Genome-wide association analysis for susceptibility to infection by Mycobacterium avium ssp. paratuberculosis in US Holsteins.

Paratuberculosis, or Johne's disease, is a chronic, granulomatous, gastrointestinal tract disease of cattle and other ruminants caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). Control of Johne's disease is based on programs of testing and culling animals positive for infection with MAP and concurrently modifying management to reduce the likelihood of infection. The current study was motivated by the hypothesis that genetic variation in host susceptibility to MAP infection can be dissected and quantifiable associations with genetic markers identified. Two separate GWAS analyses were conducted, the first using 897 genotyped Holstein artificial insemination sires with phenotypes derived from incidence of MAP infection among daughters based on milk ELISA testing records. The second GWAS analysis was a case-control design using US Holstein cows phenotyped for MAP infection by serum ELISA or fecal culture tests. Cases included cows positive for either serum ELISA, fecal culture, or both. Controls consisted of animals negative for all tests conducted. A total of 376 samples (70 cases and 306 controls) from a University of Minnesota Johne's management demonstration project and 184 samples (76 cases and 108 controls) from a Michigan State University study were used. Medium-density (sires) and high-density (cows) genotype data were imputed to full genome sequence for the analyses. Marker-trait associations were analyzed using the single-step (ss)GWAS procedure implemented in the BLUPF90 suite of programs. Evidence of significant genomic contributions for susceptibility to MAP infection were observed on multiple chromosomes. Results were combined across studies in a meta-analysis, and increased support for genomic regions on BTA7 and BTA21 were observed. Gene set enrichment analysis suggested pathways for antigen processing and presentation, antimicrobial peptides and natural killer cell-mediated cytotoxicity are relevant to variation in host susceptibility to MAP infection, among others. Genomic prediction was evaluated using a 5-fold cross-validation, and moderate correlations were observed between genomic breeding value predictions and daughter averages (∼0.43 to 0.53) for MAP infection in testing data sets. These results suggest that genomic selection against susceptibility to MAP infection is feasible in Holstein cattle.

Use of a voluntary testing program to study the spatial epidemiology of Johne's disease affecting dairy herds in Minnesota: a cross sectional study.

BACKGROUND: One of the key steps in the management of chronic diseases in animals including Johne's disease (JD), caused by Mycobacterium avium subsp. paratuberculosis (MAP), is the ability to track disease incidence over space and time. JD surveillance in the U.S. dairy cattle is challenging due to lack of regulatory requirements, imperfect diagnostic tests, and associated expenses, including time and labor. An alternative approach is to use voluntary testing programs. Here, data from a voluntary JD testing program, conducted by the Minnesota Dairy Herd Improvement Association, were used to: a) explore whether such a program provides representative information on JD-prevalence in Minnesota dairy herds, b) estimate JD distribution, and, c) identify herd and environmental factors associated with finding JD-positive cows. Milk samples (n = 70,809) collected from 54,652 unique cows from 600 Minnesota dairy herds between November 2014 and April 2017 were tested using a MAP antibody ELISA. Participant representativeness was assessed by comparing the number of JD-tested herds with the number of herds required to estimate the true disease prevalence per county based on official statistics from the National Agricultural Statistical Services. Multivariable logistic regression models, with and without spatial dependence between observations, were then used to investigate the association between herd status to JD (positive/negative), as indicated by milk ELISA results, and available covariates at the herd level. RESULTS: Within the study population, at least one test-positive cow was found in 414 of 600 (69%) herds. Results indicated that large herds that test frequently and herds located in loamy or silt soils are more likely to have at least one MAP test-positive cow. After adjusting for herd size, testing frequency, and soil type, there was no spatial dependence in JD risk between neighboring dairies within 5 to 20 km. Furthermore, the importance of collecting data on herd management, feed, and biosecurity for insightful interpretations was recognized. The study suggested that, although limited, the voluntary testing database may support monitoring JD status. CONCLUSIONS: Results presented here help elucidate the spatial characteristics of JD in Minnesota and the study may ultimately contribute to the design and implementation of surveillance programs for the disease.

Developing a risk management framework to improve public health outcomes by enumerating Salmonella in ground turkey.

Salmonella spp. continue to be a leading cause of foodborne morbidity worldwide. To assess the risk of foodborne disease, current national regulatory schemes focus on prevalence estimates of Salmonella and other pathogens. The role of pathogen quantification as a risk management measure and its impact on public health is not well understood. To address this information gap, a quantitative risk assessment model was developed to evaluate the impact of pathogen enumeration strategies on public health after consumption of contaminated ground turkey in the USA. Public health impact was evaluated by using several dose-response models for high- and low-virulent strains to account for potential under- or overestimation of human health impacts. The model predicted 2705-21 099 illnesses that would result in 93-727 reported cases of salmonellosis. Sensitivity analysis predicted cooking an unthawed product at home as the riskiest consumption scenario and microbial concentration the most influential input on the incidence of human illnesses. Model results indicated that removing ground turkey lots exceeding contamination levels of 1 MPN/g and 1 MPN in 25 g would decrease the median number of illnesses by 86-94% and 99%, respectively. For a single production lot, contamination levels higher than 1 MPN/g would be needed to result in a reported case to public health officials. At contamination levels of 10 MPN/g, there would be a 13% chance of detecting an outbreak, and at 100 MPN/g, the likelihood of detecting an outbreak increases to 41%. Based on these model prediction results, risk management strategies should incorporate pathogen enumeration. This would have a direct impact on illness incidence linking public health outcomes with measurable food safety objectives.

Knowledge gaps that hamper prevention and control of Mycobacterium avium subspecies paratuberculosis infection.

In the last decades, many regional and country-wide control programmes for Johne's disease (JD) were developed due to associated economic losses, or because of a possible association with Crohn's disease. These control programmes were often not successful, partly because management protocols were not followed, including the introduction of infected replacement cattle, because tests to identify infected animals were unreliable, and uptake by farmers was not high enough because of a perceived low return on investment. In the absence of a cure or effective commercial vaccines, control of JD is currently primarily based on herd management strategies to avoid infection of cattle and restrict within-farm and farm-to-farm transmission. Although JD control programmes have been implemented in most developed countries, lessons learned from JD prevention and control programmes are underreported. Also, JD control programmes are typically evaluated in a limited number of herds and the duration of the study is less than 5 year, making it difficult to adequately assess the efficacy of control programmes. In this manuscript, we identify the most important gaps in knowledge hampering JD prevention and control programmes, including vaccination and diagnostics. Secondly, we discuss directions that research should take to address those knowledge gaps.

Epidemiologic Investigation of Highly Pathogenic H5N2 Avian Influenza Among Upper Midwest U.S. Turkey Farms, 2015.

In 2015, an outbreak of H5N2 highly pathogenic avian influenza (HPAI) occurred in the United States, severely impacting the turkey industry in the upper midwestern United States. Industry, government, and academic partners worked together to conduct a case-control investigation of the outbreak on turkey farms in the Upper Midwest. Case farms were confirmed to have HPAI-infected flocks, and control farms were farms with noninfected turkey flocks at a similar stage of production. Both case and control farms were affiliated with a large integrated turkey company. A questionnaire administered to farm managers and supervisors assessed farm biosecurity, litter handling, dead bird disposal, farm visitor and worker practices, and presence of wild birds on operations during the 2 wk prior to HPAI confirmation on case premises and the corresponding time frame for control premises. Sixty-three farms, including 37 case farms and 26 control farms were included in the analysis. We identified several factors significantly associated with the odds of H5N2 case farm status and that may have contributed to H5N2 transmission to and from operations. Factors associated with increased risk included close proximity to other turkey operations, soil disruption (e.g., tilling) in a nearby field within 14 days prior to the outbreak, and rendering of dead birds. Observation of wild mammals near turkey barns was associated with reduced risk. When analyses focused on farms identified with H5N2 infection before April 22 (Period 1), associations with H5N2-positive farm status included soil disruption in a nearby field within 14 days prior to the outbreak and a high level of visitor biosecurity. High level of worker biosecurity had a protective effect. During the study period after April 22 (Period 2), factors associated with HPAI-positive farm status included nonasphalt roads leading to the farm and use of a vehicle wash station or spray area. Presence of wild birds near dead bird disposal areas was associated with reduced risk. Study results indicated that the initial introduction and spread of H5N2 virus likely occurred by both environmental and between-farm pathways. Transmission dynamics appeared to change with progression of the outbreak. Despite enhanced biosecurity protocols, H5N2 transmission continued, highlighting the need to review geographic/topologic factors such as farm proximity and potential dust or air transmission associated with soil disruption. It is likely that biosecurity improvements will reduce the extent and speed of spread of future outbreaks, but our results suggest that environmental factors may also play a significant role in farms becoming infected with HPAI.

Patterns of Cattle Farm Visitation by White-Tailed Deer in Relation to Risk of Disease Transmission in a Previously Infected Area with Bovine Tuberculosis in Minnesota, USA.

The main objective of this study was to characterize spatial patterns of white-tailed deer (Odocoileus virginianus) movement related to bovine tuberculosis (bTB) transmission risk to cattle in north-western Minnesota. Twenty-one adult deer (16 females and 5 males) were captured during winter (January-March) 2011 in areas adjacent to where an outbreak (2005-2009) of bTB occurred in deer and cattle. Deer were fitted with GPS collars programmed to collect deer location information every 90 min over a 15-month period. The exact locations of cattle, cattle feeding areas, and stored forage that were available to collared deer were assessed seasonally. In total, 47% (n = 9) of collared deer survived to the end of the study. Causes of mortality included wolves (n = 6), hunters (n = 1) and unknown (n = 2); additionally, 2 deer were censored due to collar malfunctions. Our results indicated that 5 deer (25%) had home ranges that included 6 cattle farms (20%). Most (77%) of the deer visits occurred in areas where cattle were present, with most visits (60%) from 00:00 to 06:00. March to May revealed the most farm visitations by deer (37%). This study provided baseline information regarding cattle-deer interactions critical to transmission of bTB in this region and suggested that risk mitigation practices should be implemented to separate wildlife and domestic livestock when feasible.

Evaluation of performance of bacterial culture of feces and serum ELISA across stages of Johne's disease in cattle using a Bayesian latent class model.

The objective of this study was to evaluate the performance of bacterial culture of feces and serum ELISA to correctly identify cows with Mycobacterium avium ssp. paratuberculosis (MAP) at heavy, light, and non-fecal-shedding levels. A total of 29,785 parallel test results from bacterial culture of feces and serum ELISA were collected from 17 dairy herds in Minnesota, Pennsylvania, and Colorado. Samples were obtained from adult cows from dairy herds enrolled for up to 10 yr in the National Johne's Disease Demonstration Herd Project. A Bayesian latent class model was fitted to estimate the probabilities that bacterial culture of feces (using 72-h sedimentation or 30-min centrifugation methods) and serum ELISA results correctly identified cows as high positive, low positive, or negative given that cows were heavy, light, and non-shedders, respectively. The model assumed that no gold standard test was available and conditional independency existed between diagnostic tests. The estimated conditional probabilities that bacterial culture of feces correctly identified heavy shedders, light shedders, and non-shedders were 70.9, 32.0, and 98.5%, respectively. The same values for the serum ELISA were 60.6, 18.7, and 99.5%, respectively. Differences in diagnostic test performance were observed among states. These results improve the interpretation of results from bacterial culture of feces and serum ELISA for detection of MAP and MAP antibody (respectively), which can support on-farm infection control decisions and can be used to evaluate disease-testing strategies, taking into account the accuracy of these tests.

From network analysis to risk analysis--An approach to risk-based surveillance for bovine tuberculosis in Minnesota, US.

Bovine tuberculosis (bTB) was first detected in 2005 in cattle in northwestern Minnesota (MN) through slaughter surveillance. By the end of 2008, 12 cattle herds were infected with bTB, and the main cause for infection was determined to be the movement of infected animals between herds. Bovine tuberculosis was contained in a smaller area in northwestern Minnesota classified as modified accredited (MA), corresponding to a prevalence inferior to 0.1% in cattle. From January 2008 to 2011, all cattle movements within the bTB MA were recorded electronically. The primary objectives of this study were to characterize cattle movements within this region and identify cattle herds with higher risk of bTB introduction based on network parameters and known risk factors from the published literature. During the period that data was collected, 57,460 cattle were moved in 3762 movements corresponding to permits issued to 682 premises, mostly representing private farms, sale yards, slaughter facilities and county or state fairs. Although sale yards represented less than 2% of the premises (nodes), 60% of the movements were to or from a sale yard. The network showed an overall density of 0.4%, a clustering coefficient of 14.6% and a betweenness centralization index of 12.7%, reflecting the low connectivity of this cattle network. The degree distribution showed that 20% of nodes performed 90% of the movements. Farms were ranked based on the total risk score and divided into high, medium, and low risk groups based on the score and its variability. The higher risk group included 14% (n=50) of the farms, corresponding to 80% of the cumulative risk for the farms in the bTB area. This analysis provides a baseline description about the contact structure of cattle movements in an area previously infected with bTB and develops a framework for a targeted surveillance approach for bTB to support future surveillance decisions.

Emergency vaccination use in a modelled foot and mouth disease outbreak in Minnesota.

Epidemiological modelling is an important approach used by the Veterinary Services of the United States Department of Agriculture Animal and Plant Health Inspection Service to evaluate the potential effectiveness of different strategies for handling foot and mouth disease (FMD). Identifying the potential spread of FMD by modelling an outbreak, and then considering the impacts of FMD vaccination, is important in helping to inform decision-makers about the potential outcomes of vaccination programmes. The objective of this study was to evaluate emergency vaccination control strategies used in a simulated FMD outbreak in Minnesota. The North American Animal Disease Spread Model (NAADSM, Version 3.2.18) was used to simulate the outbreak. Large-scale (1,500 herds per day) emergency vaccination reduced the size of the modelled outbreak in both swine and dairy production types, but the effect was larger when the outbreak began in a dairy herd. Large-scale vaccination also overcame limitations caused by delays in vaccine delivery. Thus, even if vaccination did not begin until 21 days into the outbreak, large-scale vaccination still reduced the size and duration of the outbreak. The quantity of vaccine used was markedly larger when large-scale vaccination was used, compared with small-scale (50 herds per day) vaccine administration. In addition, the number of animals and herds vaccinated in an outbreak originating in a herd of swine was substantially lower than in an outbreak beginning in a herd of dairy cattle.

Epidemic simulation of a foot and mouth disease outbreak in Minnesota.

Foot and mouth disease (FMD) is a primary transboundary livestock disease of international concern. Outbreaks of the disease have recently occurred in several countries that were previously FMD-free. For countries with limited direct experience of this disease, modelling is a useful tool for the study of a potential outbreak. The objectives of this study were to determine specific FMD risk parameters for Minnesota and the United States (USA) and to use these parameters to create a baseline FMD outbreak model for Minnesota. Of specific interest was to assess whether the type of herd in which the outbreak began (a dairy herd or a large-scale swine herd) influenced the basic model outcomes of outbreak size and duration, and to examine the effects of depopulation and movement controls. The mean values for disease duration, outbreak duration and number of farms and animals infected were larger in the scenario with a dairy index herd. The results of these two outbreak models demonstrated the entire spectrum of FMD outbreak types; that is, from limited, focal outbreaks to widespread, uncontrolled outbreaks. The findings from this study provide details of a baseline model that emergency preparedness planners can use to evaluate response strategies for a potential incursion of FMD into the USA. These findings are also of value for all countries as veterinary authorities develop or adjust their FMD emergency response plans.

Electron shell ionization of atoms with classical, relativistic scattering.

We investigate forward scattering of ionization from neon, argon, and xenon in ultrahigh intensities of 2 × 10(19) W/cm(2). Comparisons between the gases reveal the energy of the outgoing photoelectron determines its momentum, which can be scattered as far forward as 45° from the laser wave vector k(laser) for energies greater than 1 MeV. The shell structure in the atom manifests itself as modulations in the photoelectron yield and the width of the angular distributions. We arrive at an agreement with theory by using an independent electron model for the atom, a dipole approximation for the bound state interaction, and a relativistic, three-dimensional, classical radiation field including the laser magnetic field. The studies provide the atomic physics within plasmas, radiation, and particle acceleration in ultrastrong fields.

A novel bipolar electric fence for excluding white-tailed deer from stored livestock feed.

Where cattle (Bos taurus) and free-ranging white-tailed deer (Odocoileus virginianus) coexist, they frequently share space and resources, potentially resulting in damage to stores of livestock feed and risk of interspecies disease transmission. Preventing use of stored feed by deer can be an important objective in farm management, depending on amount of damage experienced and perceived risk of disease transmission. Woven wire fences (2.4 to 3.0 m high) are generally considered to be the most effective means for excluding deer. However, rapidly deployable temporary means of excluding deer could be useful, especially during late winter when deer are most physiologically stressed and motivated to consume feed meant for cattle. Thus, the objective of this study was to evaluate a novel 1.2-m-tall electric fence consisting of 4 strands of bipolar tape (not requiring separate ground wires or animal contact with ground) for excluding deer from artificially established feed piles during late winter 2008 in northwestern Minnesota. To induce deer to pause, investigate the fence, and receive negative stimuli before attempting to jump the fence, the bipolar tape was baited with a viscous fluid attractive to deer. The fence was estimated to be >80% effective at reducing deer presence at feed piles (10 treatment sites and 11 control sites) given the late winter to early spring conditions. Despite the efficacy, using the fence as a primary means of protecting stored feed from deer in areas with known disease transmission risk (e.g., presence of bovine tuberculosis) is not recommended because risk could remain unacceptably high if even low numbers of deer access stored feed. Yet, the fence could be effective as immediate protection of stored feed in winter before a more permanent and effective deterrence strategy, such as woven-wire fencing, could be installed during the subsequent summer. The fence would also be effective for reducing deer depredation of stored feed, as well as gardens, small orchards, or other localized or seasonal resources.

Reduction in incidence of Johne's disease associated with implementation of a disease control program in Minnesota demonstration herds.

This prospective longitudinal observational study was conducted to evaluate the effect of a standardized control program on the incidence of Johne's disease in 8 dairy herds in Minnesota. Depending on recruitment year, herds were followed for between 5 and 10 yr. Program compliance was evaluated using a cohort risk assessment score by birth cohort. Fecal samples from cows in study herds were tested annually using bacterial culture to detect Mycobacterium avium ssp. paratuberculosis (MAP), and serum samples from study cows were tested using an ELISA to detect antibodies to MAP. Clinical Johne's disease was also recorded. Cohort risk assessment score decreased along birth cohorts. Depending on the follow-up period in each herd, 5 to 8 birth cohorts were followed to describe changes in time to MAP bacterial culture positivity, serum ELISA positivity, MAP heavy shedding status, and clinical Johne's disease. The analysis of time to bacterial culture positivity, serum ELISA positivity, heavy fecal shedding status, and clinical Johne's disease using a time-dependent Cox regression indicated a reduction of the instantaneous hazard ratio by birth cohorts and by cohort risk score; however, the strength of association between the cohort risk score and each of the 4 disease outcomes decreased over time. The age at which the cows first tested positive for bacterial culture, serum ELISA, and heavy fecal shedding, and the age of the cows at onset of clinical Johne's disease signs remained constant for all birth cohorts. Based on herd risk scores, overall herds complied with the recommended management practices in the program. Results were consistent with a within-herd reduction of Johne's disease transmission, and that reduction was associated with herd-level management practices implemented as part of the control program.

Postmortem titin proteolysis is influenced by sarcomere length in bovine muscle.

The calpain protease system, in particular, µ-calpain is involved in the disassembly of specific myofibrillar proteins, resulting in tenderization of meat postmortem. Given the size, complexity, and integral nature of titin to the structure of the sarcomere, it is plausible that the length of a sarcomere may alter the susceptibility of various domains of titin to cleavage by the calpains. Therefore, we hypothesized titin degradation differs in a sarcomere-length-dependent manner in beef. After slaughter, beef carcasses were split and sides were either suspended by the Achilles tendon (normal suspension, NS) or by the aitchbone (hip suspension, HS). Immediately after suspension, samples were dissected from the LM, psoas major (PM), and semitendinosus (STN) muscles to serve as 0-d controls. After 24 h, 4 steaks were removed from each muscle and randomly assigned to 1-, 4-, 7-, or 10-d aging treatments. After the assigned aging period, myofibrils were purified for determination of sarcomere length. Warner-Bratzler shear force analysis was also performed to evaluate differences in tenderness. Muscle proteins were solubilized and subjected to SDS-VAGE (vertical agarose gel electrophoresis) to evaluate titin degradation. Sarcomere lengths differed (P < 0.0001) between contralateral muscles of NS and HS carcasses. Quantification of SDS-VAGE gels revealed less (P < 0.05) intact titin in the PM muscle of NS carcasses at each aging period compared with the PM of HS carcasses. No significant differences (P > 0.05) were detected in the disappearance of intact titin among suspension methods in the LM or STN. These data demonstrate that suspension method alters proteolysis of titin and suggest an increase in sarcomere length may contribute to the susceptibility of titin to postmortem proteolysis in beef.

'Post-lunch' sleepiness during prolonged, monotonous driving - effects of meal size.

The 'post-lunch' dip is a bi-circadian phenomenon, largely unrelated to lunch, and worsened by a disturbed prior night's sleep. Despite anecdotal claims of adverse effects of larger lunches on afternoon driving ability, there is little actual driving data to support this belief. Although there have been various (non-driving) laboratory studies assessing meal size and micronutrient effects on psychological performance tests, findings are mixed. Moreover, most have not utilised heightened afternoon sleepiness after a shortened night's sleep, and few tested beyond 20 min. Using a real car interactive simulator having full size screen projection, we compared the effects on a 2h monotonous afternoon drive, of two very similar, palatable lunches ('light': 305 cal vs 'heavy': 922 cal [having 3× fat and 2× carbohydrate contents]), given double blind in a repeated measures counterbalanced design, to 12 young male drivers whose prior night's sleep had been restricted to 5h. Sleepiness-related lane drifting ('incidents'), subjective sleepiness and EEG (4-11 Hz power - indicative of sleepiness) were logged throughout. The heavy lunch caused significant increases to both incidents and EEG power, and a trend for greater subjective sleepiness. All three indices showed a significant worsening of sleepiness over the drive under both lunch conditions. Whilst there were no significant condition×time interactions, there was no difference between lunches for at least the first 30 min of the drive when, thereafter, the differences appeared. Ours was a realistic driving study, utilising typical lunches, following an unexceptional level of prior sleep loss, and where a heavy lunch exacerbated inherent sleepiness, to further impair monotonous driving.

Long-Term Survival of Mycobacterium avium subsp. paratuberculosis in Fecal Samples Obtained from Naturally Infected Cows and Stored at -18°C and -70°C.

The objective was to evaluate the survival of Mycobacterium paratuberculosis (Map) in naturally infected dairy cows feces under long periods of freezing at -18°C and -70°C. Samples were collected from cows previously tested positive with serum ELISA or fecal culture, or with clinical signs of Johne's disease. Samples were stored at -18°C and/or -70°C and recultured in Herrold's egg yolk media every 3-6 months. A proportional odds mixed model was used for data analysis. Sixty nine fecal samples were stored for different periods between September 2002 and January 2005. Of these, 45 (65%) were stored at -18°C and 24 (35%) at -70°C. Average number of days between repeated culture dates was 98 and 84 for -18°C and -70°C, respectively. Median number of repeated cultures was 6 and 4 for samples stored at -18°C and -70°C, respectively. After adjusting for initial sample bacterial load, the effects of temperature or number of thawing and refreezing cycles on Map viability were not significant. The probability that a sample decreases from high to moderate-low bacterial load and from moderate-low to negative bacterial load was 13.5% per month. Although this study found gradual reduction of Map concentration in stored fecal samples through time, overall survival in -18°C can ease fecal samples management in laboratories with low-processing capacity or lack of -70°C freezer.

Effect of Johne's disease status on reproduction and culling in dairy cattle.

Among the costs attributed to Mycobacterium avium ssp. paratuberculosis (MAP) infection in dairy cattle, the effects on reproduction and culling are the least documented. To estimate the cost of MAP infections and Johne's disease in a dairy herd, the rates of calving and culling were calculated for cows in each stage of MAP infection relative to uninfected cows. Data from 6 commercial dairy herds, consisting of 2,818 cows with 2,754 calvings and 1,483 cullings, were used for analysis. Every cow in each study herd was tested regularly for MAP, and herds were followed for between 4 and 7 yr. An ordinal categorical variable for Johne's disease status [test-negative, low-positive (low-shedding or ELISA-positive only), or high-shedding] was defined as a time-dependent variable for all cows with at least 1 positive test result or 2 negative test results. A Cox regression model, stratified on herd and controlling for the time-dependent infection variable, was used to analyze time to culling. Nonshedding animals were significantly less likely to be culled in comparison with animals in the low-shedding or ELISA-positive category, and high-shedding animals had nonsignificantly higher culling rates than low-shedding or ELISA-positive animals. Time to calving was analyzed using a proportional rates model, an analog to the Andersen-Gill regression model suitable for recurrent event data, stratifying on herd and weighted to adjust for the dependent censoring caused by the culling effects described above. High-shedding animals had lower calving rates in comparison with low-shedding or ELISA-positive animals, which tended to have higher calving rates than test-negative animals.

Imaging optical diffuse reflectance in beef muscles for tenderness prediction.

The objective of this study was to investigate the potential of a novel optical reflectance imaging method to predict beef tenderness. Two-dimensional (2D) optical reflectance in beef muscles induced by a point incident light was acquired. A set of five parameters were extracted from each reflectance image to describe quantitatively the reflectance profiles. Two parameters, q and B, were derived by numerically fitting the equi-intensity contours of the reflectance pattern. Two spatial gradients were calculated along the directions parallel and perpendicular to muscle fibers and total scattering intensity was obtained by excluding the specular reflectance. This method was applied to analyze 2D images of optical diffuse reflectance in 336 beef samples obtained from 14 steers in which large variations in tenderness were generated by altering animal genetics, suspension method and aging time as well as utilizing muscles varying in their inherent tenderness. Tenderness was evaluated using Warner-Bratzler shear force (WBSF). The effects of animal breed, muscle, types of suspension, and aging were investigated and results indicate that the scattering intensity measured at 1-d was correlated (R(2)=0.50 at lambda=720 nm) with 10-d WBSF in M. longissimus dorsi muscles; and the q parameters measured at 1-d was correlated (R(2)=0.46 at lambda=720 nm) with 10-d WBSF in M. psoas major muscles. These results show analyzing 2D reflectance images of meat surfaces provides valuable information regarding the physical characteristics of meat that are responsible for beef tenderness.

Loss of income from cows shedding Mycobacterium avium subspecies paratuberculosis prior to calving compared with cows not shedding the organism on two Minnesota dairy farms.

Quantification of the financial effect of Mycobacterium paratuberculosis infection on lactation performance is essential to encourage participation of dairy cattle producers in Johne's disease (JD) control programs. The objective of this study was to evaluate the differences in net income per lactation of cows shedding Mycobacterium paratuberculosis before calving compared with test-negative cows. Two Minnesota dairies were enrolled in the study and fecal samples were collected from 1,048 cows during the close-up period. Milk production, clinical diseases (other than clinical JD), and reproductive performance data were recorded for each cow. Overall, fecal-culture-positive (FCP) cows produced 1,355 kg less than fecal-culture-negative (FCN) cows. Fecal-culture-positive cows that survived their current lactation produced $276 less in milk income than cows that were FCN ($1,956 vs. $1,680; SD $526, $570). Fecal-culture-positive cows were 3.0 (95% confidence interval: 1.6-5.8) times more likely to be culled than FCN cows. The mean days open (number of days from calving to conception) was not statistically significant and the cost differences for clinical disease other than JD were small and neither statistically nor economically significant between FCP and FCN cows. Among all FCP cows, income over feed costs losses were $366 per cow per lactation compared with FCN cows. Among FCP nonculled cows, income over feed costs losses were $276 more compared with FCN cows and this difference was statistically significant. There was a total loss of $155 per lactation for nonculled FCP cows retained in the herd compared with FCN cows retained in the herd. Among culled cows, FCP cow losses were $50 less because of age at culling and $120 for reduced beef value. This totaled a loss of $441 for culled FCP cows compared with culled FCN cows. The losses as a result of lower lactation performance and early culling from the herd should alarm dairy producers and motivate them to implement the appropriate control measures for the disease.