DRY COW ANTIMICROBIALS USE TO CONTROL MASTITIS IN NORTHERN ALGERIA

The control of mastitis is a crucial step in the preparation of the next lactation in dairy cows. In order to assess the practices and attitudes surrounding the use of antimicrobials at dry-off, a survey was conducted among veterinary practitioners in fifteen provinces of Northern Algeria. The results revealed that 45.95% of the farms followed by the respondents were rather small in size comprising about ten cows per farm and that a large majority of the farmers practised gradual drying off (72.97%) without adjusting the feed ration (70.27%) to this stage. Antibiotic dry cow therapy (DCT) was a common practice and selectively performed in 86.49% of cases regardless of udder health status. Cefalexin was the most infused intra-mammary (IMM) antibiotic (40.54%), while tylosin was the one favoured for parenteral administration (48.15%). Analysis of factors influencing the antibiotic DCT efficacy showed that a frequent (13.51%) occurrence of new intramammary infections (IMIs) was related to farmers’ attitudes (self-medication) and the policy of blanket DCT. Although the use of a teat sealant was uncommon (71.43%) in the farming traditions, the substitution of antibiotics seems to be a plausible prospect, since the majority of participants (89.19%) agreed with the implementation of aromatherapy concept at dry-off, mainly as a complement to antibiotics. This survey gives an overview of risk practices regarding mastitis management in northern Algeria. Hence, further zootechnical, veterinary and organizational efforts need to be made to promote animal production and welfare as well as public health through improved udder health.

Antimicrobial Usage for the Management of Mastitis in the USA: Impacts on Antimicrobial Resistance and Potential Alternative Approaches

Mastitis is the most frequently diagnosed disease of dairy cattle responsible for the reduction in milk quantity and quality and major economic losses. Dairy farmers use antibiotics for the prevention and treatment of mastitis. Frequent antimicrobial usage (AMU) undeniably increased antimicrobial resistance (AMR) in bacteria from dairy farms. Antimicrobial-resistant bacteria (ARB) from dairy farms can spread to humans directly through contact with carrier animals or indirectly through the consumption of raw milk or undercooked meat from culled dairy cows. Indirect spread from dairy farms to humans can also be through dairy manure fertilized vegetables or run-off waters from dairy farms to the environment. The most frequently used antibiotics in dairy farms are medically important and high-priority classes of antibiotics. As a result, dairy farms are considered one of the potential reservoirs of ARB and antimicrobial resistance genes (ARGs). To mitigate the rise of ARB in dairy farms, reducing AMU by adopting one or more of alternative disease control methods such as good herd health management, selective dry-cow therapy, probiotics, and others is critically important. This chapter is a concise review of the effects of antimicrobials usage to control mastitis in dairy cattle farms and its potential impact on human health.

Herd Routines and Veterinary Advice Related to Dry-Cow Therapy and Treatment with Internal Teat Sealants in Dairy Cows

Dry-cow therapy with antibiotics (DCT) and treatment with internal teat sealants (ITS) are often used to control mastitis in dairy cows. However, the knowledge on farmer and veterinary compliance with recommendations for DCT and ITS is scarce. Thus, the main aim was to collect information on farmer routines and veterinary advice for such treatments. Associations with herd and veterinary variables were also studied. Web-based questionnaires including questions on demographics and the use of DCT and ITS were sent to 2472 farmers and 517 veterinarians in Sweden. The answers were summarized descriptively, and associations with demographics were evaluated using univariable regression models. The response rate was 14% for farmers and 25% for veterinarians. Among the farmers, 81% used selective DCT (SDCT), 3% used blanket DCT (BDCT), and 16% did not use DCT. Almost all (93%) veterinarians prescribed DCT and among those most recommended SDCT while 8% recommended BDCT. Eighty-two percent of the farmers did not use ITS and 45% of the veterinarians never prescribed ITS. Milking system and milk production, and post-graduate training and number of mastitis cases per month were associated with the largest numbers of farmer and veterinary answers, respectively. In conclusion, many farmer routines and veterinary advice complied with the recommendations available at the time, but a clear need for more education was also identified. The results also indicated that an up-date of the national recommendations was warranted.

The Genetic Relatedness and Antimicrobial Resistance Patterns of Mastitis-Causing Staphylococcus aureus Strains Isolated from New Zealand Dairy Cattle

Staphylococcus aureus is one of the leading causes of bovine mastitis worldwide and is a common indication for use of antimicrobials on dairy farms. This study aims to investigate the association between on-farm antimicrobial usage and the antimicrobial resistance (AMR) profiles of mastitis-causing S. aureus. Whole-genome sequencing was performed on 57 S. aureus isolates derived from cows with either clinical or subclinical mastitis from 17 dairy herds in New Zealand. The genetic relatedness between isolates was examined using the core single nucleotide polymorphism alignment whilst AMR and virulence genes were identified in-silico. The association between gene presence-absence and sequence type (ST), antimicrobial susceptibility and dry cow therapy treatment was investigated using Scoary. Altogether, eight STs were identified with 61.4% (35/57) belonging to ST-1. Furthermore, 14 AMR-associated genes and 76 virulence-associated genes were identified, with little genetic diversity between isolates belonging to the same ST. Several genes including merR1 which is thought to play a role in ciprofloxacin-resistance were found to be significantly overrepresented in isolates sampled from herds using ampicillin/cloxacillin dry cow therapy. Overall, the presence of resistance genes remains low and current antimicrobial usage patterns do not appear to be driving AMR in S. aureus associated with bovine mastitis.

The Relationship between Animal Welfare and Antimicrobial Use in Italian Dairy Farms

Information regarding the relationship between animal welfare (AW) and antimicrobial use (AMU) in dairy cows is limited. The current study aimed to investigate this relationship on Italian farms and to identify potential targets of AMU reduction. The study was performed at 79 Italian dairy farms housing over 15,000 cows during 2019. AW was scored with an on-farm protocol assessing farm management and staff training, housing systems, and animal-based measures. AMU was estimated using a defined daily dose per kg of animal biomass (DDDAit/biomass) for Italy. The median AW score was 73% (range: 56.6–86.8%). The median AMU was 4.8 DDDAit/biomass (range: 0–11.8). No relationship between the total AMU and AW was found. Management and staff training were positively associated with the use of the European Medicines Agency’s category B antimicrobials, which are critical for human medicine, and with intramammary products for dry cow therapy. In those farms, antimicrobial stewardship should aim to reduce the category B antimicrobials and selective dry cow therapy. Our results underline the importance of implementing both an integrated monitoring system (AW, AMU, etc.) and antimicrobial stewardship tailored to the specific needs of each dairy farm.

Managing dry cow udder health

The dry period lays a foundation for a successful next lactation, especially from the udder health perspective. It is a high-risk period for acquiring new intramammary infections (IMI), but it also provides an excellent opportunity for eliminating existing subclinical infections. The way cows are dried off and milking is halted at the end of lactation impacts the involution process, mammary health and cow comfort. Antibiotic dry cow therapy (DCT) has played a crucial part in mastitis control, but due to global concerns about increasing antibiotic resistance, the approach to DCT is evolving. This chapter reviews the current knowledge about the impact of milk cessation methods (abrupt vs. gradual dry-off) on mammary involution, udder health and cow comfort. The importance of dry cow therapy is discussed, especially in the light of current global concerns related to antibiotic resistance.

Effectiveness of dry cow therapy and/or internal teat sealant on existing infections in smallholder dairy farms in Kenya

Background and Aim: Dry cow therapy (DCT) can be an effective treatment of mastitis that has not responded to conventional treatment during lactation. The aim of this study was to establish the effectiveness of DCT options available in reducing intramammary infections in smallholder dairy farms in Kiambu County, Kenya. Materials and Methods: The study targeted smallholder dairy farms which were registered at the local dairy cooperatives and which had cows that were at the point of dry-off. A total of 32 cows with 121 quarters that were California Mastitis Test (CMT) positive were recruited, with the quarters randomly allocated to receive either DCT (DCT – neomycin sulfate, penethamate hydriodide, and procaine benzylpenicillin) and internal teat sealant (ITS) or ITS alone (bismuth nitrate) after aseptically collecting quarter milk samples for bacterial culture. Farm- and animal-level factors were captured through a questionnaire which was administered to the principal farmer or a person who was managing the animals. Post-calving, milk samples were also collected for bacterial culture to establish if the infection was cleared or if there was a new infection. Results: DCT with ITS significantly reduced the proportion of quarters infected with Staphylococcus aureus from 64.0% at dry-off to 44.0% post-calving (35% reduction). In the control group, ITS alone, there was a small reduction in proportions of S. aureus from 46.8% to 40.4%. Proportions of quarter infections by coagulase-negative Staphylococcus in the treatment group reduced from 16.0% at dry-off to 2.0% post-calving, with a significant reduction in the control group too from 19.1% to 4.3%, which could be due to self-cure. Actinomyces species, Escherichia coli, Streptococcus species, and Pseudomonas species proportions slightly increased in the treatment group, as did E. coli and Pseudomonas species proportions in the control group. Conclusion: In smallholder dairy farms with subclinical mastitis, DCT of CMT-positive cows leads to a significant decrease of S. aureus infections at calving.

Antimicrobial susceptibility profile of Streptococcus agalactiae strains isolated from bovine mastitis

Bovine mastitis is the most important disease of dairy herds worldwide. Its main etiologic agents are bacteria, including Streptococcus agalactiae. The importance of this agent in bovine mastitis is because it is highly contagious and has a high impact on the occurrence of clinical mastitis cases and in the increase of the bulk milk somatic cell counts. The dry cow therapy and the treatment of the clinical mastitis cases stand out among the measures to control intramammary infections in cows. However, these strategies require knowledge about the antimicrobial susceptibility of the causal microorganisms. Thus, this study aimed to evaluate the antimicrobial susceptibility of 89 S. agalactiae strains isolated from bovine mastitis between the years 2004 and 2008 in dairy herds from Campo das Vertentes region, Minas Gerais State, Brazil. The disc diffusion technique was used and the antimicrobials currently used in mastitis therapy were tested. The isolates tested showed 100% susceptibility to chloramphenicol, ceftiofur, cefotaxime, enrofloxacin, and cefquinome. High frequencies of susceptibility (>95%) were also observed for the beta-lactams (penicillin G, ampicillin, and oxacillin), cephalosporins (cephalotin, ceftiofur, cefotaxime, cefoperazone, and cefquinome), florfenicol, gentamicin, lincomycin, nitrofurantoin, and sulfamethoprim. The strains showed high frequencies of resistance to neomycin (15.74%), and tetracycline (21.35%). Multidrug resistance was detected in 2.25% of the tested isolates. The results pointed to variations in the antimicrobial susceptibility profiles of the studied strains and the importance of the use of the susceptibility tests to determine the correct antimicrobial to be applied in the treatment of bovine mastitis caused by S. agalactiae. The high frequencies of resistance observed to some antimicrobials, such as neomycin and tetracycline, commonly used in the treatment of mastitis and other pathologies, highlighted the need for more judicious use of antimicrobials on dairy farms.

Cultura microbiológica na fazenda - revisão

Mastitis can be considered the main obstacle to Brazilian dairy productivity, resulting in further risks to public health, especially due to the indiscriminate use of antimicrobials. Therefore, technologies that aim to contribute to the dynamization of the diagnosis and the consequent adoption of control, prevention and treatment measures are of high importance for the sector. In this sense, the present review addresses the concept of on-farm culturing (microbiological), arguing about its implementation, available methodologies, execution and results interpretation. In addition, the performance of selective dry cow therapy, and health monitoring of animals submitted to robotic milking systems is argued in view of on-farm culture routine. In conclusion, it is an efficient alternative for on-farm microbiological monitoring of mastitis.