The association between teat end hyperkeratosis and teat canal microbial load in lactating dairy cattle

Most pathogens that cause bovine mastitis invade the udder lumen through the teat canal. Amino acids and intercellular lipids may support microbial colonisation of the teat canal epithelium by pathogenic microorganisms. The aim of this study was to investigate the association between teat end hyperkeratosis, which is induced by machine milking, and teat canal microbial load. Contralateral teats, which differed in teat end hyperkeratosis scores, were identified in a split-udder experiment. The teat canal's microbial load was evaluated using the wet and dry swab technique. Staphylococcus (S.) aureus, Streptococcus (Sc.) uberis, Escherichia (E.) coli and other coliforms were detected by agar plate cultures. The positive detection of E. coli and the log(10)-transformed E. coli load of a teat canal were significantly associated with the teat end hyperkeratosis score (P<0.05). There were significant differences with respect to positive findings for E. coli, as well as the microbial load of E. coli and Sc. uberis, between the less-calloused and the more-calloused teat of a pair. For S. aureus, no significant associations between hyperkeratosis score and teat canal microbial load were detected. In general, a teat with a highly calloused teat end had an increased teat canal microbial load compared with the contralateral teat, characterised by a lower callosity. The results of the present study indicate that the environmental pathogen load is associated with teat end hyperkeratosis. Further research is needed to identify factors that may affect teat canal microbial load in lactating dairy cattle.     

Teat canal closure in non-lactating heifers and its association with udder health in the consecutive lactation

Prevention of heifer mastitis is a key element in preventing mastitis. Since pathogenesis of heifer mastitis is not fully understood yet, combating it is arduous. The goal of this study was to examine whether the premature loss of the keratin plug of the teat canal represents an important risk factor for the development of heifer mastitis. 84 dairy heifers (German Holstein) from six high-yielding dairy herds in Northern Germany were examined between March 2005 and June 2006. Each quarter was examined clinically at least three times before calving. If the teat canal of a quarter was open, secretion samples were collected for bacteriological analysis. After calving, four quarter samples were collected during the first lactation. A rapid increase of the proportion of open teat canals was detected in the preparturition period. No teat canals were open till 80 days before parturition, while 60% of the teat canals were open at 60 days before parturition. A time-scheduled infection pattern was observed: during the days 90-61, 60-31, and 30-0 before calving, skin inhabitants (coagulase-negative staphylococci, coryneform bacteria), cow-related, and environment-related microorganisms prevailed, respectively. A total of 77% of intramammary infections encountered at parturition had established previously. No significant association between the duration of open teat canals before calving and the udder health post partum was found. However, the incidence of clinical mastitis during first lactation was influenced largely by the duration of infection ante partum and the mastitis pathogen involved. This study shows that a high proportion of teat canals already opens several months before calving and that opening of the teat canal before calving is an important factor in the aetiology of heifer mastitis.     

Scanning electron microscopy-aided observations on and therapy of teat canal infections

An examination of teat canal swabs established that 51 teat canals out of 68 quarters of machine-milked cows were colonized by Staphylococcus aureus. Only 31 of these quarters yielded milk from which S. aureus could be cultured, and 6 out of the 31 produced milk containing somatic cell counts in excess of 500 000/ml. No inhibitory substances could be detected in milk samples 12 h after 10 mg of sodium cloxacillin had been deposited in the test canal on 1-4 successive occasions. Teat canal swabs and milk sample cultures of the same quarters became and remained bacteriologically negative for at least a week after the last treatment. Six quarters, which according to the International Dairy Federation criteria were suffering from subclinical mastitis, became negative after local teat canal therapy. Scanning electron micrographs of one infected teat canal revealed the presence of cocci in depressions and crevices on the epithelial surface, suggesting that such cocci are not always flushed out into milk samples. Teat canal therapy should make a marked contribution to the control of bovine mastitis.     

Prepartum teat apex colonization with Staphylococcus chromogenes in dairy heifers is associated with low somatic cell count in early lactation

A high number of dairy heifers freshen with udder health problems. The prevalence of teat apex colonization (TAC) with Staphylococcus chromogenes, one of the most widespread coagulase-negative staphylococci (CNS) in milk samples from freshly calved dairy heifers, was measured cross-sectionally in non-lactating heifers on eight commercial dairy farms in Belgium. The influence of age on this prevalence, and the association between teat apex colonization with S. chromogenes prepartum and quarter milk somatic cell count (SCC) in early lactation were studied. In total, 492 teat apices were sampled from 123 heifers. The age of the heifers varied from 8 to 34 months. Overall, 20% of the heifers had at least one teat apex colonized with S. chromogenes. Of all teats sampled, 10% were colonized with S. chromogenes. The chance of having at least one teat apex colonized with S. chromogenes increased with age of the heifer. The presence of prepartum teat apex colonization with S. chromogenes was not associated with intramammary infection (IMI) early postpartum with the same bacterium. On the contrary, teat apex colonization with S. chromogenes prepartum appeared to protect quarters in the first few days of lactation from having somatic cell count >or=200000cells/ml milk, commonly accepted as the threshold for intramammary infection.     

Coagulase-negative staphylococci-emerging mastitis pathogens

Coagulase-negative staphylococci (CNS) have become the most common bovine mastitis isolate in many countries and could therefore be described as emerging mastitis pathogens. The prevalence of CNS mastitis is higher in primiparous cows than in older cows. CNS are not as pathogenic as the other principal mastitis pathogens and infection mostly remains subclinical. However, CNS can cause persistent infections, which result in increased milk somatic cell count (SCC) and decreased milk quality. CNS infection can damage udder tissue and lead to decreased milk production. Staphylococcus simulans and Staphylococcus chromogenes are currently the predominant CNS species in bovine mastitis. S. chromogenes is the major CNS species affecting nulliparous and primiparous cows whereas S. simulans has been isolated more frequently from older cows. Multiparous cows generally become infected with CNS during later lactation whereas primiparous cows develop infection before or shortly after calving. CNS mastitis is not a therapeutic problem as cure rates after antimicrobial treatment are usually high. Based on current knowledge, it is difficult to determine whether CNS species behave as contagious or environmental pathogens. Control measures against contagious mastitis pathogens, such as post-milking teat disinfection, reduce CNS infections in the herd. Phenotypic methods for identification of CNS are not sufficiently reliable, and molecular methods may soon replace them. Knowledge of the CNS species involved in bovine mastitis is limited. The dairy industry would benefit from more research on the epidemiology of CNS mastitis and more reliable methods for species identification.     

Resistance mechanisms of the bovine udder: new implications for mastitis control at the teat end

Investigations on bovine teat-end defenses and their role in mastitis control were reviewed. Alteration of teat canal keratin by method of intramammary drug infusion through the teat canal influenced the number of new infections. At the beginning of the nonlactating period, 2 methods of administering antibiotic were studied: full insertion of treatment syringe cannulas into teat cisterns and expelling contents and partial insertion of cannulas into the distal 2 to 3 mm of teat canals and slowly infusing contents. Partial cannula insertion reduced new infections by 50% and is an easily adopted management tool to reduce prevalence of mastitis. Intramammary devices used during lactation and the nonlactating period increased leukocyte concentrations in mammary secretions. An abraded polyethylene coil device reduced clinical mastitis and increased milk yield. Staphylococci colonize teat canal keratin and lacteal secretions of dairy heifers as early as 9 months of age, leading to intramammary infection at time of calving and persisting into lactation. Subsequent somatic cell counts are associated with milk production losses. Previously, such infections were shown to be associated only with older, mature animals.     

Factors for the genesis of bovine subclinical mastitis

The infection risk of the bovine mammary gland is determined by susceptibility of the cow and contamination and invasion by mastitis pathogens. Genetic (e.g. yield) and lactational physiologic (e.g. stage of lactation) factors support the genesis of subclinical mastitis. This paper considers new data on cow individual and milking related influences on defence mechanisms in the teat end tissue acting in prevention of penetration through the teat canal by mastitis pathogens.     

海藻酸钠成膜基质奶牛乳头药浴液研制及临床应用

为探讨食品保鲜剂海藻酸成膜基质奶牛乳头药浴可行性及临床应用效果研制海藻酸钠成膜基质奶牛乳头药浴液,并进行了实验室检测与临床应用试验效果评估.结果表明:海藻酸钠成膜基质对动物皮肤无显微病理损伤;对奶牛乳腺炎临床分离菌株大肠埃希菌、金黄色葡萄球菌及无乳链球菌30s杀菌率均达99.99％以上,6个月杀菌率可达98.99％以上...     

The bacterial flora in the teat duct of ewes can protect against and can cause mastitis

We studied the possible effects of bacterial populations within the teat duct, in the pathogenesis of ovine mastitis. In experiment I, 32 ewes were allocated into group A (ewes from which we isolated (+++ growth) coagulase-negative staphylococci), B (ewes from whose duct we isolated (+ growth) coagulase-negative staphylococci) or C (ewes from which we isolated Bacillus spp.) and subdivided into A1, B1, C1 (n=4; challenged by deposition of 1.250 cfu of Mannheimia haemolytica into the teat duct) or A2, B2, C2 (n=4; used as uninoculated controls); group D (n=8) contained ewes with no bacteria in their teat ducts and were challenged as above. There were less bacteriological isolations of flora (P = 0.018) and challenge (P<0.05) organisms from A1 than from A2 and D ewes; the severity of pathological findings in A1 (summed up score: 27) ewes was smaller than in D (summed up score: 36) ewes (P = 0.038). No such findings were evident with B1 or C1 ewes (P>0.4). In experiment II, ewes (groups E and F, n=6) from whose duct we isolated coagulase-negative staphylococci (+ growth) were used; in group G (n=6) ewes with no bacteria in their teat ducts were included. Teat chapping was applied in E and G ewes. All E ewes developed acute clinical mastitis within 24 h after teat chapping, although we had carried out no challenge; there were more bacteriological isolations of flora organisms from E than from F and G ewes (P < 0.001); the severity of pathological findings in E (score: 28) was greater than in F (score: 3) or G (score: 14) ewes. In experiment III, eight ewes with no bacteria in their teat ducts were allocated into group H or I (n=4) and challenged into the teat (group H) or into the gland (group I) with 10(6) cfu of a Staphylococcus simulans recovered from the teat duct of a group E ewe. Group H ewes developed transiently clinical followed by subclinical mastitis (based on bacteriological and cytological evidence), whilst group I ewes developed severe clinical disease. We conclude that staphylococcal flora present in high numbers within the teat duct of ewes can afford some protection against invading microorganisms. However with impeded defence mechanisms of the teat, the same flora may invade the mammary parenchyma and cause clinical mastitis.     

Mastitis in Post-Partum Dairy Cows

Transition from the dry period to lactation is a high risk period for the modern dairy cow. The biggest challenge at that time is mastitis. Environmental bacteria are the most problematic pathogens around parturition. Coliforms are able to cause severe infections in multiparous cows, and heifers are likely to be infected with coagulase-negative staphylococci. During the periparturient period, hormonal and other factors make the dairy cows more or less immunocompromised. A successful mastitis control programme is focused on the management of dry and calving cows and heifers. Clean and comfortable environment, proper feeding and adequate supplementation of the diet with vitamins and trace elements are essential for maintaining good udder health. Strategies which would enhance closure of the teat canal in the beginning of the dry period and would protect teat end from bacteria until the keratin plug has formed decrease the risk for mastitis after calving. Dry cow therapy has been used with considerable success. Yet, a selective approach could be recommended rather than blanket therapy. Non-antibiotic approaches can be useful tools to prevent new infections during the dry period, in herds where the risk for environmental mastitis is high. Vaccination has been suggested as a means to support the immune defence of the dairy cow around parturition. In some countries, implementation of Escherichia coli core antigen vaccine has reduced the incidence of severe coliform mastitis after calving.     

奶牛胃肠道菌群与奶牛乳房炎关联性及其对乳房炎调控潜力的研究进展

乳房炎是严重影响奶牛机体健康状态及乳品质量的疾病之一。一直以来,外源致病菌入侵乳房并引发感染被认为是奶牛乳房炎发病的主要因素。然而,最近的研究表明,胃肠道菌群同样能够影响奶牛乳房炎的发病并对炎症进行调控。其主要机制可能涉及"肠道-乳腺"内源途径,即来自胃肠道的某些细菌可以通过涉及单核免疫细胞（主要是吞噬细胞）机制进行转移,通过内源性细胞途径（细菌性肠-乳途径）迁移到乳腺。本文就奶牛乳房炎的致病因素及其影响、胃肠道菌群与奶牛乳房炎的关联性及其对乳房炎的调控（包括饮食、短链脂肪酸（short-chain fatty acids,SCFAs）、益生菌及共生菌等因素）等方面进行了综述,旨在为奶牛乳房炎的发病机制及缓解措施提供新的思路。     

Epidemiology of teat lesions in a dairy herd. II. Associations with subclinical mastitis

Even small teat lesions are significantly associated with subclinical mastitis and the risk of mastitis increases as the lesions approach the teat canal. Analyses show that at least 7% of cases of subclinic mastitis would have been avoided if no teat lesions had occurred in the herd in question. Analyses also indicate that the risk of mastitis in a quarter increases by about 50% across a 10 months follow-up period (equivalent to one lactation period) after the teat has been injured.     

CD44 is highly expressed on milk neutrophils in bovine mastitis and plays a role in their adhesion to matrix and mammary epithelium

Mastitis, inflammation of the mammary gland, is a common and economically important disease in dairy animals. Mammary pathogenic organisms, such as Escherichia coli, invade the teat canal,milk ducts, and mammary alveolar space, replicate in mammary secretions, and elicit a local inflammatory response characterized by massive recruitment of blood polymorphonuclear neutrophil leukocytes (PMN) into the alveoli and milk ducts. CD44 is a trans-membrane glycoprotein previously shown to play a role in mediation and control of blood PMN recruitment in response to inflammatory signals. Here we show, for the first time, increased expression of CD44 on recruited milk PMN in bovine mastitis and the expression of a CD44 variant, CD44v10, on these PMN. Furthermore, we demonstrate that CD44 mediates specific adhesion of bovine blood PMN to hyaluronic acid and mammary epithelial cells. Our results suggest that in mastitis CD44 plays a role in recruiting blood PMN into the mammary glands, the exact nature of this role needs to be elucidated.     

奶牛乳腺的防御机制与乳腺炎病理学

乳头管的结构和内衬的角质蛋白是乳腺抵御微生物侵入的物理性屏障,角蛋白中的低级脂肪酸、阳离子蛋白质对侵入的病原微生物具有抗性;环境性致病菌是引起机体免疫应答的主要因子,巨噬细胞、单核细胞、中性粒细胞和淋巴细胞之间的相互协调组成了自然的免疫系统,它们通过分泌细胞因子、抗体和吞噬作用等活动来灭杀、清除侵入机体的病原体;乳中的可溶性因子具有免疫调节作用,对细菌的结构具有破坏性;妊娠期及围产期奶牛由于内分泌的变化而导致免疫抑制,结果造成临床型和亚临床型乳腺炎的发病率相对较高;牛奶体细胞计数对亚临床型乳腺炎的监控具有参考性。     

Influence of milking technique and lactation on the bovine teat by means of ultrasonographic examination

The teats of Brown Swiss and Austrian Simmental cows, divided into two groups, one milked by means of an automatic milking system, the other using a conventional milking parlour, were examined monthly by ultrasonography. Aim of the study was to compare the effects of two different milking machines upon the structures of the bovine teat canal and wall by ultrasonography and thereby evaluate ultrasonography as a research tool for visualisation of different influences on the bovine teat. Length and thickness of the teat canal and teat wall thickness were measured and analysed. During lactation, teat canal length and thickness increased in both groups, teat canal length decreased in conventional milked cows at the end of lactation. Shorter and narrower teat canals were observed in automatic milked cows. Differences between the groups in teat canal length and thickness were determined in early lactation. During lactation teat wall thickness showed a slight increase. Automatic milked cows displayed thinner teat walls than cows milked in the milking parlour. Teat morphology was influenced by the number and duration of lactations, milk yield, quarter of the udder and time and date of examination. It was concluded that the effect of the two different milking machines caused significant differences in bovine teat morphology and that ultrasonography proved to be an appropriate method for visualising influences of the milking technique on the bovine teat.     

Teat skin normal flora and colonization with mastitis pathogen inhibitors

Isolates of bacteria from normal teats were used to attempt colonization of teats of dry cows or neonatal calves. Isolates for inoculation were chosen on the basis of ability to inhibit mastitis pathogens in vitro, with the ultimate goal of in vivo inhibition of mastitis pathogens at the teat surface. Three bacterial normal flora isolates (Corynebacterium xerosis, Bacillus sp. and Aerococcus viridans) persisted less than 10 days on the teats of dry cows. The fourth isolate, Staphylococcus hominis 1, was studied in greatest detail because studies characterizing the normal teat flora showed staphylococci to be the predominant flora. The S. hominis 1 isolated used for inoculation was an inhibitor of Gram-positive mastitis pathogens. It was a biotype not found on these teats prior to inoculation, thus facilitating identification of the inoculated isolate on sequential sampling. Colonization of newborn calves, before other bacterial floral became established, resulted in recovery of inoculated S. hominis 1 for an average of 51 days or longer. On dry cow teats it was detected for up to 28 days. On several occasions the inoculated S. hominis 1 was found in pure culture. Since many new infections occur during the dry period, the colonization of dry cow tests with S. hominis 1 organisms inhibitory for Gram-positive pathogens should be tested as an adjunct to other methods of mastitis prevention.     

Pathogenicity of different species of staphylococci in caprine udder

Aseptic foremilk samples were collected from Finnish landrace goats. Ten different species of staphylococci, causing subclinical infections were detected. Twelve goats with persistent subclinical staphylococcal infection were followed on a monthly basis and compared with foremilk samples of nine goats suffering from clinical mastitis. Parameters of inflammation based on the activity of the California Mastitis Test (CMT). N-acetyl-beta-D-glucosaminidase (NAGase) and antitrypsin were determined from the milk. Staphylococci were further classified using the API STAPH system. On the basis of elevations of activities of CMT, NAGase and antitrypsin, Staphylococcus aureus was the most pathogenic in clinical and subclinical mastitis, S. hyicus showed only marginal pathogenicity. Subclinical infections were persistent and the infective organism was not always detected from milk by culture. The biochemical reactions of subclinical staphylococci seemed to vary within the same gland by time. Antitrypsin was most effective in differentiating between subclinical and clinical infection. A teat cistern puncture technique was found to be suitable for the goat.     

Coliform mastitis

Gram-negative bacteria that commonly cause bovine mastitis are classified as environmental pathogens. The point sources of coliform bacteria that cause infections include bedding materials, soil, manure and other organic matter in the environment of cows. Rates of coliform mastitis increase during climatic periods that maximize populations in the environment. The portal of entry into the mammary gland for Gram-negative bacteria is the teat canal. Once in the gland, bacteria must utilize available substrates in the mammary secretion to replicate and evade host defenses. Rates of coliform mastitis are greater during the transitional phases of the non- lactating period than during lactation. The ability to infect the non-lactating gland is directly related to the ability of bacteria to acquire iron from the mammary secretion. The primary host defense against coliform mastitis during lactation is the elimination of bacteria by neutrophils migrating into the gland in response to inflammation. Damage to the host is mediated by the release of endotoxin. The severity and duration of clinical signs associated with coliform mastitis are reduced by the use of core-antigen bacterins.     

Association af Changes in the Bacterial Ecology of Bovine Mastitis with Changes in the use of Milking Machines and Antibacterial Drugs

The results of mastitis bacteriology made by the National Veterinary and Food Research Institute in Finland during the past 50 years (1.15 million samples) are viewed in relation to simultaneous changes in dairy cow management. Although intensive preventive measures have been applied for decades, the prevalence of bovine mastitis has not decreased. Instead, pathogenic bacteria are becoming progressively less susceptible to the available therapy. In part this must be due to the emergence of antibiotic resistant strains of bacteria, but it seems that the bacterial spectrum has also changed. The incidence of Streptococcus agalactiae (group B streptococci) has decreased, while in contrast, the incidence of staphylococci, initially Staphylococcus aureus and later coagulase-negative staphylococci, has increased. Results suggest that external pressure, like changes in animal husbandry, including antimicrobial treatments and introduction of modern milking machines, act as selective forces on the bacterial species which cause bovine mastitis.     

乳房炎源生鲜乳中病原微生物的污染现状及防控措施

主要介绍了乳房炎患病牛乳中病原微生物污染情况、耐药情况及防控措施。总结出乳房炎患病牛乳中的病原微生物种类较多, 主要有大肠杆菌、金黄色葡萄球菌、链球菌和克雷伯菌, 不同地区乳房炎乳样中的病原微生物不同, 产生的耐药性和耐药基因存在差异。旨在为减少因滥用和乱用抗生素导致药物残留和耐药性产生、降低乳房炎患病牛乳中病原微生物的污染以及科学、合理用药提供参考。