Effects of Machine‐milking on the Bacterial Flora of Teat Duct and Mammary Gland of Ewes

In total, 308 paired‐samples of teat duct material and milk, were collected before and 50–70 min after machine‐milking, from 30 ewes. Samples were processed bacteriologically. For analysis of results, we compared changes in bacterial isolation following milking, for duct and milk samples; statistical significance was assessed by the Sign Test. Bacteria were isolated from 18 (6%) duct and 19 (6%) milk samples collected before the milking procedure; respective figures after it, were 81 (26%) and 33 (11%). In 77 (25%) cases, bacteriological findings in the two duct samples of each pair were different; in seven cases bacteria were isolated only before, whilst in 70 cases bacteria were isolated only after milking (P < 0.005); respective results for milk samples were 26 (8%): 6 and 20 cases (P = 0.693). The majority of bacterial isolates were staphylococci, accounting for 63% of 99 isolates. The milking procedure predisposes to entrance of bacteria into the teat duct; however, increased bacterial isolation from the teat did not result to increased mammary infections, likely as a consequence of defence mechanisms present in healthy teats.     

Bacterial flora and risk of infection of the ovine teat duct and mammary gland throughout lactation

We collected samples of teat duct material and mammary secretion from ewes in three farms (flock A, polyparous n = 7; flock B, polyparous n = 6, primiparous n = 4; flock C, polyparous n = 4): 14 samples immediately after lambing (before sucking of lambs), 244 samples during the suckling period and 156 samples during the milking period. Conventional bacteriological techniques were used. The results were modeled using survival analysis, initially by the Kaplan–Meier method and then by the Cox Proportional Hazards method. Then, we calculated the minimum true risk of an “at-risk” teat or mammary gland being infected and analyzed these data with STATA using the GLLAMM program for Generalised Linear Latent and Mixed Models. During the suckling period, bacteria were isolated from 52 (21%) duct material and 19 (8%) secretion samples; respective results for the milking period were 20 (13%) and 9 (6%). There was an increased risk of duct rather than secretion samples being infected (P < 0.001). There was a significant difference among flocks in isolating bacteria from duct (P < 0.01) or secretion (P < 0.001) samples during suckling period, but not during hand-milking period (P > 0.4 and 0.1, respectively). There were no differences between isolation of bacteria from duct (P > 0.5) or secretion (P > 0.7) samples among primiparous and polyparous animals. Most bacterial isolates were staphylococci. Persistent isolation of the same bacterial species from duct material samples obtained from a particular ewe was recorded with five Staphylococcus spp. and two Mannheimia haemolytica isolates. The results indicate that infections of the teat duct can take place easily; however, not all infections result to infection of the mammary gland. The results support experimental evidence that defence mechanisms of the healthy teat are able to limit the infection. Maintenance of healthy teats contributes to effective defence mechanisms, and coupled with minimal infections of the teat duct, would contribute to the prevention of mastitis in ewes.     

Effects of lamb sucking on the bacterial flora of teat duct and mammary gland of ewes.

We aimed (i) to determine differences in bacterial flora of teat duct and mammary gland of ewes before and after suckling, (ii) to evaluate factors potentially affecting those. We collected samples of teat duct material and mammary secretion from 11 ewes immediately before and after sucking by lambs, as well as 120 min later. We processed samples bacteriologically and compared changes in infection by the Sign Test. We isolated bacteria from 3.5% duct and 1.5% secretion samples before suckling. Respective figures post-suckling were 10.6% and 2.0%, and 120 min later 6.8% and 1.5%. We recorded differences in infection of duct samples before and after suckling in 40 cases; bacteria were isolated before suckling from six samples, whereas after it from 34 (p < 0.001). Also, we recorded differences in samples collected after suckling and 120 min later in 12 cases; bacteria were isolated immediately post-suckling from eight samples, whereas 120 min later from four (p = 0.375). No significant changes were seen for secretion. We found neither difference between ewes with single or twin lambs, nor among stages of lactation. Mostly, we isolated staphylococci: 70% of isolates before suckling, 80% of isolates after it, 91% of isolates 120 min later. After suckling we also isolated two Mannheimia haemolytica strains. Suckling predisposes to entrance of bacteria into the teat; however, increased teat infections did not result in mammary infections. Isolation of M. haemolytica post-suckling indicates that lambs act as source of infection for this pathogen.     

Biofilm production by Staphylococcus aureus associated with intramammary infection

Biofilm production by 221 Staphylococcus aureus isolates from 45 dairy herds was evaluated. Isolates were from composite milk of 117 cows, from teat skin of 70 cows, and from 34 milking machine unit liners. Of S. aureus from milk samples, 41.4% were biofilm producers, as compared to 24.7 and 14.7% of the isolates collected from skin and liners. Pulsed field gel electrophoresis (PFGE) best categorized S. aureus biofilm producers as compared to phage typing and binary typing. PFGE types that were significantly associated with isolation from milk as opposed to teat skin or liners, had isolates that were more likely to produce biofilm than PFGE types that were isolated from milk, skin and liners at similar frequencies. By contrast, PFGE type A was significantly associated with isolation from teat skin and had few biofilm producers. PFGE type Q, which is exclusively a milk, isolate produced more biofilm as evidenced by absorbance values. Given S. aureus that are associated with milk are more likely to produce biofilm as compared to extramammary sources (teat skin and milking unit liners), suggests that biofilm production is a risk factor for infection.     

Influence of milking technique, milking hygiene and environmental hygiene parameters on the microbial contamination of milking machines

It was the aim of this study to investigate the effect of various factors of the milking technique, milking hygiene and environment on microbial contamination of the milking machine. In 31 dairy herds, the degree of bacterial contamination was examined by taking swabs at four locations (teat cup liner, claw, short and long milk tube) before the milking procedure was started using a standardized protocol (DIN ISO 6887-1:1999). Furthermore, the total germ count was determined in the first milk entering the bulk tank as well as in the bulk tank milk following milking. For each farm, the quality of the milking process and the condition of the milking machine as well as of various environmental factors were recorded. A subjective evaluation of the status of the milking cluster or other parts of the milking machine ("good" or "moderate-poor") gave more information about bacterial contamination than the determination of age and type of material used. A temperature of the rinsing water of < 42 degrees C increased the contamination with Pseudomonas spp. and coliform bacteria. Milking clusters kept out of the cluster pick-up between milking had a higher risk of microbial contamination. Various methods of teat cleaning before milking or of postmilking teat disinfection did not affect the contamination of the milking machine and the bulk tank milk with environmental bacteria. Furthermore, type of bedding material affected bacterial contamination of milking clusters and bulk tank milk. In conclusion, our results suggest that the microbial contamination of the milking machine is not only influenced by the sanitation pro-     

Transmission of Mannheimia haemolytica from the tonsils of lambs to the teat of ewes during sucking

Objective of the work was to study whether Mannheimia haemolytica may be transmitted from the mouth of the lambs into the teat of the dam during sucking. We compared bacterial populations within the teat duct and milk of ewes immediately before and immediately after sucking by the lambs. Tonsils of lambs of the ewes were swabbed. M. haemolytica strain DAG21T recovered from a teat duct of a ewe was compared to strain DAG21R recovered from the tonsils of her lamb by using 16s rRNA sequencing. We used those two isolates and another one of known pathogenicity, for challenging ewes: (i) 2-mm deep into healthy teats, (ii) 2-mm deep into teats with chapping lesions or (iii) into the cistern of healthy mammary glands. Of samples collected before suckling, 20/792 were bacteriologically positive, and of those after, 50/792 were bacteriologically positive (P < 0.001); in 37 cases, a negative sample became positive. One M. haemolytica (DAG21T) was recovered after suckling from a teat duct of a ewe. The organism was isolated from 57/90 tonsillar swabs from lambs. Risk of infection of ewe’ teats was 0.004 throughout lactation, being greatest (0.021) during the 3rd week of lactation. The 16s rRNA sequences of strains DAG21T and DAG21R were identical over 1450 nucleotides. Phylogenetic analysis showed that the two isolates clustered together with isolates of M. haemolytica. Organism deposition into healthy teats caused subclinical mastitis; deposition into teats with lesions or directly into mammary gland caused clinical mastitis. When results of inoculation of the three strains were compared between them, statistical significance was always P > 0.9. Results provide clear evidence that suckling by lambs can lead to transmission of M. haemolytica into the teats of the ewes; the bacteria have the potential to cause mastitis if circumstances are favourable.     

Fomites and reservoirs of Staphylococcus aureus causing intramammary infections as determined by phage typing: the effect of milking time hygiene practices

We studied the association of milkers' hands and milking unit liners as fomites, and teat skin as a reservoir, with S. aureus intramammary infections (IMI). Samples were collected from 40 commercial herds and S. aureus isolates were phage typed. Only 10 of 257 isolates were not typable. Of the milk samples, 8.4% had typable S. aureus; 4.5% and 9.2% of the skin and liner swabbings had typable S. aureus. Twenty-three different phage types were identified, 1 type was found in nearly 75% of the herds. Herds in which milking unit backflush was used were less likely to have the same phage type on the liners and the teat skin, and on the liners and milk samples, than herds that did not backflush. A greater percentage of liners had S. aureus of the same type as those causing S. aureus IMI, than skin swabbing solutions with the same type as that associated with IMI. Herds which did not use post-milking teat asepsis (teat dip) did not have a greater percentage of S. aureus isolates on the teat skin, nor were the S. aureus test skin isolates more likely to be of the same type as those causing intramammary infection. Results would suggest that the liner appears to be a significant fomite, that backflushing reduces its significance, and that teat skin is a less significant reservoir for S. aureus intramammary infection.     

Presence of subepithelial lymphoid nodules in the teat of ewes

A total of 87 clinically healthy ovine teats were examined bacteriologically (by scraping the mucosa) and histologically. Teats examined were those of lactating mammary glands with no bacteria isolated (n = 23); of mammary glands after cessation of lactation with no bacteria isolated (n = 25); of lactating mammary glands with bacteria isolated (n = 22); and of mammary glands after cessation of lactation with bacteria isolated (n = 17). The salient histological feature was subepithelial leucocytic infiltration. In teat cisterns, lymphocytes were the predominant cell type and in teat ducts, lymphocytes and neutrophils were seen in equal proportions. Subepithelial lymphoid nodules, some with germinal centres, were detected in 43 (49%) teats. The majority of lymphoid nodules was observed at the border between teat duct and teat cistern. Presence of bacteria was significantly associated with the presence of leucocytic activity (P < 0.001) and with the presence of lymphoid nodules (P = 0.032). We conclude that the presence of induced subepithelial lymphoid tissue at the border between teat duct and teat cistern appears to be important in protecting the mammary gland during the early stages of bacterial invasion. The findings call for further investigations into the lymphoid structures of the teat; these should elucidate the role and development of mammary mucosa-associated lymphoid tissues and may lead to strategies for enhancing non-specific defence mechanisms of the mammary gland.     

Comparison of media to isolate Staphylococcus aureus from teat skin and milking unit liners.

Four procedures were compared for isolation of Staphylococcus aureus from swabbing solutions of teat skin and milking unit liners from commercial dairies. In 2 procedures, 0.1 ml of swabbing solutions were added to either 5 ml Vogel-Johnson or Baird Parker broth media and enriched at 37 degrees C, 4 h. Following enrichment, 0.1 ml culture was transferred to modified Baird-Parker agar and incubated at 37 degrees C, 48 h. In the other 2 procedures, 0.1 ml of swabbing solution was directly placed on either blood or modified Baird-Parker agar plates and incubated at 37 degrees C 48 h. Combining results from all methods, Staphylococcus aureus were isolated from 72 of 913 (7.9%) skin samples, and 34 of 268 liners (12.6%). On average, 43.1% (31/72) of the S. aureus isolates were found by the enrichment in liquid Vogel-Johnson procedure. The average isolation percentage for other methods ranged from 19.4% to 25.0%. Isolation of S. aureus from milking unit liner or teat skin swabbing solutions was approximately twice as likely after enrichment in Vogel-Johnson liquid media as opposed to other methods of isolation. This indicates that enrichment in Vogel-Johnson liquid media improved recovery of S. aureus from swabbing solutions.     

The influence of iodine teat dipping and an external teat sealant in heifers on bacterial isolation from quarter milk culture obtained post-calving

A longitudinal observational 2 year field study including 178 dairy herds was conducted in Norway. The aim of the study was to investigate the influence of iodine post milking teat dipping (PMTD) and an external teat sealant (ETS) in first calvers (heifers) on bacterial isolation from milk culture post-calving. Every heifer was either sampled in connection with a clinical mastitis (CM) event at calving or otherwise approximately 6 days post-calving. Milk culture results were available from 3218 individual heifers and 12,872 quarter milk samples. Separate multivariable logistic regression models were used for each bacterium. Neither use of PMTD nor ETS did decrease the risk of bacterial isolation post-calving. However, if iodine PMTD had been used, there was an increased risk of clinical mastitis (Odd ratio (OR) = 1.6 (0.9–2.7)) and an increased risk of isolation of coagulase negative staphylococci OR = 1.5 (1.0–2.1). If ETS had been used, there was an increased risk of isolation of coliform bacteria (coliform and Escherichia coli) (OR = 2.9 (1.2–7.3)). There was significantly less Streptococcus dysgalactiae during the summer and autumn compared to the winter and spring. There was a significant herd effect for Streptococcus uberis and for coliforms with an OR = 5.1 (2.1–12) and 4.5 (2.7–7.6) respectively.     

Removal of hair surrounding the teat and associated bacterial counts on teat skin surface, in milk, and intramammary infections

The effectiveness of monthly removal of hair surrounding teats on the reduction of teat skin surface bacteria, and the incidence of intramammary infection (IMI), was studied for 10 months in a dairy farm. A split udder design was used where hair was removed on one side, left or right, with the other side serving as a control. Controls and treatment sides were randomly applied in a systematic fashion to 218 cows. Standard milking time pre- and post-milking hygiene practices were applied to all udders during the trial. Collection of teat skin swab solutions preceded aseptic collection of milk samples, performed at monthly intervals, immediately prior to milking. Teat skin bacterial counts did not differ between control and treated teats. Incidences of IMI were similar for treatment when compared with control mammary quarters, as measured by total or by pathogen type. In a second study, the effect of hair removal on the bacterial content of milk was determined using 40 cows. Treatments and allocations were as described. Udder half milk, milk from both mammary quarters of each udder half, was combined and diverted into separate buckets. Buckets were thoroughly cleaned and sanitized between milkings. A portion of bucket milk was collected 24 h after removal of udder hair. The total milk bacterial counts, and counts of psychrotrophs and thermoduric organisms were not reduced by udder hair removal. Results do not suggest that removal of udder hair leads to an improvement in milk quality as determined by milk bacterial content in the herd studied.     

Prevalence of coagulase-negative staphylococci in bovine mastitis in Zimbabwe

This study was carried out to determine the prevalence of coagulase-negative staphylococci in clinical and subclinical mastitis in commercial and small-scale farms in Zimbabwe. Thirty five quarter milk samples from clinical mastitis cases and 371 quarter milk samples from cows with subclinical mastitis were cultured for bacterial pathogens. The most frequent pathogens isolated in clinical mastitis were the enteric bacteria (31.4%), followed by coagulase negative staphylococci (22.9%) and then Staphylococcus aureus (17.1%), whereas in subclinical mastitis S. aureus (34.2%) and coagulase-negative staphylococci were (33.2%) the most common. Bacillus species were only isolated in milk samples from subclinical mastitis. Coagulase-negative staphylococci were observed in mixed infections with other bacteria in only 2.2 of the 406 milk samples from clinical and subclinical mastitis where they were isolated together with Bacillus species in 6 of the 9 mixed infection cases. About 95% of the milk samples from which 131 coagulase-negative staphylococci were isolated had correspondingly high somatic cell counts. The coagulase-negative staphylococci isolated most frequently were S. chromogenes (7.9%), S. epidermidis (7.4%) and S. hominis (5.9%). They were all associated with high somatic cell counts. All the coagulase-negative staphylococci isolates were susceptible to cloxacillin and erythromycin, and more than 90% of the isolates were susceptible to neomycin, penicillin and streptomycin. The highest resistance was to tetracycline (17.6%), followed by lincomycin (13.7%). About 8% of the isolates were resistant to both penicillin and streptomycin.     

Effect of setting a maximum milking time,from peak lactation,on production,milking time and udder health

Abstract

AIM: To examine the effect of setting a maximum milking time, from peak lactation until drying-off, on production, duration of milking, and udder health of dairy cows.

METHODS: Forty cows were assigned in twin-pairs to be either milked until cups were removed at a milk flow-rate threshold of 0.35 kg/minute (Control), or until cups were removed at a milk flow-rate threshold of 0.35 kg/minute, or maximum time, whichever came first (MaxT). The maximum time was set by determining the milking time of the 70th percentile cow when ranked from fastest to slowest, irrespective of yield. The milking routine was typical of that practised on dairy farms in New Zealand, and involved no pre-milking preparation. The study began at peak lactation (68 (SD 7) days in milk; DIM) and continued for 26 weeks. Duration of milking and milk yield were measured for each milking. Composition of milk was determined from weekly herd tests, and milk quality from fortnightly somatic cell counts (SCC). Completeness of milking and teat condition were assessed during the study. The bacterial status of quarter milk samples was determined at the beginning and end of the study, and all treated cases of clinical mastitis recorded. ANOVA was used to examine the effect of treatment group on variables of interest.

RESULTS: Total milk, fat and protein yields during the study period did not differ between treatments. On average, 30.3% of the morning and 27.6% of the afternoon milkings of MaxT cows reached the maximum time at which cups were removed, and were therefore shortened. While the average milking time of the slowest-milking cow was longer for the Control compared with MaxT group in Weeks 1–18, the average milking time did not differ between treatments. There was no difference in overall SCC, and the incidence of clinical mastitis, or the percentage of infected quarters at drying-off, was similar for the MaxT and Control cows.

CONCLUSION: The results show that setting a maximum milking time can reduce the milking time of slower-milking cows in a herd without compromising overall herd production and udder health.

CLINICAL RELEVANCE: Although the numbers of cows in the study were small there was no evidence of a major increase in SCC, or subclinical or clinical mastitis when a maximum milking time was set for slower-milking cows.     

Flotation of mastitis pathogens with cream from subclinically infected quarters. Prospects for developing a cream-rising test for detecting mastitis caused by major mastitis pathogens

Bacterial isolates, originating from 36 subclinically infected quarter milk samples, were labelled with 75Se and checked for cream-rising at various temperatures in a system analogous to the ABR test ("Abortus Bang Ringprobe"; the cream-rising test based on stained brucella organisms for detection of brucellosis). Diagnostic specificity and sensitivity were analyzed in experiments where labelled bacterial isolates were mixed with a number of quarter milk samples with known bacteriological status as well as samples from healthy control quarters. Creaming at 37 degrees C resulted in specific "recognization" as the bacterial isolates showed preferential flotation in the milk samples from which they had been isolated as well as is milk samples harbouring the same bacterial species. At lower creaming temperatures, the specificity was lost since all the isolates became concentrated in the cream phase irrespective of the milk sample. When comparing the specific recognization by cream of the respective bacteria, bacterial species vary: The prospects for developing diagnostic cream-rising tests for Streptococcus agalactiae, Staphylococcus aureus and Escherichia coli seems promising, but less so for coagulase-negative staphylococci, Streptococcus dysgalactiae, and Streptococcus uberis. The mechanism behind the cream-rising of labelled bacteria at 37 degrees C seems to lie in specific fat globule membrane-bound immunity of IgA type. Therefore the milk fat globules from chronically infected quarters function as absorbents for the respective isolates. Flotation of bacteria with cream indicates an in vivo mechanism enabling bacteria to invade the upper parts of milk ducts within the udder.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of inoculation of Mannheimia haemolytica into the teat of lactating ewes

The objectives of the work described in this paper were: (i) to study the outcome of challenging ewes with Mannheimia haemolytica, at different sites of their teats, (ii) to compare the effects of two different isolates of the organism and (iii) to describe the features of the resulting lesions. Thirty-two ewes were used in the study and allocated into one of two groups (A or B, n = 16); they were challenged with one of two isolates of M. haemolytica, respectively, strain ES26L of known pathogenicity or strain VSM08L from the teat duct of a healthy ewe. Each group was further divided into four equal subgroups: the ewes in the A1/B1 subgroups were intramammarily challenged; one teat of the ewes in the A2/B2 subgroups was immersed into a broth-culture of the organisms; one teat of the ewes in the A3/B3 subgroups was inoculated 2 mm-deep, whilst one teat of the ewes in the A4/B4 subgroups was inoculated 6 mm-deep. The animals were monitored clinically, bacteriologically and cytologically before and after challenge; one animal in each subgroup was euthanised 2, 4, 7 and 11 days after challenge. All ewes in the A1/B1 subgroups developed clinical mastitis, whilst of the other animals, only one ewe in each of the A4/B4 subgroups did. Neither of the two strains used was associated with more positive bacteriological or CMT results; the A2/B2 subgroups were associated with less positive results than the A3/B3 and A4/B4 subgroups. In some ewes of the A2/B2 subgroups, mild leucocytic infiltration in the teat was evident; in the ewes of the A3/B3 subgroups, leucocytic infiltration (neutrophils, lymphocytes, plasma cells) was seen, as well as a lymphoid hyperplasia at the border between the teat duct and teat cistern; in ewes of the A4/B4 subgroups, intense subepithelial leucocytic infiltration was the salient feature. No differences were found in the severity of lesions between the two strains used or the three treatments carried out. Although strain VSM08L had been isolated from the teat duct of a healthy ewe, it caused mastitis when inoculated intramammarily; although strain ES26L is of known pathogenicity for the mammary gland, it did not cause clinical mastitis when deposited 2 mm-deep into the teat. These findings point to a protective role of the teat of ewes, which appear to limit bacterial penetration from the teat duct or cistern to the mammary gland. The lymphoid tissue, at the border between the teat duct--teat cistern, may play a significant protective role.     

Effect of liner design,pulsator setting,and vacuum level on bovine teat tissue changes and milking characteristics as measured by ultrasonography

: Friesian-type dairy cows were milked with different machine settings to determine the effect of these settings on teat tissue reaction and on milking characteristics. Three teat-cup liner designs were used with varying upper barrel dimensions (wide-bore WB = 31.6 mm; narrow-bore NB = 21.0 mm; narrow-bore NB1 = 25.0 mm). These liners were tested with alternate and simultaneous pulsation patterns, pulsator ratios (60:40 and 67:33) and three system vacuum levels (40, 44 and 50 kPa). Teat tissue was measured using ultrasonography, before milking and directly after milking. The measurements recorded were teat canal length (TCL), teat diameter (TD), cistern diameter (CD) and teat wall thickness (TWT).Teat tissue changes were similar with a system vacuum level of either 50 kPa (mid-level) or 40 kPa (low-level). Widening the liner upper barrel bore dimension from 21.0 mm (P < 0.01) or 25.0 mm (P < 0.001) to 31.6 mm increased the magnitude of changes in TD and TWT after machine milking. Milk yield per cow was significantly (P < 0.05) higher and cluster-on time was reduced (P < 0.01) with the WB cluster as compared to the NB1 cluster. Minimum changes in teat tissue parameters were achieved with system vacuum level of 40 kPa and 50 kPa using NB and WB clusters, respectively. Similar changes in teat tissue and milk yield per cow were observed with alternate and simultaneous pulsation patterns. Widening pulsator ratio from 60:40 to 67:33 did not have negative effects on changes in teat tissue and had a positive effect on milk yield and milking time. Milk liner design had a bigger effect on teat tissue changes and milking characteristics than pulsation settings.     

Clinical findings related to intramammary infections in meat-producing ewes

The aim of this study was to investigate the relationship between clinical findings and bacterial isolation in milk samples of meat-producing ewes. The study was conducted in 17 commercial flocks and 550 udder halves from suckling Santa Ines ewes. Initially, the clinical examination of the mammary glands and teats was performed by visual inspection and palpation of the teats and udder halves; then a scoring system was devised for all the findings. After that, the strip cup test and the California mastitis test (CMT) were performed. Then, milk samples for somatic cell counts (SCCs) and bacteriological analyses were collected. Staphylococci bacteria were the main etiological agent isolated in the present study. Upon investigation of the correlations between bacterial isolation and the clinical findings, only the presence of teat injury, pendulous udder, and alterations in the palpation of the teat were associated with bacterial isolation. A significant correlation between bacteriologically positive milk samples and CMT and SCC was also found. Thus, some clinical findings appeared as a risk factor for bacteriologically positive milk samples and can be used as a tool in mastitis control programs. However, a complete and extensive diagnosis, an appropriate therapy, and an efficient mastitis control program will require the combination of clinical examination, microbiological tests, and SCC.     

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.     

Clinical, bacteriological and therapeutic aspects of bovine mastitis caused by aerobic and anaerobic pathogens.

Twenty cows and three heifers with summer mastitis-like signs were included in the study. Forty aerobic and 38 anaerobic bacterial isolates representing 23 different species were isolated from udder secretions, the mean number of species being 3.4/sample. Pathogens most often were recovered in quantities exceeding 10(5) CFU/ml. Growth of pathogenic bacteria in the blood was found in only one case. Most cases occurred in housed animals and had often been preceded by teat injury. No anaerobic growth was found in milk samples of a control group consisting of 29 cows with ordinary acute mastitis. Values of indicators of inflammation in milk (NAGase and plasmin activity) were high, mean values being 914.1 and 1.3 units. The animals with aerobic/anaerobic mastitis were treated using various antimicrobial agents. All but three quarters were lost to milk production. Two animals with complete recovery were given a combination of penicillin G and tinidazole.     

Radiographic method for anatomic study of the teat canal: changes between milking periods.

Radiographs of the teat canal (papillary duct) of 14 Holstein-Friesian cows were made immediately after removal of the milking machine and at 2, 4, 6, and 8 hours. The distal, middle, and proximal diameters of the canal were dilated when the machine was removed. The distal and the middle parts of the teat canal were more dilated than the proximal part of the canal. Two hours later, the canal was constricted in the 3 areas. During the next 6 hours, the canal dilated-the greatest kilation being at the proximal paet of the teat canal. The average lenght of the teat canal remained unchanged. Apparently, microorganisms can easily pass through the teat canal when it is dilated at the end of machine milking and for up to 2 hours after milking.