Relationships among bedding materials, bedding bacteria counts, udder hygiene, milk quality, and udder health in US dairy herds

A combination of calcium hydroxide and sodium hydrosulphate controls pathogens causing environmental mastitis in recycled manure solids

Recycled manure solids (RMS) are dried cow dung processed using a manure dewatering machine and subsequently sun-dried to ~ 20% moisture. Benefits of RMS include abundant availability, low cost, and eco-friendliness, but its use as bedding material for cows is hindered by a moisture content that promotes microbial growth. This in vitro study evaluated impacts of calcium hydroxide (CH; 5 and 7.5%) and sodium hydrosulphate (SHS; 6 and 8%), independently and in combinations, at various depths of RMS, on physicochemical and microbial properties. The CH-treated groups had increased pH and reduced moisture on Day 0. Incorporating 7.5% CH + 6% SHS at 15-20 cm, and 7.5% CH + 8% SHS at all depths, effectively suppressed Escherichia coli and Klebsiella spp. Furthermore, a combination of 7.5% CH + 8% SHS at 20 cm inhibited coliform growth, whereas 7.5% CH with 6% SHS inhibited Streptococcus spp. In conclusion, a combination of 7.5% CH with either 6 or 8% SHS at a depth of 15 cm in RMS was particularly effective in controlling environmental mastitis-causing pathogens, specifically E. coli and Klebsiella spp.

The Contribution of Dairy Bedding and Silage to the Dissemination of Genes Coding for Antimicrobial Resistance: A Narrative Review

Antimicrobial resistance (AMR) is a concern in the dairy industry. Recent studies have indicated that bedding serves as a reservoir for antimicrobial-resistant bacteria and antimicrobial-resistance genes (ARGs), while silage has been proposed as another possible source. The impact of AMR in dairy farming can be significant, resulting in decreased productivity and economic losses for farmers. Several studies have highlighted the safety implications of AMR bacteria and genes in bedding and silage, emphasizing the need for further research on how housing, bedding, and silage management affect AMR in farm environments. Exposure to sub-lethal concentrations of antibiotics, such as those from contaminated bedding and silage, can prompt bacteria to develop resistance mechanisms. Thus, even if antimicrobial usage is diminished, ARGs may be maintained in the dairy farm environment. By implementing proactive measures to tackle AMR in dairy farming, we can take steps to preserve the health and productivity of dairy cattle while also protecting public health. This involves addressing the prudent use of antibiotics during production and promoting animal welfare, hygiene, and management practices in bedding and farm environments to minimize the risk of AMR development and spread. This narrative review compiles the growing research, positioning the contribution of bedding and silage to the prevalence and dissemination of AMR, which can elicit insights for researchers and policymakers.

Impact of sample refrigeration and freezing on the bacteriological counts of different bedding materials for dairy cows

BACKGROUND

Different organic and inorganic bedding materials can be used in dairy farms. Among organic materials, there is an increasing interest in alternative substrates based on recycled manure solids (RMS). Microbiological analyses are crucial to monitor the microbial load and evaluate the presence of pathogens impacting animal welfare and health. However, logistic factors may hamper the possibility of immediately sending fresh samples to the laboratory, requiring storage in cooled conditions before analysis.

METHODS

We assessed the impact of sample refrigeration and freezing of different organic and inorganic bedding substrates including separated raw manure solids (SRMS), anaerobically digested manure solids (ADMS), and new sand (NS), on the total bacterial count (TBC) and on different microbial classes.

RESULTS

The TBC was higher in fresh NS and ADMS than in refrigerated and frozen samples of the same substrates; in addition, the TBC of ADMS was higher in refrigerated than frozen samples. The TBC of SRMS did not change significantly with refrigeration and freezing. Freezing reduced the total Gram-negative bacterial count more than refrigeration in all substrates. In fresh NS, Gram-negatives were higher than in both refrigerated and frozen NS. Escherichia coli counts were significantly lower in frozen than in refrigerated SRMS. However, both refrigeration and freezing of ADMS resulted in no E. coli growth. The coliform counts were also lower in frozen than refrigerated NS and SRMS. Frozen NS and ADMS showed lower counts compared to refrigeration for Gram-negative bacteria other than E. coli and coliforms. On the other hand, cold storage did not significantly impact the streptococci and streptococcus-like organisms (SSLO) count of all evaluated bedding substrates.

CONCLUSION

Refrigeration and freezing affect the bacteriological results of bedding substrates, with freezing generally leading to lower counts than refrigeration. Whenever possible, preference should be given to analyzing fresh bedding samples, however, when necessary, refrigeration would be recommended over freezing, while acknowledging that the measured bacterial load might underestimate the actual microbial content.

Comparisons of recycled manure solids and wood shavings/sawdust as bedding material-Implications for animal welfare, herd health, milk quality, and bedding costs in Swedish dairy herds

Increasing shortages and costs of common bedding materials have led dairy farmers in Sweden to consider using recycled manure solids (RMS), which are readily available and low cost, as an alternative bedding material. The main risks are effects on udder health and milk quality, but RMS could also affect animal welfare and claw health. The advantages and disadvantages of using RMS bedding have not been fully investigated, and findings in other countries cannot be directly applied to Swedish conditions and climate. This observational cross-sectional study investigated the use of RMS as bedding, regarding associations with certain aspects of animal welfare, herd health, milk quality, and bedding costs in Swedish dairy herds. Thirty-four dairy farms using RMS or wood shavings/sawdust (each n = 17) were compared. Each farm was visited 2 times during the housing period from 2020 to 2021, once from October to December and once from March to May. Dairy barns were observed, animal welfare was assessed, and freestall dimensions were measured. Farm owners were interviewed about housing system characteristics, herd performance, and herd management. Data on milk production and herd health were obtained from the Swedish official milk recording scheme for the indoor period from October to March. The prevalence of claw disorders and abnormal claw conformation were collected from the national claw health database for the period from October to May. On each farm visit, composite samples of unused bedding outside the barn and used bedding material from the freestalls, respectively, were taken for total bacterial count and DM analysis. Samples of bulk tank milk for determination of total bacterial count were taken in connection to the visits. In addition, samples of unused and used bedding material and manure from alleys for analysis of 3 Treponema species associated with digital dermatitis (DD) were gathered and analyzed. Total bacterial count was significantly higher in unused (8.50 log10 cfu/g) and used RMS bedding (9.75 log10 cfu/g) than in wood shavings/sawdust (used 4.74; unused 8.63 log10 cfu/g), but there were no significant differences in bulk milk total bacterial count (median 4.07 vs. 3.89 log10 cfu/mL) or SCC (median 243,800 vs. 229,200 cells/mL). The aspects of animal welfare assessed did not differ significantly between the 2 bedding systems, whereas the prevalence of total claw disorders (25.9% vs. 38.0% of trimmed cows), dermatitis (6.9% vs. 16.2% of trimmed cows) and sole ulcers (2.0% vs. 4.0% of trimmed cows) were significantly lower in the RMS herds. Treponema spp. were not detected in unused RMS material, but all RMS herds had presence of DD recorded at foot trimming. An economic assessment based on the interview results and price level from winter 2021 revealed that the costs of RMS bedding varied with amount of RMS produced. Thus, RMS is a potential alternative bedding material for dairy cows in Sweden and can be a profitable option for large dairy herds. However, the high level of total bacteria in the material requires attention to bedding and milking routines as well as regular monitoring of herd health.

Effect of a lime-based bedding conditioner on physical-chemical characteristics and microbiological counts of recycled manure solids

Bedding materials are aimed at providing a safe and comfortable resting environment for cows. Control of pathogen proliferation in these substrates is crucial to prevent intramammary infections in dairy cows, as these can significantly impact milk quality, cow health, and farm productivity. This is particularly relevant in the case of organic bedding substrates, including manure-derived materials. This study aimed to evaluate the in vitro effect of a lime-based conditioner (LBC), composed of CaCO3MgCO3 andCa(OH) 2 * Mg(OH)2, at increasing concentrations on the physical-chemical characteristics and bacterial counts of untreated anaerobically digested manure solids (ADMS) and separated raw manure solids (SRMS). Unused ADMS and SRMS were evaluated at four LBC weight-based concentrations: 0 (as untreated control), 10, 15, and 20% of LBC inclusion. The bedding materials were assessed immediately after LBC addition (0 h) and after 24, 72, and 168 h of storage at 28°C. The dry matter content (DM), and pH were measured for all the time points. Standard microbiological methods were used to assess total bacterial counts (TBC), other Gram-negative bacteria, coliforms, Escherichia coli, and streptococci and streptococci-like organism (SSLO). It was observed a linear increase in both DM and pH with increasing concentrations of LBC. Specifically, for each percentage unit increase of LBC, the DM of ADMS and SRMS increased by 0.73 and 0.71%, respectively. Similarly, for each percentage unit of LBC, the pH of ADMS and SRMS increased by 0.15 and 0.19, respectively. Conversely, a linear decrease in TBC, Gram-negative bacteria, coliforms, E. coli, and SSLO was observed with increasing concentrations of the LBC. Manure-derived materials without the inclusion of the LBC had bacterial counts that tended to remain high or increase over time. Otherwise, bedding materials with LBC application had reduced bacterial counts. Based on the results of the present study, it was observed that the higher the concentration of LBC, the more significant the reduction of bacterial counts. Specifically, bacterial recovery was lower when higher concentrations of LBC were applied. Our findings underscore the potential of LBC in effectively controlling environmental bacteria and improving the physical-chemical characteristics of manure-derived bedding materials to improve cow health and welfare.

Relationship Between Facility Type and Bulk Tank Milk Bacteriology, Udder Health, Udder Hygiene, and Milk Production on Vermont Organic Dairy Farms

The primary objective of this cross-sectional observational study was to determine whether bulk tank milk quality, udder health, udder hygiene and milk production outcomes were associated with facility type on organic dairies. A secondary objective was to identify other management-related risk factors associated with bulk tank milk quality, udder health, udder hygiene, and milk production on organic dairy herds in Vermont. We aimed to enroll 40 farms, to compare herds using the 2 most common systems (freestalls, tiestalls) for housing organic dairy cattle in the state with those using a bedded pack during the non-grazing season (typically November-May). Two general styles of bedded packs were observed: cultivated bedded packs and untilled deep bedded packs. Due to the limited number of herds using bedded packs to house lactating dairy cattle in Vermont, we combined untilled and cultivated bedded packs to describe udder hygiene, milk quality, and udder health on these loose-housing systems deeply-bedded with organic material. The study was completed on 21 farms (5 bedded packs, 6 freestalls, 10 tiestalls) before interruption due to the COVID-19 pandemic. Data captured from Dairy Herd Improvement Association records from the test closest to the date of the farm visit included average somatic cell score (SCS), standardized 150-d milk (pounds), % cows with current high SCS (SCS ≥ 4.0), % cows with newly elevated SCS (previous SCS < 4.0 to current ≥ 4.0), and % cows with chronically elevated SCS (SCS ≥ 4.0 last 2 tests). Multivariable linear regression models were used to describe outcomes by facility type, but suffered from limited statistical power due to small group sample sizes. Unconditional comparisons failed to find statistically significant differences between farms grouped by facility type in metrics captured from Dairy Herd Improvement Association test data, bulk tank milk somatic cell count (BTSCC) and aerobic culture data, or udder hygiene scores. A secondary analysis was conducted using univariate linear regression to identify associations between herd management factors and outcomes for all 21 farms combined. Although not all differences found were statistically significant in this secondary analysis combining all farms, numeric differences that may be biologically important are reported showing farms with deeper bedding had a lower BTSCC, lower newly elevated SCS, lower chronically elevated SCS, lower elevated current SCS, lower average SCS, and better udder hygiene metrics. Farms with lower mean udder hygiene scores had numerically lower chronically elevated SCS, lower elevated current SCS, and lower average SCS. We could not reject the null hypothesis that milk quality and udder health outcomes did not differ by facility type, and this does not preclude the existence of biological differences in these outcomes between facility types. The current study provides insight on factors affecting bulk tank milk quality, udder health and hygiene measures on organic dairy farms in Vermont. Bedded packs may be a viable option for confinement housing during the winter non-grazing season for pasture-based herds interested in a loose-housing system in the Northeastern US, but more research such as longitudinal studies with a larger sample size is needed to test this hypothesis.

Molecular and phenotypic identification of bacterial species isolated from cows with mastitis from three regions of Poland

BACKGROUND

Bovine mastitis is a widespread disease affecting dairy cattle worldwide and it generates substantial losses for dairy farmers. Mastitis may be caused by bacteria, fungi or algae. The most common species isolated from infected milk are, among others, Streptococcus spp., Escherichia coli, Staphylococcus aureus and non-aureus staphylococci and mammaliicocci. The aim of this paper is to determine the frequency of occurrence of bacterial species in milk samples from cows with mastitis from three regions of Poland: the north-east, the south-west and the south. To this end 203 milk samples taken from cows with a clinical form (CM) of mastitis (n = 100) and healthy animals (n = 103) were examined, which included culture on an appropriate medium followed by molecular detection of E. coli, S. aureus, Streptococcus agalactiae and Streptococcus uberis, as one of the most common species isolated from mastitis milk.

RESULTS

The results obtained indicated that S. uberis was the most commonly cultivated CM species (38%, n = 38), followed by S. aureus (22%, n = 22), E. coli (21%, n = 21) and S. agalactiae (18%, n = 18). Similar frequencies in molecular methods were obtained for S. uberis (35.1%) and S. aureus (28.0%). The variation of sensitivity of both methods may be responsible for the differences in the E. coli (41.0%, p = 0.002) and S. agalactiae (5.0%, p = 0.004) detection rates. Significant differences in composition of species between three regions of Poland were noted for E. coli incidence (p < 0.001), in both the culture and molecular methods, but data obtained by the PCR method indicated that this species was the least common in north-eastern Poland, while the culture method showed that in north-eastern Poland E. coli was the most common species. Significant differences for the molecular method were also observed for S. uberis (p < 0.001) and S. aureus (p < 0.001). Both species were most common in southern and south-western Poland.

CONCLUSIONS

The results obtained confirm the need to introduce rapid molecular tests for veterinary diagnostics, as well as providing important epidemiological data, to the best of our knowledge data on Polish cows in selected areas of Poland is lacking.

Conditioner application improves bedding quality and bacterial composition with potential beneficial impacts for dairy cow's health

Recycled manure solids (RMS) is used as bedding material in cow housing but can be at risk for pathogens development. Cows spend several hours per day lying down, contributing to the transfer of potential mastitis pathogens from the bedding to the udder. The effect of a bacterial conditioner (Manure Pro, MP) application was studied on RMS-bedding and milk qualities and on animal health. MP product was applied on bedding once a week for 3 months. Bedding and teat skin samples were collected from Control and MP groups at D01, D51, and D90 and analyzed through 16S rRNA amplicon sequencing. MP application modified bacterial profiles and diversity. Control bedding was significantly associated with potential mastitis pathogens, while no taxa of potential health risk were significantly detected in MP beddings. Functional prediction identified enrichment of metabolic pathways of agronomic interest in MP beddings. Significant associations with potential mastitis pathogens were mainly observed in Control teat skin samples. Finally, significantly better hygiene and lower Somatic Cell Counts in milk were observed for cows from MP group, while no group impact was observed on milk quality and microbiota. No dissemination of MP strains was observed from bedding to teats or milk.

IMPORTANCE

The use of Manure Pro (MP) conditioner improved recycled manure solids-bedding quality and this higher sanitary condition had further impacts on dairy cows' health with less potential mastitis pathogens significantly associated with bedding and teat skin samples of animals from MP group. The animals also presented an improved inflammation status, while milk quality was not modified. The use of MP conditioner on bedding may be of interest in controlling the risk of mastitis onset for dairy cows and further associated costs.

Staphylococcus aureus and biofilms: transmission, threats, and promising strategies in animal husbandry

Staphylococcus aureus (S. aureus) is a common pathogenic bacterium in animal husbandry that can cause diseases such as mastitis, skin infections, arthritis, and other ailments. The formation of biofilms threatens and exacerbates S. aureus infection by allowing the bacteria to adhere to pathological areas and livestock product surfaces, thus triggering animal health crises and safety issues with livestock products. To solve this problem, in this review, we provide a brief overview of the harm caused by S. aureus and its biofilms on livestock and animal byproducts (meat and dairy products). We also describe the ways in which S. aureus spreads in animals and the threats it poses to the livestock industry. The processes and molecular mechanisms involved in biofilm formation are then explained. Finally, we discuss strategies for the removal and eradication of S. aureus and biofilms in animal husbandry, including the use of antimicrobial peptides, plant extracts, nanoparticles, phages, and antibodies. These strategies to reduce the spread of S. aureus in animal husbandry help maintain livestock health and improve productivity to ensure the ecologically sustainable development of animal husbandry and the safety of livestock products.

Variations in milk, udder skin, and fecal microbiota and their relationships with blood metabolites and milk composition in dairy cows

This study examined the milk, udder skin, feces, and bedding microbiota in a dairy farm. Blood metabolites concentration and milk composition were also determined to examine their relationship with variations in the microbiota. Samples were collected from 10 healthy cows during the summers of 2018 and 2020. Milk protein, fat, and solid-not-fat contents were higher, and blood urea nitrogen and nonesterified fatty acid levels were lower in the 2020 samples. Principal coordinate analysis demonstrated that milk, udder skin, and fecal microbiota were separate groups. Year-to-year differences were distinct for milk and udder skin microbiota; however, the fecal microbiota of the 2018 and 2020 samples were similar. The bedding microbiota grouped with the udder skin microbiota of the 2018 samples. Although nonpathogens found as prevalent taxa in udder skin microbiota were likely to be found as abundant taxa in milk microbiota, selection and elimination occurred during transmission. Network analysis suggested that bacterial taxa of milk, udder skin, and fecal microbiota were unrelated to blood metabolites and milk composition, regardless of pathogens or nonpathogens.

Antibiotics in semen extenders - a multiplicity of paradoxes

Addition of antibiotics to semen extenders was taken for granted for many years, from the time that commercial artificial insemination in livestock first began many decades ago. However, there is now a growing realisation that this non-therapeutic utilisation of antibacterial agents is contrary to current recommendations for prudent use that medical and veterinary professionals are advised to follow. Furthermore, antibiotics are not benign, having negative effects on sperm samples, the inseminated female, personnel and potentially the environment. The purpose of this review is three-fold: to highlight the fact that antibiotics are used in semen extenders, with the result that considerable amounts are used globally in animal breeding, to review recent studies on the negative aspects of using antibiotics for this purpose, and to look at possible alternatives. Recent changes in the legislation regarding semen extenders occurred in some, but not all, countries, leaving question marks for semen producers as to whether antibiotics should be added to semen extenders or not.

Understanding mastitis: Microbiome, control strategies, and prevalence - A comprehensive review

Mastitis significantly affects the udder tissue in dairy cattle, leading to inflammation, discomfort, and a decline in both milk yield and quality. The condition can be attributed to an array of microbial agents that access the mammary gland through multiple pathways. The ramifications of this ailment are not merely confined to animal welfare but extend to the financial viability of the livestock industry. This review offers a historical lens on mastitis, tracing its documentation back to 1851, and examines its global distribution with a focus on regional differences in prevalence and antimicrobial resistance (AMR) patterns. Specific microbial genes and communities implicated in both mastitis and AMR are explored, including Staphylococcus aureus, Streptococcus agalactiae,Streptococcus dysagalactiae, Streptococcus uberis Escherichia coli, Klebsiella pneumoniae, Mycoplasma bovis, Corynebacterium bovis, among others. These microorganisms have evolved diverse strategies to elude host immune responses and neutralize commonly administered antibiotics, complicating management efforts. The review aims a comprehensive overview of the current knowledge and research gaps on mastitis and AMR, and to highlight the need for a One Health approach to address this global health issue. Such an approach entails multi-disciplinary cooperation to foster judicious antibiotic use, enhance preventive measures against mastitis, and bolster surveillance and monitoring of AMR in pathogens responsible for mastitis.

A short-term comparison of wheat straw and poplar wood chips used as litter in tiestalls on hygiene, milk, and behavior of lactating dairy cows

A short-term study was conducted to compare the effect of using poplar wood chips (PWC) instead of wheat straw (WS) litter in dairy cows. A total of 38 lactating Holstein cows (204 ± 119 days in milk, 26.9 ± 6.5 kg of milk yield [MY]) were housed in a tiestall farm for a 10-d trial including 5 d of adaptation followed by 5 sampling days (from d 5 to 10). Cows were divided into 2 homogeneous groups: one group was bedded with WS, and the second with PWC. Both litter materials were provided in the amount of 7 kg/stall per d. Each group was composed of 3 subgroups of 6 or 7 cows; the subgroups were physically separated along the feeding line by wooden boards. During the sampling days, fecal composition, used litter composition, and bacterial count (Clostridium spp., Salmonella spp., Escherichia coli, Lactobacillus, and total bacterial count) were analyzed by subgroup twice a day. On d 1 and from d 5 to 10, udder hygiene score and cow cleanliness score were also evaluated individually twice a day. Meanwhile MY, milk hygiene (total bacterial count [TBC], coliform bacterial count [CBC], and spore-forming units [SFU]) and quality were measured and analyzed from 9 animals per group. Moreover, individual animal behavior (body position and behavioral traits) and subgroup dry matter intake were measured on d 9 and 10. Fecal dry matter did not differ between groups, PWC had the lowest used litter moisture and N content favoring the highest clean cow frequency, but also gave rise to the greatest used litter microbial contamination. The MY, milk quality, TBC, SFU, and CBC were similar. The lying behavior frequency was similar between groups. However, the PWC group showed the lowest sleeping frequency, the highest frequency of other behaviors (including discomfort signs), and the lowest dry matter intake. However, despite this apparent reduction in cow comfort, no biologically important differences were observed in this short-term study between cows on PWC and WS in milk production or hygiene.

Comparison of non-aureus staphylococcal and mammaliicoccal species found in both composite milk and bulk-tank milk samples of dairy cows collected in tandem

Non-aureus staphylococci and the closely related mammaliicoccal species (NASM) are the most common causes of bovine subclinical mastitis on modern dairy farms and are highly prevalent in bulk-tank milk. The purpose of this study was to determine the distribution of NASM in both composite cow milk (CCM) and bulk-tank milk (BTM) samples collected in tandem in commercial Flemish dairy herds and to estimate the origin of the different (subgroups of) NASM species present in BTM by applying strain typing (random amplification of polymorphic DNA or random amplified DNA [RAPD]). A single cross-sectional sampling was performed over 5 herds that volunteered to participate in the study. Composite cow milk samples (n = 356) were collected from all lactating cows (except those with clinical mastitis) during a milking in tandem with 6 BTM samples per herd sequentially collected immediately post that milking (n = 30). In total, 421 and 80 NASM isolates were recovered and identified by MALDI-TOF mass spectrometry from the CCM and BTM samples, respectively and a total of 21 and 12 different NASM species were identified from CCM and BTM samples, respectively. Staphylococcus cohnii was the most prevalent NASM species found in BTM followed by Staphylococcus haemolyticus, Staphylococcus epidermidis, Mammaliicoccus lentus, and Staphylococcus equorum, whereas from CCM samples the most common species were S. hemolyticus, S. cohnii, S. equorum, S. epidermidis, and Staphylococcus chromogenes. The prevalent NASM species in both CCM and BTM samples was distinct for each herd, corroborating other studies observing a herd-specific NASM microbiota. Random amplified DNA analysis was performed on 9 NASM species (S. chromogenes, S. epidermidis, S. haemolyticus, S. equorum, Mammaliicoccus sciuri, Staphylococcus xylosus, S. cohnii, Staphylococcus debuckii, and M. lentus) because these species were isolated from both sample types in a herd. The same RAPD types were found in both sample types for all NASM species selected for strain typing in varying degrees. When assessing the distribution of NASM species, differences within NASM species should be examined meaning a closer look should be taken at the strain level rather than at the species level only.

Usefulness of the total and differential somatic cell count based udder health group concept for evaluating herd management practices and udder health in dairy herds

Subclinical mastitis and associated economic losses are a steady challenge in the dairy industry. The combination of the well-established somatic cell count (SCC) parameter and the new differential SCC (DSCC) opens up the possibility to categorise cows into four different udder health groups (UHG) based on results from a single milk recording/dairy herd improvement (DHI) test: UHG A: healthy/normal, ≤ 200,000 cells/mL and DSCC ≤ 65 %; B: suspicious, ≤ 200,000 cells/mL and DSCC > 65 %; C: (subclinical) mastitis, > 200,000 cells/mL and DSCC > 65 %; D: chronic/persistent mastitis, > 200,000 cells/mL and DSCC ≤ 65 %. The objectives of this study were to investigate 1) herd management practises among herds in different UHG categories and 2) herd performance parameters depending on the proportion of cows in UHG A. A total number of 41 herds in Styria, Austria, and Thuringia, Germany, were visited and interviewed for the first part of the study. The herds were categorised into 3 UHG categories depending on the proportion of cows in UHG A: I = >65 %; II = 55-65 %; and III = <55 %. Those with good udder health and best herd performance (+9 % milk yields, +11 % longevity, -35 % antibiotic treatments) applied distinct preventive measures, in particular excellent cubicle management and early antibiotic treatment (P < 0.05 each). However, preventive measures were applied to a lower extent in other herds. Herds were categorised differently using the UHG concept compared to SCC alone as the UHG-based categorisation allowed to clearer distinguish herds with medium-good from those with good udder health. A total number of 129,812 regular milk recording/DHI test day results of 890 Austrian and 183 German herds was used for the second part of the study. Results revealed a trend of increasing daily production as proportions of cows in UHG A increase. In conclusion, the UHG concept allowed clearer distinction of herds with good, medium-good, and poor udder health and could be used to promote practises leading to better animal health, less antibiotic treatments, and higher milk quality.

Use of Danish National Somatic Cell Count Data to Assess the Need for Dry-Off Treatment in Holstein Dairy Cattle

In Denmark, PCR testing of dairy cattle is commonly used to select animals for the antibacterial treatment of intramammary infection (IMI) during the dry-off period. IMI is associated with a high somatic cell count (SCC), routinely recorded for milk quality control for most commercial dairy herds. This study aimed to compare SCC curves over the lactation among dairy cows with positive vs. negative PCR test results for four major IMI pathogens. Data from 133,877 PCR-tested Holstein cows from 1364 Danish conventional dairy herds were used to fit a nonlinear mixed-effects model using a modified four-parameter Wilmink function. We stratified the data into first, second, third or fourth and later parity and fitted Wilmink curves to all SCC observations between 6 and 305 days in milk. The PCR tests were taken before dry-off at the end of the lactation to investigate which animals qualified for selective dry cow therapy. A PCR Ct-value of 37 and below was used to determine if an animal was PCR positive for any of the following IMI pathogens: Staphylococcus aureus, Streptococcus agalactiae, Str. dysgalactiae and Str. uberis. Our findings showed that mean SCC curve fits were higher for PCR-positive animals in all four parity groups and across lactations. The use of SCC data fitted to the entire lactation for multiple lactations enabled quantification of overall differences in SCC curves between cattle with and without detected IMI, adjusted for parity group and stage of lactation. These findings are relevant to the use of SCC to support treatment decisions.

Biofilm-Producing Ability of Staphylococcus aureus Obtained from Surfaces and Milk of Mastitic Cows

This study was conducted to evaluate the incidence of mastitis in 153 dairy cows and to evaluate the kinetics of adhesion of isolates obtained from surfaces and milk in comparison with the reference strain (RS), CCM 4223. The surfaces of the floor, teat cup, and cow restraints were aseptically swabbed in three replicates (n = 27). Of the total number of infected cows (n = 43), 11 samples were found to be positive for Staphylococcus aureus, 12 samples tested positive for non-aureus staphylococci, 6 samples tested positive for Streptococcus spp., and 11 samples tested positive for other bacteria (Escherichia coli, Pseudomonas spp.) or a mixed infection. The most represented pathogen in milk (11/43) and on surfaces (14/27) was S. aureus. The kinetics of adhesion of the reference strain and isolates of S. aureus on stainless steel surfaces were determined after 3, 6, 9, 12, 24, and 48 h, and 3, 6, 9, 12, and 15 days of incubation. All strains reached counts higher than 5 Log₁₀ CFU/cm² needed for biofilm formation, except RS (4.40 Log₁₀ CFU/cm²). The isolates of S. aureus revealed a higher capability to form biofilm in comparison with RS during the first 3 h (p < 0.001). Thus, there is a significant difference between the occurrence of S. aureus on monitored surfaces-floor, teat cup, and cow restraints-and the frequency with which mastitis is caused by S. aureus (p < 0.05). This finding raises the possibility that if various surfaces are contaminated by S. aureus, it can result in the formation of biofilm, which is a significant virulence factor.

Association between Mastitis Occurrence in Dairy Cows and Bedding Characteristics of Compost-Bedded Pack Barns

Compost-bedded pack barns (CB) are receiving increasing attention as a housing system that can potentially improve the welfare of dairy cows. This study characterized the frequency and profile of pathogens isolated from clinical (CM) and subclinical (SCM) mastitis in dairy cows housed in CB. It evaluated the association between mastitis occurrence and bedding characteristics in CB systems. Over six months, seven dairy herds were visited monthly for milk and bedding sample collections. Milk samples from mastitis cases were submitted to microbiological identification by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF MS). Bedding samples were submitted to physical-chemical (pH, organic matter, moisture, and carbon to nitrogen ratio) and microbiological counting (total bacterial counts, coliforms, streptococci, and staphylococci) analyses. Regression analysis was used to determine the association between mastitis occurrence and CB characteristics. Our results showed that Escherichia coli and environmental streptococci were the most frequently isolated pathogens from CM cases, while Staphylococcus chromogenes and contagious pathogens (Staphylococcus aureus and Streptococcus agalactiae) were the most commonly isolated from SCM cases. Bedding moisture content was positively associated with the incidence of CM. The bedding carbon to nitrogen ratio was negatively associated with the incidence of SCM, and the bedding total bacteria counts tended to be associated with the incidence of SCM. Bedding counts of coliforms positively associated with the prevalence of SCM. Our results can support decision-makers in the dairy industry seeking strategies for bedding management and mastitis control.

Impact of recycled manure solids bedding on hygiene and odds of hock lesions in dairy cows

The use of recycled manure solids (RMS) as bedding for dairy cows has become more popular over the last decade. Once producers own the RMS producing equipment, they are not restricted in the amount of bedding they can use in stalls, due to its large availability and low production costs. Thus, they are usually able to provide a soft lying area for their cows. Nevertheless, the potential positive impact of RMS on cows' hygiene and odds of hock lesions is not clearly demonstrated. Objectives of this research were, therefore, to compare RMS-bedded cows' hygiene level and odds of hock lesions to straw-bedded cows (comparative group). To achieve this, an observational cross-sectional study was conducted in 27 RMS- and 61 straw-bedded herds. During the farm visit, 30 cows per herd were scored for hygiene of three body regions (udder, lower legs and flank/upper legs) using a score ranging from 1 to 4 (1 being the cleanest and 4 the dirtiest). In addition, both hocks were scored (0 to 3) to evaluate the presence of lesions (0 when there was no lesion and 3 when a swelling protrusion > 2.5 cm was present). Continuation-ratio models were used to compute the odds of having a given score to the odds of having a lower score. Recycled manure solids usage was associated with lower odds of having an udder hygiene score ≥3 [odds ratio (OR): 0.43; 95% CI: 0.20, 0.95] and of having a score of 4 (OR: 0.29; 95% CI: 0.09, 0.93). It was also associated, compared to straw, with cleaner lower legs. We observed lower odds of having a score ≥2 (OR: 0.45; 95% CI: 0.21, 0.98), ≥3 (OR: 0.16; 95% CI: 0.04, 0.66), or a score of 4 (OR: 0.07; 95% CI: 0.01, 0.40) in RMS-bedded herds. No statistically significant association could be highlighted between RMS usage and flank/upper legs hygiene. Furthermore, we did not observe any statistically significant associations between bedding type (RMS vs. straw) and odds of hock lesions. In conclusion, cows bedded with RMS had generally cleaner udders and cleaner lower legs than straw-bedded ones. No association was found between bedding type and odds of hock lesions.

Compost Dairy Barn Layout and Management Recommendations in Kentucky: A Descriptive Study

This study was conducted to describe the building layout and dimensions, characterize the bedding material, and observe the management practices in 42 compost-bedded pack (CBP) barns in Kentucky (USA). The average herd size found in the study was 90 cows and the breeds consisted of Jersey (6.8%), Holstein (72.7%), and mixed (20.5%). The average CBP barn dimensions were 49.1 m (length) by 21.9 m (width). Many of these barns had feed alleys and driveways; overshot ridges with frequent orientation from NE to SW; and green sawdust, kiln-dried sawdust, or a mixture of both as the most common bedding materials. The bed-turning process was performed mechanically at depths of less than 0.25 m, and the loading of fresh material was performed every one to five weeks, varying by season, weather conditions, barn size, and cow density. The average bedding moisture content was found to be 59.0% (wet bulb-w.b.) and ranged from 36.2 to 71.8%. Coliforms were not present in barns that had a higher compost temperature, and the E. coli, Bacillus, and Streptococcus counts were higher in the barns that had a lower moisture content. In conclusion, it was observed that heterogeneous management was used among the barns and that the producers were satisfied with the compost barn system.

Graduate Student Literature Review: Farm management practices: Potential microbial sources that determine the microbiota of raw bovine milk

Environmental and herd-associated factors such as geographical location, climatic conditions, forage types, bedding, soil, animal genetics, herd size, housing, lactation stage, and udder health are exploited by farmers to dictate specific management strategies that ensure dairy operation profitability and enhance the sustainability of milk production. Along with milking routines, milking systems, and storage conditions, these farming practices greatly influence the microbiota of raw milk, as evidenced by several recent studies. During the past few years, the increased interest in high-throughput sequencing technologies combined with culture-dependent methods to investigate dairy microbial ecology has improved our understanding of raw milk community dynamics throughout storage and processing. However, knowledge is still lacking on the niche-specific communities in the farm environment, and on the factors that determine bacteria transfer to the raw milk. This review summarizes findings from the past 2 decades regarding the effects of farm management practices on the diversity of bacterial species that determine the microbiological quality of raw cow milk.

Distribution of staphylococcal and mammaliicoccal species from compost-bedded pack or sand-bedded freestall dairy farms

The purpose of this prospective observational study was to determine whether dairy cattle housing types were associated with staphylococcal and mammaliicoccal populations found on teat skin, bedding, and in bulk tank milk. Twenty herds (n = 10 sand-bedded freestall herds; n = 10 compost-bedded pack herds) were enrolled. Each herd was visited twice for sample collection, and at each visit, 5 niches were sampled, including bulk tank milk, composite teat skin swab samples collected before premilking teat preparation, composite teat skin swab samples collected after premilking teat preparation, unused fresh bedding, and used bedding. All samples were plated on Mannitol salt agar and Columbia blood agar and staphylococcal-like colonies were selected for further evaluation. Bacterial colonies were speciated using MALDI-TOF mass spectrometry. All species were grouped into 4 categories included host-adapted, opportunistic, environmental, and unclassified. Absolute numbers and proportions of each genus and species were calculated. Proportional data were compared between groups using Fisher's exact test. Data representing 471 staphylococcal-like organisms were analyzed. Overall, 27 different staphylococcal and mammaliicoccal species were identified. Staphylococcus chromogenes was the only species identified from all 20 farms. A total of 20 different staphylococcal-like species were identified from bulk tank milk samples with the most prevalent species being S. chromogenes, followed by Staphylococcus aureus and Mammaliicoccus sciuri. Overall, more staphylococcal and mammaliicoccal isolates were identified among used bedding than unused bedding. The increased numbers of isolates within used bedding were primarily from used sand bedding samples, with 79% (76/96) of used bedding isolates being identified from sand bedding and only 20.8% (20/96) from used compost-bedded pack samples. When comparing categories found among sample types, more unclassified species were found in used sand bedding than in used compost-bedded pack samples. This finding is possibly related to the composting temperatures resulting in reduced growth or destruction of bacterial species. The prevalence of S. aureus was high in bulk tank milk for all herds, regardless of herd type, which may represent the influence of unmeasured management factors. Overall, staphylococcal and mammaliicoccal species were highly prevalent among samples from both farm types.

Association Between Recycled Manure Solids Bedding and Subclinical Mastitis Incidence: A Canadian Cohort Study

Recycled manure solids (RMS) are increasingly used as bedding for dairy cows. However, potential impact of RMS bedding on animal health is not well described. The objective of this study was to evaluate subclinical mastitis incidence in cows housed on RMS bedding. Twenty RMS farms and a comparative group of 60 straw-bedded farms were enrolled in a 1-year longitudinal study (2018–2019). Data from 11,031 dairy cows were collected. Variations of individual somatic cell count were evaluated using three different methods. First, we compared the cow's mean lactation linear score between cows housed on the two bedding types. Then, we compared across bedding types the risk for a given cow of having a milk test with a linear score ≥ 4. Finally, we evaluated the dynamics of somatic cell count using pairs of tests within a cow. More specifically, we considered that only pairs of DHI tests where the first test yielded a linear score < 4 were at risk of an incident subclinical mastitis event. Then, we defined a newly acquired subclinical mastitis when the second test was ≥ 4. All models were adjusted for putative confounders. We could not highlight a significant association between bedding type and cow's mean lactational linear score (least square mean of 2.47 in cows from RMS farms vs. 2.37 in straw farms; 95%CI for linear score's difference: −0.20, 0.40). Furthermore, we could not find an association between bedding type and the risk of a high linear score (≥ 4). For the latter, cows housed on RMS had 0.93 times the risk of having a high linear score than straw-bedded cows (%95 CI: 0.68, 1.28). Moreover, cows on recycled manure solids farms had 0.73 time the risk of acquiring subclinical mastitis when compared to straw-bedded farms. Again, this risk was not statistically significant (%95 CI: 0.54, 1.00). In our study, RMS bedding was not associated with subclinical mastitis, as measured by somatic cell count, when compared to cows housed on a more conventional bedding, straw bedding.

Udder health, conceptual construct, and uses of the term: A systematic review from 1962 to 2019

Background and Aim:

Udder health management is essential for the further development of milk production systems and public health. This process depends on the generation of knowledge regarding control, prevention, and promotion of health. In scientific literature, it is impossible to find a synthesis of the categories that would allow comprehension of the complex phenomenon udder health. Different research approaches have allowed this polysemic concept, described by some researchers as multifactorial and by philosophical perspectives as a social phenomenon, to be further studied. Thus, the objective of this systematic review was to systematize the conceptual categories of udder health and the use of the term in the original articles published in the scientific literature from the period 1962 to 2019.

Materials and Methods:

A systematic review with a broad approach was designed by applying the phases of identification, screening, selection, and inclusion criteria described in the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes guide. An exhaustive search of original articles by specificity was carried out in the Science Direct, PubMed, Scielo, LILACS, and Google Scholar databases. The investigation was carried out on November 22, 2019. According to the inclusion criteria established, articles needed to be original studies, to be publications on bovine livestock, written in English, Spanish and Portuguese. Furthermore, the articles considered needed to tackle the term udder health so that its conceptual categorization could be extracted. Google Scholar patents and citations and articles removed from databases or not available were excluded from the study and those that, based on the reading of the complete text, considered the farming of animal species other than bovine. A qualitative synthesis of the year of publication, continent, approach, type of study, and conceptual category of udder health was carried out by calculating frequencies (Statistical Package for the Social Sciences version 24).

Results:

In total, 165 articles were included in the study. Eight conceptual categories, consolidated over time, were systematized, showing that udder health is not a static problem, and that science has been responding through the generation of new knowledge around conceptual categories as different udder health problems emerge.

Conclusion:

Culture and politics were two categories, related to all the others, that stood out in the results. These two categories were of great interest in countries advanced in milk production and in the implementation of udder health policies, which acknowledge the producer and other actors of the production chain as fundamental political actors for policies, decision-making processes, and public health care to be effective. The lack of synonyms for the term udder health (e.g., mastitis) may have led to the exclusion of important articles in each category. However, the constriction to the term udder health was intentional and aimed at constructing the concept. Udder health is hereby understood as a health-disease process, different from the term mastitis, which from its semantic origin, refers only to the disease process. According to this study, the concept can be understood through the categories of traditional epidemiology based on risk factors and disease; microbiology; genetics, resistance, and immunity; animal welfare; nutrition; organic production; culture; and politics.

The microbiome of common bedding materials before and after use on commercial dairy farms

Background

Bovine mastitis is one of the most economically important diseases affecting dairy cows. The choice of bedding material has been identified as an important risk factor contributing to the development of mastitis. However, few reports examine both the culturable and nonculturable microbial composition of commonly used bedding materials, i.e., the microbiome. Given the prevalence of nonculturable microbes in most environments, this information could be an important step to understanding whether and how the bedding microbiome acts as a risk factor for mastitis. Therefore, our objective was to characterize the microbiome composition and diversity of bedding material microbiomes, before and after use.

Methods

We collected 88 bedding samples from 44 dairy farms in the U.S. Unused (from storage pile) and used (out of stalls) bedding materials were collected from four bedding types: new sand (NSA), recycled manure solids (RMS), organic non-manure (ON) and recycled sand (RSA). Samples were analyzed using 16S rRNA sequencing of the V3–V4 region.

Results

The overall composition as well as the counts of several microbial taxa differed between bedding types, with Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes dominating across all types. Used bedding contained a significantly different microbial composition than unused bedding, but the magnitude of this difference varied by bedding type, with RMS bedding exhibiting the smallest difference. In addition, positive correlations were observed between 16S rRNA sequence counts of potential mastitis pathogens (bacterial genera) and corresponding bedding bacterial culture data.

Conclusion

Our results strengthen the role of bedding as a potential source of mastitis pathogens. The consistent shift in the microbiome of all bedding types that occurred during use by dairy cows deserves further investigation to understand whether this shift promotes pathogen colonization and/or persistence, or whether it can differentially impact udder health outcomes. Future studies of bedding and udder health may be strengthened by including a microbiome component to the study design.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-022-00171-2.

Effect of Peanut Shell and Rice Husk Bedding for Dairy Cows: An Analysis of Material Properties and Colostrum Microbiota

Simple Summary

The provision of appropriate bedding is important for the welfare of dairy cows. Before bedding can be selected, it is critical to understand the properties of the bedding, including its impact on milk microbiota. The objective of this article was to evaluate the influence of three materials for use as bedding on physicochemical properties, bacterial counts and colostrum microbiota of cows. Our results demonstrate that peanut shells appear to be a suitable bedding material for cows. These experiments provide empirical support for the use of peanut shells and rice husks as bedding material for dairy cows and illustrates the effects of bedding types on the colostrum microbiota of dairy cows.

Abstract

The aim of this study was to evaluate peanut shells and rice husks as bedding for dairy cows. We analyzed material properties including dry matter, water holding capacity, pH level and bacterial counts. Bedding treatments were compared with a one-way ANOVA using twelve cows split into three groups. Colostrum microbiota was analyzed by sequencing of the V3–V4 region of the 16S rRNA gene. Dry matter content was higher in rice husks compared with peanut shells. No treatment effects were found for water holding capacity and pH level. Streptococcus agalactia counts in peanut shell bedding were lower than in rice husk bedding, and Pseudomonas aeruginosa counts were not different between beddings. A significant enrichment for Enhydrobacter and Pantoea were detected in the colostrum of cows that used peanut shells compared with other beddings. Colostrum of cows housed on a peanut–rice combination had a greater relative abundance of Pseudomonas and Corynebacterium than those housed on peanut shells or rice husks. Higher numbers of Bacteroides, Akkermansia, Alistipes, Ruminococcaceae_UCG-014, Coriobacteriaceae_UCG-002 and Intestinimona were found in the colostrum of cows housed on rice husk bedding over other bedding types. These results suggest that bedding types were associated with the growth and diversity of colostrum bacterial loads. In addition, dry matter in peanut shells was lower than found in rice husks, but there was also a lower risk of mastitis for peanut shell bedding than other beddings.

Assessing the microbiota of recycled bedding sand on a Wisconsin dairy farm

BACKGROUND

Sand is often considered the preferred bedding material for dairy cows as it is thought to have lower bacterial counts than organic bedding materials and cows bedded on sand experience fewer cases of lameness and disease. Sand can also be efficiently recycled and reused, making it cost-effective. However, some studies have suggested that the residual organic material present in recycled sand can serve as a reservoir for commensal and pathogenic bacteria, although no studies have yet characterized the total bacterial community composition. Here we sought to characterize the bacterial community composition of a Wisconsin dairy farm bedding sand recycling system and its dynamics across several stages of the recycling process during both summer and winter using 16S rRNA gene amplicon sequencing.

RESULTS

Bacterial community compositions of the sand recycling system differed by both seasons and stage. Summer samples had higher richness and distinct community compositions, relative to winter samples. In both summer and winter samples, the diversity of recycled sand decreased with time drying in the recycling room. Compositionally, summer sand 14 d post-recycling was enriched in operational taxonomic units (OTUs) belonging to the genera Acinetobacter and Pseudomonas, relative to freshly washed sand and sand from cow pens. In contrast, no OTUs were found to be enriched in winter sand. The sand recycling system contained an overall core microbiota of 141 OTUs representing 68.45% ± 10.33% SD of the total bacterial relative abundance at each sampled stage. The 4 most abundant genera in this core microbiota included Acinetobacter, Psychrobacter, Corynebacterium, and Pseudomonas. Acinetobacter was present in greater abundance in summer samples, whereas Psychrobacter and Corynebacterium had higher relative abundances in winter samples. Pseudomonas had consistent relative abundances across both seasons.

CONCLUSIONS

These findings highlight the potential of recycled bedding sand as a bacterial reservoir that warrants further study.

Comparison of microbiota of recycled manure solids and straw bedding used in dairy farms in eastern Canada

Recycled manure solids (RMS) bedding is an alternative bedding option that is growing in popularity on Canadian dairy farms. However, the microbiological characteristics and production of RMS bedding are poorly documented under on-farm conditions in eastern Canada. This bedding could support the presence of pathogens and could have an effect on cow and human health. The aim of this study was to describe the RMS microbiota when used under dairy cows and compare it with straw bedding. Unused and used bedding from 27 RMS and 61 straw-bedded dairy farms were collected and compared using 16S amplicon sequencing, bacterial counts, and Salmonella spp. and Listeria monocytogenes detection. Microbiota composition of unused RMS and unused straw were different. After use, both bedding microbiota were similar in their bacterial composition, structure, and diversity. Unused RMS generally contained higher bacterial counts than did unused straw, except for Klebsiella spp. counts. Salmonella spp. and L. monocytogenes were more frequently detected in unused RMS (Salmonella spp.: 11%; L. monocytogenes: 30%), than in unused straw (Salmonella spp.: 0%; L. monocytogenes: 11%). Finally, 2 RMS production systems (extraction of the liquid fraction followed by maturation in an opened or enclosed container vs. in a heap) did not influence the microbiota richness and bacteria distribution (α-diversity), but did influence the microbiota structure (β-diversity). In conclusion, animal and human pathogens were found in greater numbers and more frequently in unused RMS than unused straw, and this could eventually affect dairy cow or human health.

Clinical Mastitis Incidence in Dairy Cows Housed on Recycled Manure Solids Bedding: A Canadian Cohort Study

Bedding can affect mammary health of dairy cows. The objectives of this study were to evaluate clinical mastitis incidence in cows housed on recycled manure solids bedding and, more specifically, to determine which pathogens were involved. We followed 26 recycled manure solids farms and 60 straw-bedded farms as a comparative group during 1 year (2018-2019). For each episode of clinical mastitis, defined as a visual alteration of the milk, with or without local or systemic signs of infection, producers sampled aseptically the affected quarter, provided some details about the animal, and sent the sample to the research team at the Université de Montréal. We received and analyzed 1,144 milk samples. The samples were cultured according to the National Mastitis Council guidelines and the different colony phenotypes were subsequently identified with mass spectrometry. In 54.6% of CM cases, a single phenotype of bacteria was cultured (pure culture), while two different phenotypes were found in 16.8% of the samples (mixed culture), and no growth was observed in 14.4% of the samples. Samples with three or more phenotypes were considered contaminated and were not included in the pathogen-specific analyses (14.3% of the submitted samples). The most frequently identified bacterial species in pure and mixed culture in farms using recycled manure solids were Streptococcus uberis (16.0%), Escherichia coli (13.8%), Klebsiella pneumoniae (13.2%), Streptococcus dysgalactiae (6.2%), and Staphylococcus aureus (3.4%). In straw farms, the most frequent species were S. aureus (16.6%), S. uberis (11.0%), E. coli (9.1%), S. dysgalactiae (8.0%), and K. pneumoniae (1.1%). The incidence of clinical mastitis (all cases together) was not higher in recycled manure solids farms (14.0 cases/100 cow-year; 95% CI: 8.3-23.7) compared with straw-bedded farms (16.3 cases/100 cow-year; 95% CI: 9.0-29.6). However, K. pneumoniae clinical mastitis episodes were 7.0 (95% CI: 2.0-24.6) times more frequent in recycled manure solids farms than in straw farms. Adjusted least square means estimates were 1.6 K. pneumoniae clinical mastitis cases/100 cow-year (95% CI: 0.8-3.4) in recycled manure solids farms vs. 0.2 cases/100 cow-year (95% CI: 0.1-0.6) in straw-bedded farms. Klebsiella pneumoniae clinical mastitis is in general severe. Producers interested in this bedding alternative need to be aware of this risk.

Prevalence, antibiotic resistance, virulence and genetic diversity of Staphylococcus aureus isolated from bulk tank milk samples of U.S. dairy herds

Background

Colonization of dairy cows by Staphylococcus aureus (S. aureus), especially those which are multi-drug resistant and toxin producing, is a concern for animal health and well-being as well as public health. The objective of this study was to investigate the prevalence, antibiotic resistance, gene content and virulence determinants of S. aureus in bulk tank milk samples (BTM) from U.S. dairy herds.

Results

BTM samples were collected, once in winter and once in summer, from 189 U.S. dairy herds. Of 365 BTM samples cultured, the sample and herd prevalence of S. aureus in BTM was 46.6% (170 of 365 samples) and 62.4% (118 of 189 herds), respectively. Among a subset of 138 S. aureus isolates that were stored for further analysis, 124 were genome sequenced after being confirmed as S. aureus using phenotypic tests. The most commonly identified antimicrobial resistance-associated gene was norA (99.2%) and mecA gene responsible for methicillin resistance (MRSA) was identified in one isolate (0.8%). The most frequently detected putative virulence genes were aur (100%), hlgB (100%), hlgA, hlgC, hlb (99.2%), lukE (95.9%) and lukD (94.3%). In the 53 staphylococcal enterotoxin positive isolates, sen (37.9%), sem (35.5%), sei (35.5%) and seg (33.1%) were the most frequently detected enterotoxin genes. Among the 14 sequence types (ST) and 18 spa types identified, the most common was ST2187 (20.9%) and t529 (28.2%), respectively. The most predominant clone was CC97 (47.6%) followed by CC unknown (36.3%). The single MRSA isolate belonged to ST72-CC8, spa type t126 and was negative for the tst gene but harbored all the other virulence genes investigated.

Conclusion

Our findings indicated a high prevalence of S. aureus in BTM of U.S. dairy herds, with isolates showing little evidence of resistance to antibiotics commonly used to treat mastitis. However, isolates often carried genes for the various enterotoxins. This study identified predominant genetic clones. Despite lower prevalence, the presence of MRSA and multi-drug resistant strains in BTM poses a significant risk to animal and public health if their number were to increase in dairy environment. Therefore, it is necessary to continuously monitor the use of antibiotics in dairy cows.

Description of the Characteristics of Five Bedding Materials and Association With Bulk Tank Milk Quality on Five New York Dairy Herds

Environmental mastitis represents a major challenge on dairy farms where contagious pathogens are controlled by improved milking procedures. Therefore, research focused on the environment is important to improve udder health programs. The objectives of this prospective and descriptive study were to (1) describe bedding bacterial counts, pH, and dry matter (DM) of five different bedding types (organic: manure solids, straw, paper fiber; inorganic: sand, recycled sand) and (2) explore the association between bedding bacterial counts with bulk tank milk quality. This study took place within five conveniently selected commercial dairy herds, each with a predominant bedding material in lactating pens. Bedding samples (used n = 237; fresh n = 53) were collected monthly from July 2018 to July 2019 following a standard operating procedure (SOP) to minimize sampling variability. Additionally, a bulk tank (BT) milk sample (n = 40) was collected on the same day unless milk had been picked up prior to arrival. Both BT and bedding samples were submitted to the laboratory for culture and bacterial identification and quantification of Streptococcus spp, coliforms, and non-coliforms as well as detection of several pathogens of mastitis importance. Somatic cell count was evaluated in BT samples. Within bedding type, the correlation between bedding characteristics and bacterial counts in bedding was evaluated using Pearson correlation. Within bedding type, the correlation between bacterial counts in bedding samples and bacterial counts in BT were determined. The Kruskal–Wallis test was used to evaluate the bacterial count by bedding type and to evaluate BT somatic cell count differences based on bedding type. In fresh bedding, bacterial counts were generally higher for manure solids for all bacterial groups compared with other materials. In used samples, organic materials had the highest levels of all bacterial groups. The proportion of samples with detectable organisms of mastitis importance varied within and among herds in both bedding and BT samples throughout the study period. In bedding samples, a higher DM content had the lowest levels of bacterial growth compared with those with lower DM content. Most bedding samples were on the alkaline side within a pH range of 8–11. No relationship between bacterial counts and pH was observed. No associations between BT bacteria counts and bedding bacterial counts were observed. No association between bulk tank somatic cell counts based on bedding type were observed. Despite using an SOP for bedding sampling in an effort to consistently collect samples, we still observed a large amount of variability both within and among bedding samples. This variability may have obscured any potential association between BT milk quality and bedding type.

Longitudinal study of herd udder hygiene and its association with clinical mastitis in pasture-based dairy cows

The objectives of this exploratory study were to (1) describe the association between herd-level udder hygiene and clinical mastitis and (2) investigate how sample size and milking stage affect the accuracy and precision of herd udder hygiene assessments made at milking time. A prospective longitudinal study was conducted in a dairy herd in Northern Australia as part of a previously published clinical trial of premilking teat disinfection. Video footage from 35 afternoon milkings was used to conduct 12,544 udder hygiene scores from 504 cows during an 89-d period and measure udder hygiene of the herd (proportion of cows with udder hygiene ≥3 out of 4). Linear interpolation was used to estimate herd udder hygiene on the days that were not scored, such that a herd-level udder hygiene measure was available for all cow-days in the study. Clinical mastitis events occurring during the study period were detected and recorded by farm staff according to a standardized definition. The relationship between herd udder hygiene on each of 1, 2, and 3 d before each study day (d -1, -2, and -3, respectively) and clinical mastitis at the cow level on each study day (each in turn being set as d 0) was determined using multivariable generalized estimating equations (family = Poisson, link = log), with the unit of analysis being the cow-day, adjusting for potential confounders and the clustering within the data. In addition, sampling strategies were evaluated by simulating herd udder hygiene assessments using a subset of cows in the herd. Herd udder hygiene from d -1, -2, and -3 was positively associated with clinical mastitis on d 0 (incidence rate ratio = 1.4 per 10-point increase in the percentage of cows with poor udder hygiene). Sampling strategy simulation found that at least 80 cows needed to be scored to achieve sufficiently precise estimations of herd udder hygiene. Furthermore, cows scored later during milking were slightly more likely to have poor udder hygiene than those scored earlier (risk ratio = 1.02 for cows that were 10% later in the milking order). More research is needed to evaluate risk factors for poor udder hygiene and potential interventions in pasture-based dairy cows.

Bacterial Load of the Teat Apex Skin and Associated Factors at Herd Level

Simple Summary

Bacterial load on the teat apex of dairy cows that causes intramammary infections is to a large extent due to environmental impacts. The aim of our study was to describe factors at herd level that are associated with bacterial load of environmental mastitis pathogens on the teat end’s skin. On visits to 31 dairy farms over a one-year period, farm conditions were documented, and environmental bacterial loads were examined. We found seasonal fluctuations and direct correlations between the temperature–humidity index (THI) in the barn and the bacterial load at the teat end. Significantly more environmental mastitis pathogens were found in herds with a high percentage of normal and slightly rough teat ends. The time since the last fresh bedding was added to the cubicles, as well as the frequency in which cubicles were cleaned, also affect the pathogen load on the teat skin. Pre-cleaning teats before milking as well as post-dipping after milking showed a decreasing effect of teat-skin bacterial load at the herd level.

Abstract

In order to reduce antimicrobial treatment and prevent environmental mastitis, the aim of the present study was to investigate associations between herd level factors and microbial load on teat ends with environmental mastitis pathogens. Quarterly farm visits of 31 dairy farms over a one-year period were used for statistical analysis. During each farm visit, teat-skin swabs, bedding and air samples were taken and management practices and herd parameters were documented. Total mesophilic bacteria, esculin-positive streptococci and coliform bacteria were examined in the laboratory procedures from teat skin and environmental samples. Esculin-positive streptococci and coliform bacteria on teat ends increased with high temperature–humidity indices (THI) in the barn during the spring and summer. Significantly more coliform bacteria on teat ends were found in herds with an increased percentage of normal or slightly rough teat ends. Cleaning cubicles more frequently, pre-cleaning teats before milking as well as post-dipping them after milking had a decreasing effect of teat-skin load with total mesophilic and coliform bacteria at the herd level. To conclude, teat-skin bacterial load with environmental pathogens is subject to fluctuations and can be influenced by aspects of farm hygiene.

Randomized equivalence study comparing the efficacy of 2 commercial internal teat sealants in dairy cows

The use of an internal teat sealant (ITS) at dry-off has been repeatedly shown to improve udder health in the subsequent lactation. However, almost all ITS research conducted in North America has evaluated one product (Orbeseal, Zoetis, Parsippany, NJ). The objective of this study was to evaluate a new ITS product (Lockout, Boehringer-Ingelheim Animal Health, Duluth, GA), by comparing it directly to Orbeseal in a multi-site, randomized, positively controlled equivalence trial for health indicators during the dry period [quarter-level new intramammary infection (IMI) risk, IMI cure risk, and IMI risk at 1 to 13 d in milk, DIM] and during the first 100 DIM [clinical mastitis and culling or death risk and test-day milk somatic cell count (SCC) and milk yield]. At dry-off, cows were randomly allocated to be treated with Orbeseal or Lockout after blanket administration of a cloxacillin dry cow therapy product. Cows were then followed from dry-off until 100 DIM. Intramammary infection status at enrollment and at 1 to 13 DIM was determined using standard bacteriological methods, allowing for the measurement of IMI dynamics during the dry period (i.e., IMI cures and new IMI). The effect of ITS group on dry period IMI cure, dry period new IMI, and IMI risk at 1 to 13 DIM was determined using generalized linear mixed models (logistic). Marginal standardization was used to derive risk difference estimates. An equivalence hypothesis test was conducted to compare ITS groups for dry period new IMI risk (margin of equivalence was ±5% units). The effect of ITS group on clinical mastitis and culling or death was determined using Cox proportional hazards regression. The effect of ITS group on test-day SCC and milk yield was determined using linear mixed models. Final models indicated that measures of quarter-level IMI dynamics were similar between ITS groups (i.e., risk difference estimates and 95% confidence intervals all close to zero). Furthermore, Lockout was found to be equivalent to Orbeseal for dry period new IMI risk using an equivalence hypothesis test. Hazard ratio estimates for clinical mastitis and culling or death were close to 1 and differences in SCC and milk yield between ITS groups were close to 0, indicating negligible effects of ITS group on test-day SCC and milk yield. In most cases, these effect estimates were relatively precise (i.e., narrow 95% confidence intervals). We conclude that producers using blanket dry cow therapy could consider including Orbeseal or Lockout treatment in their programs.

Cattle barn bedding from recycled manure: some veterinary, technological and economic aspects of application

Agriculture modernization is a topical issue for both the global and domestic economy. Intensification of livestock farming results in an increased production of manure. Recycling of manure into bedding is one of the modern utilization technologies. National regulations do not specify requirements for currently applied bedding types, including manure-based bedding. The foreign experience, however, demonstrates several economic, zootechnical and hygienic advantages of this material. The field veterinary study revealed the positive health effect of bedding. The cows housed without bedding featured threefold higher risk of surgical diseases of limbs. Technical and economic assessment of a dairy farm with 1000 dairy cows showed the following annual operating costs when the major part of manure was passively composted and a part of manure was recycled into the bedding by (1) aerobic solid-state fermentation in a chamber fermenter and finish drying in a dryer drum – 24.2 million roubles; (2) aerobic solid-state fermentation in a drum fermenter – 21.7 million roubles; and (3) thermal drying in a dryer drum – 27.5 million roubles. At the same time, if all manure produced was composted and the bedding was purchased from external sources, the costs would be 27.9 to 35.2 million roubles depending on the bedding material.