Large Feedlot Research Articles

328 Assessment of chronically ill or injured feedlot cattle populations at eight United States and nine Canadian feedlots and implications for cattle welfare

Abstract Cattle health management in the feedlot sector continues to evolve and improve cattle welfare by promoting an understanding of illness and injury to minimize their effects. Many papers have focused on treating individual ill or injured cattle in cattle feeding facilities. However, care, treatment, and outcomes for chronically ill or injured cattle (“chronic cattle”) have received little attention in the literature. The purpose of this descriptive study was to present demographics, diagnoses, and outcomes of chronic cattle in 17 feedlots in the U.S. and Canada and discuss potential risk factors and welfare implications. Individual chronic cattle information and treatment records from 17 feedlots (U.S.: 8; Canada: 9) over 7 yr (2014 – 2020) were retrospectively retrieved from a large feedlot consulting and data-management service (Feedlot Health Management Services, a division of TELUS Agriculture Solutions Inc.). Chronic cattle were defined as those that had spent time in a feedlot’s designated chronic pen. Descriptive results are presented as means ± standard deviations. U.S. feedlots averaged 31,280 ± 23,231 cattle/yr, had an average chronicity rate of 2.24 ± 2.42 % (median 1.53%), and contributed 52,709 chronic cattle to the dataset. Canadian feedlots averaged 21,913 ± 10,497 cattle/yr, had an average chronicity rate of 1.41 ± 0.82% (median 1.10%), and contributed 15,940 chronic cattle to the dataset. U.S. chronic cattle were sourced across all seasons primarily from auctions and ranches, had an average arrival weight of 163 ± 59 kg, and an average days on feed (DOF) of 362 ± 172 d. Canadian chronic cattle were primarily auction-sourced in the fall, weighed 272 ± 95 kg at arrival, and averaged 246 ± 141 DOF. Chronic cattle were treated at least once for respiratory issues (U.S.: 46.3%; Canada: 26.9%), bullers (U.S.: 34.5%; Canada: 5.8%), musculoskeletal issues (U.S.: 2.2%; Canada: 1.4%), lameness (U.S.: 1.7%; Canada: 28.1%), metabolic issues (U.S.: 0.5%; Canada: 4.5%), or other diagnoses (U.S.: 2.2%; Canada: 6.3%), with many cattle treated for multiple issues (U.S.: 12.5%; Canada: 27.0%). Outcomes for chronic cattle were shipped (U.S.: 73.1%; Canada: 52.5%), railed (U.S.: 8.1%; Canada: 20.7%), euthanized (U.S.: 0.7%; Canada: 9.9%) died unassisted (U.S.: 18.1%; Canada: 16.2%), or transferred (U.S.: < 0.1%; Canada: 0.8%). These results are some of the first to describe chronic cattle populations and present interesting trends for further analysis. For example, differences in buller and lameness rates could reflect actual differences but may be artifices of the dataset and feedlot definitions. Additionally, high marketed cattle rates (shipped and railed) indicate positive outcomes for most cattle, but variable mortality rates merit further scrutiny.

Epidemiology of Digital Dermatitis in Western Canadian Feedlot Cattle.

Digital dermatitis (DD) is an emerging disease in feedlot cattle. Our objective was to identify animal- and feedlot-level risk factors for DD by analyzing individual animal health records (n = 1,209,883) and feedlot-level records from western Canadian feedlots (n = 28) between 2014 and 2018, inclusive. The risk of a DD diagnosis was higher (incidence rate ratio (IRR) = 2.08, 95% CI 1.52 to 2.86) in cattle sourced from confined background operations (CB) versus cattle sourced from auction markets (AM). Conversely, ranch direct (RD) cattle were (IRR = 0.02, 95% CI 0.04 to 0.30) lower risk than AM cattle of being diagnosed with DD. The risk of being diagnosed with DD was higher in females than in males. The magnitude of the risk in females over males was influenced by annual DD incidence in low morbidity years (2014, 2017, and 2018) (IRR = 2.02, 95% CI 1.27 to 3.19), medium morbidity years (2016) (IRR = 2.95, 95% CI 1.64 to 5.33), and high morbidity years (2015) (IRR = 5.41, 95% CI 3.27 to 8.95). At the feedlot-level, the risk of a diagnosis of DD was lower in small capacity (SCF) versus large capacity feedlots (LCF) (IRR = 0.24, 95% CI 0.05 to 0.76). Future research should focus on identifying factors that may propagate disease transmission between cattle of different sexes and from different acquisition sources.

Evaluation of long-term supplementation of a Bacillus subtilis direct-fed microbial and enzymatically hydrolyzed yeast cell culture product used alone or in combination on Clostridia, Clostridium perfringens, Escherichia coli, and Salmonella prevalence in beef steers.

The objective was to determine the influence of long-term supplementation (258 d) of a direct-fed microbial (DFM) and/or yeast cell wall (YCW) product on bacterial populations in beef steers. Single-sourced Charolais × Red Angus steers (n = 256; body weight = 246 ± 1.68kg) were used in a randomized complete block design and blocked by location into one of four treatments: 1) fed no DFM and no YCW (Control); 2) fed only the DFM (DFM; Certillus CP B1801 Dry,28 g/steer d-1 ); 3) fed only the YCW (YCW; Celmanax; 18 g/steer d-1 ); and 4) fed the DFM and the YCW (DFM+YCW). Steers were vaccinated for respiratory and clostridial diseases and treated for internal and external parasites at processing and individually weighed on days 1, 14, 42, 77, 105, 133, 161, 182, 230, and 258. To determine bacterial prevalence, fecal samples were collected on days 1, 14, 77, 133, 182, and 230 and environmental (pen area, feed, and water) samples were collected at the beginning of the week when cattle were weighed. No treatment × day interactions or treatment effects (P > 0.05) were observed between treatment groups at any sampling days for the bacterial populations. Samples on days 1, 133, and 182 had greater (P < 0.05) Clostridia levels compared to the other sampling points but were not different from each other. Clostridia levels were also greater (P < 0.05) on day 77 compared to days 14 and 230. Samples on days 77 and 230 had greater (P < 0.05) Clostridium perfringens levels compared to the other sampling points but were not different (P > 0.05) from each other. Samples on days 1 and 14 had lower (P < 0.05) total Escherichia coli levels compared to the other sampling points but were not different (P > 0.05) from each other. Escherichia coli levels on day 77 were higher (P < 0.05) compared to days 133, 182, and 230. Little Salmonella prevalence (1.5%) was observed throughout the study. This study had greater levels of Clostridia compared to small and large commercial feedlots in the Church and Dwight research database, but C. perfringens, total and pathogenic E. coli, and Salmonella prevalence were notably lower. Collectively, there were no appreciable treatment influences on bacterial populations. These data further indicate a low pathogenic bacterial challenge at the trial site, which could partially explain the lack of differences with DFM or YCW supplementation. The DFM and YCW used alone or in combination cannot be expected to show additional benefits when animals are relatively unstressed with a low pathogenic bacterial challenge.

Integrated management of urban and rural wastes with energy recovery and low carbon emissions

Waste management is a major challenge worldwide due to the increasing amount of waste generated, which requires sustainable treatment approaches. In this paper, a mathematical model for the optimal configuration of waste treatment processes is presented that considers municipal solid waste and cattle manure from feedlots. A mixed-integer quadratically constrained formulation is proposed to maximize the net present value of investments, and a multi-objective optimization method through ε-restriction is implemented to limit the global warming potential. The model aims to resolve the trade-off between centralized and decentralized networks. The location of the facilities, the ratio of urban to rural waste for each facility, and the waste streams to be transported are also determined by the model. The optimization approach has been evaluated in a real-world scenario in Argentina. For integrated treatment, the results show the potential of anaerobic co-digestion that justifies transporting co-substrates from remote areas. Decentralized designs show that anaerobic digestion is only convenient for large cities and feedlot production sites. Economic and environmental benefits are significantly higher for the integrated alternative. Under optimized conditions, electricity price should be as high as 55.2 USD per MWh to reach the breakeven point from an economic perspective, assuming no revenues from carbon credits.

USEPA CALPUFF validation and dispersion modeling of beef cattle feedlot PM10 and PM2.5 emissions factors

Beef cattle feedlots are major sources of criteria air pollutants in the United States. To aid stakeholders in air quality modeling, emissions factors for animal waste-producing facilities are under development by the U.S. Environmental Protection Agency (USEPA). However, beef cattle feeding operations (feedlots) are not among facilities surveyed under the associated USEPA National Air Emissions Monitoring Study (NAEMS). Authors aim to supplement NAEMS through development and validation of particulate matter (PM10 and PM2.5) emission factors from a previous sampling campaign of five large feedlots in the Southern High Plains of North America via USEPA's CALPUFF dispersion model. PM concentrations were higher overall during the warm season (March–August; PM10 = 692 ± 507, PM2.5 = 114 ± 110 μg/m3) relative to cool season (November–January; PM10 = 102 ± 105, PM2.5 = 12.2 ± 8.6 μg/m3), and overall median PM10 and PM2.5 emission factors were 48.2 (day = 33.8, night = 72.4) and 5.22 (day = 8.4, night = 3.1) mg/m2/hr, respectively. Validated emissions factors were then used to model diurnal peaks and long-range transport (100 km maximum extent). Peak concentrations were most frequently observed between 2000 and 0600 h (93.9%; mean 1-hr peak ± SD = 1119 ± 1240 μg/m3) for PM10 and 1600-0600 h (80.0%; mean 1-hr peak ± SD; 178 ± 174 μg/m3) for PM2.5. Four of five feedlots exceeded ≥1 primary PM National Ambient Air Quality Standard (NAAQS) at receptors (2-m height) over a 5-km spatial extent during the modeling period (November 2010–August 2011). Moreover, present estimates of feedlot-derived inhalable PM represent human and environmental exposure pathways currently exempt from Clean Air Act monitoring and reporting standards, and spatial interpolation of federal air quality monitors cannot adequately characterize inhalable PM concentrations in non-metropolitan municipalities and unincorporated rural communities.

349 Effects of Adding a Yeast Blend to Diets with High Levels of Dried Distillers Grains on Feeding Behavior, Intake, and Performance of Beef Cattle Fattened in Feedlot

Abstract Feeding ruminants with a blend of autolyzed yeast grown on sugarcane molasses and live yeast allows nutritionists to explore synergistic effects on digestion and performance (Angulo et al.,2021; Zapata et al., 2021). However, the feeding behavior and the challenges faced in large pen feedlot operations differ from the behavior and challenges faced by animals studied in small groups or metabolic cages. Therefore, we aimed to study the feeding behavior and performance of beef cattle fed in groups in large pens, mimicking the feedlot operations of leading producers and exports of meat in the world. The trial lasted 112 days and was conducted in Nutripura’s research center in the midwest of Brazil. Six hundred five non-castrated males (Nelore and F1 Nelore-Angus), 405 kg (± 35), distributed in 20 pens, were divided into two treatments: 1) Control, a diet with no yeast additives; 2) Yeast Blend (YB), a diet with a blend of autolyzed yeast and live yeast, SymbioYeast, 7g/anima/day (ICC, São Paulo, Brazil). Both diets contained monesin (28 mg/kg DM). The data were analyzed in the software SAS following the model Yijk= μ+Ti + Fj + Bk +еijk (μ = general mean; T = treatment effect; F = Breed effect; B = backgrounding phase effect; e = error). Initial body weight was used as a covariable to analyze final body weight and average daily gain (ADG). Dry matter intake increased (P &amp;lt; 0,05) when animals were supplemented with YB (10,99kg vs. 11,12kg). Final body weight and hot carcass weight tended (0.1 &amp;gt; P ≥ 0.05) to increase when YB was added to the diet. (598 kg vs. 602 kg, 343 kg vs. 345 kg). The ADG was unaffected (P = 0.1069, control 1.735 kg, and YB 1.768 kg). Increasing DMI is a well now property of some yeast derivatives (Torres et al., 2022). This may be related to changes in digestion (Torres et al., 2022) and the diet’s palatability. The palatability of yeast products is claimed on organoleptic and flavor characteristics (Tao et al., 2023). Drone photos taken every 15 minutes suggested that YB altered how animals interact with feed. Feed was delivered between 0700 h and -0930 h and 1300 h and 1530 h. After delivery, a greater percentage of the visit of the animals to the feed bunkers in YB groups. This behavior was even more evident in the morning feed delivery (Figure 1). In summary, YB increased intake and performance. It also changed the interest of animals in visiting feed bunk.

PSIX-30 Results from a Statewide Needs Assessment of Iowa Beef Producers

Abstract Extension personnel routinely conduct needs assessments to develop programs addressing challenges faced by cattle producers. The objective of this project was to identify and evaluate the needs of cattle producers in Iowa. Needs assessment listening sessions were conducted by the Iowa Beef Center across six regions of the state of Iowa. A total of 54 stakeholders across the six regions participated, representing cow-calf, feedlot, veterinary, and allied industries. During each session, participants were asked to write down a list of challenges or opportunities they observed in the beef industry. Each producer was asked to share an item on their list that they perceived or experienced as the most challenging and briefly expand on the topic. Once every attendee had an opportunity to engage, the process was repeated until topics had been exhausted. Each listening session lasted approximately 2 to 3 hours. Notes from all six meetings were compiled, and major themes were aggregated. Common themes were found across all six regions, while others were only addressed within specific regions. Producers statewide addressed challenges in cattle marketing (n = 31), land use and availability (n = 22), herd health (n = 20), and feed costs (n = 19). Farm transition (n = 14), consumer education (n = 14), and animal handling and welfare (n = 8) were discussed in five of the six regions. Production profitability (n = 8) and labor (n = 5) were only addressed in four regions. Topics discussed in fewer than four regions tended to be specific to either cow-calf or feedlot enterprises. For example, traceability (n = 4) was only discussed in the northwestern and northcentral regions with a large feedlot presence. In contrast, heifer development (n = 4) was discussed in three regions with more cow-calf operations. In conclusion, this project illustrates the diversity and commonality of challenges facing cattle producers in the state of Iowa and is indicative of issues facing cattle producers nationally. Although these listening sessions were specific to Iowa cattle producers, the methods used to gain insight into challenges facing cattle producers have applications beyond Iowa. The diversity of responses reinforces the need for routine needs assessments for extension program development to address the needs of the beef industry nationally and globally.

263 Effects of Programmed Compensatory Gain on Feedlot Steer Performance

Abstract The objective was to determine the effects of programmed compensatory gain on feedlot steer growth performance. After a period of growth restriction, a return to ad libitum intake will result in compensatory gain as cattle convert feed more efficiently due to reduced maintenance costs. Simmental × Angus steers (n = 159; BW = 278 ± 49 kg) were blocked by BW, stratified by sire, and allotted to 10 pens. Each pen contained a 3.0 m-long bunk to allow 19 cm of linear bunk space per steer. Pens were randomly assigned to one of two treatments on d 0: control (CON) or programmed compensatory gain (PCG). To achieve programmed compensatory gain, previously growing animals were maintained at a constant BW by reducing the amount of feed offered by 3.29% daily for 10 consecutive d. Thus, on d 54, PCG steers were consuming 72% of original dry matter intake (DMI) and subsequently returned to ad libitum intake to facilitate a period of compensatory gain. Feed intake for CON pens was managed using slick bunk management for the entire experiment. Steers were fed a common diet consisting of 20% corn silage, 20% modified wet distillers grains, 25% high moisture corn, 25% dry rolled corn, and 10% supplement inclusion on a dry matter basis. Steers were feed twice daily at 0800 h and 1200 h. Data were analyzed using MIXED procedure of SAS 9.4 using a beta distribution. The model included fixed effects of treatment and block. From d 39 to 63, average daily gain (ADG) was greater (P = 0.03) for PCG steers compared with CON steers. No treatment effect (P = 0.36) for dry matter intake was observed from d 39 to 63 as PCG and CON steers were consuming 9.49 and 9.67 kg, respectively. Thus, PCG steers had a greater (P = 0.01) gain:feed (G:F) than CON steers from d 39 to 63. Body weight was not different (P = 0.38) on d 148. Also, ADG from d 0 to 148 was not different (P = 0.54) as PCG and CON steers gained 1.92 and 1.91 kg, respectively. From d 0 to 148, overall dry matter intake was not affected (P = 0.91) by treatment. However, programmed compensatory gain steers had a greater G:F (P = 0.01) compared with CON steers for the overall feeding period (0.216 vs 0.210, respectively). In conclusion, programmed compensatory gain improved G:F of feedlot steers over a 148 d-finishing phase without affecting final body weight. Effects of programmed compensatory gain should be further evaluated in a commercial setting with large feedlot pens.

Assessment of a reconfiguration of the InterSpread Plus US national FMD model as a potential tool to analyze a foot-and-mouth disease outbreak on a single large cattle feedlot in the United States.

An incursion of foot-and-mouth disease (FMD) into the United States remains a concern of high importance and would have devastating socioeconomic impacts to the livestock and associated industries. This highly transmissible and infectious disease poses continual risk for introduction into the United States (US), due to the legal and illegal global movement of people, animals, and animal products. While stamping out has been shown to effectively control FMD, depopulation of large cattle feedlots (>50,000 head) presents a number of challenges for responders due to the resources required to depopulate and dispose of large numbers of animals in a timely and effective manner. However, evaluating alternative strategies for FMD control on large feedlots requires a detailed within-farm modeling approach, which can account for the unique structure of these operations. To address this, we developed a single feedlot, within-farm spread model using a novel configuration within the InterSpread Plus (ISP) framework. As proof of concept we designed six scenarios: (i) depopulation - the complete depopulation of the feedlot, (ii) burn-through - a managed "burn-through" where the virus is allowed to spread through the feedlot and only movement restriction and biosecurity are implemented, (iii) firebreak-NV - targeted depopulation of infected pens and adjacent pens without vaccination; (iv) firebreak - targeted depopulation of infected pens and adjacent pens with vaccination of remaining pens; (v) harvest-NV - selective harvest of pens where a 100% movement restriction is applied for 28-30 days, then pens are set for selection to be sent to slaughter, while allowing a controlled "burn-through" without vaccination; and (vi) harvest - selective harvest of pens with vaccination. Overall, the burn-through scenario (ii) had the shortest epidemic duration (31d (30, 33)) median (25th, 75th percentiles), while the firebreak scenario (iv) had the longest (47d (38,55)). Additionally, we found that scenarios implementing depopulation delayed the peak day of infection and reduced the total number of pens infected compared to non-depopulation scenarios. This novel configuration of ISP provides proof of concept for further development of this new tool to enhance response planning for an incursion of FMD in the US and provides the capability to investigate response strategies that are designed to address specific outbreak response objectives.

Characterizing NH3 emissions from a sheep feedlot and a manure composting facility in North China with the inverse dispersion technique

Ammonia (NH3) emissions from manure storage in animal feedlots and post-farm treatment facilities, such as composting facilities, are the key contributors to the agricultural NH3 budget. Simultaneous quantification of NH3 emissions from these two sectors at the same site can provide information on NH3 emissions along the manure management chain, which will aid in accurately evaluating best management practices for NH3 mitigation. The NH3 emission rates of a large sheep feedlot with a full capacity of ∼30,000 heads, consisting of occupied pens, unoccupied pens (empty), and a neighboring composting facility for sheep manure in North China, were quantified using the multiple-source determination of an inverse dispersion technique in winter season. This was followed by a year-round measurement to track the NH3 emission patterns (diurnal and seasonal) of these two sectors and further quantify the NH3 emissions. The NH3 flux of the occupied pens was 2.07 and 2.64 times that of the empty pens and the composting facility, respectively. After excluding the NH3 emissions from the empty pens, the NH3 emission rates per head in four seasons changed from 11.01 to 22.43 to 8.58–11.13 g head–1 d–1. The NH3 emissions from the feedlot accounted for 25.26% of the feed N intake (or 33.68% of the excreted N), and the NH3 emissions from the manure composting facility accounted for 2.20% of the initial N in sheep manure. This study is novel in filling the data gap for both the NH3 emissions from sheep feedlots and the representative contributions of different manure management sectors.

Evaluation of feeding ruminal-protected folate and cobalt pectinate on growth performance, carcass characteristics and plasma vitamin B12 and folate status in finishing beef steers.

A large pen feedlot study was conducted to evaluate the response of yearling steers fed novel sources of rumen-protected folate (RPFA) and cobalt (cobalt pectinate; Co-PECT) on plasma levels of vitamin B12 and folate, growth performance, and carcass characteristics. A total of 2,100 steers (initial BW = 381 ± 45.2 kg.) were enrolled in the study at the time of randomization with 2,091 steers started on treatment diets following the transition to the finishing diet. A generalized randomized block design with sampling error (GRBD) with two treatments and 15 pen replications per treatment (5 blocks × 6 pens/block; 30 pens total with 70 steers/pen) were evaluated with pen serving as the experimental unit. A control (CON) treatment consisted of the standard finishing diet while the test diet consisted of the standard finishing diet providing 3.0 mg ∙ kg−1 DM of RPFA and 1.0 mg ∙ kg−1 DM total supplemental cobalt with approximately half coming from Co-PECT (TEST). Blood samples were collected from 60 randomly selected steers at study initiation and prior to shipping for plasma B12 and folate measurement. Data were analyzed with the model including fixed effects of treatment, block, and treatment within block interaction. Live growth performance was not affected by treatment; however, carcass-adjusted performance and hot carcass weight were numerically improved by TEST in 3 of the 5 blocks (treatment × within block interaction, P ≤ 0.03) of cattle. Plasma levels for both folic acid and vitamin B12 were extremely low at study initiation and increased over the course of the feeding period. Feeding TEST increased (P < 0.01) plasma B12 levels compared to CON by the completion of the trial; however, mean levels would still be considered marginal. Plasma folate was lower (P < 0.05) in TEST steers at the beginning of the study, with no difference between treatments by the time cattle were shipped. Results suggested that cattle coming into the feedlot may be of low or marginal status in both plasma folate and vitamin B12. While the status of folate and B12 improved in both CON and TEST with days on feed, providing RPFA and Co-PECT further helped improve vitamin B12 status; although, overall levels remained low, which may have affected the overall response to RPFA. Additional research is required to better understand the role of B vitamin supplementation for growing-finishing feedlots and develop methods for assessing the status and improving potential responses.

Estimation of foot-and-mouth disease windborne transmission risk from USA beef feedlots

Windborne spread of foot-and-mouth disease (FMD) requires specific epidemiological and meteorological conditions, thus modeling the risk of windborne spread involves integrating epidemiological and meteorological models. The objective of this study was to investigate the potential risk of windborne spread of FMD from an infected US feedlot using an integrated modeling approach, and to identify factors that determine this risk.To address this objective, we integrated a within-herd epidemiological model and an advanced atmospheric dispersion model, and calculated infection risk dependent on exposed herd size. A previously developed epidemiological model was used to simulate the spread of FMD through a typical U.S. feedlot, while the National Oceanic and Atmospheric Administration’s (NOAA) HYSPLIT atmospheric dispersion model, which has been validated for FMD modeling, was used to model virus dispersion. Infection risk for exposed herds was calculated as a binomial probability accounting for dose and exposed herd size. We modeled risk of windborne spread from a typical 4000 head feedlot in the U.S. state of Iowa (IA), and a typical 48,000 head feedlot in the U.S. state of Kansas (KS) during winter and summer seasons.The risk of windborne spread of FMD varied based on weather/season conditions, estimated average viral shedding rate per head, size of infected herd, and size of exposed herd. In the baseline Kansas scenario (KS/103/W), the median of the maximum daily risk of infecting a 1000-head exposed herd ranged from 58.16 % at 1 km to 0.78 % at 10 km (Table 4). In the baseline Iowa scenario (IA/103/W), the median of the maximum daily risk of infecting a 1000-head exposed herd ranged from 21.78 % at 1 km to 0.05 % at 10 km (Table 4).The minimum control area recommended by the United States Department of Agriculture (USDA) in an FMD outbreak is 10 km from the infected premise. Our results indicate that significant risk of windborne spread may extend beyond 10 km in certain situations. This is particularly a concern in areas where there are large feedlots in relatively close proximity, such as in southwestern Kansas. Our model may be useful as a research tool in the absence of an outbreak and may help direct surveillance and response efforts in the event of an outbreak.

Modeling Intervention Scenarios During Potential Foot-and-Mouth Disease Outbreaks Within U.S. Beef Feedlots.

Foot-and-mouth disease (FMD) is a highly contagious disease of livestock and has severely affected livestock industries during the past two decades in previously FMD-free countries. The disease was eliminated in North America in 1953 but remains a threat for re-introduction. Approximately 44% of the on-feed beef cattle in the U.S. are concentrated in feedlots <32,000 heads, but little information is available on dynamics of FMD in large feedlots. Therefore, there is a need to explore possible management and intervention strategies that might be implemented during potential FMD outbreaks on feedlots. We used a within home-pen stochastic susceptible-latent-infectious-recovered (SLIR) FMD dynamics model nested in a meta-population model of home-pens in a feedlot. The combinatory model was previously developed to simulate foot-and-mouth disease virus (FMDv) transmission within U.S. beef feedlots. We evaluated three intervention strategies initiated on the day of FMD detection: stopping movements of cattle between home-pens and hospital-pen(s) (NH), barrier depopulation combined with NH (NH-BD), and targeted depopulation of at-risk home-pens combined with NH (NH-TD). Depopulation rates investigated ranged from 500 to 4,000 cattle per day. We evaluated the projected effectiveness of interventions by comparing them with the no-intervention FMD dynamics in the feedlot. We modeled a small-size (4,000 cattle), medium-size (12,000 cattle), and large-size (24,000 cattle) feedlots. Implementation of NH delayed the outbreak progression, but it did not prevent infection of the entire feedlot. Implementation of NH-BD resulted in depopulation of 50% of cattle in small- and medium-size feedlots, and 25% in large-size feedlots, but the intervention prevented infection of the entire feedlot in 40% of simulated outbreaks in medium-size feedlots, and in 8% in large-size feedlots. Implementation of NH-TD resulted in depopulation of up to 50% of cattle in small-size feedlots, 75% in medium-size feedlots, and 25% in large-size feedlots, but rarely prevented infection of the entire feedlot. Number of hospital-pens in the feedlot was shown to weakly impact the success of NH-TD. Overall, the results suggest that stopping cattle movements between the home-pens and hospital-pens, without or with barrier or targeted cattle depopulation, would not be highly effective to interrupt FMDv transmission within a feedlot.

Modeling the Effect of Tylosin Phosphate on Macrolide-Resistant Enterococci in Feedlots and Reducing Resistance Transmission.

Tylosin phosphate (TYL) is administered to more than 50% of U.S. beef cattle to reduce the incidence of liver abscesses but may increase the risk of macrolide-lincosamide-streptogramin-resistant bacteria disseminating from the feedlot. Limited evidence has been collected to understand how TYL affects the proportion of resistant bacteria in cattle or the feedlot environment. We created a mathematical model to investigate the effects of TYL administration on Enterococcus dynamics and examined preharvest strategies to mitigate the impact of TYL administration on resistance. The model simulated the physiological pharmacokinetics of orally administered TYL and estimated the pharmacodynamic effects of TYL on populations of resistant and susceptible Enterococcus within the cattle large intestine, feedlot pen, water trough, and feed bunk. The model parameters' population distributions were based on the available literature; 1000 Monte Carlo simulations were performed to estimate the likely distribution of outcomes. At the end of the simulated treatment period, the median estimated proportion of macrolide-resistant enterococci was only 1 percentage point higher within treated cattle compared with cattle not fed TYL, in part because the TYL concentrations in the large intestine were substantially lower than the enterococci minimum inhibitory concentrations. However, 25% of the simulated cattle had a >10 percentage point increase in the proportion of resistant enterococci associated with TYL administration, termed the TYL effect. The model predicts withdrawing TYL treatment and moving cattle to an antimicrobial-free terminal pen with a low prevalence of resistant environmental enterococci for as few as 6 days could reduce the TYL effect by up to 14 percentage points. Additional investigation of the importance of this subset of cattle to the overall risk of resistance transmission from feedlots will aid in the interpretation and implementation of resistance mitigation strategies.

A Meta-Population Model of Potential Foot-and-Mouth Disease Transmission, Clinical Manifestation, and Detection Within U.S. Beef Feedlots.

Foot-and-mouth disease (FMD) has not been reported in the U.S. since 1929. Recent outbreaks in previously FMD-free countries raise concerns about potential FMD introductions in the U.S. Mathematical modeling is the only tool for simulating infectious disease outbreaks in non-endemic territories. In the majority of prior studies, FMD virus (FMDv) transmission on-farm was modeled assuming homogenous animal mixing. This assumption is implausible for U.S. beef feedlots which are divided into multiple home-pens without contact between home-pens except fence line with contiguous home-pens and limited mixing in hospital pens. To project FMDv transmission and clinical manifestation in a feedlot, we developed a meta-population stochastic model reflecting the contact structure. Within a home-pen, the dynamics were represented assuming homogenous animal mixing by a modified SLIR (susceptible-latent-infectious-recovered) model with four additional compartments tracing cattle with subclinical or clinical FMD and infectious status. Virus transmission among home-pens occurred via cattle mixing in hospital-pen(s), cowboy pen rider movements between home-pens, airborne, and for contiguous home-pens fence-line and via shared water-troughs. We modeled feedlots with a one-time capacity of 4,000 (small), 12,000 (medium), and 24,000 (large) cattle. Common cattle demographics, feedlot layout, endemic infectious and non-infectious disease occurrence, and production management were reflected. Projected FMD-outbreak duration on a feedlot ranged from 49 to 82 days. Outbreak peak day (with maximum number of FMD clinical cattle) ranged from 24 (small) to 49 (large feedlot). Detection day was 4–12 post-FMD-introduction with projected 28, 9, or 4% of cattle already infected in a small, medium, or large feedlot, respectively. Depletion of susceptible cattle in a feedlot occurred by day 23–51 post-FMD-introduction. Parameter-value sensitivity analyses were performed for model outputs. Detection occurred sooner if there was a higher initial proportion of latent animals in the index home-pen. Shorter outbreaks were associated with a shorter latent period and higher bovine respiratory disease morbidity (impacting the in-hospital-pen cattle mixing occurrence). This first model of potential FMD dynamics on U.S. beef feedlots shows the importance of capturing within-feedlot cattle contact structure for projecting infectious disease dynamics. Our model provides a tool for evaluating FMD outbreak control strategies.

Exploring new methods of estimating deposition using atmospheric concentration measurements: A modeling case study of ammonia downwind of a feedlot

Atmospheric ammonia is an important compound in the atmosphere because of its role in aerosol formation and its importance to the global nitrogen cycle. Livestock feeding operations are a major source of ammonia emissions to the atmosphere, and ammonia concentrations near these large feedlots can be many orders of magnitude higher than background. These feedlots can impact regional ecology and air quality, but uncertainty in the ammonia surface fluxes adjacent to these major sources can make the extent of the feedlot's impact difficult to determine. Ammonia surface fluxes are generally challenging to quantify with direct flux measurement techniques due to the challenges in conducting ammonia measurements with sufficient temporal resolution. Feedlots housing ruminant livestock such as cattle are also sources of methane. Because methane does not undergo appreciable dry deposition and is chemically inert on relevant spatial scales, we can use it as a tracer to constrain the downwind dilution of feedlot ammonia emissions. The ratio of atmospheric ammonia to methane has been shown to decrease with increasing distance downwind of a feedlot due to deposition and aerosol partitioning of gas-phase ammonia. In atmospheric conditions where inorganic aerosol formation is slow, the ratio of ammonia to methane can be used to estimate of the fraction of ammonia that has undergone deposition downwind of the feedlot. We use a Large-Eddy Simulation turbulent dispersion model to generate realistic concentration fields of atmospheric ammonia and methane concentrations downwind of a feedlot, and we sample the model output to produce synthetic measurements of these tracers. We then use the synthetic observations of background-corrected the ammonia:methane concentration ratio to derive the ammonia deposition rate. In this study, we explore conducting measurements from two platforms: sensors deployed on a small unmanned aerial vehicle and on a surface-based mobile observation platform. We find that the surface-based platform overestimates of ammonia deposition by a factor of 1.5 due to sampling near the surface where ammonia concentrations are depleted. However, use of the aerial platform allows more accurate estimation of the deposition fraction (relative error <0.09).

Planning "Plan B": The Case of Moving Cattle From an Infected Feedlot Premises During a Hypothetical Widespread FMD Outbreak in the United States.

In the event of a foot-and-mouth disease (FMD) outbreak in the United States, “stamping out” FMD infected premises has been proposed as the method of choice for the control of outbreaks. However, if a widespread, catastrophic FMD outbreak in the U.S. were to occur, alternative solutions to stamping out may be required, particularly for large feedlots with over 10,000 cattle. Such strategies include moving cattle from infected or not known to be infected operations to slaughter facilities either with or without prior implementation of vaccination. To understand the risk of these strategies, it is important to estimate levels of herd viremia. Multiple factors must be considered when determining risk and feasibility of moving cattle from a feedlot to a slaughter facility during an FMD outbreak. In addition to modeling within-herd disease spread to estimate prevalence of viremic animals, we explore potential pathways for viral spread associated with the movement of asymptomatic beef cattle (either pre-clinical or recovered) from an infected feedlot premises to offsite harvest facilities. This analysis was proactive in nature, however evaluation of the likelihood of disease spread relative to disease (infection) phase, time of movement, and vaccination status are all factors which should be considered in managing and containing a large-scale FMD outbreak in the United States.

Xylazine sedation and gunshot for depopulation of cattle

A depopulation protocol utilizing intramuscular sedation with xylazine followed by euthanasia via gunshot was evaluated for effectiveness and practicality in a group of 43 feedlot calves in a commercial feedlot setting. Sedation and euthanasia were successful in all 43 calves. The time required to complete the procedure was 46 minutes from the first xylazine injection to the last gunshot. Utilization of this depopulation method demonstrates that cattle in a commercial feedlot can be euthanized in a rapid manner that is practical and efficient, while also maintaining an acceptable level of animal welfare. Expansion to larger herds, including the total population of a large feedlot, may still be challenging. The use of this depopulation method should be considered for future livestock emergencies.

Integrated Deep Soil N and Groundwater Isotope Investigation of N Sources Captured by Municipal Wells

AbstractIdentification of major nitrate sources that adversely impact groundwater quality in municipal well capture zones in areas of emerging nitrate contamination is essential to minimize leaching and prevent exceedance of the nitrate drinking water standard. Vertical profiles of nitrate leachate in deep soils provide an estimate of the amount of nitrate in transit beneath irrigated, row‐cropped fields; depths of peak leachate; and the approximate rate of downward movement. Profiles of pore‐water soil‐nitrate concentrations in thick 60‐feet (~18 m), fine‐textured soils near Hastings, Nebraska clearly indicate that considerably more nitrate leached beneath furrow‐irrigated than center‐pivot irrigated fields. Peak leaching appeared to correlate with recorded periods of poor weather conditions during some growing seasons and may best be controlled by “spoon feeding” fertilizer to the crop through the sprinkler irrigation system at times of nutrient need. The presence of trace levels of atrazine and deethylatrazine to 60 feet (18 m) in core samples indicates that larger, more complex anthropogenic molecules also leach through the fine‐textured soils. The light δ15NNO3 values in the surficial groundwater beneath fertilized and irrigated cropland indicate that ammonium fertilizer is a major N source and suggest that the natural soil‐N contribution is negligible. δ15NNO3 values were most enriched in irrigation wells located within municipal well capture zones downgradient of a large feedlot. Dual isotope method (DIM) δ15NNO3 and δ18ONO3 values suggest that the Hastings’ municipal wells farther downgradient are contaminated with a mixture of nitrate from manure and commercial ammonium‐based fertilizer. DIM values indicate an absence of denitrification, which has implications for long‐term management of the water resources.

Genomic comparison of Histophilus somni strains shows genetic drift

Histophilus somni is a gram-negative, non-motile, non-encapsulated, coccobacillus commensal bacterium associated with nasal cavities of cattle. H. somni is an opportunistic pathogen that complicates viral infections and increases the severity of infection in association with other bacterial agents. H. somni can infect several organs once it becomes blood-borne, and is often associated with Mannheima haemolytica and Pasteurella multocida. H. somni affects the respiratory, genital, nervous (thrombotic meningoencephalitis, TME), circulatory and musculoskeletal systems (joints), either individually or together. Currently there are 22 USDA-licensed H. somni vaccines licensed by 5 companies for the US market; however, many of these are no longer being manufactured or marketed. The current manufactured vaccines are heavily used, with 69. 7% of all large feedlots in the US vaccinating cattle against H. somni. Surprisingly, their ability to confer immunity in the production setting is modest or unknown. One of the reasons for perceived low protection is high genetic diversity and genetic-drift among H. somni strains. In order to understand the genetic-drift and select candidates for inclusion in autogenous vaccines we performed whole genome sequencing (WGS) and comparative mapping analysis of 30 H. somni field isolates (named NPL#) and 2 avirulent mutant strains to the reference strains 129PT commensal isolate and 2336 and HS91 pathogenic isolates.