Characteristics and management practices associated with milk production in dairy herds in Ohio enrolled in official Dairy Herd Improvement Association programs.

OBJECTIVE: To determine herd characteristics and management practices associated with milk production in dairy herds enrolled in official Dairy Herd Improvement Association (DHIA) programs in Ohio. SAMPLE POPULATION: 186 dairy farms in Ohio. PROCEDURE: All herds in official DHIA programs in 9 counties were invited to participate. Information regarding herd characteristics and management practices was obtained, using a standardized questionnaire. Bulk-tank milk samples were obtained for bacteriologic culture. Official DHIA test-day records were obtained, and associations were identified, using multivariable ANOVA procedures. RESULTS: Of 479 eligible producers, 186 (39%) participated, and consecutive bulk-tank milk samples were available for culture from 172 (36%). Streptococcus agalactiae and Mycoplasma spp were not recovered from bulk-tank milk samples, but Staphylococcus aureus was recovered from 64 (37%) herds. Mean (+/- SD) number of lactating cows in participating herds was 97+/-66, with 123 (66%) herds milking < 100 cows. The RHA was significantly associated with number of cows in milk, estimated percentage of herd detected in estrus, reported annual percentage of heifer calves born alive that died before 8 weeks old, percentage days in milk, use of bovine somatotropin during the preceding 2 years, and sex of the person completing the questionnaire. CONCLUSIONS AND CLINICAL RELEVANCE: In this study, the strongest indicator of milk production was number of cows in milk. However, merely adding cows to a herd should not be considered to guarantee increased milk production, because other management traits could be confounded with increased number of cows in a herd.

Metabolic hoof horn disease. Claw horn disruption.

Low-quality hoof horn is a frequent underlying cause of lameness in cattle. Because the lesions that are observed are the result of insults that affect horn production at the cellular level, the term claw horn disruption has been proposed to describe the disease process. Although claw horn disruption may result from multiple etiologies, the response of the keratinocytes is relatively nonspecific in that lesions often appear the same regardless of cause. To solve herd problems, the investigation of possible etiologies must be integrated with a basic understanding of the anatomic and physiologic features of hoof horn production.

Herd characteristics and management practices associated with bulk-tank somatic cell counts in herds in official Dairy Herd Improvement Association programs in Ohio.

OBJECTIVE: To identify herd characteristics and management practices associated with bulk-tank somatic cell counts (BTSCC) in dairy herds in Ohio enrolled in official Dairy Herd Improvement Association (DHIA) programs. SAMPLE POPULATION: 186 dairies in Ohio. PROCEDURE: All herds in official DHIA programs in 9 counties were asked to participate. Extensive information regarding herd characteristics and management practices was obtained, using a standardized questionnaire. Bulk-tank milk samples were requested from all participating herds for bacterial culture. Official DHIA test-day records for January 1997 were obtained from all herds enrolled in official DHIA programs in the 9 counties. Potential associations were identified, using multivariable ANOVA. RESULTS: Participation was 186 of 479 (39%) herds. Streptococcus agalactiae and Mycoplasma spp were not isolated from bulk-tank milk samples. Staphylococcus aureus was isolated from 64 of 172 (37%) of the herds. The BTSCC were inversely associated with peak daily milk production, postmilking teat disinfection, percentage of eligible cows in the herd detected in estrus, and directly related to the extent to which BTSCC was perceived as a herd problem during the preceding 2 years. Type of housing for nonlactating cows and product used for treatment of nonlactating cows also were significantly associated with BTSCC. CONCLUSIONS AND CLINICAL RELEVANCE: Consideration of herd characteristics and implementation of management practices associated with BTSCC could result in increased milk yield and production of milk with lower BTSCC.

Subclinical laminitis in dairy cows: use of severity of hoof lesions to rank and evaluate herds.

Thirteen high-yielding Holstein herds in Ohio were ranked according to the prevalence and severity of lesions associated with subclinical laminitis (pododermatitis aseptica diffusa). One hundred and seventy-three first lactation cows, most of them in their first 100 days of lactation, and 30 pregnant heifers were assessed. The lesions evaluated were yellow waxy discoloration of the sole, haemorrhage of the sole, separation of the white line, and erosion of the heel. Each herd consisted of more than 100 lactating cows and all the herds were producing over 8500 kg of milk per cow on a rolling herd average basis. The lactating cows were housed in cubicles and maintained in concrete yards. The lesions associated with subclinical laminitis were prevalent among the 13 herds, but when each category of lesion was considered independently, significant differences in prevalence and severity were detected among the herds. These differences suggest that it may be possible to make changes in herd management which may influence the prevalence of lesions.

Evaluation of an acriflavine disk assay for differentiating Staphylococcus aureus from other staphylococci isolated from bovine milk.

OBJECTIVE: To develop an acriflavine disk assay for identification of Staphylococcus aureus and to test whether the acriflavine disk assay could be used to differentiate S aureus from other staphylococci isolated from bovine milk samples. DESIGN: Prospective study. SAMPLE POPULATION: 882 staphylococcal isolates from bovine milk samples and 3 S intermedius isolates from dogs. PROCEDURE: Paper disks saturated with various amounts of acriflavine were used in a growth inhibition assay to determine the amount of acriflavine that would most reliably differentiate S aureus from other staphylococci. For all isolates, hemolytic pattern, results of tube coagulase tests after 4 and 24 hours of incubation, growth on acriflavine-supplemented media, results of an acriflavine disk assay, and results of an automated identification system were determined. RESULTS: 10 micrograms of acriflavine/disk was determined to be the most appropriate concentration for use in the assay. All 112 isolates identified as S aureus by the automated identification system were resistant to this concentration of acriflavine, and only 1 of 236 isolates identified as non-S aureus staphylococci was resistant. There was substantial agreement between results of using the acriflavine disk assay as a diagnostic criterion for differntiating S aureus isolates from non-S aureus staphylococci and results of the automated identification system. Agreement between results of determining hemolytic pattern and results of other diagnostic tests was only moderate. CLINICAL IMPLICATIONS: The acriflavine disk assay, using 10 micrograms of acriflavine/disk, was a practical, accurate method for differentiating S aureus isolates from non-S aureus staphylococci.

Evaluation of cow-level risk factors for the development of winter dysentery in dairy cattle.

OBJECTIVE: To identify exposures to etiologic agents and to identify characteristics that could explain risk of disease for adult cattle in herds affected by winter dysentery (WD). ANIMALS: 229 lactating and nonlactating adult cattle (125 case and 104 control cattle) selected from 12 dairy herds. PROCEDURE: A case-control study, using multivariate conditional logistic regression and controlling for herd effects, was used to develop a model for risk factors associated with disease for each cow. RESULTS: Likelihood of developing disease increased as the ELISA value for bovine coronavirus (BCV) antigen detectable in feces increased (odds ratio [OR] = 2.94 for each 0.100 increase in BCV antigen ELISA value). Pregnant cattle were less likely to develop WD, compared with nonpregnant herdmates. Cows with high acute BCV antibody titers that seroresponded had greater odds of developing disease, compared with seroresponding cows with low acute titers. However, among those cows that did not serorespond, high acute antibody titers were associated with lower odds of developing the disease. CONCLUSION: In herds affected by WD, ill cows were more likely to shed detectable amounts of BCV antigen in their feces, and pregnancy appeared to protect cattle from the disease. The measured interaction between BCV seroresponse and acute BCV antibody titer may be evidence of an immunopathologic condition, but could also have been attributable to dynamics of the ELISA or study design. CLINICAL RELEVANCE: Factors that explained a cow's risk for illness within WD-affected herds may have been surrogate measures for that cow's nonspecific and BCV-specific immune profile.

Epidemiologic herd-level assessment of causative agents and risk factors for winter dysentery in dairy cattle.

OBJECTIVE: To test the association between exposure to bovine coronavirus (BCV) and outbreaks of winter dysentery (WD) in dairy herds and to examine other risk factors for outbreaks of WD in dairy herds. ANIMALS: 12 dairy herds in Ohio affected with WD (case herds). For each case herd, 2 unaffected herds from the same area were concurrently used as control herds. PROCEDURE: A case-control study was conducted, using herds as the unit of investigation. Multivariate logistic regression modeling was used to identify risk factors for contracting disease. RESULTS: 4 factors appeared to increase a herd's risk for WD: increase in herd prevalence of adult cows that had a fourfold or more increase in BCV serum IgG antibody titer; increase in herd prevalence of adult cows that had a fourfold or more increase in bovine viral diarrhea virus (BVDV) titer; housing cattle in tiestall or stanchion barns rather than free-stall facilities; and use of equipment to handle manure and subsequently handle feed. The adjusted population-attributable risk for these variables was 71, 43, 53, and 31%, respectively, and 99% overall, indicating that these variables had considerable impact on WD outbreaks for the study population. CONCLUSIONS AND CLINICAL RELEVANCE: In dairies in Ohio, recent herd exposure to BCV appeared to increase the risk for WD outbreaks. Some WD outbreaks might have been associated with acute BVDV infection. Certain housing and management practices may have increased the risk of an outbreak of WD.

Supplemental dietary biotin for prevention of lesions associated with aseptic subclinical laminitis (pododermatitis aseptica diffusa) in primiparous cows.

OBJECTIVE: To evaluate, in primiparous cows, the effect of dietary biotin supplementation on severity of lesions of aseptic subclinical laminitis. ANIMALS: 100 primiparous cows in a 800-cow commercial dairy herd. PROCEDURE: Cows were assigned after calving to a biotin-supplemented (20 mg/head/d) or control group on an alternating basis. Digits 3 and 4 of the left forelimb and right hind limb were examined at a mean of 25, 108, and 293 days after parturition. Toe length, hoof angle, and heel depth were measured, and hooves were examined for solear hemorrhage, yellow solear discoloration, separation of the white line, and heel erosion. Serum and milk biotin concentrations were also measured. RESULTS: Serum biotin concentrations were significantly higher for supplemented than for control cows. During the second examination, prevalence of separation of the white line of digits 3 and 4 of the hind limb and digit 4 of the forelimb was lower for supplemented than for control cows. Mean decrease in heel depth between the first and third examinations was approximately twice as great for digit 4 of the forelimb and 4 times as great for digit 3 of the forelimb in supplemented, versus control, cows. Other differences were not found. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that supplemental dietary biotin may have a beneficial effect on hoof health in intensively managed primiparous dairy cows.

Reproducibility of antibiogram of bovine mammary gland staphylococci under conditions of repeated subculturing.

The reproducibility of antibiogram profiles of 10 staphylococcal isolates of bovine mammary gland origin was tested under conditions of repeated subculturing. Prototype (original or index) antibiogram profiles were determined by subculturing these isolates from stock cultures stored at -70 degrees C. The isolates were then subcultured four times on blood agar and antibiogram profiles determined at each subculture on Mueller-Hinton agar. The antibiogram profiles of each isolate at each subculture were compared with the prototype profiles of that isolate. At repeat antibiogram determinations, deviations of < or = 5 mm in the individual zones of inhibition of penicillin, ampicillin and streptomycin from the prototype antibiogram profiles, resulted in a shift of only three isolates from the resistant to intermediate and one isolate from intermediate to resistant status of antibiotic susceptibility classification. It is suggested that in the interpretation of antibiogram, susceptibility classification (resistant, intermediate, or susceptible) variations accruing from a few millimetres differences in the diameter of the zones of inhibition should probably be disregarded.

Prevalence of lesions associated with subclinical laminitis in first-lactation cows from herds with high milk production.

OBJECTIVE: To determine prevalence of lesions associated with subclinical laminitis in first-lactation Holstein cows during early lactation and pregnant Holstein heifers during late gestation in herds with high milk production. DESIGN: Cross-sectional study. ANIMALS: 203 cattle in 13 herbs. PROCEDURE: Cattle were placed in lateral recumbency to allow visual examination and photography of their hooves. Claws on a forelimb and hind limb were examined on all cattle. Observable categories of lesions considered to be associated with subclinical laminitis in our study included yellow waxy discoloration of the sole, hemorrhage of the sole, separation of the white line, and erosion of the heel. RESULTS: Lesions in at least 1 of the categories were found in all herds. Lesions in all categories were found in 11 of 13 herds. Among claws, hemorrhage of the sole was observed most frequently in the lateral claw of the hoof of the hind limb. When days in milk was treated as a covariate, significant (P < 0.01) differences were detected in the prevalence of lesions between herds. CLINICAL IMPLICATIONS: Because the prevalence of lesions differed significantly among herds, it is logical to believe that causative factors and corrective measures also may have differed among herds.

Interspecific conjugal transfer of antibiotic resistance among staphylococci isolated from the bovine mammary gland.

In vitro transferability of penicillin, streptomycin, tetracycline, and erythromycin resistance from coagulase-negative staphylococci to Staphylococcus aureus and among the former species of bovine mammary gland origin was examined by bacterial mating on filters and by mixed-culture matings in broth and in skim milk. One hundred twenty-six (42 each on filter, in broth, and in skim milk) matings were performed among 37 isolates of different Staphylococcus species. Transfer of resistance to penicillin, tetracycline, or erythromycin was not detected. Of 51 matings performed to determine streptomycin-resistance transfer, 9 (3 each on filters, in broth, and skim milk) were successful. Nine strains representing 3 species of coagulase-negative staphylococci were tested as prospective donors of streptomycin resistance. Of these, 2 strains could transfer streptomycin resistance. A double-resistant donor, S hominis, not only transferred its streptomycin resistance to an S chromogenes strain lacking resistance, but also to an S aureus strain already carrying penicillin and tetracycline resistance. The transfer of streptomycin resistance from the donor S hominis, harboring 2 plasmids, to a plasmidless S chromogenes recipient strain was associated with apparent acquisition of the smaller plasmid of the donor by the recipient. The single-resistant donor, S epidermidis 681A, transferred streptomycin resistance to a tetracycline-resistant S aureus recipient. This strain however, failed to transfer its streptomycin resistance to another S aureus, 2 S hyicus, and 1 S xylosus recipient. Frequency of transfer of streptomycin resistance ranged from 1.1 x 10(-5) to 1 x 10(-4). When transfer of resistance was successful, attempts were made to characterize the transfer process.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of abnormal uterine discharge with new intramammary infection in the early postpartum period in multiparous dairy cows.

The association of abnormal uterine discharge with the development of intramammary infection (IMI) was studied in 62 multiparous Holstein cows during the nonlactating period and from lactation days 3 through 30. Duplicate milk samples were obtained from each mammary gland at approximately day 30 of the nonlactating period. Milk samples for bacteriologic culture also were obtained from each gland from all cows at the end of the previous lactation, at parturition, and on a minimum of 7 additional dates during the first 30 days of lactation. Beginning after parturition and continuing once weekly for 4 weeks, each cow was examined, using a vaginal speculum to visually estimate the quantity of abnormal uterine discharge in the vagina. Additionally, uterine swab specimens were obtained for aerobic bacteriologic culture. Cows were allotted to groups on the basis of the maximal amount of abnormal uterine discharge observed at any 1 of the 4 examinations. Cows in group 1 had normal discharge or < 30 ml of abnormal discharge; in group 2, > or = to 30 ml of abnormal discharge, observed only on examination by vaginal speculum; and in group 3, > or = to 30 ml of abnormal discharge visible externally. A difference was not detected in the development of new IMI in the nonlactating period between cows that subsequently developed uterine discharge and those that did not. Although significant differences were not found, a tendency for lactating cows with abnormal uterine discharge to be at increased risk for developing new IMI was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of coagulase-negative Staphylococci isolated from bovine intramammary infections.

Coagulase-negative Staphylococci (CNS) isolated from 86 different bovine intramammary infections (IMI) were investigated for their plasmid content, antimicrobial resistance, and infection characteristics. Plasmids were isolated from 30.2% of CNS. Number of plasmid bands ranged from 1 to 5. With the exception of tetracycline resistance, the presence of plasmids was not related to antibiotic resistance. Staphylococcus chromogenes was the CNS most frequently isolated from bovine IMI. Intramammary infections were of long duration (mean = 222 days) and resulted in a low incidence of clinical mastitis (8.1% of IMI). The greatest percentage of IMI (55%) were detected in heifers with 57% of these IMI first detected at calving. A total of 56% of IMI originated during the dry period in second lactation or older cows. The number of plasmid-positive CNS IMI was greater (P < 0.05) in multilactational cows when compared to heifers. The presence of a plasmid-positive CNS had no influence on duration of IMI, origin of IMI, clinical status of the infection, and elimination of IMI.

Concurrent experimentally induced infection with Eimeria bovis and coronavirus in unweaned dairy calves.

Over a period of 3 summers, 21 colostrum-fed Holstein bull calves, 1 to 3 days old, were assigned to 7 replicates, each consisting of 3 calves. Within each replicate of 3 calves, 2 were selected at random, to be given 100,000 to 146,000 sporulated coccidia oocysts (principally Eimeria bovis) orally 60 hours after arrival at the college research farm. On the thirteenth day after coccidia inoculation, 1 of the 2 calves that had been given coccidia and the third calf that had not been inoculated, were given coronavirus by intranasal and oral routes. Calves were observed daily, and consistency of feces was scored visually. Nasal swab specimens for indirect immunofluorescent antibody testing for coronavirus and fecal samples for oocyst determination were obtained approximately every third day. Of 7 calves that were given only coronavirus, 3 developed diarrhea of short duration. Of 7 calves that were given only coccidia oocysts, 6 developed diarrhea. All 7 calves inoculated initially with coccidia and subsequently with coronavirus developed diarrhea. For 5 of 7 replicates, calves that were given coccidia and coronavirus developed diarrhea first. When overall severity, measured by fecal score and by blood in the feces, was compared, calves inoculated with coccidia followed by coronavirus were more severely affected (P less than 0.05) than were calves that were given only coronavirus. Calves that were given only coccidia oocysts appeared more severely affected than calves that were given only coronavirus, but differences were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of partial budgeting to determine the economic outcome of Staphylococcus aureus intramammary infection reduction strategies in three Ohio dairy herds.

Efforts to reduce the prevalence of Staphylococcus aureus intramammary infection were monitored in 3 Ohio dairy herds. Bacteriologic culturing of milk from all lactating cows in each herd was completed multiple times to identify infected cows and monitor reduction. Partial budgeting techniques were used to determine the economic outcome of the reduction program. Of particular emphasis was the economic impact of culling to maintain or achieve milk quality premium payments on the basis of bulk tank somatic cell counts. The prevalence of S aureusinfected cows was reduced in each herd. Culturing of milk from all lactating cows appeared to be an effective method to identify infected cows. Although numbers were limited, it also appeared that culturing of composite quarter samples was effective as a herd screening test to identify S aureus-infected cows. Bacteriologic culturing had a negative financial impact in all 3 herds. Using partial budgeting to assess the economic impact of the programs, it was determined that 2 herds experienced negative financial impacts as a result of an excess culling rate when compared with a 12-month baseline period prior to the initiation of the project. All herds had increased milk production per cow during the study as measured by the mature-equivalent method. However, when actual production was considered, increased milk production in each herd was not as great as that of other Ohio herds enrolled on Dairy Herd Improvement Association testing programs.(ABSTRACT TRUNCATED AT 250 WORDS)

Costs associated with selected preventive practices and with episodes of clinical mastitis in nine herds with low somatic cell counts.

Nine dairy herds (mean size, 149 cows) with bulk-tank milk somatic cell counts of less than 300,000 cells/ml and greater than 80% of cows with Dairy Herd Improvement Association linear somatic cell counts less than or equal to 4 were selected for study. Each herd was monitored for 12 consecutive months. Duplicate quarter-milk specimens were collected from each cow for bacteriologic culturing at beginning of lactation, cessation of lactation, and at the time of each clinical episode of mastitis. Streptococcus agalactiae was never isolated and Staphylococcus aureus was isolated from less than 1% of all quarters. There were 554 episodes of clinical mastitis. During the year of study, the incidence rate of clinical mastitis varied from 15.6 to 63.7% of cows among the 9 herds. Mean costs per cow per year in herd for mastitis prevention were: $10 for paper towels, $3 for nonlactating cow treatment, and $10 for teat disinfectants. Mean cost associated with clinical mastitis was $107/episode. Approximately 84% ($90) of the costs attributed to a clinical episode were associated with decreased milk production and nonsalable milk. Costs of medication and professional veterinary fees per clinical episode varied significantly among the 9 herds. Three of the herds did not have a veterinarian treat a clinical episode of mastitis during the year of study even though 2 of these herds had the first and third highest incidence rates of clinical mastitis. When calculated on a per cow in herd basis, mean costs of $40/cow/year were attributed to clinical mastitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of dairy herd improvement monthly summary data to monitor intervention strategies in a dairy herd experiencing suboptimal reproductive performance and reduced milk production.

An 87-cow dairy herd with a history of high milk production was visited because of reduced reproductive performance and decreasing milk production. Cows that had recently delivered calves were thin, and many cows had evidence of previous episodes of laminitis. A ration that provided an unfavorable forage-to-concentrate ratio was being fed. In addition to various diagnostic efforts, management changes that were made included alteration of the ration and installation of a computer-operated feeder. After the initial visit, the herd was monitored for 30 months by the use of Dairy Herd Improvement monthly herd summary data. Several potential strengths and weaknesses of using selective production and reproduction monthly summary statistics were illustrated by this study. Milk production, as monitored by mature-equivalent production and average relative value-milk, continued to increase throughout the 30 months after intervention. Reproductive performance, as indicated by first-service conception rate, did not begin to improve until the final 6 months of the monitoring period. Overall, in addition to assisting in diagnostic efforts. Dairy Herd Improvement monthly herd summary data may be used to establish goals, provide comparisons, and maintain producer interest after practitioner intervention in herd management.

Mastitis control services and utilization of milk somatic cell count data by veterinarians in Ohio.

A telephone survey was conducted of 50 randomly selected Ohio-licensed veterinarians engaged in dairy practice. The survey's purpose was to determine the extent of mastitis control services offered by practitioners and to assess their utilization of milk somatic cell count (SCC) data on individual cows available from the Dairy Herd Improvement Association (DHIA). During the preceding year, 96% (48/50) of practitioners surveyed had performed bacteriologic culture of milk samples. Practitioners were twice as likely to have performed culture on milk from mastitic cows that failed to respond to treatment as they were to have performed culture for purposes of identifying pathogen trends within a herd. Veterinarians in predominantly dairy practices were more likely to have completed bacteriologic examination of milk in their own laboratories than were veterinarians who were engaged in less than 50% dairy practice (P = 0.016). Most veterinarians (83%) reported that coagulase test results were available or that Staphylococcus aureus was differentiated from other staphylococcal species. Streptococcus agalactiae was not differentiated from other streptococcal species by 35% of practitioners surveyed. For veterinarians with clients enrolled in the DHIA, 91% (43/47) reported looking at, discussing, or otherwise using the DHIA records. Eighty-one percent (35/43) of veterinarians who had clients using services from the DHIA reported that clients also received individual cow milk SCC results. Veterinarians engaged in predominantly, dairy practice expressed a greater familiarity with the linear score method of SCC reporting than did veterinarians whose practices were less than 50% dairy (P = 0.085); however, both groups reported a preference for raw SCC data.(ABSTRACT TRUNCATED AT 250 WORDS)

A longitudinal study of bovine coronavirus enteric and respiratory infections in dairy calves in two herds in Ohio.

This prospective longitudinal study examined the epidemiology and disease syndrome associated with bovine coronavirus (BCV) infections in a cohort of 8 conventional calves from 0 to 120 days of age, in two dairy herds in Ohio. The periods of respiratory shedding of BCV were determined by direct immunofluorescent (DIF) staining of nasal epithelial cells and ELISA of nasal swab supernatant fluids. The periods of fecal shedding of BCV were determined by ELISA and immunoelectron microscopy (IEM). The isotype-specific antibody titers to BCV in serum (at selected intervals between 0 and 120 days of age) and the post-suckling (24 to 48 h after birth) total immunoglobulin levels were examined by ELISA and zinc sulfate turbidity tests, respectively. Of the 8 calves studied, 4 had evidence of BCV respiratory (by DIF or ELISA) or enteric infections (by IEM or ELISA) in association with diarrhea or rhinitis, even though 7 of 8 calves showed increases in one or more serum antibody isotypes to BCV and 6 of 8 calves showed BCV respiratory or enteric antigen shedding by ELISA. Serological antibody titer increases occurred in 3 calves before 30 days of age and in 4 calves after 30 days of age; two of the latter calves had a second rise in serum antibody titers to BCV after the initial rise. A serological antibody titer increase was not observed in one calf. This suggests that BCV infections may be very common in a closed herd and may occur in older calves, although many may be subclinical and some may be recurrent. There were no statistically significant correlations between total serum immunoglobulin levels or BCV antibody isotype titers in serum (24-48 h after birth) and clinical disease or infection by BCV; however, calves with low levels of IgA BCV antibodies in serum (24-48 h after birth) had a significantly greater average number of days with diarrhea than those calves having high levels of IgA BCV-specific antibodies in serum.

Relationships among selenium, vitamin E, and mammary gland health in commercial dairy herds.

Nine well-managed dairy herds were monitored for 1 yr to determine if bulk tank SCC and rate of clinical mastitis were associated with dietary and plasma Se and vitamin E status. Intakes of Se and vitamin E were 1 to 16 mg/d and 100 to 900 mg/d, respectively. Plasma Se concentrations were correlated positively with intakes of Se below 5 mg/d but were independent of Se intakes above 5 mg/d. Feeding vitamin E increased plasma concentrations of tocopherol, but the influence of dietary vitamin E on plasma concentrations was four times greater for dry cows than for lactating cows probably due to secretion of tocopherol into colostrum and milk. Bulk tank SCC averaged 5.4 log10/ml and decreased significantly as Se concentration in plasma increased. Plasma glutathione peroxidase was correlated positively to Se intake but negatively to SCC. Rate of clinical mastitis was negatively related to plasma Se concentration and concentration of vitamin E in the diet. An apparent interaction between dietary Se and vitamin E was evident since herds fed high amounts of Se tended to have high rates of clinical mastitis, but not if high amounts of vitamin E were fed. These data confirm earlier findings that Se and vitamin E status of dairy cows are related to mammary gland health.