Quantification of bovine IgG, IgM and IgA antibodies to Clostridium perfringens B-toxin by enzyme immunoassay I. Preparturient immunization for enhancement of passive transfer of immunity

A quantitative competitive binding "triple-sandwich" enzyme immunoassay was developed and used to evaluated pathogen/class-specific antibody responses in Holstein-Friesian cows vaccinated against Clostridium perfringens B-toxin. Vaccination of cows at six weeks and again at two weeks prepartum increased pathogen-specific IgG levels in each dam's colostrum and respective calf's serum. Pathogen-specific IgG and IgM concentrations in dams' sera and colostra were related to subsequent pathogen-specific IgG and IgM neonatal sera concentrations. Only pathogen-specific IgA in dams' colostra was correlated to neonatal levels, possibly owing to a different origin and role of this immunoglobulin class. All class-specific colostral immunoglobulin levels were related to subsequent neonatal concentrations. Isotypic antibody responses against C. perfringens B-toxin were found with pathogen-specific IgM predominant in dams' sera and pathogen-specific IgA predominant in colostra and neonatal sera.     

An outbreak of dictyocaulosis in lactating cows on a dairy farm

CASE DESCRIPTION: The owner of a herd of 74 Holstein-Friesian cattle reported decreased milk production, weight loss, and coughing among lactating cows. Owner-initiated antimicrobial treatment was unsuccessful; 1 lactating cow died, and 50% of the lactating cows had clinical signs of respiratory distress, such as tachypnea and coughing. CLINICAL FINDINGS: On the basis of history, physical examination findings, and fecal examination results, affected animals were determined to have Dictyocaulus viviparus (lungworm) infestation. The disease history suggested that the herd contained cows with subclinical patent lungworm infestations; after introduction of susceptible heifers, the pastures had become heavily infested with D viviparus and clinical problems subsequently developed in both newly introduced and resident cows. TREATMENT AND OUTCOME: Affected and unaffected heifers and adult cows were treated with a pour-on formulation of eprinomectin (0.5 mg/kg [0.23 mg/lb]). One animal died, but 2 weeks after treatment, clinical signs among affected cattle were markedly improved. Ten weeks after treatment, milk production improved from 23 kg/cow/d (51 lb/cow/d) to 28 kg/cow/d (62 lb/cow/d). CLINICAL RELEVANCE: The outbreak provides additional evidence that dictyocaulosis is becoming more common among adult dairy cattle, rather than almost exclusively affecting young stock. This may be attributable to anthelmintic use and management practices on dairy farms. Combined with anecdotal reports of an increase in the incidence of dictyocaulosis among adult cattle in North America, D viviparus infestation should be included as a differential diagnosis for decreased milk production, weight loss, and coughing among adult dairy cattle.     

High frequency of Mycobacterium bovis DNA in colostra from tuberculous cattle detected by nested PCR

We evaluated by nested PCR reaction, different cow secretions from a herd with 48% of prevalence of bovine tuberculosis (BTB), seeking to determine niches where Mycobacterium bovis could be found. Postmortem examination of 18 (75%) tuberculin reacting cows allowed demonstrates BTB-compatible lesions in six, all of them PCR positives in milk and four in colostra samples. Our results showed that up to 62% of the colostra analysed contained M. bovis DNA, whereas only 18% of milk gave a positive reaction. Moreover, in bronchoalveolar lavages from cattle with compatible lesions in lungs or lymph nodes, where macrophages account up to 90% of cells, we did not find evidences of M. bovis. Altogether, these results suggest that differences in the anti-bacterial capacity of bovine macrophages, dependent upon microenvironment and organ-specific factors, exist. Alternatively, we hypothesize that hypoxic conditions that are encountered in mammary glands macrophages could induce M. bovis entrance into a 'dormancy-like' state, and that the high number of colostra samples were M. bovis was detected, could be an indicator of reactivation during 'peripartum'.     

Non-systemic erosive stomatitis of unknown aetiology in a dairy cow herd in New Zealand

CASE HISTORY: Veterinarians from the Investigation and Diagnostic Centre (IDC), Wallaceville, New Zealand, investigated a novel vesicular disease in a 397-cow dairy herd, characterised by erosive stomatitis. CLINICAL AND PATHOLOGICAL FINDINGS: The investigation commenced with a report of erosive stomatitis in four dairy cows. The herd was examined that day and 30/397 (8%) adult cows were found to be affected. Two weeks later, the oral cavity of 180 cows from one management group were re-examined, and it was estimated that 80% of this group had healing erosive lesions. During the course of the investigation, intact vesicles were observed on the muzzle of two affected animals. None of the affected animals was systemically ill and there was no decrease in milk production. DIAGNOSIS: No infectious aetiological agent was detected using virus isolation, polymerase chain reaction (PCR), electron microscopy (EM) and serological tests, for any exotic infectious vesicular disease or any endemic cause of vesicular disease. CLINICAL RELEVANCE: Lesions of erosive stomatitis occurring in cattle must be differentiated from vesicular disease during exotic disease investigations.     

Synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2alpha in combination with melengestrol acetate

Nonlactating Bos indicus x Bos taurus cows were used in three herds to determine the efficacy of different PGF2alpha treatments in combination with GnRH and melengestrol acetate (MGA) for a timed artificial insemination protocol. The start of the experiment was designated as d 0, at which time cows were assigned a body condition score and received 100 microg of GnRH. Cows were fed MGA (0.5 x mg x cow(-1) x d(-1)) on d 1 to 7. On d 7, cows received either a single injection of PGF2alpha (Lutalyse sterile solution; 25 mg; n = 297), a single injection of cloprostenol sodium (Estrumate; 500 microg; n = 297), or half the recommended dose of PGF2alpha (12.5 mg; n = 275) on d 7 and 8. On d 10, all cows were artificially inseminated and received 100 microg of GnRH. Pregnancy rates to the timed artificial insemination (39%) were not affected by treatment, herd, or treatment x herd. There was an effect (P < 0.01) of artificial insemination sire on timed artificial insemination pregnancy rate for one herd, but not the other two herds. Herd influenced (P < 0.05) 30-d pregnancy rates, but there were no treatment or treatment x herd effects as 72.3% of the cows became pregnant during the first 30 d of the breeding season. Results indicate that the type of PGF2alpha treatment administered 7 d after GnRH did not influence timed artificial insemination pregnancy rates in nonlactating Bos indicus x Bos taurus cows.     

Gastrointestinal parasites presence during the peripartum decreases total milk production in grazing dairy Holstein cows

Parasitism in cattle is known to impair growth and development. Recent findings suggest that productivity of adult animals is also affected, but little is known about the physiological mechanisms involved. Furthermore, development of nematode resistance to drugs makes imperative the search of management practices that avoid whole herd treatment. We undertook an epidemiological and endocrine study in a grass based dairy farm in Argentina to study the effect of parasites on milk production and the underlying mechanisms involved, and identify individual animals that would benefit from antiparasitic treatment. All the cows in the dairy were followed monthly for egg parasite output in feces. Samples were cultured for genera determination. Milk production and reproductive results were recorded and periodical bleedings for hormone determination were performed. Nematode egg output (EPG) was maximal in late Summer and Autumn and minimal in Spring in coincidence with the Ostertagia inhibition-disinhibition cycle as this genus had the highest prevalence in all the study. The highest proportion of positive samples was found in the high producing herd and maximal counts were found in the peripartal period. Milk production did not correlate with EPG mean values but, when cows were grouped by EPG positivity around parturition, a significant difference in total milk production between EPG null and positive cows was observed. Positive cows produced 7%, 12% or 15% less milk than null EPG cows, depending on the sampling month/s chosen for classification. The highest difference was seen when both prepartum and postpartum samples were taken into account. No difference in lactation length and a marginal effect on partum to first service interval were encountered. Endocrine studies revealed a decrease in serum growth hormone (GH), type I insulin-like growth factor (IGF-I) and prolactin during lactation in cows with positive EPG in the first postpartum sample with respect to null EPG cows at that time. GH levels decreased and prolactin and IGF-I levels increased in both groups of cows from month 0 to 6 in milk. Serum insulin levels remained stable throughout lactation and were similar in both groups of cows. In conclusion, EPG around parturition may be a useful tool for identifying cows that will have a decrease in productivity due to parasite effects and would possibly benefit from an antiparasitic treatment. Besides, our results suggest that detrimental effect of parasites on milk production may be mediated by GH, IGF-I and prolactin serum levels.     

An economic justification of "blitz" therapy to eradicate Streptococcus agalactiae from a dairy herd

Streptococcus agalactiae was identified as the cause of mastitis in a 240-cow dairy herd. Forty-five per cent of the herd had cell counts over 500,000/ml, and 28 per cent had cell counts over 1,000,000/ml. Dry cow therapy was used regularly but teat dipping had not been used for three years. The procedures at milking were modified, teat dipping was introduced, and the herd was divided into two according to cell count. The 120 cows with higher cell counts were treated with 300 mg erythromycin (Erythrocin intramammary; Sanofi Animal Health) preparation per quarter at two consecutive milkings. Towards the end of lactation, all the 90 lactating cows in the herd were again treated with erythromycin. Milk samples were collected from all the cows in the herd 12 months after the initial treatment, and S agalactiae was isolated from only one replacement heifer which had been purchased after the treatments with erythromycin. The butterfat and protein levels in the milk were compared with those of a similar, but untreated, herd for 12 months before and after therapy. The butterfat levels rose sharply after treatment, and financial assessment showed a 41 per cent return on investment in the 12 months following the treatment.     

An experiment to measure the dose-response relationship of ovulation rate to FSH in cows selected with a history of twinning

Fifteen mature cows and 12 two-year-old heifers were superovulated with purified follicle stimulating hormone (FSH-P) to study the relationship between FSH-P dose level and response (measured as number of palpated corpora lutea (CL) and plasma progesterone concentration). The cattle came from a high prolificacy breeding herd for which cows were originally purchased after producing at least two sets of twins; the heifers were bred in the herd. At dose levels of 8, 16, 24 and 28 mg FSH-P in cows, averages respectively of 2.3, 3.5, 6.9 and 11.1 palpable CLs were found. There was an average difference in response of two CLs between heifers and cows (higher in heifers, though not significantly so). The relationship found between progesterone concentration and CL number could be a useful indicator of superovulation success in future experiments. The regression for cows was 1.25±0.11 ng/ml progesterone per unit increase in CL number, with a correlation of 0.92 between the two variables over the CL range 1 to 25. The corresponding value for heifers was 2.74±0.24 ng/ml per CL (correlation 0.94), or 2.50±0.40 ng/ml per CL (correlation 0.83) if one record (29 CL, 84 ng progesterone/ml) was excluded.     

Diurnal and individual variations in bile acids in the plasma of normal dairy cows

Blood samples were collected every 2 h during a 24 h period from 6 cows of one herd and 10 cows of another herd. In a third herd 9 cows were sampled every 2 h from 6 a.m. to 8 p.m. Concentrations of total bile acids, acetoacetate, glucose and free fatty acids were determined in blood plasma. A marked difference in individual bile acid concentrations and patterns of diurnal variation was found. For most cows the highest bile acid values were observed between 2 and 6 a.m. (overall mean (+/- SD) at 6 a.m.: 104 +/- 84 mumol/l, range: 20-307 mumol/l). Fourteen cows with a bile acid value greater than 90 mumol/l at 6 a.m. ("high BA") were characterized as a group by showing a pronounced decrease in the mean bile acid concentration after morning feeding. In the group of 11 cows with a 6 a.m. bile acid value less than 90 mumol/l ("low BA") the time of day did not contribute significantly to the bile acid variation. For the "high BA" group a nearly synchronous variation between the mean values of the 3 feeding dependent parameters (acetoacetate, glucose and free fatty acids) and the mean values of bile acids was found. The within animal coefficients of correlation between bile acids and the feeding dependent parameters were significantly higher in the "high BA" group than in the "low BA" group. No direct connection was found between bile acid levels and the quantity of concentrates fed or the individual milk yield.     

Seroprevalence of Mycobacterium avium subsp paratuberculosis infection among dairy cows in Colorado and herd-level risk factors for seropositivity

OBJECTIVE: To estimate seroprevalence of Mycobacterium avium subsp paratuberculosis (MAP) infection among adult dairy cows in Colorado and determine herd-level factors associated with the risk that individual cows would be seropositive. DESIGN: Cross-sectional observational study. ANIMALS: 10,280 adult (> or = 2 years old) dairy cows in 15 herds in Colorado. PROCEDURE: Serum samples were tested with a commercial ELISA. A herd was considered to be infected with MAP if results of mycobacterial culture of > or = 1 individual cow fecal sample were positive or if > or = 1 culled cow had histologic evidence of MAP infection. RESULTS: 424 of the 10,280 (4.12%) cows were seropositive. Within-herd prevalence of seropositive cows ranged from 0% to 7.82% (mean, 2.6%). Infection was confirmed in 11 dairies. Cows in herds that had imported > or = 8% of their current herd size annually during the preceding 5 years were 3.28 times as likely to be seropositive as were cows in herds that imported < 8%. Cows in herds with > or = 600 lactating cows were 3.12 times as likely to be seropositive as were cows in herds with < 600 lactating cows. Cows in herds with a history of clinical signs of MAP infection were 2.27 times as likely to be seropositive as were cows in herds without clinical signs. CONCLUSIONS AND CLINICAL RELEVANCE: Annual importation rate, herd size, and whether cows in the herd had clinical signs typical of MAP infection were associated with the risk that individual cows would be seropositive for MAP infection.     

Copper poisoning in a dairy herd fed a mineral supplement

Copper poisoning in a dairy herd resulted in the death of 9 of 63 (14%) adult Holstein cows. Clinical signs were acute anorexia, weakness, mental dullness, poor pupillary light reflexes, and scant nasal discharge. These were followed by recumbency, chocolate-colored blood, jaundice, and death. Four animals exhibited signs of hyperesthesia and/or rumen stasis prior to death. At necropsy there was generalized icterus of body tissues, with the liver appearing orange and the kidneys dark blue. Histologically, there was accumulation of hemosiderin in Kupffer cells, and severe to moderate hepatocellular necrosis in all cases. Ammonium molybdate added to the ration, combined with the cessation of mineral supplementation, arrested the outbreak.

These cases illustrate significant mortality, due to copper poisoning, in adult cattle fed a low-dose mineral dietary supplement for over two years. Dietary copper intake of the herd (on a dry matter basis) was 37.5 mg/kg for lactating cows and 22.6 mg/kg for dry cows.

     

An experiment to measure the dose-response relationship of ovulation rate to FSH in cows selected with a history of twinning

Fifteen mature cows and 12 two-year-old heifers were superovulated with purified follicle stimulating hormone (FSH-P) to study the relationship between FSH-P dose level and response (measured as number of palpated corpora lutea (CL) and plasma progesterone concentration). The cattle came from a high prolificacy breeding herd for which cows were originally purchased after producing at least two sets of twins; the heifers were bred in the herd. At dose levels of 8,16, 24 and 28 mg FSH-P in cows, averages respectively of 2.3, 3.5, 6.9 and 11.1 palpable CLs were found. There was an average difference in response of two CLs between heifers and cows (higher in heifers, though not significantly so). The relationship found between progesterone concentration and CL number could be a useful indicator of superovulation success in future experiments. The regression for cows was 1.25 +/- 0.11 ng/ml progesterone per unit increase in CL number, with a correlation of 0.92 between the two variables over the CL range 1 to 25. The corresponding value for heifers was 2.74 +/- 0.24 ng/ml per CL (correlation 0.94), or 2.50 +/- 0.40 ng/ml per CL (correlation 0.83) if one record (29 CL, 84 ng progesterone/ml) was excluded.     

Characteristics of protein-protease inhibitors, 17-beta estradiol and progesterone in the blood of heifers returning to estrus following LH/FSH-RH treatment]

Tests were performed to study the inhibitive capacity of protein-protease inhibitors, 17-beta estradiol, and progesterone in the blood serum of 21 heifers returning to oestrus which had been treated intramuscularly with 400 microgram LH/FSH-RH. Four selected heifers were examined as to the relationships between the concentrations of 17-beta estradiol, progesterone and the inhibitive capacity of the serum. Heifer no. 1 had low concentrations of 17-beta estradiol and higher concentrations of progesterone (average levels 7.8 and 657.4 pg ml-1 of serum). On the other hand, heifer no. 4 was found to have higher concentration of 17-beta estradiol and lower values of progesterone (average levels 28.3 and 325 pg ml-1 of serum). Having shown heat, the heifers were fertilized and remained in calf. Heifer no. 2 with a low concentration of progesterone (292 pg ml-1 of serum) and 17-beta estradiol (12.4 pg ml-1 of serum), as well as heifer no. 3 with a high concentration of both (830 pg ml-1 of serum and 22.7 pg ml-1 of serum, respectively) showed no heat and they were not mated. Heifers with significant differences in the concentrations of progesterone and 17-beta estradiol and with low values of protein-protease inhibitory capacities remained in-calf, whereas heifers with lower progesterone and 17-beta estradiol values, or adversely, with higher inhibition values, showed no heat. Synthetic LH/FSH-RH was found not to increase the amount of protein-protease inhibitors in heifer serum, as distinct from the cervical mucus of breeding cows treated with gestagens in heat synchronization.     

Sensitivity of test strategies used in the Voluntary Johne's Disease Herd Status Program for detection of Mycobacterium paratuberculosis infection in dairy cattle herds

OBJECTIVE: To evaluate sensitivities at the herd level of test strategies used in the Voluntary Johne's Disease Herd Status Program (VJDHSP) and alternative test strategies for detecting dairy cattle herds infected with Mycobacterium paratuberculosis. DESIGN: Nonrandom cross-sectional study. SAMPLE POPULATION: 64 dairy herds from Pennsylvania, Minnesota, Colorado, Ohio, and Wisconsin. Fifty-six herds had at least 1 cow shedding M. paratuberculosis in feces; the other 8 herds were free from paratuberculosis. PROCEDURE: For all adult cows in each herd, serum samples were tested for antibodies to M. paratuberculosis with an ELISA, and fecal samples were submitted for bacterial culture for M. paratuberculosis. Sensitivities at the herd level (probability of detecting infected herd) of various testing strategies were then evaluated. RESULTS: Sensitivity at the herd level of the testing strategy used in level 1 of the VJDHSP (use of the ELISA to test samples from 30 cows followed by confirmatory bacterial culture of feces from cows with positive ELISA result) ranged from 33 to 84% for infected herds, depending on percentage of cows in the herd with positive bacterial culture results. If follow-up bacterial culture was not used to confirm positive ELISA results, sensitivity ranged from 70 to 93%, but probability of identifying uninfected herds as infected was 89%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the testing strategy used in the VJDHSP will fail to identify as infected most dairy herds with a low prevalence of paratuberculosis. A higher percentage of infected herds was detected if follow-up bacterial culture was not used, but this test strategy was associated with a high probability of misclassifying uninfected herds.     

Epidemiological and bacteriological aspects of mastitis associated with yellow-jacket wasps (Vespula germanica) in a dairy cattle herd

The German wasp, Vespula germanica has been observed to injure teats of dairy cows, causing lesions that are associated with clinical and subclinical mastitis. The presence of skin lesions on the teats, caused by the wasps, was recorded in a dairy cattle herd located in the Samaria foothills during July-October 1999. Wasp-inflicted injuries were found in 43.6% (58 of 133) of the adult cows and 1.4% (one of 71) of the first-calving cows. They were located in 42.4% of cows (n = 25) on all quarters, 18 cows (30.5%) had lesions on the front quarters and 27.1% (n = 16) of cows on the hind quarters only. Clinical and subclinical mastitis were diagnosed in 61% (36 of 59) and 28.8% (17 of 59), respectively, of the injured adult and first-calving cows. The most common bacterial isolates from the mastitic cows were Staphylococcus aureus 45.1% (n = 14), Streptococcus dysgalactiae 16.1% (n = 5), Streptococcus spp. 19.4% (n = 7) and others 13.9% (n = 5). The loss of milk production was estimated at 300 kg milk for each cow injured by wasps and exhibiting clinical mastitis. An increase in the bulk-milk somatic cell count, from 186 x 103 at 1 month prior to the outbreak to a peak of 1200 x 10(3) in the post-outbreak month, was noted. The culling rate reached 13.6% (eight of 59) of the affected cows. In summary, the considerable economic losses caused by the wasp infestation resulted from decreased milk production and a decline in milk quality, culling of affected cows, and increased demand for use of drugs and veterinary care.     

Neospora caninum seroprevalence in dairy cattle in central Thailand

The seroprevalence, in dairy cattle, of antibodies to Neospora caninum, the relationship between seropositivity and age (heifer versus cow), the relationship of herd infection with herd size and the relationship of herd infection with the presence of dogs on the farm were studied. The study involved 549 cows and 82 dogs in 59 dairy herds in Nakhon Pathom, Thailand. A competitive enzyme-linked immunosorbent assay (cELISA) with NC-specific monoclonal antibody was used to detect the NC antibodies in the sera. Individual and herd seroprevalence of NC were 5.5% (30/549) and 34% (20/59), respectively. No significant relationships between NC seropositivity with the age of the cows (heifer versus cow; P > 0.05) and between herd infection and the presence of dogs on the farm (P > 0.05) were found. Herd size significantly affected herd infection (P < 0.05) with higher infection in large than small herds (> or = 21 versus < or = 20 cows). Of 12 cows with a history of abortion, one was seropositive to NC. The seroprevalence of NC antibodies in dogs was 1.2% (1/82). This is the first NC seroprevalence study in dogs in Thailand. It was concluded that Neospora infection was more common at the herd level rather than the individual level in Thailand and the presence of dogs on the farm was not related to the level of herd infection. Caution should be taken in the interpretation of serological tests from the farm dogs.     

Clinical acidosis in a Gippsland dairy herd

OBJECTIVE: To report on spontaneous clinical and subclinical acidosis in a large dairy herd, to evaluate the diets and feeding strategies involved, and to report on measures of rumen function in the cows affected. DESIGN: A Gippsland dairy herd was sampled as part of a wider randomised cross-sectional study that examined the prevalence, risk factors for, and effects of, acidosis on rumen function of dairy cattle. Three herds on the farm were involved in the study: the transition herd (cows 3 weeks prior to calving), the very fresh lactating herd (1 < days in milk < 10, herd 1) and the fresh lactating herd (10 < days in milk < 120, herd 2) including a small lame herd fed separately. The transition cows were fed 2 kg dry matter triticale per cow per day and hay with an estimated total dry matter intake of 4.8 kg per cow per day. The lactating cow diet included 6.75 kg dry matter triticale per cow per day with total concentrate fed being 8.1 kg dry matter per cow per day in the milking parlour. Silage, lucerne cubes, hay and pasture (herd 2 only) was also fed to the lactating cows with the estimated total dry matter intake for cows in herds 1 and 2 being 13.7 kg and 20.8 kg per cow per day respectively. Three primiparous and five multiparous cows in early lactation (< 100 days in milk) were randomly selected from each of two lactating herds: herds 1 and 2. Rumen fluid was sampled from each cow by both rumenocentesis and stomach tube. The rumenocentesis samples were tested for pH at the time of sampling. Stomach tube samples were frozen and subsequently tested for volatile fatty acid, ammonia, and D- and L-lactate concentration. RESULTS: In the very fresh herd, there was a high prevalence of severe lameness and scouring, coupled with a mean rumen pH 5.67, low mean total volatile fatty acid concentration 71.0 mM and high mean concentrations of L- and D-lactate, (7.71 mM and 7.31 mM), respectively. Cows in the fresh herd had moderate signs of scouring and lameness. A lame herd comprising approximately 50 cows separated from the fresh herd was also present on the farm. The mean rumen pH of the fresh herd was 5.74 and mean rumen concentrations of volatile fatty acids, ammonia, L- and D-lactate were within ranges considered normal. CONCLUSIONS: The transition diet failed to supply sufficient energy and protein for maintenance of cows of this live weight in late gestation. The diet fed to the very fresh herd was low in effective fibre and contained an excessive content of non-structural carbohydrate in the form of processed, rapidly fermentable grain. The sudden change from the transition diet to the diet fed to the very fresh herd probably also precipitated the outbreak of acidosis. This case report provides unique detail, including information on diets and rumen parameters, of an outbreak of acidosis in a pasture-fed herd.     

Relationship between mastitis pathogen numbers in bulk tank milk and bovine udder infections in California dairy herds

Samples of bulk tank milk and cow-composite milk from 23,138 dairy cows from 50 California dairies were examined by use of microbiologic procedures. The number of colonies of mastitis pathogens isolated per milliliter of bulk tank milk (used as a predictor of the percentage of infected cows in the herd) was evaluated, using simple regression analysis and Spearman's rank correlation. Correlations between the pathogens and the percentage of cows in each herd shedding the pathogens were found for Streptococcus agalactiae (r = 0.71) and mycoplasma (r = 0.59), but were considerably lower for other pathogens. When greater than or equal to 4,000 colonies of Streptococcus agalactiae were found per milliliter of bulk tank milk, at least 7% of the cows in the herd was shedding this organism. However, a pattern was not found between the number of mycoplasma colonies per milliliter of bulk tank milk and the percentage of infected cows in the herd.     

The effects of dietary biotin supplementation on vertical fissures of the claw wall in beef cattle

A clinical field trial was performed on a herd of Hereford beef cows in central Saskatchewan. The herd had a history of being severely affected with vertical fissures. The objective of the study was to determine the effects of supplemental dietary biotin on the prevalence of vertical fissures in beef cows. In June 1994 and June 1995, 1- and 2-year-old heifers were randomly allocated into 2 treatment groups, each composed of 79 animals. One group received a 10 mg/head/day biotin-supplemented free-choice mineral supplement, while the other groups received an identical free-choice mineral without the biotin supplementation. The claws from these animals were evaluated in June 1994, October 1994, June 1995, October 1995, and June 1996 for the presence of vertical fissures. Supplemental dietary biotin significantly increased serum levels of biotin and significantly increased claw hardness in supplemented cows. Both groups of heifers started the trial without vertical fissures. After 18 months, 15% of the cows fed supplemental dietary biotin had vertical fissures compared with 33% in the nonsupplemented group. The difference was statistically significant (P = 0.01).     

Giardia duodenalis and Cryptosporidium spp. in a veterinary college bovine teaching herd

In a preliminary study, we commonly identified Giardia duodenalis in adult dairy cattle from a veterinary college teaching herd. Therefore, the present study was carried out in order to better understand the potential of adult cattle to act as a source for G. duodenalis infections for students and staff at the veterinary college. Fecal samples were collected bi-weekly from this herd of adult cattle (n=30) over an 8-month period to determine the prevalence of G. duodenalis and Cryptosporidium spp. within the herd. Nested PCR followed by DNA sequencing was then performed on a subset of positive samples in order to better understand the zoonotic potential of these infections. Every cow was sampled between 11 and 18 times, depending on the date the animal joined the teaching herd. In total, 507 fecal samples were collected from 30 different cows and examined for cysts and oocysts using epifluorescence microscopy. G. duodenalis prevalence during the course of the study ranged from 37% (11/30) to 64% (18/28), with a mean of 49%. Cumulative G. duodenalis prevalence was 73% (22/30). Zoonotic G. duodenalis assemblage A genotype was identified in 43% (6/14) of the G. duodenalis-positive samples on which PCR and genetic sequencing were successfully performed. G. duodenalis assemblage E was identified in 57% (8/14) of these samples. Cryptosporidium spp. oocysts were not detected in the feces of any cows during the study period. The presence of the zoonotic G. duodenalis assemblage A in 43% of the sequenced samples indicates that there is a potential risk of infection for students and staff at this research and teaching facility, although the roles of cows as sources of giardiasis in humans remain uncertain. Furthermore, due to the large amount of feces they produce, adult cattle may serve as important sources for G. duodenalis infections in young cattle, or other animals in the facility, despite relatively low numbers of cysts excreted per gram of feces. In contrast, the results of this study indicate that this herd posed a negligible risk of transmitting Cryptosporidium parvum infections to humans.