Schmallenberg virus in Dutch dairy herds: Potential risk factors for high within-herd seroprevalence and malformations in calves,and its impact on productivity

In November 2011, the new orthobunyavirus Schmallenberg virus (SBV) was identified in dairy cows that had induced fever, drop in milk production and diarrhoea in the Netherlands (Muskens et al., 2012. Tijdschrift voor Diergeneeskunde 137, 112–115) and a drop in milk production in cows in Northwestern Germany (Hoffmann et al., 2012. Emerging Infectious Diseases 18 (3), 469–472), in August/September 2011. This study aimed at quantifying risk factors for high within-herd prevalence of SBV and SBV-induced malformations in newborn calves in dairy herds in the Netherlands. Additionally, the within-herd impact of SBV infection on mortality rates and milk production was estimated.A case-control design was used, including 75 clinically affected case herds and 74 control herds. Control herds were selected based on absence of malformations in newborn calves and anomalies in reproductive performance. SBV-specific within-herd seroprevalences were estimated. Risk factors for high within-herd SBV seroprevalence (>50%) and the probability of malformed newborn calves in a herd were quantified. In addition, within-herd impact of SBV with regard to milk production and mortality was estimated.Animal-level seroprevalence was 84.4% (95% confidence interval (CI): 70.8–92.3) in case herds and 75.8% (95% CI: 67.5–82.5) in control herds. Control herds that were completely free from SBV were not present in the study. Herds that were grazed in 2011 had an increased odds (OR 9.9; 95% CI: 2.4–41.2)) of a high seroprevalence (>50%) compared to herds that were kept indoors. Also, when grazing was applied in 2011, the odds of malformations in newborn calves tended to be 2.6 times higher compared to herds in which cattle were kept indoors. Incidence of malformations in newborn calves at herd level was associated with both within-herd seroprevalence and clinical expression of the disease in adult cattle.The rate of vertical transmission of SBV to the fetus once a dam gets infected seemed low. A total of 146 stillborn or malformed calves were submitted by 65 farmers during the study period, of which 19 were diagnosed as SBV-positive based on pathological investigation and/or RT-qPCR testing of brain tissue. Based on these results combined with calving data from these herds we roughly estimated that at least 0.5% of the calves born between February and September 2012 have been infected by SBV.A drop in milk production was observed between the end of August 2011 and the first half of September (week 35–36), indicating the acute phase of the epidemic. During a 4-week period in which SBV infection was expected to have occurred, the total loss in milk production in affected dairy herds was around 30–51 kg per cow. SBV had no or limited impact on mortality rates which was as expected given the relatively mild expression of SBV in adult cows and the low incidence of malformations in newborn calves.     

Factors associated with colostrum quality in individual cows from dairy herds in the Waikato region of New Zealand

AIMS: To examine associations between various cow-level factors and quality of first-milking colostrum (measured as Brix), and to evaluate herd-level associations between vaccination against calf diarrhoea and colostrum quality, in cows from dairy herds in the Waikato region of New Zealand.

METHODS: A single colostrum sample was collected, by complete udder evacuation, from each of 20 cows from 29 dairy herds in the Waikato region of New Zealand during the 2016 spring calving period. Vaccination pre-partum with a calf diarrhoea vaccine was used in 15 herds. Each colostrum sample was tested using a digital Brix refractometer. The body condition score of each cow was recorded at the time of sample collection and farmers provided records of clinical mastitis and facial eczema from the previous 12 months, as well as the age and breed of cows. Associations between cow-level variables in non-vaccinated herds and Brix were examined using a multivariable linear mixed model and estimated marginal means obtained for different categories.

RESULTS: Mean Brix of 281 samples from cows in non-vaccinated herds was 18.7 (SD 0.26)%; 63/281 (22.4%) samples had Brix ≥22% and 152/281 (54.1%) had Brix ≥18%. Mean Brix of colostrum samples from cows aged ≥6 years (20.2 (95% CI=19.1–21.2)%) was higher than for samples from 2-year-old cows (18.6 (95% CI=17.3–19.9)%) (p=0.005). Colostrum that was collected at the first milking on the day of calving had higher Brix (20.0 (95% CI=19.1–20.9)%) than colostrum collected from cows that calved the previous day (17.5 (95% CI=16.5–18.4)%) (p<0.001). Mean Brix of colostrum samples from cows which produced ≥8?L (18.2 (95% CI=17.1–19.2)%) tended to be lower than from cows which produced <8?L first-milking colostrum (19.1 (95% CI=18.3–20.0)%) (p=0.08). Among vaccinating herds, 9/15 (60%) had ≥60% colostrum samples with Brix ≥18% compared with 4/14 (29%) of non-vaccinating herds (p=0.04).

CONCLUSIONS AND CLINICAL RELEVANCE: Colostrum quality, as measured by Brix, was associated with the total volume of first-milking colostrum, interval from calving to colostrum collection and cow age. Vaccination against calf diarrhoea was associated with a higher proportion of colostrum samples with adequate Brix. Careful selection of colostrum donor cows should ensure newborn calves are fed adequate quality colostrum which should be beneficial in preventing failure of passive transfer of IgG. Testing of colostrum from individual cows with a Brix refractometer is advocated for the selection of colostrum for feeding newborn calves.     

Cattle-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria on dairy farms, Minnesota, USA

The objective of this study was to identify individual cattle-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria (STB), a surrogate for Shiga toxin-producing E. coli (STEC), on 28 organic and conventional dairy farms. It was found that small organic herds (fewer than 100 cows) were associated with higher odds of Shiga toxin-encoding bacteria (STB) shedding from 2 (all cattle and all cows) of 3 cattle models, followed by small conventional herds, compared with large conventional herds. Preweaned calves [odds ratio (OR) = 2.6, 95% confidence interval (CI): 1.2, 5.7] had higher odds of shedding STB compared with adult cows. Calves more than 28 days of age (OR = 2.0, 95%CI: 1.0, 4.4) were more likely to shed STB than calves less than 28 days of age. This information may be helpful for identifying potential control strategies such as targeted vaccination or management practices.     

Herd-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria on dairy farms in Minnesota,USA

This study aimed to identify herd-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria (STB) on dairy cattle farms in Minnesota, USA. After adjustment for farm size, risk factors included: use of total mixed ration (TMR) for lactating dairy cows [odds ratio (OR) = 3.0; 95% confidence interval (CI): 1.8 to 5.1], no use of monensin for weaned calves (OR = 4.8, 95% CI: 2.5, 9.3), and no use of decoquinate for preweaned calves (OR = 2.2, 95% CI: 1.4, 3.6). Fecal shedding of STB was more common in small herds (< 100 cows, OR = 3.6, 95% CI: 2.1, 6.2) than in large herds (≥ 100 cows). Herd management factors related to cattle feeding practices were associated with fecal shedding of STB.     

Seroprevalence of bluetongue serotype 8 in cattle in the Netherlands in spring 2007, and its consequences

A cross-sectional study was carried out in spring 2007, at the end of the first bluetongue outbreak season, to determine the geographical spread of bluetongue virus serotype 8 (btv-8) infection in cattle in the Netherlands and the consequences for some production parameters. Blood samples from cattle submitted to the laboratory of the Dutch Animal Health Service for other voluntary and obligatory health programmes were tested serologically for btv-8. In total, 37,073 samples were tested and 659 (1.78 per cent) were seropositive. The samples came from 5436 herds, of which 45 per cent of herds had only one sample submitted from them. The prevalence was highest in the south of the country, where the outbreak had started, and decreased towards the north. In 340 herds more than 50 per cent of cattle were tested, of which 156 herds were located in infected compartments, and in 37 of these herds (10.9 per cent) at least one positive cow was detected. The average within-herd prevalence in the 37 herds was 39.3 per cent: 2.2 per cent in 11 dairy herds, 68.4 per cent in 20 small-scale herds and 14 per cent in four suckler cow herds. The prevalence differed significantly between herd types but did not show a geographical trend. The average net return for milk production amounted to euro2417/cow/year and it decreased significantly on average by euro48/cow/year in the bluetongue-infected dairy herds during the bluetongue period. On the small-scale farms, the incidence of mortality increased by 3.2 (95 per cent confidence interval [CI] 1.2 to 9.1) times in the infected herds during the bluetongue period, but the voluntary culling rate decreased by a factor of 2.3 (95 per cent CI 1.1 to 4.8).     

Field observations during the Bluetongue serotype 8 epidemic in 2006. II. Morbidity and mortality rate, case fatality and clinical recovery in sheep and cattle in the Netherlands

Data collected in the Netherlands during the Bluetongue serotype 8 (BTV-8) epidemic indicated that in outbreak cattle herds, predominantly dairy and nursing cows were clinically affected and not young stock, beef cattle, beef calves, or breeding animals. In outbreak sheep flocks, mainly ewes and - if present - rams, were clinically affected and not the lambs. Median morbidity rate in outbreak herds was 1.85 per 100 sheep-month at risk and 0.32 per 100 cattle-month at risk for sheep and cattle, respectively. The mean proportion of BT-affected animals in outbreak herds that recovered from clinical disease was approximately eight times higher for cattle compared to sheep in the Netherlands. Median mortality rate in outbreak herds was 0.5 per 100 sheep-month at risk of dying and 0 per 100 cattle-month at risk of dying for sheep and cattle, respectively. Median recovery time of both sheep and cattle that recovered from clinical disease in outbreak herds was 14 days. Median case fatality was 50% in sheep outbreak flocks and 0% in outbreak cattle herds. It is concluded that morbidity and mortality in outbreak cattle herds was very limited during the BTV-8 epidemic in the Netherlands in 2006. In outbreak sheep flocks, morbidity was limited, with exceptions for a few flocks. However, almost 50% of the clinically sick sheep died in outbreak sheep herds.     

In utero infection of cattle with Mycobacterium avium subsp. paratuberculosis: a critical review and meta-analysis

Mycobacterium avium subsp. paratuberculosis (Mptb) causes Johne's disease in ruminants. Disease control programmes aim to break the faecal-oral cow-calf transmission cycle through hygienic calf rearing and removal of affected cows from the herd, but these programmes do not take account of the potential for congenital infection. The aims of this study were to critically review research on in utero infection, determine the prevalence of fetal infection in cattle through meta-analysis and estimate the incidence of calves infected via the in utero route. About 9% (95% confidence limits 6-14%) of fetuses from subclinically infected cows and 39% (20-60%) from clinically affected cows were infected with Mptb (P<0.001). These are underestimates for methodological reasons. The estimated incidence of calf infection derived via the in utero route depends on within-herd prevalence and the ratio of sub-clinical to clinical cases among infected cows. Assuming 80:20 for the latter, estimates of incidence were in the range 0.44-1.2 infected calves per 100 cows per annum in herds with within-herd prevalence of 5%, and 3.5-9.3 calves in herds with 40% prevalence. These estimates were not markedly sensitive to the value chosen for the proportion of clinical cases. In utero transmission of Mptb could retard the success of disease control programmes if the opportunities for post natal transmission via colostrum/milk and environmental contamination were able to be controlled. The consequences of fetal infection for the calves so infected are discussed in the context of diagnosis and vaccination together with recommendations for future research.     

Factors affecting calf mortality in Iranian Holstein dairy herds

The objective of this study was to document mortality reasons and risk factors for mortality in dairy calves in the northeast of Iran. This was a prospective cohort study of calves born on ten commercial dairy herds from 21 March 2009 to 20 March 2010. A total of 4097 live calves were followed for 90 days after birth. For each calf details of sex, parity of the dam, type of parturition and season of birth were recorded. The interval (in days) from the date of birth to the date of death and the reason for death was recorded for those calves that died before 90 days of age. A Cox proportional hazards model, including a frailty term to account for unmeasured herd-level effects was developed to quantify the effect of factors associated with time to death. Two hundred and sixty-six (6.5%, 95% CI: 5.8-7.3%) of the 4097 live-born calves died or were euthanised before 90 days of age. The most important reasons for death were digestive tract disorders (58% of all deaths, 95% CI: 52-64%) followed by respiratory diseases (13% of all deaths, 95% CI: 9-17%). Calves exposed to dystocia at birth had 2.09 (95% CI: 1.49-2.92) times the daily hazard of death compared with calves born from a normal calving. The daily hazard of death for calves born in the summer was 1.93 (95% CI: 1.41-2.64) times greater than the hazard for those calves born in the autumn. Inclusion of the herd-level frailty term had a significant effect on hazard estimates indicating that the study herds were heterogeneous in the distribution of unmeasured herd-level factors influencing calf survival. Our results show that diarrhoea is the most important cause of calf mortality in dairy herds in this area of Iran and that environmental and management factors affect calf mortality rate.     

Validation of a bulk tank milk antibody ELISA to detect dairy herds likely infected with bovine viral diarrhoea virus in New Zealand

AIMS: To assess the sensitivity and specificity of a bulk tank milk (BTM) antibody enzyme-linked immunosorbent assay (ELISA) to detect likely infection of a dairy herd with bovine vi- ral diarrhoea virus (BVDV). The ELISA was subsequently used to estimate the prevalence of likely infected herds in parts of the North Island of New Zealand.

METHODS: BTM samples from 724 randomly selected dairy herds in the Waikato, Bay of Plenty and Northland regions of New Zealand were tested for BVDV antibodies. From this group, 20 herds were again randomly selected from each of the quartiles of the ELISA percentage inhibition (%INH) result. From each participant herd, serum from 15 randomly selected calves aged 6–18 months and 15 cows was collected and tested using an indirect blocking ELISA for BVDV antibodies.

RESULTS: Among serum results from calves from 50 herds available for analysis, 34 (68%) herds were classified as likely non-infected (0-3 seropositive among 15 calves) and 16 (32%) as likely infected (5–15 seropositive among 15 calves). Receiver- operator characteristic (ROC) analysis identified an optimal cut-off for BTM of 80%INH associated with 81% sensitivity and 91% specificity for likely herd infection. The prevalence of BVDV antibodies in cows within herds and %INH for BVDV in bulk milk were positively correlated (p<0.01). The association between bulk milk %INH and the prevalence of BVDV antibodies in calves was stronger than the same association in cows. Based on the threshold of 80%INH, the 95% confidence interval (CI) for prevalence of likely infection in the 724 herds in the Waikato, Bay of Plenty and Northland regions of New Zealand was 12–17%. Vaccination against BVDV was not significantly associated with the likely infection status of the herd based on prevalence of BVDV antibodies among calves.

CONCLUSION: An ELISA test result for BVDV antibodies in BTM ≥80%INH can be used as a threshold to indicate the presence of likely infection with BVDV in dairy herds in New Zealand, with 81% sensitivity and 91% specificity.     

An examination of the prevalence of and risk factors for shedding of Cryptosporidium spp. and Giardia spp. in cows and calves from western Canadian cow-calf herds

The primary objectives of this study were to describe the prevalence and risk factors for Cryptosporidium spp. and Giardia spp. infection in cows and calves during the calving season in western Canadian cow-calf herds. Through the calving season of 2002, fresh fecal samples were collected from 560 beef cows and 605 calves in western Canada. Feces were examined for the presence of Cryptosporidium spp. and Giardia spp. using a quantitative sucrose gradient immunoflourescent antibody test. Samples were collected from mature cows on 59 farms and from calves on 100 farms. Only 1.1% (5/560) of the cows were positive for Cryptosporidium spp. whereas 3.1% (19/605) of the calves were positive. Prevalence for Giardia spp. was much higher; Giardia spp. was detected in 17.0% (95/560) of the cow and 22.6% (137/605) of calf fecal samples. Data describing herd management practices, treatment and disease history, age, gender, breed and fecal consistency were gathered to assess potential risk factors associated with shedding. The association between the risk of shedding and average precipitation from December to June and ecological region were also evaluated. Risk factors for infection with Cryptosporidium spp. in either cows or calves could not be evaluated because the multilevel model would not converge due to the relatively low prevalence of the organism in this sample. The prevalence for Giardia spp. was sufficient to explore potential risk factors in both cows and calves. No risk factors were identified for Giardia spp. in beef cows following calving. After the construction of a multivariable model, the only significant predictors for Giardia spp. presence in beef calves was dam age and calf age. Calves born to 2-year-old heifers were 2.3 (95% CI, 1.09-5.06; P = 0.031) times more likely to be shedding Giardia spp. then calves born to cows that were 4-10 years of age. Calves that were 9-18 days of age and calves that were > 18 days of age were 22.4 (95% CI, 5.88-88.18; P < 0.001) and 150 (95% CI, 39.72-603.19; P < 0.001) times more likely, respectively, to be shedding Giardia spp. than calves < or = 4 days of age.     

Seroprevalence and risk factors for bovine brucellosis in Jordan

We investigated the seroprevalence and risk factors for Brucella seropositivity in cattle in Jordan. The sera from 671 cows were randomly collected from 62 herds. The antibodies against Brucella were detected using a Rose Bengal plate test and indirect ELISA. A structured questionnaire was used to collect information on the cattle herds'' health and management. A multiple logistic regression model was constructed to identify the risk factors for Brucella seropositivity. The true prevalence of antibodies against Brucella in individual cows and cattle herds was 6.5% and 23%, respectively. The seroprevalence of brucellosis in cows older than 4 years of age was significantly higher than that in the younger cows. The seroprevalence of brucellosis in cows located in the Mafraq, Zarqa and Ma''an governorates was significantly higher than that of the other studied governorates. The multiple logistic regression model revealed that a larger herd size (odd ratio = 1.3; 95% CI: 1.1, 2.6) and mixed farming (OR = 2.0; 95% CI: 1.7, 3.7) were risk factors for cattle seropositivity to Brucella antigens. On the other hand, the use of disinfectants (OR = 1.9; 95% CI: 1.1, 2.1) and the presence of adequate veterinary services (OR = 1.6; 95% CI: 1.2, 3.2) were identified as protective factors.     

Validation of a bulk tank milk antibody ELISA to detect dairy herds likely infected with bovine viral diarrhoea virus in New Zealand

AIMS: To assess the sensitivity and specificity of a bulk tank milk (BTM) antibody enzyme-linked immunosorbent assay (ELISA) to detect likely infection of a dairy herd with bovine viral diarrhoea virus (BVDV). The ELISA was subsequently used to estimate the prevalence of likely infected herds in parts of the North Island of New Zealand. METHODS: BTM samples from 724 randomly selected dairy herds in the Waikato, Bay of Plenty and Northland regions of New Zealand were tested for BVDV antibodies. From this group, 20 herds were again randomly selected from each of the quartiles of the ELISA percentage inhibition (%INH) result. From each participant herd, serum from 15 randomly selected calves aged 6-18 months and 15 cows was collected and tested using an indirect blocking ELISA for BVDV antibodies. RESULTS: Among serum results from calves from 50 herds available for analysis, 34 (68%) herds were classified as likely non-infected (0-3 seropositive among 15 calves) and 16 (32%) as likely infected (5-15 seropositive among 15 calves). Receiver-operator characteristic (ROC) analysis identified an optimal cut-off for BTM of 80%INH associated with 81% sensitivity and 91% specificity for likely herd infection. The prevalence of BVDV antibodies in cows within herds and %INH for BVDV in bulk milk were positively correlated (p<0.01). The association between bulk milk %INH and the prevalence of BVDV antibodies in calves was stronger than the same association in cows. Based on the threshold of 80%INH, the 95% confidence interval (CI) for prevalence of likely infection in the 724 herds in the Waikato, Bay of Plenty and Northland regions of New Zealand was 12-17%. Vaccination against BVDV was not significantly associated with the likely infection status of the herd based on prevalence of BVDV antibodies among calves. CONCLUSION: An ELISA test result for BVDV antibodies in BTM >/=80%INH can be used as a threshold to indicate the presence of likely infection with BVDV in dairy herds in New Zealand, with 81% sensitivity and 91% specificity.     

Transplacental and oral transmission of wild-type bluetongue virus serotype 8 in cattle after experimental infection

Potential vertical transmission of wild-type bluetongue virus serotype 8 (BTV-8) in cattle was explored in this experiment. We demonstrated transplacental transmission of wild-type BTV-8 in one calf and oral infection with BTV-8 in another calf. Following the experimental BTV-8 infection of seven out of fifteen multi-parous cows eight months in gestation, each newborn calf was tested prior to colostrum intake for transplacental transmission of BTV by RRT-PCR. If transplacental transmission was not established the calves were fed colostrum from infected dams or colostrum from non-infected dams spiked with BTV-8 containing blood. One calf from an infected dam was born RRT-PCR positive and BTV-specific antibody (Abs) negative, BTV was isolated from its blood. It was born with clinical signs resembling bluetongue and lived for two days. Its post-mortem tissue suspensions were RRT-PCR positive. Of the seven calves fed colostrum from infected dams, none became infected. Of the six calves fed colostrum from non-infected dams spiked with infected blood, one calf became PCR-positive at day 8 post-partum (dpp), seroconverted 27 days later, and remained RRT-PCR and Abs positive for the duration of the experiment (i.e., 70 dpp). This work demonstrates that transplacental transmission in late gestation and oral infection of the neonate with wild-type BTV-8 is possible in cattle under experimental conditions.     

Association between risk-assessment scores and individual-cow Johne's disease-test status over time on seven Michigan, USA dairy herds

To evaluate the effectiveness of management practices implemented to control the spread of Johne's disease (JD), we conducted a 5-year observational study (January 2003 to December 2007) on seven Michigan, USA dairy herds containing cows infected with Mycobacterium avium subsp. paratuberculosis (MAP; the causative agent of the disease). The JD incidence and prevalence was monitored in each herd annually by serum ELISA and/or fecal culture of all adult cows. A JDCP was designed specifically for each herd based on the results of an initial risk-assessment. The risk-assessment was repeated annually and the control program updated as needed. Herd risk-assessment scores were used to measure compliance with the control program and create JD-risk profiles for individual cows raised on the farms. The association between specific risk-assessment scores and the JD-test status of individual cows was evaluated using logistic regression. We accounted for clustering of cows within herds using generalized estimating equations (GEE). Multivariable models were built with purposeful selection of risk factors assessed on univariable analyses. The dataset analyzed consisted of 3707 cows raised on the respective farms, of which 616 were classified as infected with MAP based on testing positive on fecal culture or serum ELISA. Of the cows that were not exposed to the control program, 20% were classified as infected, while only 7% of cows that were exposed to the control program were infected. The final multivariable model consisted of two factors: exposure to adult cows other than dam at birth (OR=1.09, 95% CI: 1.06, 1.13), and feeding colostrum from one cow to multiple calves (OR=1.10, 95% CI: 1.09, 1.12). Based on this study, implementing practices that minimize the exposure of newborn calves to MAP being shed by infected adult cows should take priority.     

Cattle and environmental sample-level factors associated with the presence of Salmonella in a multi-state study of conventional and organic dairy farms

The objective of this study was to evaluate associations between cattle-level factors and environmental samples with the isolation of Salmonella from dairy farms in Minnesota, Wisconsin, Michigan, and New York. The study farms included 129 conventional and organic farms enrolled without regard to previous history of Salmonella infection. Herds were sampled at two-month intervals over a one-year period. Cattle groups more likely to be associated with Salmonella shedding (compared to preweaned calves) were cows designated as sick by farm personnel (OR=2.5, 95% CI: 1.7, 3.7), cows within 14 days of calving (OR=1.8, 95% CI: 1.1, 2.8), and cows due for culling within 14 days (OR=1.9, 95% CI: 1.0, 3.4). State of origin was also associated with the presence of Salmonella in samples from cattle and the farm environment; Midwestern states were more likely to have Salmonella-positive samples compared to New York. Cattle treated with antimicrobials within 14 days of sampling were more likely to be Salmonella-negative compared with nontreated cattle (OR=2.0, 95% CI: 1.1, 3.4). Farms with at least 100 cows were more likely to have Salmonella-positive cattle compared with smaller farms (OR=2.6, 95% CI: 1.4, 4.6). Season was associated with Salmonella shedding in cattle, and compared to the winter period, summer had the highest odds for shedding (OR=2.4, 95% CI: 1.5, 3.7), followed by fall (OR=1.9, 95% CI: 1.2, 3.1) and spring (OR=1.8, 95% CI: 1.2, 2.6). Environmental samples significantly more likely to be Salmonella-positive (compared to bulk tank milk) included, in descending order, samples from sick pens (OR=7.4, 95% CI: 3.4, 15.8), manure storage areas (OR=6.4, 95% CI: 3.5, 11.7), maternity pens (OR=4.2, 95% CI: 2.2, 8.1), haircoats of cows due to be culled (OR=3.9, 95% CI: 2.2, 7.7), milk filters (OR=3.3, 95% CI: 1.8, 6.0), cow waterers (OR=2.8, 95% CI: 1.4, 5.7), calf pens (OR=2.7, 95% CI: 1.3, 5.3), and bird droppings from cow housing (OR=2.4, 95% CI: 1.3, 4.4). Parity, stage of lactation, and calf age were not associated with Salmonella shedding.     

Survey of gastrointestinal nematode parasites in Saskatchewan beef herds

A survey of gastrointestinal parasites in Saskatchewan beef herds was conducted over the summer of 2014. Fecal samples were collected on 3 occasions during the summer grazing season from beef cows and calves from 14 herds. The mean number of strongylid eggs per gram of feces recovered from calves increased 9-fold (95% CI: 4.5 to 18) over the summer period, while egg counts in the cows remained constant over the same period. The prevalence and infection intensities of gastrointestinal nematode parasites in cow-calf herds in Saskatchewan were comparable to what is seen in cattle grazing in the northern regions of the United States and for which anthelmintic treatments have resulted in positive production benefits.     

Associations between management practices and colostrum quality on New Zealand dairy farms

Abstract

AIMS: To describe colostrum quality in spring-calving dairy herds in New Zealand, in terms of Brix, pH and total and coliform bacterial counts and to investigate associations between farm management practices and these measures of colostrum quality.

METHODS: In June 2015, commercial dairy farms (n=105), located in North and South Islands of New Zealand, were visited shortly after the first cows had calved, and when approximately 50% and 80% of the herd had calved (early, middle and late visits). One litre of pooled colostrum that was being fed to newborn calves was collected at each visit and used to determine Brix, pH, total bacterial and coliform counts. A survey of calf management practices was conducted with the herd manager or calf rearer after the final visit.

RESULTS: Of 298 pooled colostrum samples tested 29/298 (9.7%) had Brix >22%. Brix was higher on farms where calves were picked up twice daily compared with once daily (18.2 (95% CI=16.5–19.9)% vs. 15.9% (95% CI=15.2–16.6)%; p=0.012), and was lower where first milking colostrum was combined with colostrum obtained at later milkings (15.0 (95% CI=13.9–16.1)%) compared with where it was not (16.9 (95% CI=16.3–17.6)%; p=0.002). Vaccination of all cows against calf diarrhoeal pathogens was associated with increased Brix compared with no vaccination (18.1 (95% CI=16.6–19.6)% vs. 16.3 (95% CI=15.6–17.0)%; p=0.033). Mean pH of samples tested decreased from 5.97 (95% CI=5.84–6.09) to 5.58 (95% CI=5.45–5.71) for early and late-season visits, respectively (p<0.001). Of 268 samples tested, 23 (8.6%) had bacterial counts below the recommended threshold of 1.00×10⁵ cfu/mL. Mean bacterial counts increased from 2.75 (95% CI=1.80–3.70)×10⁸ to 4.99 (95% CI=3.95–6.03)×10⁸ cfu/mL for early and late-season visits, respectively (p<0.001). Of 259 samples tested, 23 (8.9%) had coliform counts below the recommended threshold of 1.00×10⁴ cfu/mL.

CONCLUSIONS AND CLINICAL RELEVANCE: On a large majority of dairy farms included in this study the pooled colostrum fed to newborn calves had sub-optimal Brix and excessive bacterial counts. Farm-level risk factors such as twice daily pick up of calves from the paddocks, herd vaccination and feeding pooled colostrum that did not combine colostrum obtained at later milkings with first milking colostrum were associated with colostrum quality measures.     

Risk factors for calf mortality in large Swedish dairy herds

The aim of this study was to identify possible risk factors for 1-90 day calf mortality in large Swedish dairy herds. Sixty herds with a herd size of ≥160 cows were visited once between December 2005 and March 2006. Thirty herds were known to have low mortality (LM) and 30 were known high mortality herds (HM). Upon the visit, data about housing and management was collected from interviews with personnel responsible for the calves. The herd status regarding the calves' passive transfer (total protein), levels of α-tocopherol, β-carotene and retinol, and excretion of faecal pathogens (Cryptosporidium spp., Escherichia coli F5, rota and corona virus) was evaluated based on targeted sampling of high risk calf groups; in each herd, blood and faecal samples were collected from calves 1-7 and 1-14 days old, respectively. Similarly, the herd status regarding clinical respiratory disease in calves and history of respiratory virus exposure was evaluated based on lung auscultations and blood samplings of calves 60-90 days old. The median calf mortality risk (in calves 1-90 days of age) among HM herds was 9% (Range: 6-24%) and among LM herds 1% (Range: 0-2%). LM and HM herds were compared using five logistic regression models, covering potential risk factors within different areas: "Disease susceptibility", "Factors affecting the gastrointestinal tract", "Factors related to transmission of infectious disease", "Hygiene" and "Labour management". The percentage of calves, 1-7 days old, with inadequate serum concentrations of α-tocopherol and β-carotene were significantly higher in HM herds compared to LM herds and also associated with higher odds of being a HM herd (OR=1.02; p=0.023 and OR=1.05; p=0.0028, respectively). The variable "Average number of faecal pathogens in the sampled target group" was significantly associated with higher odds of being a HM herd (OR=4.65; p=0.015), with a higher average in HM herds. The percentage of calves with diarrhoea treated with antibiotics was significantly higher in HM herds and was associated with higher odds of being a HM herd (OR=1.08; p=0.021). The median age at death of calves in the age interval 1-90 days that died during a one-year period was significantly lower among HM herds (13 days) than in LM herds (24 days) (p=0.0013) The results indicate that gastrointestinal disorders may be an important cause of calf mortality in large Swedish dairy herds. Furthermore, our study provides additional indications that fat soluble vitamins might play an important role for calf health.