Bacteria associated with clinical mastitis in dairy heifers

A 1-yr field investigation of clinical mastitis in heifers was carried out in 24 veterinary districts in Norway. Quarter lacteal secretions from cases that occurred prepartum or within 14 d postpartum were examined bacteriologically. The study included 1040 heifers with clinical mastitis, and the total number of quarters that were clinically affected was 1361. The organisms that were most frequently isolated from samples from these quarters were Staphylococcus aureus (44.3%), Streptococcus dysgalactiae (18.2%), Staph. aureus together with Strep. dysgalactiae (1.2%), coagulase-negative staphylococci (12.8%), Arcanobacterium pyogenes (3.5%), A. pyogenes together with Strep. dysgalactiae (0.5%) or Staph. aureus (0.4%), and Escherichia coli (6.4%). Of the coagulase-negative staphylococci, Staphylococcus simulans (53.7%), Staphylococcus hyicus (14.8%), and Staphylococcus chromogenes (14.8%) were the most prevalent species. Except for a higher relative percentage of A. pyogenes in cases that occurred before parturition (8.2%) than in cases that occurred after parturition (2.7%), no significant differences were observed in the distribution of the various organisms among prepartum and postpartum cases. Regional variations were observed in the distribution of organisms. The proportions of Staph. aureus and A. pyogenes were highest, and the proportion of coagulase-negative staphylococci was lowest, in late autumn and early winter. The proportion of E. coli was highest in summer. In heifers in which mastitis was associated with increased rectal temperature or other systemic signs, the proportion of clinically affected quarters that were infected with Staph. aureus was larger than that in heifers without systemic reaction.     

Multiplex polymerase chain reaction as a mastitis screening test for Staphylococcus aureus,Streptococcus agalactiae,Streptococcus dysgalactiae and Streptococcus uberis in bulk milk samples

Effective diagnostic tools for screening herds for mastitis pathogens are important in development and monitoring of mastitis control programmes. A multiplex polymerase chain reaction (PCR) assay for simultaneous detection of Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae and Streptococcus uberis was used in preliminary studies to assess its applicability as an alternative method for monitoring mastitis caused by these organisms at the herd level. PCR was used to detect the presence of these organisms in bulk milk samples. Correlations with bulk milk somatic cell counts (BMCC), total bacteria counts and thermoduric bacteria counts were evaluated. A total of 176 bulk milk samples were collected from 42 herds on five consecutive occasions at approx. 10-d intervals. Str. uberis was the most common organism in these bulk milk samples. There was no relationship between presence of either Staph. aureus, Str. dysgalactiae or Str. uberis and BMCC, total bacteria counts or thermoduric bacteria counts. However, presence of Str. agalactiae was associated with high BMCC and total bacteria counts. The results of this study show that regular analysis of bulk milk using this multiplex PCR assay may be a useful tool for monitoring herd status with respect to Str. agalactiae, but is of less value for monitoring occurrence of Staph. aureus, Str. dysgalactiae and Str. uberis. Further investigations are needed to clarify the relationship between positive PCR results and the prevalence of infected cows in the herd.     

Outcome of clinical mastitis in dairy heifers assessed by reexamination of cases one month after treatment

Heifers that were treated for clinical mastitis prior to parturition or within 14 d postpartum were reexamined approximately 1 mo after treatment. Clinical examination of the heifers and microbiological examination of quarter milk samples were carried out on both occasions. Of the 1000 heifers included in the study, 10.9% were culled within 28 d after treatment. Udder damage caused by mastitis was the only or main reason for culling in 96% of those heifers. In comparison, 4.5% of nonmastitic heifers from the same herds were culled within 30 d postpartum. Twenty-five percent of those heifers that were not culled at d 28 after treatment had at least one nonfunctional quarter at that time. One thousand one hundred twenty-two quarters that were clinically affected at the time of treatment were reexamined; 22% were nonfunctional, 14% were still affected by clinical mastitis, 12% had subclinical mastitis, 5% had a latent infection with coagulase-positive staphylococci or Streptococcus dysgalactiae, and 46% were bacteriologically negative and had a normal cell count at the time of reexamination. High percentages of nonfunctional quarters were observed among those quarters that were infected with Arcanobacterium pyogenes or with coagulase-positive staphylococci at treatment. When all quarters that were clinically affected at treatment were considered, 40% of quarters were cured and were still in lactation at reexamination. Quarters infected with coagulase-negative staphylococci had a higher cure rate than quarters infected with other organisms. At reexamination, clinical signs of thelitis were observed in many of those quarters that were nonfunctional following the episode of clinical mastitis and also in 25% of lactating quarters in which clinical mastitis persisted.     

Effect of mastitis-related bacteria on total bacterial count of bulk milk supplies

Seven hundred and fifty-four bulk milk samples from a total of 9,066 tested by the Aberdeen and District Milk Marketing Board in 1984 had total bacterial counts greater than 45,000 per ml. Of the failed samples, 43.8% had more mastitis-related bacteria present than non-mastitis types. More than a quarter of the failed samples had almost pure cultures of Streptococcus agalactiae, Str. dysgalactiae, Str. uberis, Staphylococcus aureus or coagulase-negative staphylococci. No relation was found between the failed samples resulting from subclinical mastitis infections and the somatic cell count of the bulk milk. Seventy-five per cent of the financial penalties imposed on producers were attributable to mastitis bacteria in bulk milk samples .     

Risk factors for isolation of Staphylococcus aureus or Streptococcus dysgalactiae from milk culture obtained approximately 6 days post calving

Milk culture results at approximately 6 d post calving were assessed in a 2-year retrospective single-cohort study in 178 Norwegian herds. A combined teat dipping and selective antibiotic therapy trial was performed in these herds where cows with composite milk somatic cell count (CMSCC) >100,000 cells/ml before drying-off (geometric mean of the last three CMSCC test-days) and isolation of Staphylococcus aureus or Streptococcus dysgalactiae were selected for either short-acting lactation antibiotic treatment or long-acting dry cow antibiotic treatment. Milk culture results at approximately 6 d post-calving were available from 437 treated cows and 3061 non-treated cows before drying-off and separate multivariable logistic regression models were ran for these two groups. Risk factors associated with isolation of Staph. aureus 6 d post calving for non-treated cows were CMSCC >400,000 cells/ml before drying-off v. <400,000 cells/ml (Odd ratio (OR) = 2.4) and clinical mastitis (CM) in the previous lactation v . non-treated (OR=1.5). Risk factors associated with Staph. aureus 6 d post calving for treated cows was a CMS > 200,000 cells/ml before drying-off v. <200,000 cells/ml (OR=2.3) and CM in the previous lactation verus non-treated (OR=1.7). For non-treated cows it was 1.7 times more likely to isolate Str. dysgalactiae 6 d post-calving if the CMSCC was > 50,000 cells/ml compared with <50,000 cells/ml. For treated cows it was 3.7-5.8-times more likely to isolate Str. dysgalactiae 6 d post calving if given short-acting lactation formula at quarter level compared with long-acting dry cow formula used at cow level. Regular use of iodine post-milking teat disinfection (PMTD) did not influence the isolation of Staph. aureus 6 d post calvin, but it was less likely to isolate Str. dysgalactiae 6 d post calving if iodine PMTD was used regularly rather than irregularly. The external teat sealant had no effect on either of the two bacteria. This study indicates that the CMSCC limit for sampling cows before drying-off can be reduced to 50,000 cells/ml in herds with a Str. dysgalactiae problem. Iodine PMTD should also be recommended in these herds. Cows with a CMSCC > 400,000 cells/ml prior to drying-off should receive long-acting dry cow formula irrespective of the milk result.     

Evaluation of tRNA intergenic spacer length polymorphism analysis as a molecular method for species identification of streptococcal isolates from bovine mastitis

Sixty-nine bovine mastitis streptococci belonging to the species Str. agalactiae (n = 13), Str. dysgalactiae (n = 16), Str. canis (n = 22), Str. uberis (n = 20) and Str. parauberis (n = 4) and six reference strains of the five streptococcal species were examined for their tRNA gene intergenic length polymorphism (tDNA-ILP) fingerprint pattern. Epidemiologically unrelated isolates from bovine mastitis cases were selected by macrorestriction analysis with pulsed-field gel electrophoresis (PFGE). Their results were compared with those obtained from biochemical and serological studies and with those obtained by PCR-mediated identification amplifying species-specific gene segments of the five streptococcal species. According to the present results tDNA-ILP allowed a correct identification of all Str. agalactiae, Str. uberis and Str. parauberis strains investigated also including the reference strains of each species showing species-specific banding pattern. However, all Str. dysgalactiae ssp. dysgalactiae and all Str. canis strains appeared with an undistinguishable pattern which did not allow an identification of the species.     

Effect of prepartum dry cow antibiotic treatment in dairy heifers on udder health and milk production

A high percentage of heifers calve with intramammary infections. One of the measures available to control intramammary infections is treatment with antibiotics before calving. In this study, the effects of prepartum treatment of nonlactating heifers with a 600-mg cloxacillin dry cow treatment on the prevalence of culture-positive milk samples at calving and 10 to 14 d in milk (DIM), the incidence of clinical mastitis, somatic cell count (SCC), and milk production during first lactation were quantified. A total of 184 heifers on 13 dairy farms were treated with antibiotics 8 to 10 wk before the expected calving date. Another 185 heifers served as untreated controls. Coagulase-negative staphylococci were the most frequently isolated group of bacteria in the treatment and control groups at calving (32 and 42%), and at 10 to 14 DIM (15 and 19%), respectively. The prevalence of minor pathogens at calving was lower in the treatment group compared with the control group (34 and 43%, respectively). Staphylococcus aureus was the most frequently isolated major pathogen in the treated and control heifers at calving (4 and 5%) and at 10 to 14 DIM (2 and 3%), respectively. The prevalence of major pathogens was lower in the treated heifers at 10 to 14 DIM compared with the control group (4 and 6%, respectively). Cumulative incidence risk of clinical mastitis during the lactation was 9 and 18% in the treatment and control groups, respectively. Treatment with cloxacillin 8 to 10 wk before calving resulted in a lower prevalence of culture-positive milk samples at calving and lower quarter milk SCC in early lactation [30,000 ± 4,600 (standard deviation) cells/mL in treated heifers versus 40,000 ± 4,600 cells/mL in control heifers], and was associated with lower average test-day SCC (55,000 ± 1,400 cells/mL in treated heifers versus 71,000 ± 1,500 cells/mL in control heifers) and lower incidence of clinical mastitis throughout lactation. The improved udder health resulted in a higher average test-day milk production in the first lactation (24.5 ± 3.2 kg in treated heifers versus 23.6 ± 3.1 kg in control heifers). Dairy farms with heifer mastitis problems need to analyze their mastitis management. Prepartum treatment of heifers with dry cow antibiotics may be helpful by decreasing the prevalence of mastitis-causing pathogens at calving and at 10 to 14 DIM.     

Susceptibility of coagulase-negative staphylococci to a kanamycin and cefalexin combination

A combination of kanamycin and cefalexin was licensed in Europe in 2008 to treat bovine clinical mastitis. Preliminary broth and disk clinical breakpoints for this antibiotic combination have been proposed for Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis, and Escherichia coli. This study indicates that these proposed breakpoints also hold for coagulase-negative staphylococci (CNS), a group of bacteria frequently isolated in milk samples from cows with clinical mastitis. The data show that clinical bovine mastitis isolates of CNS from Europe have a high degree of susceptibility to the kanamycin/cefalexin combination, with minimal resistance to either agent alone. The use of the available kanamycin and cefalexin combination disk for testing the susceptibility of bovine mastitis isolates of Staph. aureus, Strep. uberis, Strep. dysgalactiae, and E. coli is also reliable for use in the testing of CNS, as disk results correlated with broth minimum inhibitory concentrations. The study reports, for the first time, the approved Clinical Laboratory Standards Institute quality control ranges for the kanamycin/cefalexin combination and wild-type cutoff values for major bacterial pathogens implicated in bovine mastitis.     

Prepartum antibiotic treatment of heifers: milk production,milk quality and economic benefit

Prepartum intramammary antibiotic infusion of heifer mammary glands at 7 or 14 d before expected parturition is an effective procedure for eliminating many infections in heifers during late gestation and for reducing the prevalence of mastitis in heifers during early lactation and throughout lactation. Mastitis pathogens were isolated from 76% of samples obtained from untreated control quarters 7 d before expected calving, from 47% of samples obtained 3 d after calving, and from 29% of samples obtained 10 d postpartum. Mastitis pathogens were isolated from about 30% of control quarters through 240 d of lactation. A similar percentage of samples (70%) was positive for mastitis pathogens at C-7 before antibiotic treatment. However, only 8% of samples obtained at 3 d after calving and 4% of samples obtained at 10 d postpartum from quarters of antibiotic-treated heifers contained mastitis pathogens. Throughout the remainder of lactation, mastitis pathogens were isolated from an average of about 11% of quarters. The percentage of samples with mastitis pathogens was higher in untreated controls than in antibiotic-treated quarters at all sampling intervals during lactation. A similar response was observed in heifers that were treated with antibiotics at 14 d before expected parturition. Prepartum antibiotic-treated heifers produced significantly more milk than control heifers and had significantly lower somatic cell count scores than untreated control heifers. These observations are likely associated with or due to the lower prevalence of mastitis pathogen isolation in prepartum antibiotic-treated heifers throughout lactation. Prepartum antibiotic-treated heifers produced 531 kg more milk than heifers in the untreated control group. Multiplying this increase by a milk price of 0.407 dollars/kg yielded a 216.24 dollars per-heifer increase in gross revenue. The cost of treatment, including the cost of testing for antibiotic residues, was estimated at 15.60 dollars for a net revenue of 200.64 dollars per heifer. Prepartum antibiotic treatment to reduce the rate of mastitis in heifers during lactation was highly effective and economically beneficial.     

Bacterial counts in bedding materials used on nine commercial dairies

Bacterial counts were monitored for 1 yr in bedding materials used on nine commercial dairies. Organic materials used to bed lactating cows had significantly higher moisture content and gram-negative bacterial, coliform, Klebsiella species, and streptococcal counts than did inorganic materials. Klebsiella species counts were higher in sawdust than in chopped straw. Streptococcal counts were higher in chopped straw than sawdust. Bacterial counts did not differ between sand and crushed limestone. Gram-negative bacterial and coliform counts were higher during summer and fall than in winter and spring months. Streptococcal counts did not differ among seasons of the year. Linear relationships were significant between total rates of clinical mastitis during lactation and both gram-negative bacterial and Klebsiella species counts in lactating cow bedding. These data indicate that bacterial populations differed between both types of bedding and among seasons of the year. Rates of clinical mastitis were related to bacterial counts in bedding.     

Determinants of bacterial replication rates in mastitic whey

Bacterial growth was measured by a turbidimetric microtechnique in the whey of milk samples from quarters of cows with subclinical mastitis. Samples were grouped according to bacterial isolates recovered and the effects of bacterial species and whey on bacterial growth rates were analysed. Different strains of bacteria and different whey samples gave highly significant differences in bacterial replication rates. Except for penicillin-resistant Staphylococcus aureus, bacteria grew better in whey from mastitic milk where the inflammation was caused by the same bacterial species than in other mastitic milk samples. Inflammation caused by major pathogens generally enhanced the growth in whey of any type of major pathogen. Since mastitis pathogens showed enhanced growth in whey prepared from the same milk from which they were isolated, specific antibacterial factors in the whey did not appear to restrict bacterial growth in whey. The nutritional quality of the medium seems to be the important determinant of bacterial growth.     

Effects of periparturient systemic treatment with penethamate hydriodide on udder health and milk yield of dairy heifers

Sixty dairy heifers from seven Austrian herds, with high prevalence of Staphylococcus aureus mastitis, were used in this pilot study. Heifers were randomly allocated to two groups. The treatment group received at parturition intramuscularly 10 million i.u. of penethamate hydriodide and then 24 h later, 5 million i.u.; the control group received no treatment. Bacteriological examination was conducted on 7, 14, 21, 35 and 49 d post partum (pp) and milk yield data, fat and protein contents and SCC data were collected every 5th week for the first 200 d of lactation. Occurrence of retained placenta and endometritis were recorded, and the days open of both groups were compared. No effect was observed on the postparturient genital tract health and reproduction indicators. On day 7 pp, four intramammary infections (IMI; two severe clinical; one mild clinical; and one subclinical mastitis) were detected in the untreated control group, whereas there were no IMI in the antibiotic-treated group. At subsequent samplings, there were fewer IMI in the antibiotic-treated group, which were later in lactation, less severe and less persistent. Although SCC was numerically lower in the treatment group, significant differences in SCC between groups could not be detected. Antibiotic-treated heifers produced significantly more milk during the first 15 weeks of lactation than untreated heifers. Over the whole observation period (200 d), peripartum antibiotic-treated heifers produced 323 kg more milk than heifers in the untreated control. Periparturient antibiotic treatment of heifers with penethamate hydriodide prevented IMI during the first week after parturition and achieved a significant increase in milk yield, which was found to be economically beneficial.     

Relationship between the level of N-acetyl-beta-D-glucosaminidase (NAGase) in bovine milk and the presence of mastitis pathogens

Changes in the level of the tissue damage marker enzyme, N-acetyl-beta-D-glucosaminidase (NAGase) in quarter fore milks were found to be related to the presence and types of pathogenic bacteria present and to somatic cell counts (SCC). Minor pathogens (coagulase-negative staphylococci, Corynebacterium bovis) elicited a mild SCC increase (from a mean of 243 X 10(3)/ml in healthy quarters to 504 X 10(3)/ml in infected quarters) with marginal tissue damage (mean NAGase activity increased from 21 in healthy quarters to 28 in infected quarters). Major pathogens (i.e. Staphylococcus aureus, Streptococcus agalactiae, Str. dysgalactiae and Str. uberis) caused more severe tissue damage (mean NAGase of 48) and SCC increases (mean, 2803 X 10(3)/ml). The NAGase test could also be used effectively on composite milk samples where regular monthly NAGase analysis was able to identify correctly 74% of animals having infected quarters. The possibility of combining SCC and NAGase data in order to give a more definite diagnosis of bovine mastitis is discussed.     

Subclinical mastitis in dairy cows in Swiss organic and conventional production systems

The objective was to compare the prevalence of subclinical mastitis (SM) and of udder pathogens in 60 Swiss organic (OP) and 60 conventional production systems (CP). Cows (n=970) were studied for SM prevalence and udder pathogens at median 31 d and 102 d post partum. Cows showing a >or=1+ positive California Mastitis Test (CMT) in at least one quarter were considered to have SM. Cow-level prevalences of SM for visits at 31 d and 102 d post partum (39% and 40% in OP and 34% and 35% in CP) were similar, but quarter-level prevalences of SM were higher (P<0.02) in OP than CP (15% and 18% in OP and 12% and 15% in CP). Median somatic cell counts in milk at 31 d post partum were higher (P<0.05) in OP than CP cows (43000 and 28000 cells/ml, respectively), but were similar at 102 d post partum in OP and CP cows (45000 and 38000 cells/ml, respectively). In milk samples from quarters showing a CMT reaction >or=2+ the prevalences of coagulase negative staphylococci were lower (P<0.05) at 102 d post partum, whereas prevalences of non-agalactiae streptococci were higher (P<0.05) in OP than in CP cows at 31 d and 102 d post partum. In conclusion, under Swiss conditions, subclinical mastitis is a greater problem in organic than in conventional production systems, but differences are not marked.     

Protein degradation in bovine milk caused by Streptococcus agalactiae

Streptococcus (Str.) agalactiae is a contagious mastitis bacterium, often associated with cases of subclinical mastitis. Different mastitis bacteria have been evaluated previously from a diagnostic point of view, but there is a lack of knowledge concerning their effect on milk composition. Protein composition is important in achieving optimal yield and texture when milk is processed to fermented products, such as cheese and yoghurt, and is thus of great economic value. The aim of this in vitro study was to evaluate protein degradation mainly caused by exogenous proteases originating from naturally occurring Str. agalactiae. The samples were incubated at 37°C to imitate degradation caused by the bacteria in the udder. Protein degradation caused by different strains of Str. agalactiae was also investigated. Protein degradation was observed to occur when Str. agalactiae was added to milk, but there were variations between strains of the bacteria. Caseins, the most economically important proteins in milk, were degraded up to 75% in milk inoculated with Str. agalactiae in relation to sterile ultra-high temperature (UHT) milk, used as control milk. The major whey proteins, α-lactalbumin and β-lactoglobulin, were degraded up to 21% in relation to the sterile control milk. These results suggest that different mastitis bacteria but also different strains of mastitis bacteria should be evaluated from a milk quality perspective to gain knowledge about their ability to degrade the economically important proteins in milk.     

Mastitis prevalence in primigravid heifers at parturition

Prevalence of intramammary infection was determined for 382 primigravid heifers within 3 d postpartum on 11 Vermont dairy farms. Data collected during a 5-yr period are summarized. Duplicate quarter milk samples were cultured on tryptose-blood agar plates containing .1% esculin. Intramammary infections were diagnosed in 45.5% of the heifers and 18.7% of quarters. Staphylococcus species were the most prevalent bacteria isolated: they appeared in 25.4% of the heifers and 12.1% of quarters. Only 2.6% of the heifers were diagnosed with Staphylococcus aureus; 22.8% had udder infection caused by other staphylococcal species. Environmental mastitis pathogens, coliforms, and streptococci other than Streptococcus agalactiae were isolated from 14.9% of the heifers and 4.8% of quarters. The prevalence of mastitis among these primigravid heifers at parturition indicates a need to improve methods of diagnosis and control programs.     

Influence of dry period bacterial intramammary infection on clinical mastitis in dairy cows

Milk samples were taken from 1920 quarters (480 cows, six herds) on four occasions to examine the relationship between quarter level intramammary infection (IMI) during the dry period and clinical mastitis in the next lactation. All quarters were sampled at drying off and within 1 wk of calving, and two quarters from each cow were sampled both 0 to 7 and 8 to 14 d before calving. Milk samples were collected from all cases of clinical mastitis during the following lactation. Logistic regression models were developed to investigate the associations between IMI present during the sampling period and clinical mastitis. The probability of a quarter succumbing to clinical mastitis increased when Streptococcus dysgalactiae, Streptococcus faecalis, Escherichia coli, or Enterobacter spp. were cultured at drying off and when Escherichia coli, coagulase-positive staphylococcus, Serratia spp., or Streptococcus faecalis were cultured in two out of three late dry and post-calving samples. Quarters from which Corynebacterium spp. were isolated at drying off were at an increased risk of clinical mastitis, whereas the presence of Corynebacterium spp. in the late dry and post-calving samples was associated with a reduction in the risk of clinical mastitis. The risk of mastitis for specific pathogens increased if the same species of bacteria that had caused mastitis was isolated at least twice in the late dry and post-calving samples. Kaplan-Meier survival plots indicated that clinical mastitis associated with dry period infections was more likely to occur earlier in lactation than clinical mastitis not associated with dry period infections. There was evidence of quarter susceptibility to IMI or the possibility that infection with one organism led to clinical mastitis with another.     

Management practices associated with the incidence rate of clinical mastitis.

Risk factors for the incidence rate of clinical mastitis were studied in 274 Dutch dairy herds. Variables that were associated with resistance to disease were the feeding, housing, and milking machine factors. Variables that were associated with exposure were grazing, combined housing of dry cows and heifers, and calving area hygiene. Postmilking teat disinfection in herds with a low bulk milk somatic cell count and years of practicing dry cow therapy were positively associated with the incidence rate of clinical mastitis. Herds with a low bulk milk somatic cell count and in which postmilking teat disinfection was not used had lower incidence rates of clinical mastitis than did other herds. The incidence rate of clinical mastitis caused by Escherichia coli was mostly related to housing conditions, hygiene, and machine milking. The incidence rate of clinical mastitis caused by Staphylococcus aureus was mostly related to factors associated with bulk milk somatic cell count and factors that might be due to cause and effect reversal. A strong positive correlation existed between the incidence rate of clinical mastitis caused by Streptococcus dysgalactiae and the incidence rate of clinical mastitis caused by Staph. aureus. The incidence rate of clinical mastitis caused by Streptococcus dysgalactiae was related to nutrition, milking technique, and machine milking. The incidence rate of clinical mastitis caused by Streptococcus uberis was associated with factors related to housing, nutrition, and machine milking.     

Subclinical and clinical mastitis in heifers following the use of a teat sealant precalving

This study investigated the effect in heifers of infusion of a bismuth subnitrate teat-canal sealant and bacterial intramammary infection (IMI) precalving on prevalence of postcalving IMI and incidence of clinical mastitis in the first 2 wk postcalving. Glands (n = 1,020) from heifers (n = 255) in 5 seasonally calving, pasture-fed dairy herds were randomly assigned within heifer to 1 of 4 treatment groups (no treatment; mammary gland secretion collection; infusion of a teat sealant; or sample collection with infusion of teat sealant). Heifers within a herd were enrolled on one calendar day, 31 d on average before the planned start of the seasonal calving period. Duplicate milk samples were collected from each gland within 4 d after calving for bacterial culture. Herd owners collected duplicate milk samples, before treatment, for bacterial culture from glands they defined as having clinical mastitis. The gland prevalence of IMI precalving was 15.5% and did not differ between herds. Bacteria isolated precalving included coagulase-negative staphylococci (76.9% of all bacteriologically positive samples), Streptococcus uberis (14.1%), Staphylococcus aureus (5.1%), Corynebacterium spp. (3.8%), and others (0.1%). The presence of an IMI precalving increased the risk of an IMI postcalving 3.6-fold and the risk of clinical mastitis 4-fold, relative to no IMI precalving. Infusion of the teat sealant reduced the risk of postcalving IMI due to Strep. uberis by 84%, and of clinical mastitis by 68%. Sampling the glands precalving had no effect on postcalving IMI or on clinical mastitis incidence. Use of an internal teat canal sealant in heifers precalving may be a useful tool for reducing the risk of subclinical and clinical mastitis in heifers.     

Prepartum milking effects on parlour behaviour, endocrine and immune responses in Holstein heifers

Transition of primiparous heifers to the milking herd is a period with multiple stressors. The objective of these studies was to determine effects of parlour experience and prepartum milking (pre-milking) on behavioural and physiological indicators of stress after calving. Two experiments were conducted, one was in a free-stall housing confinement system and the second was in a modified grazing system. Forty-eight first-calf heifers were assigned to three treatments: control; experienced heifers taken through the parlour without milking; or pre-milk heifers milked for 3 weeks prior to estimated parturition. Blood was collected within 24 h of parturition and on days 3, 5, 7, 10 and 14 following parturition for cortisol and acute phase protein determination. In the grazing system, 20 heifers were assigned to a prepartum milked or control group as in the confinement system and behaviour observations included days -21, -14, -7, -5, -3 and -1 relative to calving and days 1, 3, 7, 9, 14, and 16 post-calving. Milk production was greatest for prepartum milked heifers in both housing systems. However, somatic cell score was reduced by prepartum milking only in the confinement system. Balking occurred least in parlour-experienced heifers. In confinement housing, shifting while in the parlour was the only behaviour that was greater at first milking in control heifers. Kicking was most frequent for parlour experienced heifers on day 2. Grazing system pre-milked heifers shifted more at their first milking (day -21) than did the controls at their first milking (day 1). Shifting within cow was greatest on day -21 compared with day -5 (P<0.05). Pre-milked heifers shifted more on day 1 post-calving than did the control heifers (P<0.05). These results showed that shifting was the most indicative behaviour of restlessness, was transient, and decreased by day 5 prior to calving. Cortisol and alpha1-acid glycoprotein concentrations were not different; however, haptoglobin increased for all treatments up to and including day 3 and haptoglobin concentrations of pre-milked heifers began to decrease by day 5 post-calving. Pre-milked heifers had lower haptoglobin concentrations than the control heifers and tended to have lower concentrations than experienced heifers on day 10 post partum. By day 14 post partum, all haptoglobin concentrations were <200 microg/ml, but the haptoglobin concentration of control heifers was greater than that of pre-milked and experienced heifers. These results showed that prepartum milking and parlour experience shorten some acute phase protein responses, but minimally affect early parlour behaviours.