The inner membrane protein YhiM links copper and CpxAR envelope stress responses in uropathogenic E. coli.

Urinary tract infection (UTI) is a ubiquitous infectious condition, and uropathogenic Escherichia coli (UPEC) is the predominant causative agent of UTI. Copper (Cu) is implicated in innate immunity, including against UPEC. Cu is a trace element utilized as a co-factor, but excess Cu is toxic due to mismetalation of non-cognate proteins. E. coli precisely regulates Cu homeostasis via efflux systems. However, Cu import mechanisms into the bacterial cell are not clear. We hypothesized that Cu import defective mutants would exhibit increased resistance to Cu. This hypothesis was tested in a forward genetic screen with transposon (Tn5) insertion mutants in UPEC strain CFT073, and we identified 32 unique Cu-resistant mutants. Transposon and defined mutants lacking yhiM, which encodes a hypothetical inner membrane protein, were more resistant to Cu than parental strain. Loss of YhiM led to decreased cellular Cu content and increased expression of copA, encoding a Cu efflux pump. The CpxAR envelope stress response system was activated in the ΔyhiM mutant as indicated by increased expression of cpxP. Transcription of yhiM was regulated by CueR and CpxR, and the CpxAR system was essential for increased Cu resistance in the ΔyhiM mutant. Importantly, activation of CpxAR system in the ΔyhiM mutant was independent of NlpE, a known activator of this system. YhiM was required for optimal fitness of UPEC in a mouse model of UTI. Our findings demonstrate that YhiM is a critical mediator of Cu homeostasis and links bacterial adaptation to Cu stress with the CpxAR-dependent envelope stress response in UPEC.IMPORTANCEUPEC is a common bacterial infection. Bacterial pathogens are exposed to host-derived Cu during infection, including UTI. Here, we describe detection of genes involved in Cu homeostasis in UPEC. A UPEC mutant lacking YhiM, a membrane protein, exhibited dramatic increase in resistance to Cu. Our study demonstrates YhiM as a nexus between Cu stress and the CpxAR-dependent envelope stress response system. Importantly, our findings establish NlpE-independent activation of CpxAR system during Cu stress in UPEC. Collectively, YhiM emerges as a critical mediator of Cu homeostasis in UPEC and highlights the interlinked nature of bacterial adaptation to survival during Cu and envelope stress.

Deep Parasternal Intercostal Plane Block for Postoperative Analgesia After Sternotomy for Cardiac Surgery-A Retrospective Cohort Study.

OBJECTIVE: To examine the analgesic efficacy of postoperative deep parasternal intercostal plane (DPIP) blocks for patients having cardiac surgery via median sternotomy. DESIGN: This single-center retrospective study compared patients receiving bilateral DPIP blocks with a matched cohort of patients not receiving DPIP blocks. SETTING: Large quaternary referral center. PARTICIPANTS: Adult patients admitted to the authors' institution from January 1, 2016, to August 14, 2020, for elective cardiac surgery via median sternotomy. INTERVENTIONS: Patients received ultrasound-guided bilateral DPIP blocks. MEASUREMENTS AND MAIN RESULTS: A total of 113 patients received a DPIP block; 3,461 patients did not. The estimated multiplicative change in cumulative opioid consumption through 24 hours was 0.42 (95% CI 0.32-0.56; p < 0.001), indicating that patients receiving DPIP blocks required 60% fewer opioids than patients who did not. Proportional odds ratios for the average pain score on postoperative day (POD) 0 was 0.46 (95% CI 0.32-0.65; p < 0.001), and POD 1 was 0.67 (95% CI 0.47-0.94; p = 0.021), indicating lower pain scores for patients receiving blocks. The exploratory analysis identified an inverse correlation between DPIP blocks and atrial fibrillation incidence (2% v 15%; inverse probability of treatment weighting odds ratio 0.088, 95% CI 0.02-0.41; p = 0.002). CONCLUSIONS: The use of DPIP blocks in patients undergoing cardiac surgery via median sternotomy was associated with less opioid use and improved pain scores in the early postoperative period compared with patients not receiving blocks. Prospective randomized controlled studies should further elucidate the efficacy and risks of DPIP blocks in cardiac surgery.

Superficial versus deep parasternal intercostal plane blocks: cadaveric evaluation of injectate spread.

BACKGROUND: Deep and superficial parasternal intercostal plane blocks provide anterior chest wall analgesia for both breast and cardiac surgery. Our primary objective of this cadaveric study was to describe the parasternal spread of deep and superficial parasternal intercostal plane blocks. Our secondary objectives were to describe needle proximity to the internal mammary artery when performing deep parasternal intercostal plane blocks, and compare lateral injectate spread and extension into the rectus sheath. METHODS: We performed ultrasound-guided deep and superficial parasternal intercostal plane blocks 2 cm from the sternum at the T3-4 interspace in four fresh frozen cadavers as described in clinical studies. RESULTS: Parasternal spread of injectate was greater with the deep parasternal intercostal plane injection than with the superficial parasternal intercostal plane injection. The internal mammary artery was ∼3 mm away from the needle trajectory in cadaver #1 and ∼5 mm from the internal mammary artery in cadaver #2. Lateral spread extended to the midclavicular line for all deep parasternal intercostal plane blocks and beyond the midclavicular line for all superficial parasternal intercostal plane blocks. Neither block extended to the rectus sheath. CONCLUSIONS: A greater number of parasternal interspaces were covered with the deep parasternal intercostal plane block than with the superficial parasternal intercostal plane block when one injection was performed at the T3-4 interspace. However, considering proximity to the internal mammary artery, and potential devastating consequences of an arterial injury, we propose that the deep parasternal intercostal plane block be classified as an advanced block and that future studies focus on optimising superficial parasternal intercostal plane parasternal spread.

Pectoral Fascial Plane Versus Paravertebral Blocks for Minimally Invasive Mitral Valve Surgery Analgesia.

OBJECTIVES: This study examined the postoperative analgesic efficacy of single-injection pectoral fascial plane (PECS) II blocks compared to paravertebral blocks for elective robotic mitral valve surgery. DESIGN: A single-center retrospective study that reported patient and procedural characteristics, postoperative pain scores, and postoperative opioid use for patients undergoing robotic mitral valve surgery. SETTING: This investigation was performed at a large quaternary referral center. PARTICIPANTS: Adult patients (age ≥18) admitted to the authors' hospital from January 1, 2016, to August 14, 2020, for elective robotic mitral valve repair who received either a paravertebral or PECS II block for postoperative analgesia. INTERVENTIONS: Patients received an ultrasound-guided, unilateral paravertebral or PECS II nerve block. MEASUREMENTS AND MAIN RESULTS: One hundred twenty-three patients received a PECS II block, and 190 patients received a paravertebral block during the study period. The primary outcome measures were average postoperative pain scores and cumulative opioid use. Secondary outcomes included hospital and intensive care unit lengths of stay, need for reoperation, need for antiemetics, surgical wound infection, and atrial fibrillation incidence. Patients receiving the PECS II block required significantly fewer opioids in the immediate postoperative period than the paravertebral block group, and had comparable postoperative pain scores. No increase in adverse outcomes was noted for either group. CONCLUSIONS: The PECS II block is a safe and highly effective option for regional analgesia for robotic mitral valve surgery, with demonstrated efficacy comparable to the paravertebral block.

Media Multitasking in Medical Students: A Theory-Based Approach to Understanding this Behavior.

PHENOMENON: While technology is useful and encouraged in medical school, the effect of media multitasking on academic performance remains concerning. Past research has investigated performance and cognitions associated with college students' in-class media multitasking behavior, but the extent and correlates among medical students is relatively unknown. APPROACH: We surveyed medical students at our institution to quantify media multitasking behaviors and related beliefs, and we collected corresponding course grades. Our research applies the Integrative Model of Behavioral Prediction theory to analyze course and cognitive factors influencing media multitasking behavior in medical students. Correlation of media multitasking behavior with average and block grades assessed potential academic impact of the behavior. FINDINGS: Media multitasking was common among medical students. Reported extent of media multitasking among medical students (N = 119) was not related to course grades but was driven by an interplay of beliefs about the behavior and specific course factors. Based on our hierarchical regression model, concerns about boredom appear to be the major cognitive belief underlying behavior. INSIGHTS: Our findings, in the context of the Integrative Model of Behavioral Prediction theory, show influential factors that impact medical students' behavior regarding media multitasking. A campaign targeting these factors influencing behavior may be the most effective approach to limit students' media multitasking and its potential impact on performance. Though our research did not find an association between the extent of media multitasking and course grades, our study was limited by self-report of media multitasking and relatively crude measures of academic performance. Further research is required to measure these behaviors and potential outcomes.Supplemental data for this article is available online at.

Influence of high cyclic ambient temperature and water drinker design on growth performance and water disappearance of growing-finishing pigs.

The objective of this study was to determine effects of room temperature and drinker design on growth and water disappearance of growing-finishing pigs (26.9 ±â€…3.67 to 130.9 ±â€…5.10 kg live body weight). A split-plot design was used with a 2 × 2 factorial arrangement of treatments: Room Temperature (RT) [Thermoneutral (TN) vs. High (HI); main plot], Drinker Design (DD; Nipple vs. Cup; sub-plot). A total of 316 pigs were used, housed in 32 pens in 4 rooms (8 pens/room; 7 pens of 10 pigs and 1 pen of 9 pigs). Two rooms were on each RT treatment. Room temperature for the TN treatment was constant throughout each day but decreased from 24°C at the start to 20°C and 18°C on d 14 and 45 of the study period, respectively. For the HI treatment, a single, cyclic RT protocol was used throughout the study (30°C from 08:00 to 19:00 h and 20°C from 20:00 to 07:00 h, with 1-h transition periods). Pens had fully-slatted concrete floors and 1 feeder and drinker (either nipple or cup); floor space was 0.67 m2/pig. Pigs had ad libitum access to standard corn-soybean diets, formulated to meet or exceed NRC (2012) nutrient requirements. Water disappearance was measured using a meter fitted to the water line supplying each drinker. There were no interactions (P > 0.05) between RT and DD treatments. Drinker Design did not affect (P > 0.05) growth performance; water disappearance was 7.3% greater (P ≤ 0.05) for Nipple than Cup drinkers. Compared to the TN treatment, the HI treatment had no effect (P > 0.05) on gain:feed ratio, but resulted in lower (P ≤ 0.05) average daily gain (6.5%) and average daily feed intake (5.5%) and greater (P ≤ 0.05) average daily water disappearance (16.8%). These results suggest that both drinker design and RT can affect water disappearance, and that the high, cyclic RT regime used reduced growth performance of growing-finishing pigs. Further research is needed to determine the contribution of water intake and wastage to treatment differences in water disappearance.

Cardiac tamponade in a patient supported by veno-arterial extracorporeal membrane oxygenation.

Cardiac tamponade occurring in a patient supported on central veno-arterial extracorporeal membrane oxygenation is depicted in a transesophageal echocardiography image and associated rendering. Prompt recognition of tamponade, which can be assisted with echocardiography, and emergent evacuation is critical to restoring cardiovascular stability.

Effect of drinker type on water disappearance of nursery pigs.

This study was conducted to evaluate the water disappearance of nursery pigs (from weaning to 6 wk post-weaning; 6.4 ±â€…1.07 to 22.0 ±â€…3.39 kg live body weight) using a randomized complete block design to compare two Drinker Type treatments: Nipple vs. Cup. A total of 336 pigs housed in 16 pens with 21 pigs per pen in 2 rooms (8 pens per room) were used. Pens had fully-slatted concrete floors; floor space was 0.32 m2/pig and there was one feeder and one drinker per pen. Pigs were fed corn-soybean-based diets formulated to meet or exceed nutrient requirements. Pigs and feeders were weighed at the start and end of the study. Water disappearance was measured using a water-flow meter fitted to the water pipeline supplying the drinker in each pen. For the overall study period, Drinker Type did not affect (P > 0.05) growth performance; however, average daily water disappearance was greater (P < 0.05) for Nipple than Cup drinkers (2.74 and 2.25 liters/d, respectively; SEM = 0.139). Water to feed disappearance ratio was greater (P < 0.05) for the Nipple than the Cup treatment (5.23 vs. 4.22 liters:kg, respectively; SEM = 0.263). These results suggest that water disappearance from nipple drinkers was greater than for cup drinkers. The lack of an effect of Drinker Type treatment on pig growth performance suggests that the treatment difference for water disappearance was most likely due to greater water wastage for the nipple drinkers rather than any effect on water intake per se.

Experimental Effects of Tweets Encouraging Social Distancing: Effects of Source, Emotional Appeal, and Political Ideology on Emotion, Threat, and Efficacy.

CONTEXT: Public health officials and celebrities use social media to provide guidance to reduce the spread of COVID-19. Messages apply different promotional strategies to motivate behavior change, likely yielding divergent reactions from partisan audiences. The Extended Parallel Process Model (EPPM) suggests that perceived threat for a negative outcome should impact perceived need for the advocated health behavior, which should be more appealing to an audience if perceived it to be efficacious and feasible. OBJECTIVE: This study examines the interactive effects of Tweet source, message emotional appeal, and audience political affiliation on US adults' perceptions of COVID-19 threat and social distancing efficacy during early months of the pandemic. DESIGN AND SETTING: This online survey experiment applies the EPPM to assess US adults' reactions to tweets encouraging social distancing. The experiment tests 3 emotional appeals (fear, humor, and neutral) and 2 sources (Centers for Disease Control and Prevention [CDC] and celebrity) on adults' emotional reactions and perceptions of COVID-19 threat and social distancing efficacy. PARTICIPANTS: The final sample included 415 US adults (242 Democrat and 173 Republican) recruited through Amazon's Mechanical Turk. MAIN OUTCOME MEASURES: Outcome measures were adapted from the EPPM and include perceived susceptibility to and severity of COVID-19, and response efficacy and self-efficacy regarding social distancing. Each was measured through the survey on a 7-point response scale. RESULTS: Humor and fear appeal messages evoked less fear and guilt responses than a neutral tweet from the CDC. Fear and guilt emotions predicted greater perceived threat, while hope and pride predicted efficacy constructs in relationships moderated by political ideology. CONCLUSIONS: Public health messages targeting a bipartisan audience through social media may increase perceived threat by inducing fear of COVID-19 infection. EPPM theory suggests boosting efficacy is also critical to message acceptance and behavior change; thus, inducing feelings of hope and pride in addition to fear may be particularly effective.

Urban forest biodiversity and cardiovascular disease: Potential health benefits from California's street trees.

Enhanced immune functioning in response to biodiversity may explain potential health benefits from exposure to green space. Using unique data on urban forest biodiversity at the zip code level for California measured from 2014 to 2019 we test whether greater diversity of street trees is associated with reduced death from cardiovascular disease. We find that urban forests with greater biodiversity measured via the Shannon Index at the genus level are associated with a lower mortality rate for heart disease and stroke. Our estimates imply that increasing the Shannon Index by one standard deviation (0.64) is associated with a decrease in the mortality rate of 21.4 per 100,000 individuals for heart disease or 13% and 7.7 per 100,000 individuals for stroke or 16%. Our estimates remain robust across several sensitivity checks. A policy simulation for tree planting in Los Angeles based on our estimates suggests that if these relationships were causal, investment in planting for a more biodiverse set of street trees would be a cost-effective way to reduce mortality related to cardiovascular disease in urban areas.

Copper primes adaptation of uropathogenic Escherichia coli to superoxide stress by activating superoxide dismutases.

Copper and superoxide are used by the phagocytes to kill bacteria. Copper is a host effector encountered by uropathogenic Escherichia coli (UPEC) during urinary tract infection in a non-human primate model, and in humans. UPEC is exposed to higher levels of copper in the gut prior to entering the urinary tract. Effects of pre-exposure to copper on bacterial killing by superoxide has not been reported. We hypothesized that copper-replete E. coli is more sensitive to killing by superoxide in vitro, and in activated macrophages. We utilized wild-type UPEC strain CFT073, and its isogenic mutants lacking copper efflux systems, superoxide dismutases (SODs), regulators of a superoxide dismutase, and complemented mutants to address this question. Surprisingly, our results reveal that copper protects UPEC against killing by superoxide in vitro. This copper-dependent protection was amplified in the mutants lacking copper efflux systems. Increased levels of copper and manganese were detected in UPEC exposed to sublethal concentration of copper. Copper activated the transcription of sodA in a SoxR- and SoxS-dependent manner resulting in enhanced levels of SodA activity. Importantly, pre-exposure to copper increased the survival of UPEC within RAW264.7 and bone marrow-derived murine macrophages. Loss of SodA, but not SodB or SodC, in UPEC obliterated copper-dependent protection from superoxide in vitro, and from killing within macrophages. Collectively, our results suggest a model in which sublethal levels of copper trigger the activation of SodA and SodC through independent mechanisms that converge to promote the survival of UPEC from killing by superoxide. A major implication of our findings is that bacteria colonizing copper-rich milieus are primed for efficient detoxification of superoxide.

Transport losses in market weight pigs: II. U.S. incidence and economic impact.

An industry survey representing approximately 310 million (M) market weight pigs was conducted with 20 U.S. slaughter facilities over the calendars years of 2012 to 2015 to determine the incidence, seasonal patterns, and estimated economic impact of dead and non-ambulatory pigs. Each plant entered daily totals in a secure online database for the following variables: 1) pigs slaughtered, 2) dead on arrival (DOA; dead on the truck), 3) euthanized on arrival (EOA; non-ambulatory pig with an injury that required euthanasia), 4) dead in pen (DIP; died after unloading), and 5) non-ambulatory (pig unable to move or keep up with the rest of the group from unloading to stunning). Total dead pigs were calculated as DOA + EOA + DIP, and total losses were calculated as non-ambulatory + total dead. The economic impact was estimated based on the 4-yr weighted averages from USDA annual reports for market swine slaughtered (108,470,550 pigs), live market weight (126.9 kg), and live market price ($1.44/kg). The 4-yr weighted averages for total dead, non-ambulatory, and total losses were 0.26%, 0.63%, and 0.88%, respectively. Total dead consisted of 0.15% DOA, 0.05% EOA, and 0.05% DIP. The months with the highest rates of total dead were July (0.29%), August (0.32%), and September (0.30%), while the lowest incidence rates occurred in February (0.22%), March (0.22%), and April (0.22%). The months with the highest rates of non-ambulatory pigs were observed during the months of October (0.70%), November (0.71%), and December (0.70%), whereas the lowest rates of non-ambulatory pigs were observed during the months of April (0.57%), May (0.53%), and June (0.54%). The following assumptions were used in the economic analysis: 1) dead pigs received no value and 2) non-ambulatory pigs were discounted 30%. Based on these assumptions, the annual cost to the industry for dead and non-ambulatory pigs was estimated to be $52 M ($0.48 per pig marketed) and $37 M ($0.35 per pig marketed), respectively. Therefore, total losses represent approximately $89 M in economic losses or $0.83 per pig marketed. This is the first industry-wide survey on the incidence of transport losses in market weight pigs at U.S. slaughter facilities, and this information is important for establishing an industry baseline and benchmark for transport losses that can be used for measuring industry improvements.

Child-Oriented Marketing on Cereal Packaging: Associations With Sugar Content and Manufacturer Pledge.

OBJECTIVE: To assess sugar content and child-oriented promotional features on packaging among cereals manufactured by companies with varying Children's Food and Beverage Advertising Initiative (CFBAI) participation. DESIGN: Ready-to-eat dry cereals (n = 159) were purchased from southeastern US grocery stores in September 2018. Content analysis of 159 ready-to-eat dry cereal boxes, coded for sugar content and presence of 8 child-oriented features. MAIN OUTCOME MEASURES: Frequencies of each promotional feature and number of features per box, level of participation in CFBAI, and sugar content by serving and ounce. ANALYSIS: Chi-square tests of independence analyzed correspondence between measures of sugar content. Extent of features per box based on sugar content and CFBAI participation were assessed with analyses of variance (ANOVAs). RESULTS: Most cereals (81%) contained <13 g of sugar per serving, meeting the sugar content requirement for child-directed advertising. Cereals' sugar content classifications varied between sugar per serving and sugar per ounce metrics (P < .001). Among low-sugar per serving cereals, 28% were classified as moderate-sugar per ounce, whereas 55% of moderate-sugar per serving cereals had high-sugar per ounce. Games/activities and trade characters were especially common (62% and 49%, respectively), particularly on high-sugar per ounce cereals (P < .001, respectively). Child-oriented features were rare on low-sugar cereals and highest on cereals with higher sugar content per ounce produced by CFBAI-participating companies (F8,158 = 12.33, P < .001). CONCLUSIONS AND IMPLICATIONS: Variable cereal-suggested serving sizes may contribute to consumers' misunderstanding of sugar content. CFBAI manufacturers continue to market cereals with high sugar to children. Food and beverage regulatory policy could be strengthened if CFBAI companies apply marketing pledges to brand mascots, adopt standardized metrics for sugar content, and limit added sugar content to the recommended <6 g/serving target used by the Special Supplemental Nutrition Program for Women, Infants, and Children program.

Stellate Ganglion Blockade for Refractory Ventricular Arrhythmias: Implications of Ultrasound-Guided Technique and Review of the Evidence.

Refractory ventricular arrhythmias (VAs) carry high mortality rates despite electrical and pharmacologic therapy utilization. These patients often require aggressive hemodynamic support, including mechanical circulatory devices such as extracorporeal membrane oxygenation because of progressive hemodynamic and metabolic deterioration. Sympathetic nervous system stimulation and neuronal remodeling after myocardial insults have been implicated as drivers of refractory VAs. This understanding has led to interest in and a growing body of experience with percutaneous blockade of the stellate ganglion as a means of interrupting the vicious cycle of refractory VAs. A number of techniques have been described for stellate ganglion blockade, including landmark-driven approaches, fluoroscopy-assisted blockade, and ultrasound guidance. Herein, the literature is evaluated and the authors' experience with stellate ganglion blockade using ultrasound guidance for refractory VAs is described.

New Q Waves and T-Wave Inversions Following Endovascular Surgery Lead to Diagnosis of Clinically Silent Myocardial Infarction Despite Negative Preoperative Cardiovascular Risk Evaluation: A Case Report.

In this case, a 79-year-old male presented with new anteroseptal Q waves and T-wave inversions across the precordial leads following an otherwise uneventful endovascular repair of his thoracoabdominal aortic aneurysm. The patient had no history of cardiac disease and had undergone a dobutamine stress echocardiogram within the preceding 6 months that showed no evidence of inducible ischemia. Nevertheless, routine postoperative electrocardiogram (EKG) revealed new Q waves and T-wave inversions and transthoracic echocardiogram that demonstrated akinesis of the left ventricle (LV) apex with chronic-appearing apical thrombus. We will further discuss preoperative evaluation of cardiovascular risk along with postoperative interpretation of EKG abnormalities.

Undiagnosed Systemic Mastocytosis Presenting as Postoperative Distributive Shock: A Case Report.

Systemic mastocytosis (SM) is a rare clinical condition resulting from a clonal proliferation of abnormal mast cells. The clinical presentation may vary from mild cutaneous manifestations to aggressive systemic symptoms including intermittent episodes of anaphylaxis. We present a case of a 69-year-old male with abrupt and recurrent episodes of anaphylaxis with refractory distributive shock following cardiac surgery with cardiopulmonary bypass. Following a complex postoperative course, a bone marrow biopsy ultimately confirmed the diagnosis. Although rare, SM should be considered in the differential diagnosis of postoperative patients with unexplained and recurrent episodes of distributive shock.

Asymmetrical selection maintains heritable phenotypic variation between two subspecies of Monardella villosa.

PREMISE: Monardella villosa is an evolutionarily young species complex distributed across a large geographic range. Our goal was to determine whether the phenotypic difference between two subspecies of M. villosa was heritable and whether the alternative phenotypes were adaptive to their respective local habitats. METHODS: We collected seeds from 25 populations of M. villosa, 14 from subspecies franciscana, which grows closer to the coast, and 11 from subspecies villosa, which has a larger and more inland geographic distribution. We reciprocally transplanted the two subspecies into their respective habitats and compared plant germination, post-emergence survival, and growth. We used linear mixed models to quantify the effects of genotype and environment to determine whether subspecies were locally adapted and whether leaf traits that distinguish these subspecies were genetically based. RESULTS: Plants of both subspecies grown at the coastal site had significantly lower survival and biomass than the inland site. The subspecies were not locally adapted; however, the coastal subspecies franciscana did have a home site advantage. We also found that distinctive leaf morphological traits were genetically based, with high broad-sense heritability of traits. CONCLUSIONS: The two subspecies of Monardella villosa were not locally adapted to their respective habitat, but rather we found that selection for local genotypes may be stronger at the coastal site. Despite the lack of evidence for local adaptation in the strict sense, the subspecies had heritable variation in several leaf phenotypes, indicating that heterogeneous selection imposes an adaptive trade-off for leaf trichome production within this species.

Birth weight threshold for identifying piglets at risk for preweaning mortality.

Several studies have suggested there is a critical relationship between piglet birth weight and preweaning mortality. Thus, the objective of the current work was to identify a birth weight threshold value for preweaning mortality. Birth weight and survival data from two studies involving a combined total of 4,068 piglets from 394 litters on four commercial farms (three European, one U.S.) were compiled for a pooled, multistudy analysis. Overall preweaning mortality across the two studies was 12.2%. Key variables used in the analysis were piglet birth weight (measured within 24 h of birth) and corresponding survival outcome (dead or live) by weaning at 3-4 wk of age. A mixed effects logistic regression model was fit to estimate the relationship between preweaning mortality and birth weight. A random effect of study was included to account for overall differences in mortality between the two studies. A piecewise linear predictor was selected to best represent the drastic decrease in preweaning mortality found as birth weight increased in the range of 0.5-1.0 kg and the less extreme change in weight above 1.0 kg. The change point of the birth weight and preweaning mortality model was determined by comparing model fit based on maximizing the likelihood over the interval ranging from 0.5 to 2.3 kg birth weight. Results from the analysis showed a curvilinear relationship between birth weight and preweaning mortality where the birth weight change point value or threshold value was 1.11 kg. In the combined data set, 15.2% of pigs had birth weights ≤1.11 kg. This subpopulation of pigs had a 34.4% preweaning mortality rate and represented 43% of total preweaning mortalities. These findings imply interventions targeted at reducing the incidence of piglets with birth weights ≤1.11 kg have potential to improve piglet survivability. Additional research is needed to validate 1.11 kg as the birth weight threshold for increased risk of preweaning mortality.