-dressed on the basal TMR devoid of monensin. Individual and interaction effects of monensin and BLFE on DMI, milk production parameters, multiple feed and nutrient utilization efficiency matrices, and body measurements were analyzed with a mixed-effect model accounting for the repeated measures and baseline measurement variability. Additionally, treatment effects on volatile fatty acid concentrations and molar percentages in rumen fluid obtained with an oral stomach tube and feces, apparent total tract digestibility of nutrients, and blood amino acid concentrations were analyzed. Monensin did not affect the milk yield or gross feed efficiency (milk yield: DMI), but it increased milk fat yield (0.10 kg/d), fat-corrected (FCM), energy-corrected (ECM), and solids-corrected (SCM) milk yields by 2.06, 1.92, and 1.83, respectively (P = 0.02). BLFE increased milk protein content by 0.06 percentage units (P = 0.01), irrespective of whether the diet contained monensin or not. However, BLFE tended to increase milk yield (0.98 kg/d; P = 0.07), and increased gross feed efficiency, dietary protein utilization efficiency, and average daily gain, only in the absence of monensin in the diet (P < 0.05). BLFE also increased serum total concentrations of both essential and non-essential amino acids only in the absence of monensin in the diet. Despite the blood amino acid concentrations reflecting an increased metabolizable protein supply, BLFE decreased apparent total tract CP digestibility in the absence of monensin, and monensin attenuated that digestibility reduction (P = 0.04). Monensin or BLFE did not affect acetate or propionate concentrations in rumen fluid but tended to interactively modify the fecal concentrations (P < 0.10), indicating that rumen modifiers can affect hindgut microbiota function, which can lead to perturbed apparent total tract digestibility estimates. Overall, this study data supported the potential of BLFE to improve the feed efficiency of lactating dairy cows, particularly when added to diets without monensin. Additionally, they support the potential of monensin to increase milk fat yield under some feeding conditions. Furthering the investigations into the interactive effects of novel rumen modifiers and monensin, the experiment described in Chapter 3 was designed to determine the effects of feeding a blend of secondary plant metabolites, such as cinnamaldehyde and garlic oil (NECGO) alone or with monensin in lactating dairy cows. In this study, 20 primiparous and 40 multiparous Holstein cows (81 ± 29 DIM) were assigned to treatments in a 2 × 2 factorial arrangement, with monensin [0 and 406 mg/cow/day] and NECGO [N; 0 and 710 mg/cow/day] doses (n = 15 cows/treatment). In alignment with the previous study, cows received the basal TMR containing monensin in the training (10 d) and baseline measurement (10 d) periods. Monensin was removed from the TMR, and the treatment doses were top-dressed on the TMR devoid of monensin during the adaptation (21 d) and measurement (49 d) periods. The same production and efficiency responses of the previous study were measured in this study, and milk fatty acid composition was an additional response variable of interest. Treatment effects were analyzed with the same procedure used in the previous study. The results indicated a milk yield increase (1.2 kg/d; P = 0.01) that did not change gross feed efficiency or DMI in response to feeding monensin. Monensin increased milk fat yield (0.1 kg/d; P = 0.04) and FCM, ECM, and SCM by 2.6, 2.3, and 2.1 kg/d, respectively (P < 0.05). The increase in milk fat yield in response to monensin was associated with increased palmitate concentration in milk fat (P = 0.02). NECGO decreased DMI by 1.9 kg/d (P = 0.02) and increased gross feed efficiency by 8% (P < 0.01) without affecting milk yield in the absence of monensin. Independent of monensin, NECGO increased milk fat content by 0.3 percentage units (P < 0.01) but did not increase the milk fat yield, because of the unchanged milk yield. The increased milk fat content by NECGO was associated with increased saturated and preformed fatty acids concentrations (P < 0.05). NECGO increased milk protein efficiency (P = 0.03), again in the absence of monensin. In conclusion, the findings of both studies highlight the potential of the novel feed additives to improve feed efficiency by increasing milk yield or decreasing DMI when fed without monensin. Those feed additives may also improve dietary crude protein utilization efficiencies, implying positive implications for economic and environmental sustainability. A comprehensive cost-benefit analysis would help draw robust conclusions on their economic advantage against monensin.

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Dissertation

The impact of dietary crude protein level, fiber inclusion, and arginine supplementation on post-weaning pig performance and clinical response during enteric health challenges

2024-12 , Hagen, Chloe Sue , Greiner, Laura L , Gabler, Nicholas , Burrough, Eric , Silva, Gustavo , Rosero, David , Department of Animal Science

The weaning period is characterized as the most stressful time in a pig's life, often leading to post-weaning diarrhea (PWD). Enterotoxigenic Escherichia coli (ETEC) is a leading cause of PWD, resulting in secretory diarrhea, weight loss, morbidity, mortality, and significant economic losses. While antibiotics (e.g., carbadox) and zinc oxide (ZnO) can reduce the incidence of PWD and improve nursery pig performance, regulatory pressures to reduce their use drive the search for alternatives. Potential approaches include reducing the crude protein (CP) level of the early nursery diet, incorporating insoluble fiber to decrease pathogen proliferation in the intestinal tract, and supplementing dietary or water-based arginine (Arg) to support piglet growth and intestinal development. However, inconsistent reports on their benefits for pigs facing enteric challenges warrant further investigation. The overall objective of this dissertation was to evaluate the efficacy of three strategies as methods to manage nursery pig performance during enteric health challenges, focusing on their effects on growth performance, PWD, intestinal morphology, and pathogen shedding during enteric challenges. These strategies included: 1) low CP diets with subsequent reductions in standardized ileal digestible (SID) lysine (Lys), 2) inclusion of insoluble fiber (FIB), and 3) arginine (Arg) supplementation provided in feed and/or water. To achieve this objective, three experiments were conducted using commercially sourced pigs with poor enteric health at the time of weaning with rotaviral infections. Two experiments then followed the natural rotavirus challenge with an ETEC F18 challenge (Chapters 2 and 4). The ETEC challenge bacteria isolate contained F18 fimbriae and expressed enterotoxins heat-labile toxin (LT), heat-stable toxin b (STb), and enteroaggregative Escherichia coli heat-stable enterotoxin 1 (EAST1). This isolate was inoculated at a dose of 6 mL per pig and approximately 5 x 108 CFU/mL. Scouring was observed within the first week post-weaning due to rotavirus, with Chapters 2 and 4 demonstrating resolution of rotavirus-induced diarrhea around 10 days post-weaning. In Chapter 2, inoculation with ETEC occurred for one day at 14 days post weaning, while in Chapter 4, inoculation was conducted over two days at 15- and 16-days post weaning. The challenge with ETEC resulted in peak scouring at three days post inoculation (DPI) in Chapter 2 and two DPI in Chapter 4. Both studies confirmed the shedding of ETEC genes F18 and STb after inoculation; however, ETEC inoculation did not lead to reductions in growth or increased mortality in either experiment Results from Chapter 2 indicated no benefit from LCP or FIB diets for nursery pigs challenged with ETEC compared to the PC diet. The PC diet, which contained carbadox (55mg/kg) and ZnO (3,750 mg/kg), consistently reduced scouring both pre- and post-ETEC challenge and resulted in rapid shedding of ETEC, confirmed via qPCR. Neither the LCP nor FIB diet improved fecal consistency, and the LCP diet prolonged ETEC shedding. Chapter 3 investigated dietary and water-based Arg supplementation on piglet performance and intestinal integrity during a natural rotavirus outbreak. Increasing dietary SID Arg:Lys from 0.85 to 1.05 improved growth rates and final body weight after recovery from rotavirus, suggesting that SID Arg:Lys requirements may be higher than previously recommended. Water-based Arg supplementation, provided as an 8% stock solution dosed through a 1:128 proportioner for the first week post weaning, did not benefit growth performance or intestinal structure/permeability, as measured via the lactulose and mannitol dual-sugar absorption test. Chapter 4 combined the LCP dietary strategy from Chapter 2 with the water-based supplementation strategy from Chapter 3, supplying water for the first three weeks post weaning at levels of 8%, 6%, and 4% Arg stock for weeks one, two, and three, respectively. Lowering the CP level of the diet or supplementing Arg in the water did not reduce scouring pre- or post-ETEC challenge. However, water supplementation increased ileal villous height (VH) both pre- and post-ETEC challenge, and the LCP diet improved ileal VH pre-ETEC. Notably, the combination of LCP and water-based Arg supplementation prolonged ETEC shedding, without prolonging clinical signs. The LCP diet also reduced overall feed efficiency in Chapter 4, with increased villous atrophy observed following the ETEC challenge. Therefore, the lack of health improvements in response to ETEC F18 infection does not justify the growth performance reductions associated with the LCP diet. This dissertation demonstrated that increasing dietary SID Arg:Lys improves growth performance. However, reducing dietary CP and subsequently SID Lys, adding insoluble fiber, or using water-based Arg were not effective strategies for managing PWD caused by rotavirus or ETEC in the context of this research.

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Thesis

Supporting muscle growth of feedlot cattle administered growth enhancing technologies through strategic zinc supplementation

2024-12 , Ortner, Brock Michael , Hansen, Stephanie , Genther-Schroeder, Olivia , Lonergan, Elisabeth , Department of Animal Science

Growth enhancing technologies (GET) are a pillar of the beef production system that provide improvements to growth, feed efficiency, and carcass leanness. Steroidal implants and beta-adrenergic agonists (β-AA) are widely used in the beef industry and are critical for meeting strong consumer demand for beef with fewer animals. The performance response to GET is influenced by nutritional management, making optimized GET use paramount to capture benefits. Zinc (Zn) is an essential trace mineral involved in whole-body growth, energy metabolism, and protein and DNA synthesis. Therefore, optimizing Zn concentration in diets fed to cattle administered GET represents an opportunity to make meaningful improvements to productive efficiency. The studies described in this thesis aimed to examine the complex interactions between Zn and GET for the purpose of optimizing Zn supplementation to feedlot cattle. The studies outlined were designed to 1) examine the influence distinctly different plasma Zn concentrations (1.1 mg/L vs. 1.6 mg/L) on longissimus thoracis metabolic profile in steers who did or did not receive a high-potency combination anabolic implant, and 2) determine the effects of supplemental organic Zn concentration (30, 60 or 90 mg Zn/kg DM in addition to basal diet) on performance, carcass characteristics, and circulating metabolites of steers fed, and not fed the novel β-AA lubabegron fumarate (LUB). We have previously demonstrated improved growth performance over implanted controls with Zn supplementation up to 150 mg Zn/kg DM, and chapter 3 of this thesis sought to elucidate potential mechanisms through which Zn supports this growth. We found higher plasma Zn affected several longissimus thoracis metabolites related to energy metabolism. Lactic acid, malic acid, and hydroxybutyric acid were greater in the high plasma Zn group, suggesting Zn improves metabolic flexibility of muscle. In support of our hypothesis, these metabolites indicate greater plasma Zn aids in supplying the energy demands of lean tissue accretion. Chapter 4 of this thesis was an extension of a series of experiments examining the effects of supplemental Zn to cattle administered GET but focused on the β-3AA, LUB. All concentrations of supplemental organic Zn improved plasma Zn concentration and supported LUB-induced growth. There were minimal differences due to supplemental Zn in LUB-fed steers, but increasing supplemental Zn up to 90 mg/kg DM improved feed efficiency in steers not fed LUB. Additionally, LUB improved insulin sensitivity in late finishing steers, an effect which was magnified by increasing supplemental Zn regardless of LUB treatment, which should support improved nutrient uptake. Results from chapter 3 and 4 suggest Zn influences energy metabolism, regardless of GET utilization. Greater plasma Zn in chapter 3 influenced muscle metabolites conducive to glucose sparing and improved metabolic flexibility in muscle, and increasing dietary Zn in chapter 4 decreased glucose and insulin in circulation, potentially supporting improved growth and HCW induced by LUB. These data provide insights into metabolic mechanisms supporting our previously observed enhanced growth performance induced by Zn supplementation. Supplemental Zn studied herein ranged as high as 90 mg Zn/kg DM with no evidence of cattle requiring greater concentrations, thus, opportunities exist to refine supplementation intermediate to 30 and 90 mg Zn/kg DM to cattle fed LUB.

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Thesis

Environment-induced heat stress-mediated outcomes in the myocardium

2024-08 , Roths, Missey (Melissa) , Selsby, Joshua T , Kerns, Karl , McNeill, Elizabeth M , Department of Animal Science

Increasing global temperatures are resulting in more frequent and intense heat waves, which are detrimental to human health. However, the consequences of prolonged exposure to excess heat, termed environment-induced heat stress (EIHS), on the myocardium is largely unknown. Human heating experiments are limited to briefer heating, as well as milder heating than generally occur with naturally occurring EIHS. Therefore, a large animal model, such as swine, allows study of the pathological consequences of EIHS, using conditions that accurately resemble a typical EIHS event. Furthermore, using mouse models provides opportunities for mechanistic research. To explore the pathological consequences of EIHS on the heart, we exposed female pigs to thermoneutral (TN) or EIHS conditions for 24 h and hearts were removed. In Chapter 2, heart dimensions were measured, and portions of the left ventricle (LV) and right ventricle (RV) were collected. We discovered EIHS altered cardiac dimensions such that LV thickness increased, RV thickness decreased, and heart weight decreased. We also discovered EIHS caused ventricle-specific biochemical changes such that RV had metabolic dysregulation and increased mitochondrial injury, whereas the left ventricle LV seemed resistant to these changes. Due to the ventricle thickening and thinning, in Chapter 3, we next considered increased proteolysis in the RV, which may contribute to thinning of the RV, and dysregulated calcium signaling which may contribute to increased thickness of the LV. Herein, we discovered RV had some increased markers of proteolysis and LV showed increased calcium handling proteins supporting a role of calcium dysregulation and subsequent dysfunction of the contraction/relaxation cycle. Our findings indicate the detrimental EIHS outcomes in a human sized model, importantly showing structure and biochemical changes of the LV and RV. Finally, these finding led us to consider a mouse model for the same duration of heating (Chapter 4) as a first step toward mechanistic investigation. In Chapter 4, contrary to what we found in Chapter 2, we discovered EIHS increased heart weight and tissue water content, suggesting edema. We further discovered histopathological damage from EIHS causing myocyte vacuolation, which was a feature of the pig model that failed to reach significance. We also discovered EIHS caused biochemical changes including increased autophagic flux and endoplasmic reticulum stress, as well as mitochondrial remodeling in the murine model heart. In total, these data make clear that EIHS damages the myocardium in porcine and murine models. These data demonstrate, for the first time, that sub-heat stroke thermic injury is sufficient to cause structural and biochemical injury to the heart. Moreover, this work also allows, for the first time, accurate recapitulation of thermic injuries anticipated during an EIHS-related heat emergency. While injury was apparent in both models, future work will be focused on gaining a mechanistic understanding of these distinctions as well as gaining a better appreciation of EIHS-mediated changes in humans so the ideal model can be used for future work.

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Dissertation

An investigation of branched-chain amino acid interactions in nursery pigs and lactating sows

2024-12 , Humphrey, Dalton Charles , Greiner, Laura L , Gabler, Nicholas K , Baumgard, Lance H , Appuhamy, Ranga , Steibel, Juan P , Department of Animal Science

Amino acids (AA) are fundamental nutrients that form the building blocks of tissues, milk proteins, enzymes, and various signaling molecules essential for supporting growth, reproduction, and lactation. Dietary protein is a costly component in swine diets; thus, a precise understanding of AA requirements is critical for enhancing production efficiency. With the increased use of feed-grade AA to reduce dietary crude protein, optimizing AA balance is essential to prevent deficiencies or imbalances that may impair performance. Among these, the branched-chain amino acids (BCAA) leucine, isoleucine, and valine play vital roles in protein synthesis and metabolism. However, their shared catabolic pathway creates a potential for antagonistic interactions, where an excess of one BCAA can accelerate the catabolism of the others, decreasing their availability and increasing their dietary requirements. This issue is especially relevant in diets containing corn co-products, which typically contain high levels of Leu relative to Ile and Val. There is sufficient evidence to suggest that interactions among Leu, Ile, and Val influence growth rates and feed intake in nursery pigs; however, these relationships remain incompletely defined, making it challenging to identify an ideal BCAA balance for diet formulation. For lactating sows, the data is equivocal, with variation in reported BCAA requirements suggesting that interactions between BCAA may impact lactation outcomes. However, more investigation is needed to determine these effects conclusively. Understanding the practical implications of BCAA interactions in swine nutrition is crucial for developing dietary strategies to promote efficient growth in nursery pigs and enhance lactation performance in sows. Therefore, the overall objective of this dissertation was to assess BCAA interactions in nursery pigs to determine optimal levels for growth and feed efficiency and to evaluate BCAA effects in lactating sows to explore their role in nutrient requirements and productivity. To accomplish these objectives, a series of experiments were conducted and are reported in three research chapters (Chapters 2, 3, and 4). Research presented in Chapter 2 utilized a central composite design (CCD) to simultaneously evaluate how Leu, Ile, and Val interact to influence growth performance in 10- to 20 kg nursery pigs. The results indicated that concurrently increasing dietary Leu and Ile reduces growth rate and feed efficiency, which is likely a consequence of increased BCAA catabolism limiting Val availability for growth. Furthermore, it was shown that increasing dietary Val can offset the adverse effects of excess Leu on feed intake, suggesting that optimizing Val levels is critical in practical diet formulation. However, given the mixed curvature of the response surfaces, a single optimal BCAA combination was not identified within practical dietary levels, underscoring the importance of considering both ingredient cost and specific production goals when formulating nursery pig diets. This study supports the use of CCD in evaluating complex nutrient interactions and provides a foundation for refining dietary BCAA balance to maximize production efficiency in nursery pigs. Building on the relationships identified in Chapter 2, the research reported in Chapter 3 examined whether similar BCAA interactions affect lactating sow performance. Across all metrics evaluated, there was no evidence to suggest that the various BCAA levels impacted lactating sow or piglet performance; however, high feed intake in this study resulted in potentially excessive intakes of all BCAA, which may have mitigated the potential negative consequences of BCAA interactions. Furthermore, increasing soybean meal (SBM) inclusion reduced sow lactation feed intake, independently of dietary BCAA balance, indicating other factors beyond BCAA, such as trypsin inhibitors, contributed to reduced sow feed intake with high SBM inclusion (Chapter 4). Collectively, the results of Chapters 3 and 4 do not support that BCAA interactions are altering sow lactation performance within practical dietary BCAA ranges. Overall, this research emphasizes the value of optimized BCAA ratios in nursery pig diets and suggests further exploration of AA metabolism in lactating sows to refine dietary AA requirements. These findings provide actionable insights for swine diet formulation, supporting production efficiency and sustainable practices.

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Thesis

The effects of feed restriction on energetic metabolism and inflammation in under- and over-conditioned mid-lactation dairy cows

2024-12 , Flemming, Taylor Ann , Baumgard, Lance H , Carpenter, Abigail J , Gorden, Patrick J , Department of Animal Science

he transition cow’s ability to homeorhetically adapt and meet the demands of lactation ultimately determines her ability to maintain optimal health, become pregnant and synthesize copious amounts of milk. Over-conditioned cows tend to be more susceptible to health problems during the transition period, but the mechanism behind why fat cows transition poorly is currently ill-defined. This phenomenon was first described as “Fat Cow Syndrome” where corpulent transition cows experience metabolic disorders or infectious diseases and infertility at increased rates. Some investigators have reported that excessive lipid mobilization, decreased appetite, and excessive inflammation are responsible for Fat Cow Syndrome. As part of this dissertation, we used under- and over-conditioned mid-lactation cows to evaluate the whole-body response to feed restriction as a model for periparturient cow energetics and inflammation. To assess this acute phase proteins and metabolites associated with basal and stimulated carbohydrate and lipid metabolism were evaluated. This experiment suggests that carbohydrate and lipid metabolism were affected by feed restriction similarly between thin and fat cows. Unexpectedly, thin cows had a more inflammatory response to feed restriction than fat cows. While this thesis did not identify the physiological mechanism(s) that explain why over-conditioned cows underperform during the transition period, it does provide strong evidence that excessive adipose tissue mobilization and hyperinflammation are not responsible.

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Dissertation

Understanding the effects of obesity on DNA damage response during DMBA-induced ovotoxicity

2024-08 , Rishi, Jaspreet Kaur , Keating, Aileen F , Tuteja, Geetu , Essner, Jeffery , Kerns, Karl , Ross, Jason , Department of Animal Science

The ovary plays a central role in the healthy reproductive function of a mammalian female. It is responsible for the production of oocytes and secretion of hormones. The normal function of the ovary can be altered by environmental exposures and the metabolic status of the female can dictate the ability of the ovary to respond to xenobiotic exposures. The research described in this dissertation investigated the combined impacts of the environmental genotoxicant, 7,12-dimethlbenz[a]anthracene (DMBA), and obesity on the ovarian protective DNA damage response (DDR) in mice. Chapter 2 investigated the acute ovarian response to DMBA-induced DSBs in vivo and the influence of obesity thereon. The hypothesis tested was that obesity potentiates ovotoxicity through ineffective DNA damage repair. Findings from this study suggest a follicle stage-specific ovarian response to DMBA exposure, which is blunted by obesity. Chapter 3 investigated the hypothesis that DMBA-induced ovotoxicity alters the ovarian proteome, explicitly affecting the abundance of histones and histone variants, and that this response would vary due to obesity. Data from this study indicate a role for initiation of DDR by the histone variant, H3.3, in lean mice, regulated by RBB7, which is lagging in obese mice. In Chapter 4, the role of the post translational modification, SUMOylation was explored during DMBA exposure in lean and obese mice. Increased levels of all SUMO isoforms and a higher level of basal SUMO-ome was discovered in the obese mice. Specific SUMO targets were also identified in both lean and obese mice during DMBA exposure. The objective for chapter 5 was to test whether the acute effects of DMBA observed in the previous studies would cease immediately post-exposure or persist and, in obese mice, a trajectory of continued follicle loss after the cessation of DMBA exposure was discovered, which is not the case in lean mice. Finally, in Chapter 6, the ovarian role of the DDR mediator, ataxia telangiectasia mutated (ATM) was studied. The hypothesis tested was that inhibiting ATM during DMBA exposure would enhance DMBA-induced ovotoxicity and conversely, ATM activation will enhance the DDR and ameliorate DMBA-induced ovotoxicity. Proteomic analysis detected increased DDR in the ATM-activated ovaries exposed to DMBA as compared to ATM-inhibited ovaries exposed to DMBA. Additionally, classifying the DDR into specific pathways revealed that homologous recombination is selectively preferred over non homologous end joining in ovarian ATM-mediated DDR. Specific ovarian ATM targets were also identified. Taken together, these findings illustrate both molecular and post-translational mechanisms by which obesity influences the ovarian response to the ovotoxicant, DMBA, and demonstrate that in obese mice, detrimental effects on follicular composition are observed even after removal of the genotoxic insult.

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