Dairy Farms In Minnesota Research Articles

Estimation and analysis of cow-level cumulative lifetime break-even on financial resiliency

A dairy farm's ability to generate positive profit is dependent on the cow's response to management decisions made in conjunction with input cost management. Therefore, farm managers consider a multifaceted set of choices, managing their herd not as a homogeneous group of animals, but justifying the influence of individual cows on the farm's financial performance. We combined cow-level performance records from Minnesota DHIA and farm-level financials from the University of Minnesota Center for Farm Financial Management database FINBIN (https://finbin.umn.edu/) from 2012 to 2018 to evaluate farm- and cow-level profitability. The objective of this study was to evaluate individual cow performance matched with farm-level input expenses allocated to the cow level to measure a dairy farm's ability to be profitable over time, considering input and milk price fluctuations. Conventional Minnesota dairy farms were divided into 2 groups-financially resilient and non-resilient-based on their adjusted net farm income ratio over time. Yearly farm-level expenses and revenues were allocated to cows based on performance measures provided in monthly DHIA test data, and a cumulative lifetime break-even was calculated for all cows with consecutive farm data from 2012 to 2018. Herd-level and cow-level characteristics were analyzed to test for statistical difference between resilient and non-resilient farms as well as cows who achieved their break-even versus those that did not for resilient and non-resilient farms. Results showed that resilient farms had statistically different and lower expenses than non-resilient farms, with lower heifer raising expenses ($1,839.32 vs. $1,886.20), lifetime feed expenses ($4,197.07 vs. $4,975.39), and lifetime non-feed expenses ($2,761.63 vs. $4,502.67). Resilient farms had 38.3% of cows reach break-even, whereas non-resilient farms had 25.2% of cows break even. On average, cows who achieved their break-even remained in the herd for approximately 1 yr longer for both resilient farms (1,011 d for cows who break even and 627 d for those that do not) and non-resilient farms (1,033 d for cows who break even and 683 d for those that do not). Cows on resilient farms who achieved their lifetime break-even had an average lifetime profit of $1,613.48, which was $3,095.10 higher than the lifetime profit of -$1,481.62 of cows who never reach their break-even. Cows who reached their break-even on non-resilient farms had a lifetime profit of $1,270.51, which was $3,854.11 higher than the lifetime profit of -$2,583.60 for those who did not break even. Therefore, financially resilient dairy farms were utilizing a low-input, low-output model that proved to be successful and resulted in maintained profitability across volatile and fluctuating commodity prices.

COVID-19 Awareness and Preparedness of Minnesota and Wisconsin Dairy Farms

ABSTRACT Dairy farms that had participated in previous and ongoing projects with the National Farm Medicine Center (NFMC), Migrant Clinicians Network (MCN), and Upper Midwest Agricultural Safety and Health Center (UMASH) were asked to participate in a 17-question survey by phone or email to investigate biosecurity principles on Minnesota and Wisconsin dairy farms in response to COVID-19 and the effects of the pandemic on the dairy industry. Three additional farms were recruited via a press release published in agricultural newsletters. Of 76 farms contacted, 37 chose to participate in this study from June to July 2020. In response to the COVID-19 pandemic, dairies have implemented or increased biosecurity measures and COVID-19 precautions. Dairies reported adequate personal protective equipment for their workers, though face masks were not required on most dairies (n = 32, 86%). Producers were concerned about the safety of their families, maintaining a healthy workforce, and keeping their farms profitable. Access to healthcare was not perceived to be an issue for their workers. One-quarter of dairies reported COVID-19 infections on their farms. Even though the majority had an isolation protocol in place if someone on the farm were to become ill, less than half of respondents felt their farm was protected against COVID-19. Two-thirds of producers have not had to decrease production, and a majority of operations have not furloughed or terminated employees due to COVID-19. Our data suggest that dairy farms in Minnesota and Wisconsin have implemented biosecurity and safety measures in response to COVID-19. These measures can be improved. Farms would benefit from additional guidance and education on implementation of personal protective measures and disease prevention strategies to keep workers employed and safe.

Exposure to antimicrobials through the milk diet or systemic therapy is associated with a transient increase in antimicrobial resistance in fecal Escherichia coli of dairy calves

The objective of this prospective cohort study was to describe the relationship between exposure to antimicrobials, through both the milk diet and systemic therapy, and to describe antimicrobial resistance of fecal Escherichia coli in dairy calves pre- and postweaning. A convenience sample of 15 Minnesota dairy farms was chosen, representing 3 equal cohorts of milk diet fed to preweaned calves: medicated milk replacer (MMR), nonmedicated milk replacer (NMR), or pasteurized nonsaleable milk (PNM). Five newborn calves were enrolled on each farm, with fecal samples collected from each calf at 1, 3, 5, and 16 wk of age. After isolation, 3 colonies of E. coli were randomly selected from each sample to determine antimicrobial susceptibility by minimum inhibitory concentration (Sensititer, Thermo Scientific, Waltham, MA) to 8 antimicrobials in 8 classes. The isolate was given an antimicrobial resistance score (ARS) according to the number of antimicrobial classes to which it was resistant. Any isolate resistant to 3 or more antimicrobials was defined as being multidrug resistant (MDR). Relationships between ARS and MDR (dependent variables) and possible explanatory variables were analyzed using mixed multivariable linear and logistic regression models, respectively, with critical P-values adjusted for multiple contrasts. Seventy percent of isolates were resistant to sulfadimethoxine. For wk 1 and 3, the mean ARS values were greatest for fecal E. coli from calves fed MMR or PNM compared with NMR, with no difference in ARS values between the MMR and PNM groups at either time point. At wk 5, the mean ARS value was greatest for fecal E. coli from calves fed MMR (3.56 ± 0.45; mean ± SE), intermediate for calves fed PNM (2.64 ± 0.45), and lowest for calves fed NMR (1.54 ± 0.45). However, by wk 16, the mean ARS values were ≤1.0 and did not differ among milk diets. Evaluation of the proportion of isolates with MDR mirrored the results of the ARS analysis (MDR more prevalent in MMR and PNM groups preweaning; no difference among milk diets at 16 wk). There was a tendency for an increase in ARS at wk 5 (1.28 ± 0.70), and the odds for MDR in fecal E. coli were estimated to be 5.2 (95% confidence interval = 0.67, 35.7) and 101.1 (95% confidence interval = 1.15, >999.9) higher at wk 3 and 5 if the calf was treated with a systemic antimicrobial within the 14-d period before sampling. These findings suggest that exposure to antimicrobials through the milk diet or systemic therapy may result in a transient increase in resistance in fecal E. coli, but once the antimicrobial pressure is removed, susceptible E. coli are able to flourish again, resulting in an overall decrease in resistance.

Randomized clinical trial of the effect of a fixed or increasing milk allowance in the first 2 weeks of life on health and performance of dairy calves

The objective of this study was to describe the effect of offering a fixed or increasing milk allowance in the first 1 to 2 wk of life. We hypothesized that calves offered a fixed amount of milk early in life would not experience more scours, but rather would experience improved health and growth compared with calves that had their daily milk allowance slowly increased over a period of 1 to 2 wk. This randomized controlled clinical trial was conducted on 5 dairy farms in Minnesota with both a summer (June-August 2016) and winter (December-February 2017) period of enrollment. Heifer calves were enrolled at birth, weighed, and systematically assigned by birth order to either the slowly increasing (INC) control group or fixed allowance (FIX) treatment group by farm personnel. Calves assigned to the INC group were slowly increased from 4 to 5 L/d to gradually reach the full peak milk allowance of 6 to 8 L/d over a 7- to 14-d period, whereas calves assigned to the FIX group were offered a full peak milk allowance of 6 to 8 L/d beginning on d 1 after birth. The average FIX calf consumed an extra 14 L of milk as compared with INC calves over the first 2 wk of life, corresponding to an average INC intake of 5 L/d during first 1 to 2 wk of life as compared with an average intake of 6.8 L/d in FIX calves. Study technicians visited all farms weekly to collect health and performance data. Multivariable mixed models were used to describe the effect of treatment (INC/FIX) on 3-wk average daily gain (kg/d), 3-wk weight (kg), and hip height at wk 1, 3, and 7, controlling for the effect of season, birth weight, and the random effect of calf within farm. Multivariable logistic regression models were used to describe the effect of treatment on odds of technician and producer reported health events. A total of 1,264 heifer calves were enrolled (FIX n = 641; INC n = 623) with no difference in enrollment weight or hip height between groups. By 3 wk of age, FIX calves weighed 1.4 (0.59) kg more than INC calves, though the magnitude of this difference varied depending on the period of time INC calves were slowly increased in milk allowance (7 vs. 10 vs. 14 d). Calves in the FIX group grew 0.1 kg/d faster and were taller at wk 3 (0.3 ± 0.15 cm) of life. Forty-two percent (536/1,264) of all enrolled calves had a first treatment event, with no effect of treatment on technician-reported health scores and no overall effect on producer-reported treatment or mortality events. Under the conditions of this study, offering a fixed milk allowance from d 1 of life improved calf growth during the first 3 wk as compared with a gradual increase in milk allowance, with no detrimental effect on calf health.

Management, operational, animal health, and economic characteristics of large dairy herds in 4 states in the Upper Midwest of the United States

Recent trends in dairy farm structure in the United States have included a decreasing number of farms, although farm size has increased, especially the share of milk production from very large herds (>2,500 cows). The objectives of this observational study were to describe common management practices; to characterize labor and operational structure; to measure some aspects of animal health, including lameness, hock lesions, mortality, and mastitis incidence; and to summarize cost of production on farms with more than 2,500 cows in 4 states in the Upper Midwest of the United States. The study included 15 dairy farms in Minnesota, Wisconsin, Iowa, and South Dakota. Farms were visited twice, once each year, and on-farm herd records were collected for those 2 yr. On-farm herd records were used to investigate mortality, culling, pregnancy rate, and clinical mastitis incidence. At least 1 high-producing pen of mature cows and 1 pen of fresh cows were scored for locomotion. Likewise, at least 1 pen of high-producing mature cows was scored for cleanliness and hock lesions. Median herd size was 3,975 cows (range = 2,606-13,266). Milk sold per employee was 1,120,745 kg and the number of cows per employee was 105. Eighty percent of the farms had Holstein cows, 13% had Jersey, and 7% had Jersey-Holstein crosses. All farms used artificial insemination as the sole form of breeding and 100% of the farms used hormonal synchronization or timed artificial insemination programs in their reproductive protocols; 21-d pregnancy rate was 21.7%. Median lameness prevalence was 18.3% and median severe lameness prevalence was 5.1%. Median hock lesion prevalence was 17.4% and median severe hock lesion prevalence was 1.9%; mortality rate was 7.4%. Clinical mastitis incidence was 62.5 cases per 100 cow-years. Feed costs accounted for approximately 53% of the total cost of producing milk, followed by labor at 11%, interest and depreciation expenses at 10%, and replacement costs at 9.5%. Herds in the top 50th percentile for profitability had a net income of $2.40 per hundredweight of milk sold compared with $0.95 per hundredweight for herds in the bottom 50th percentile. Although results of this study were helpful in understanding how large dairy systems operate in the Upper Midwest, more research is yet needed with a larger number of farms and wider variety of management practices to identify factors within these large farms that promote optimal animal health and profitability.

Perception of the importance of human-animal interactions on cattle flow and worker safety on Minnesota dairy farms

Proper cattle-handling techniques (stockmanship) are important to ensure calm animals and a safe work environment for dairy workers on farm. The objectives of this study were to (1) assess Minnesota dairy herd owners’ attitudes toward stockmanship, its perceived importance for cow comfort and worker health, and the establishment of calm cattle movement; and (2) identify current resources and methods of stockmanship training on Minnesota dairy farms. A stratified-random sample of Minnesota dairy farmers were contacted via mail to participate in a 28-question survey. One hundred eight bovine dairy producers participated. Most commonly, respondents learned their cattle handling skills from family members (42.6%) and 29.9% of producers had participated in previous stockmanship training. Producers thought that the skill of the human handler was the most important factor in establishing good cattle flow. Cattle-handling techniques was the third most common topic for new-employee orientation after training in milking parlor protocols and milking parlor disinfection. Time limitations and language barrier were considered serious challenges for worker training. Work-related injuries were responsible for lost work days in the previous year in 13.3% of dairy herds and 73.3% of those injuries occurred while working with cattle. Producers perceived that cattle-related injuries were predominantly the handler’s fault: either because of not paying enough attention to the animal or due to poor cattle handling skills. Facility design was considered the least important for the occurrence of worker injuries. Although no causal inference can be made, herds that had workers who had previously participated in stockmanship training had a 810±378kg (mean ± standard error of the mean) higher rolling herd average than those that did not, even after adjusting for herd size and bulk tank somatic cell count. However, 50% of respondents were not interested in attending future stockmanship training sessions. In conclusion, cattle handling skills are considered important by Minnesota dairy producers to ensure worker safety and cow flow. Limited availability of time, language barrier, and a perceived lack of training materials were considered challenges during the training of workers on farms.

Factors associated with morbidity, mortality, and growth of dairy heifer calves up to 3 months of age

Calfhood disease is an important problem on many dairy operations that can have substantial effects on heifer survival and productivity, and has economic and welfare impacts. Neonatal calf diarrhea (NCD) and bovine respiratory disease (BRD) are the most common causes of morbidity and mortality in young dairy cattle. The objective of this observational study was to investigate factors associated with the risks of morbidity and mortality, and with growth, in commercial dairy heifers calves. A total of 2874 heifer calves from 19 commercial dairy farms in Minnesota and Ontario were enrolled at 1–7 days of age and followed for approximately 3 months. Using cut-points of serum total protein of 5.2 and 5.7g/dl, the incidences of failure of transfer of passive immunity (FTPI) were 11 and 32%, respectively. A cut-point of 5.7g/dl was the most predictive of BRD before 5 weeks of age (sensitivity=40%, specificity=69%). The positive predictive value was poor (PPV=18%), but the negative predictive value was good (NPV=87%). A cut-point of 5.2g/dl was most predictive of death before 5 weeks of age (sensitivity=27%, specificity=89%, PPV=5%, NPV=98%). Serum total protein during the first week of life was a poor predictor of NCD. Over 23% of calves were treated for diarrhea. Risk factors were weight at enrollment, other diseases before 2 weeks of age, and an interaction between season of birth and herd-level incidence of NCD. Almost 22% of calves were treated at least once for BRD. Factors associated with an increased risk of BRD included herd-level incidence of BRD, season of birth, navel dipping, other diseases before 2 weeks of age, failure of transfer of passive immunity, and manual control of temperature in pre-weaning housing. Administration of supplemental antibody products at birth was associated with a reduced incidence of BRD. Overall mortality was 3.5%. Risk of mortality was increased by treatment for BRD and other diseases. The mean average weight gain was 0.95kg/day (range: 0.11–1.62kg/day; SD=0.2). Twinning status, FTP, treatment for NCD or other diseases, and month of birth influenced body weight. This study illustrated relationships among various diseases, mortality, and growth. Furthermore, it demonstrated the importance of colostrum for protection against BRD and improved growth performance, while bringing into question the optimal method of determining failure of transfer of passive immunity.

Feeding heat-treated colostrum reduces morbidity in preweaned dairy calves

Previous studies have demonstrated that batch pasteurizers can be used on farms to heat-treat bovine colostrum at 140QF (60QC) for 60 minutes, resulting in a significant reduction in bacterial exposure to the calf while maintaining overall colostral immunoglobulin G (IgG) concentrations. However, no studies have demonstrated that feeding heat-treated colostrum results in improved calf health.
 A randomized controlled clinical trial was conducted using 1,071 newborn calves from six commercial dairy farms in Minnesota and Wisconsin, with the primary objective being to describe the effects of feeding heat-treated colostrum on serum immunoglobulin G concentration and health in the pre-weaning period. A secondary objective was to complete a path analysis to identify intermediate factors that may explain how feeding heat-treated colostrum reduced risk for illness.

The effects of viral vaccination of dairy heifer calves on the incidence of respiratory disease, mortality, and growth

Bovine respiratory disease (BRD) is one of the most common infectious causes of morbidity and mortality in young dairy cattle. The objective of this randomized clinical trial was to determine the effectiveness of 1 or 2 doses of a 5-way, modified-live viral vaccine, administered to heifer calves before weaning to aid in the prevention of BRD. The hypotheses were that vaccination would reduce the incidence of BRD and mortality, and that 2 doses would be more effective than 1. A total of 2,874 heifer calves from 19 commercial dairy farms in Minnesota and Ontario were enrolled at 1 to 7d of age and were followed until 3mo of age. Calves were randomly assigned to receive a commercial, intramuscular, modified-live vaccine against bovine viral diarrhea virus types 1 and 2, bovine respiratory syncytial virus, bovine herpesvirus type 1, and parainfluenza virus type 3 at 15 to 21d of age (2wk only), 35 to 42d (5wk only), both 2 and 5wk, or sterile saline at both times (unvaccinated controls). The incidence of failure of passive transfer was 11 or 32%, using cut-points of serum total protein of 5.2 and 5.7g/dL, respectively. Overall, 22% of calves were treated at least once for BRD. The incidence risk of naturally occurring BRD was 7.7% before 2wk of age, 8.0% between 2 and 5wk, and 9.5% between 5wk and 3mo of age, and was not different between vaccination groups. Overall mortality throughout the 3-mo study period was 3.5%. Mortality was 1.6% before 2wk of age, 0.5% between 2 and 5wk, and 1.2% between 5wk and 3mo of age. The risk of mortality was not affected by vaccination. Mean average daily gain of 1.07kg/d from 5wk to 3mo of age was not different between vaccine groups. In this population of commercial, home-raised calves, with an overall low incidence of failure of passive transfer, intramuscular vaccination with a multivalent, modified live viral vaccine at 2 or 5wk of age or both was not associated with a decreased risk of BRD or mortality, or with growth until 3mo of age. Reasons for these findings may include interference by maternal antibodies, unresponsiveness of the neonatal immune system, timing of immunity relative to pathogen exposure, disease caused by pathogens other than the viruses in the vaccine, or herd immunity. However, in populations with higher incidence of failure of passive transfer or risk of BRD, calves with low levels of specific antibodies may respond differently to vaccination.

Heat-treated colostrum and reduced morbidity in preweaned dairy calves: Results of a randomized trial and examination of mechanisms of effectiveness

A randomized controlled clinical trial was conducted using 1,071 newborn calves from 6 commercial dairy farms in Minnesota and Wisconsin, with the primary objective being to describe the effects of feeding heat-treated colostrum on serum immunoglobulin G concentration and health in the preweaning period. A secondary objective was to complete a path analysis to identify intermediate factors that may explain how feeding heat-treated colostrum reduced the risk for illness. On each farm, colostrum was collected each day, pooled, and divided into 2 aliquots; then, one aliquot was heat-treated in a commercial batch pasteurizer at 60°C for 60min. Samples of fresh and heat-treated colostrum were collected for standard microbial culture (total plate count and total coliform count, cfu/mL) and for measurement of immunoglobulin G concentrations (mg/mL). Newborn calves were removed from the dam, generally within 30 to 60min of birth, and systematically assigned to be fed 3.8L of either fresh (FR, n=518) or heat-treated colostrum (HT, n=553) within 2h of birth. Venous blood samples were collected from calves between 1 and 7d of age for measurement of serum IgG concentrations (mg/mL). All treatment and mortality events were recorded by farm staff between birth and weaning. Regression models found that serum IgG concentrations were significantly higher in calves fed HT colostrum (18.0±1.5mg/mL) compared with calves fed FR colostrum (15.4±1.5mg/ml). Survival analysis using Cox proportional hazards regression indicated a significant increase in risk for a treatment event (any cause) in calves fed FR colostrum (36.5%, hazard ratio=1.25) compared with calves fed HT colostrum (30.9%). In addition, we observed a significant increase in risk for treatment for scours in calves fed FR colostrum (20.7%, hazard ratio=1.32) compared with calves fed HT colostrum (16.5%). Path analysis suggested that calves fed HT colostrum were at lower risk for illness because the heat-treatment process caused a significant reduction in colostrum total coliform count, which was associated with a reduced risk for illness as a function of improved serum IgG concentrations.

Heat treatment of colostrum on commercial dairy farms decreases colostrum microbial counts while maintaining colostrum immunoglobulin G concentrations

This study was conducted on 6 commercial dairy farms in Minnesota and Wisconsin to describe the effect of heat treatment (at 60°C for 60min) on colostrum, on colostrum bacteria counts, and immunoglobulin G concentrations. First-milking colostrum was collected each day, pooled, divided into 2 aliquots, and then 1 aliquot was heat treated in a commercial batch pasteurizer at 60°C for 60min. Frozen samples of pre- and post- heat-treated colostrum were submitted for standard microbial culture (total plate count and total coliform count, cfu/mL) and testing for immunoglobulin G concentrations (mg/mL). Data were analyzed from 266 unique batches of colostrum. Linear regression showed that heat treatment decreased colostrum total plate counts (−2.25 log10) and coliform counts (−2.49 log10), but, overall, did not affect colostrum IgG concentration. Though higher-quality batches of colostrum did experience a greater magnitude of loss of IgG as a result of heat treatment as compared with lower- or intermediate-quality batches of colostrum, the colostral IgG concentrations in these batches remained high overall, and within acceptable limits for feeding. This study demonstrates that batch heat treatment of colostrum at 60°C for 60min can be successfully conducted on commercial dairy farms by farm staff to decrease colostrum microbial counts while maintaining colostrum IgG concentrations.

Prevalence and Characterization of Staphylococcus aureus, Including Methicillin-Resistant Staphylococcus aureus, Isolated from Bulk Tank Milk from Minnesota Dairy Farms

Staphylococcus aureus is a common causative agent of bovine mastitis in dairy herds. The emergence of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals as well as the community is a significant and costly public health concern. S. aureus-related bovine mastitis is a common reason for therapeutic and/or prophylactic use of antibiotics on dairy farms. In this study, herd prevalence of S. aureus, including MRSA, was estimated from bulk tank milk (BTM) from Minnesota farms. A total of 150 pooled BTM samples from 50 farms, collected over 3 seasons (spring, summer, and fall of 2009), were assessed. Herd prevalence of methicillin-susceptible S. aureus (MSSA) was 84%, while MRSA herd prevalence was 4%. A total of 93 MSSA isolates and 2 MRSA isolates were recovered from 150 BTM samples. Antibiotic susceptibility testing of S. aureus isolates showed pansusceptibility in 54 isolates, resistance to a single antibiotic class in 21 isolates, resistance to two antibiotic classes in 13 isolates, and resistance to ≥3 antibiotics classes and thus multidrug resistance in 5 isolates. The two MRSA isolates displayed resistance to β-lactams, cephalosporins, and lincosamides and were multiresistant. Staphylococcal protein A gene (spa) typing identified spa types t529 and t034 most frequently among methicillin-susceptible isolates, while t121 was observed in MRSA isolates. Seven isolates, including the two MRSA isolates, produced staphylococcal enterotoxins B, C, D, and E on overnight culture. MRSA isolates were further genotyped using multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Of the 2 MRSA isolates, one had a composite genotype profile of MLST ST 5-PFGE USA100-unknown spa type, which has been reported among hospital-associated MRSA isolates, while the second isolate carried the MLST ST 8-PFGE USA300-spa type t121 genotype, commonly identified among community-associated MRSA isolates. These results suggest that MRSA genotypes associated with hospitals and community can be isolated from milk at very low rates.

Alternative Bedding Materials for Compost Bedded Pack Barns in Minnesota: A Descriptive Study

Bedding availability for compost bedded pack barns is a concern for dairy producers who use this type of daily stirred bedded pack housing system. The material most commonly used in these barns is sawdust. The objective of this study was to describe management practices of dairy operations utilizing alternative bedding materials for partial or total replacement of sawdust in their compost barns. This study was conducted on six Minnesota dairy farms having compost bedded packs. Bedding materials used on these farms included: sawdust, wood chips, flax straw, wheat straw, oat hulls, strawdust, and soybean straw. Each farm was visited four times, once each season between January 2008 and November 2008. Replicated samples of the bedded pack material were collected during winter and summer. Samples were analyzed for dry matter, carbon, nitrogen, C:N ratios, ammonium, nitrate, pH, and bacterial counts. Temperatures of each pack were measured seasonally at various depths. Cows were scored for hygiene (1=clean, 5=dirty), body condition (1=thin, 5=obese), and locomotion (1=normal, 5=severely lame), and hock lesions were observed. Aerial ammonia and hydrogen sulfide concentrations, air velocity, and light intensity were measured each season. Overall average aerial ammonia was 3.92 ppm and hydrogen sulfide was 22.8 ppb across all farms and season. Average light intensity was 3,250 lux and air velocity was 0.81 m/s. Bedding pack material averaged 15.8% for total C, 0.93% for total N, 17.8 for C:N ratio, 37.3% for dry matter, 8.83 for pH, 4.25 mg/kg for nitrate, 955 mg/kg for ammonium, 15 g/kg for total potassium, 2.8 g/kg for total phosphorus, 8.5 dS/m for EC, 31.7°C for pack temperature, 7.6°C for outside temperature, and 9.42 million cfu/mL for total bacterial counts in the bedding. Based on these results and our observations, it appears that any of the bedding materials evaluated in this study used to substitute or partially substitute for sawdust can work well in compost dairy barns if the pack is consistently well managed by tilling twice daily, providing proper ventilation to keep surface of pack dry, and adding new material when it is visually adhering to the cows.

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 1,355kg 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.

Economical Value of Mycobacterium avium subsp paratuberculosis Fecal Shedding and Culling Due to Clinical Johne's Disease on Minnesota Dairy Farms

Johne's disease (JD) is increasingly recognized as an important disease in dairy cattle in USA and throughout the world. The National Animal Health Monitoring System (NAHMS, 1996) has estimated that the annual cost to infected U.S. dairy operations is over $100 per cow in inventory, with higher costs of more than $200 per cow in inventory per year in herds with high infection levels. It is not only that these estimations were performed more than 10 years ago, they were based on serum ELISA test results, which is known to have less sensitivity than bacterial fecal culture and therefore can bias any prevalence estimation. The scientific literature provides limited information about the economical impact of Mycobacterium paratuberculosis (Map) fecal shedding in dairy cattle on lactation performance. Quantification of the monetary impact of Map fecal shedding or clinical JD on lactation performance is critical to participation by dairy cattle producers in JD control programs, because it enhances the relationship between stage of disease and economic loss. This information will allow dairy producers to make appropriate management decisions within their operations regarding implementation of control measures to decrease herd JD prevalence. The objective of this study was to evaluate the economical cost of Mycobacterium paratuberculosis (Map) fecal shedding prior to calving and of cows that were culled due to clinical Johne's disease (CCJD) during the subsequent lactation.

The association between Mycobacterium avium subsp. paratuberculosis fecal shedding or clinical Johne's disease and lactation performance on two Minnesota, USA dairy farms

Lactation performance of cows infected with Mycobacterium avium subsp. paratuberculosis (Map) was previously studied using only serum ELISA as a diagnostic method. This study evaluated on two dairy farms in Minnesota, USA the lactation performance (measures of health, production, reproduction, and survival) of cows shedding Map in feces before calving and of cows culled with clinical signs consistent with Johne's disease (JD) during the subsequent lactation. Fecal samples were collected from 1052 cows within 21 day before calving and tested for Map with bacterial culture. Producers’ observed signs of clinical disease (milk fever, retained placenta, metritis, ketosis, displaced abomasum, lameness, mastitis, pneumonia, and JD) and production and reproduction data were recorded for each cow. The association between fecal shedding or clinical JD and lactation performance was evaluated. Logistic regression was used to evaluate the association with any clinical and subclinical diseases as the outcome. General linear model was used to evaluate the association with milk production, and survival analysis techniques were used to evaluate the association with days in the study before culling and days from calving to conception. In 84 cows (8% of 1052 cows) fecal samples were positive for Map (46% light, 26% moderate, and 28% heavy shedders). In multivariable analysis, light, moderate, and heavy fecal shedding cows produced on average 537, 1403, and 1534 kg, respectively, less milk per lactation and 1.4, 5.2, and 7.5 kg, respectively, less milk per day than fecal negative cows. Fecal culture positive cows were less likely to be bred and conceive. In the multivariable analysis the 56 cows culled with presumed JD produced approximately 1500 kg/lactation or 5 kg/day less than all other cows. The negative economic impact implied by decreased lactation performance in cows shedding Map or with clinical JD may motivate producers to implement programs to control Map infection and subsequent JD.

Prevalence and Characterization of Escherichia coli O157 Isolates from Minnesota Dairy Farms and County Fairs

Samples were collected from 26 organic and conventional farms and 12 county fairs in Minnesota during 2001 and 2002 to identify the presence of Escherichia coli O157. Immunomagnetic separation was used for isolation of E. coli O157. Isolates were further characterized by the presence of virulence marker genes (stx1, stx2, eaeA, E-hly, katP, etpD, and espP), antimicrobial susceptibility profiles, and genotypes. During 2001, E. coli O157 was isolated from 16 (5.2%) of 305 fecal samples and from 7 (36.8%) of 19 farms. During 2002, E. coli O157 was isolated from 6 (4.5%) of 132 fecal samples from weaned calves at 4 (23.5%) of 17 farms. During 2001 and 2002, cattle manure samples were collected from 12 county fairs, and E. coli O157 was isolated from 19 (11%) of 178 samples and 9 (75%) of 12 county fairs. Among 40 E. coli O157 isolates, 17 isolates (43%) had both the stx1 and stx2 genes, and 21 strains (53%) had the stx2 gene only. Thirteen percent of O157 isolates were resistant to tetracycline, and 25% were resistant to sulfadimethoxine. Heterogeneity of E. coli O157 strains was demonstrated by the presence of 22 different pulsed-field gel electrophoresis (PFGE) patterns. Four PFGE patterns matched those of isolates previously found in humans. The presence of E. coli O157 at county fairs suggests the potential for transmission to the public, who may have contact with cattle or their environment.

Herd-level factors associated with isolation of Salmonella in a multi-state study of conventional and organic dairy farms : II. Salmonella shedding in calves

The objective of this study was to evaluate associations between herd-level factors and the isolation of Salmonella in calves from dairy farms in Minnesota, Wisconsin, Michigan and New York. Study farms were 129 conventional and organic farms enrolled without regard to previous history of Salmonella infection. Herds were sampled at 2-month intervals over a 1-year period. Salmonella was isolated in fecal samples from 176 (3.8%) of 4673 preweaned calves with 40 (31.0%) of 129 farms having at least one positive calf sample over the course of the study. Multivariable logistic regression using the generalized estimating equations approach was used to evaluate risk factors for Salmonella shedding after adjustment for effects of herd size, season, state of origin and the multiple sampling occasions per herd. Factors retained in the final model that were associated with an increased odds for Salmonella shedding were lack of routine feeding of milk replacer containing antimicrobials to preweaned calves (OR = 2.8, 95% CI: 1.4, 5.8), use of maternity housing as a hospital area for sick cows more than once a month (OR = 2.1, 95% CI: 1.1, 4.0), and cow prevalence level by visit, categorized into the following four-levels: ≥20% (OR = 11.6, 95% CI: 5.7, 23.7), 10–19.9% (OR = 4.7, 95% CI: 2.0, 11.5), 0.1–9.9% (OR = 3.6, 95% CI: 1.5, 8.7) and 0% (reference level). Herd size was not associated with Salmonella shedding in the final multivariable model.

Cattle and environmental sample-level factors associated with the presence of Salmonella in a multi-state study of conventional and organic dairy farms

The objective of this study was to evaluate associations between cattle-level factors and environmental samples with the isolation of Salmonella from dairy farms in Minnesota, Wisconsin, Michigan, and New York. The study farms included 129 conventional and organic farms enrolled without regard to previous history of Salmonella infection. Herds were sampled at two-month intervals over a one-year period. Cattle groups more likely to be associated with Salmonella shedding (compared to preweaned calves) were cows designated as sick by farm personnel (OR = 2.5, 95% CI: 1.7, 3.7), cows within 14 days of calving (OR = 1.8, 95% CI: 1.1, 2.8), and cows due for culling within 14 days (OR = 1.9, 95% CI: 1.0, 3.4). State of origin was also associated with the presence of Salmonella in samples from cattle and the farm environment; Midwestern states were more likely to have Salmonella-positive samples compared to New York. Cattle treated with antimicrobials within 14 days of sampling were more likely to be Salmonella-negative compared with nontreated cattle (OR = 2.0, 95% CI: 1.1, 3.4). Farms with at least 100 cows were more likely to have Salmonella-positive cattle compared with smaller farms (OR = 2.6, 95% CI: 1.4, 4.6). Season was associated with Salmonella shedding in cattle, and compared to the winter period, summer had the highest odds for shedding (OR = 2.4, 95% CI: 1.5, 3.7), followed by fall (OR = 1.9, 95% CI: 1.2, 3.1) and spring (OR = 1.8, 95% CI: 1.2, 2.6). Environmental samples significantly more likely to be Salmonella-positive (compared to bulk tank milk) included, in descending order, samples from sick pens (OR = 7.4, 95% CI: 3.4, 15.8), manure storage areas (OR = 6.4, 95% CI: 3.5, 11.7), maternity pens (OR = 4.2, 95% CI: 2.2, 8.1), haircoats of cows due to be culled (OR = 3.9, 95% CI: 2.2, 7.7), milk filters (OR = 3.3, 95% CI: 1.8, 6.0), cow waterers (OR = 2.8, 95% CI: 1.4, 5.7), calf pens (OR = 2.7, 95% CI: 1.3, 5.3), and bird droppings from cow housing (OR = 2.4, 95% CI: 1.3, 4.4). Parity, stage of lactation, and calf age were not associated with Salmonella shedding.

Use of Environmental Sampling as a Herd Screening Diagnostic Tool for the Detection of Mycobacterium avium Subsp paratuberculosis on Minnesota Dairy Farms

Johne's disease (JD) is a chronic and progressive intestinal disease in ruminants caused by Mycobacterium avium subspecies paratuberculosis (Map). The usual route of infection is fecal-oral. The disease manifests in adult cows and results in economic losses. Although Map does not propagate in the environment, it survives for long periods in different environmental conditions expected on many dairy farms. Johne's disease control programs have been developed in different countries and in several US states with a goal to test and classify herds of cattle as infected or presumptively noninfected with maximum accuracy and least cost. Generally, these programs utilize recognized laboratory tests such as ELISA or direct microbiological individual fecal culture. However, these tests have several disadvantages, especially when applied in herds with subclinical disease or low prevalence. Since Map is shed into the environment by dairy cattle through fecal contamination and appears to survive well, a better understanding of Map distribution in the environment could lead to improved herd-screening alternatives.
 Objectives of the study were: 1) to describe Map distribution and prevalence in the environment on Minnesota dairy farms, and 2) to assess the relationship between culture status of Map in the farm environment and fecal-pooled culture status on dairy farms.