Risk factors associated with leptospirosis in dairy goats under tropical conditions in Brazil

Serum samples from 248 adult dairy goats from 13 flocks with lowered fertility farmed in the Rio de Janeiro region of Brazil were examined for Leptospira antibodies by MAT with 24 serovars, cut off 100. A questionnaire was completed for each herd. Antibodies were detected in 20.8% of these goats, mainly to serovar Hardjo. Risk factors associated with seroprevalence to leptospirosis were the frequency of professional veterinary supervision (OR = 2.35), climate (OR = 2.63) and grazing for more than 2h a day. Flock factors as size, type of milking and offering of food supplementation, as well as the location and topography, the type of animal housing or the presence of silos did not significantly affect seroprevalence. We suggest that a successful control program for goat leptospirosis should include a complete investigation of herd management practices, which could influence in the occurrence of the infection.     

A cross-sectional pilot study to estimate the prevalence of and risk factors for leptospirosis in South-Western Victorian dairy herds, 2017

Leptospirosis is a zoonosis, found worldwide, affecting many species of animals. We conducted a cross-sectional study to estimate the prevalence of Leptospira borgpetersenii sv Hardjo and Leptospira interrogans sv Pomona in cattle in dairy herds in South-Western Victoria, Australia. Fifty-three herds were enrolled in the study. Urine samples were collected from 15 late-lactation cows in each herd. A questionnaire was provided to herd managers at the time of each herd visit, asking them to describe the methods they used for controlling leptospirosis, including vaccination. Urine samples were pooled at the herd level and tested for leptospira spp. using real time PCR. Urine samples from individual cows within the positive pooled samples were then tested for Leptospira Hardjo and Leptospira Pomona using qPCR. Four of the 53 herds showed positive leptospirosis results giving an apparent prevalence of 8 (95% CI 2–18) leptospira-positive herds per 100 herds at risk. Based on the 53 completed questionnaires, leptospirosis vaccination programs were not compliant with label directions in 36 of the 52 vaccinated herds: 69 (95% CI 55–81) of 100 herd managers that routinely vaccinated for leptospirosis did not comply with label directions. One herd was completely unvaccinated. Based on our findings, we estimate that approximately 10% of dairy farms in South-Western Victoria are likely to be infected with leptospirosis. While most herds are vaccinating for leptospirosis, most are not doing so according to label directions. We conclude that herd managers need to be better educated regarding leptospirosis vaccination programs.     

Association of herd BHV-1 seroprevalence with respiratory disease in youngstock in Estonian dairy cattle

The associations between herd bovine herpesvirus 1 (BHV-1) seroprevalence, along with other infectious and farm management factors with bovine respiratory disease (BRD) in dairy calves and heifers, were investigated. Serum samples from 103 dairy cattle herds were analyzed for antibodies against BHV-1, bovine respiratory syncytial virus (BRSV), bovine viral diarrhea virus (BVDV), and Mycoplasma bovis (M. bovis). A questionnaire was used to record herd management practices. A high occurrence of respiratory disease in unweaned calves was associated with low to moderate and high prevalence of BHV-1 among cows (OR=14.8, p=0.005 and OR=19.2, p=0.002, respectively) and positive BVDV status of a herd (OR=5.1, p=0.02). The presence of BVDV in a herd was related to a high incidence of respiratory disease in heifers 3-16 months old (OR=4.3, p=0.027). Based on the results of multiple correspondence analysis, holding youngstock separately from cows until pregnancy, introducing new animals and the activities of on-farm employees may contribute to a higher incidence of BRD.     

Prospective serology and analysis in diagnosis of dairy cow abortion

A prospective serologic investigation was undertaken on 3 California dairies (herds 1, 3, and 4, as previously designated in a report on abortion surveillance) to determine if fetal loss was associated with infectious disease agents in cows. The diagnostic problem in these herds was typical of many dairies in that abortions were not discovered for several months and aborted fetuses were seldom recovered. Blood from approximately 100 pregnant cows in each herd was sampled at monthly intervals, beginning when the cows were palpated at approximately 40 days gestation. Sera were tested for antibodies to infectious bovine rhinotracheitis virus and bovine viral diarrhea virus (BVDV) and to the Leptospira serovars pomona, hardjo, grippotyphosa, icterohemorrhagiae, canicola, and szwajizak. Logn antibody titers were examined for an association with fetal loss, using multivariate methods of logistic regression and survival analysis. Of the 325 cows followed, 37 aborted, and no fetuses were recovered. Statistical analyses indicated that significant fetal loss was associated with high titers to L. hardjo and with low titers to L. szwajizak (herds 1 and 4) and BVDV (herd 1). Results for herd 3 revealed a connection between abortion and L. icterohemorrhagiae (P = 0.036) and L. canicola (P = 0.050) and possible vaccinal protection against abortion caused by L. grippotyphosa (P = 0.027 and 0.015). For herd 4, there was a marginally significant tendency for the first vaccination of the gestation against leptospirosis to have protected against fetal death (P = 0.077). Advantages of the diagnostic design were that it permitted comparison of titers of aborted cows with those of nonaborted cows and it considered vaccination-induced titers in analyses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Risk factors for Brucella spp. infection In dairy cattle farms in Asmara, State of Eritrea

A cross-sectional study was conducted to identify risk factors for herd infection by Brucella spp. in dairy cattle in the suburbs of Asmara, Eritrea. Data were collected from 64 herds, randomly selected from a total of 99 herds with a minimum herd size of 9 cows. A questionnaire was used to gather data on management, hygiene and herd structure. Serum samples collected from all pregnant heifers, cows and bulls, were screened for Brucella infection by the Rose Bengal test (RBT), and all RBT-positive sera re-tested with the complement-fixation test (CFT) for confirmation. A seropositive herd was defined as one in which at least one animal tested positive in the CFT. There were 23 (36%) positive herds among the 64 studied. Both multiple logistic and multiple betabinomial regression modeling were used to analyze the data. Mixed-breed herds, compared to single (exotic)-breed herds, were found to be independently associated with increased herd seroprevalence (OR=5.2, 95% confidence interval 1.4–18.7) in the multiple logistic model with the herd infection status as the dependent variable. The importance of this variable was supported by the multiple betabinomial regression model (OR=3.3, 1.4–7.6) with animal-level prevalence within herd as the outcome variable. Both models also revealed the presence of a negative association between seropositivity and cattle stocking density.     

A comparison of the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts after calving in cows also given internal teat sealants

AIM: To compare, in cows treated with an internal teat sealant, the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts (SCC) after calving.

METHODS: Cows from a spring-calving, pasture-based dairy farm in the Manawatu-Whanganui region of New Zealand were randomly allocated to receive either a short-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=291) or a long-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=288) at the end of lactation. Cows were managed on-farm with routine husbandry procedures through the dry period and following calving. A multivariable logistic regression model was used to determine the association between length of action of dry-cow therapy and the proportion of cows with a SCC >150,000?cells/mL at the first herd test after calving.

RESULTS: Age of cow, mean SCC for the preceding season and interval from calving to the first post-calving herd test were all associated with the proportion of cows with an individual SCC >150,000?cells/mL at the first herd test (p<0.001) Treatment with the short-acting dry-cow therapy was not associated with decreased odds of cows having a SCC >150,000?cells/mL at the first herd test compared with treatment with long-acting dry-cow therapy (OR=0.724; 95% CI=0.40–1.30).

CONCLUSIONS AND CLINICAL RELEVANCE: In this herd, which routinely used internal teat sealants, the use of short-acting cloxacillin-based dry-cow therapy did not result in an increased proportion of cows with elevated SSC post-calving. This was a single farm, single year study but indicates that in this herd, changing from a long-acting to a short-acting antimicrobial may have no impact on the prevalence of subclinical mastitis.     

Risk factors associated with Neospora caninum abortion in Ontario Holstein dairy herds

The objective of this epidemiological study was to identify risk factors for Neospora caninum-related abortions in Ontario Holstein dairy herds. A total of 88 herds, consisting of 5080 cattle, and utilizing Dairy Herd Improvement (DHI) services, were divided into three groups. Case (n = 30) and first control (n = 31) herds were selected from 1998 and 1999 fetal abortion submissions to the Animal Health Laboratory, University of Guelph, that were histopathologically positive or negative, respectively, for N. caninum. A second control group (n = 27) was selected from multiple sources of herds sampled within the previous 4 years that had a low seroprevalence (<7%) to N. caninum. Between May and December 1999, all available cows on all farms, in parity one or greater, were blood sampled. The sera were then analyzed for antibody to N. caninum using a kinetic ELISA. A survey administered at the time of sampling recorded information on housing, animal species present, manure management, reproduction, biosecurity practices, wildlife observations, peri-parturient cow management, herd disease history and nutrition. Production and other herd parameters were obtained from DHI records. Logistic regression indicated that the following parameters were positively associated with a N. caninum abortion in a herd: the N. caninum herd seroprevalence (OR = 1.1), the total number of dogs on a farm (OR = 2.8), the frequency that dogs were observed defecating in mangers (OR = 2.8), the number of horses on a farm (OR = 3.1), the observed annual rate of retained fetal membranes (OR = 1.2) and the observed annual rate of cows returning to estrus after pregnancy confirmation (OR = 1.2). Factors negatively associated were the frequency of stray cats and wild canids observed on a farm (OR = 0.4 and OR = 0.7, respectively) and the housing of heifers on loafing packs (a housing pen divided into feed manger, scrape alley and bedded pack areas, OR = 0.1).     

AN OUTBREAK OF BOVINE ABORTIONS ASSOCIATED WITH LEPTOSPIROSIS

A severe abortion storm on a grazing property, in which 50% of Hereford cows aborted in 2 months, is described. Serological evidence suggested that the abortion storm was due to leptospirosis. Epidemiological factors associated with the abortion storm were (a) introduction of infected cows into a susceptible population; (b) the practice of seasonal calving, which resulted in the susceptible population being in the last third of gestation when exposed to infection; and (c) environmental conditions suitable for the propagation of leptospira being coincident with the introduction of infection into the susceptible herd.     

Risk factors for post-partum anoestrus in Charolais beef cows in France

Data from 248 Charolais cows from 20 herds of the Puisaye region (Yonne, France) were collected during winter 1991–1992 to investigate risk factors affecting post-partum anoestrus. Blood was collected 60 days after calving; diagnosis of cyclicity was established by progesterone radioimmunoassay. Herd variables were housing type, lighting of herd accomodation, use of nutritional flushing and nutritional variables (protein and energy before and after calving), and individual variables were parity, ease of calving, body-condition score and body weight at calving and at Day 60, exposure to bulls and calving period. Sixty days post-partum, 62.1% of cows were cyclic. Logistic regression was used to calculate odds ratio (OR). A random effects model was used to take into account the two levels of variables (animal and herd). Although it was defined subjectively, lighting was the only significant herd-level risk factor. Odds of anoestrus were higher in dark than in light accomodation (OR = 6.2, CI 1.2–33.3). Primiparous cows had a higher anoestrus risk than multiparous cows (OR = 10.2, CI 2.9–36.5). Compared with light cows, heavy or medium weight cows at calving had a lower anoestrus risk (OR = 0.25, CI 0.07–0.91, and OR = 0.20, CI 0.07–0.61, respectively.     

Effects of periparturient diseases and conditions on the reproductive performance of New Zealand dairy cows

AIM: To determine the effect of retained foetal membranes (RFM), periparturient recumbency, calf mortality, dystocia, twin births and induction of parturition on submission and pregnancy rates of pasture-fed, seasonally-calving dairy cows in New Zealand. METHODS: Data were retrospectively collected for 2652 cows from 11 herds on the occurrence of periparturient diseases and condition, calving date, age and treatment for anoestrus prior to the planned start of mating (PSM). The effects of each disease or condition on submission and pregnancy rate by 28 days after PSM, final pregnancy rate, and the proportion of cows that conceived more than 50 days after PSM were examined using separate logistic regression models. Results are expressed as odds ratios (OR). Additionally, the effect of each disease or condition on the interval from PSM to conception was examined using survival analysis. Age, herd and late calving (i.e. cows calved < or =40 days before PSM) were included as factors in the models examined. RESULTS: Induction of parturition increased the risk of RFM (OR=3.3, p<0.01). The 28-day submission rate was affected by age and herd but not by any of the periparturient conditions examined. The 28-day pregnancy rate was reduced by RFM (OR=0.04, p<0.05), induction of parturition (OR=0.67, p<0.01), assisted calving (OR=0.61, p<0.01), late calving (OR=0.55, p<0.05) and anoestrus (OR=0.27, p<0.05). The final pregnancy rate was reduced by RFM (OR=0.013, p<0.01), induction (OR=0.25, p<0.05), assisted calving (OR=0.30, p<0.005) and anoestrus (OR=0.32, p<0.05), and was increased if the cow was submitted for mating within 28 days after PSM (OR=2.72, p<0.05). Effects of recumbency and twinning were not significant in any of the models. CONCLUSIONS: Cows that had had RFM or were assisted, induced or late to calve, had significantly lower pregnancy rates or took longer to conceive than unaffected herd-mates. CLINICAL RELEVANCE: Intervention programs aimed at the examination and treatment of cows with periparturient conditions may improve the reproductive performance of New Zealand dairy herds. Investigations of poor reproductive performance of a herd should include analysis of the prevalence and effects of periparturient diseases and conditions.     

Risk factor analysis of bovine leukemia virus infection in dairy cattle in Egypt

Identification of the risk factors associated with Enzootic bovine leukosis (EBL) is essential for the adoption of potentially prevention strategies. Accordingly, our objectives were to determine the geographic distribution of Bovine Leukemia Virus (BLV) infection and identify the risk factors associated with cow-level BLV infection in the Egyptian dairy cattle. A cross-sectional study was conducted on 1299 mixed breed cows distributed over four provinces in the Nile Delta of Egypt in 2018. The randomly selected cows on each farm were serologically tested for BLV, and the cow’s information was obtained from the farm records. Four variables (geographic location, herd size, number of parities, and age) were used for risk analysis. A total of 230 serum samples (17.7 %) were serologically positive for BLV. The highest prevalence of BLV infection was associated with parity (OR = 3.4, 95 %CI 2.4–4.9) with 80 % probability of being BLV-positive at parity ≥5, followed by herd size (OR = 1.8, 95 %CI 1.4–2.2). However, geographic location seems to have no impact on the prevalence of BLV infection in Egypt. Our findings strongly indicate that the intensive surveillance and effective prevention strategies against BLV infection in Egypt should be provided to multiparous cows with ≥5 parities and live in large farm with more than 200 cows.     

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.     

The associations between culling due to clinical Johne's disease or the detection of Mycobacterium avium subsp. paratuberculosis fecal shedding and the diagnosis of clinical or subclinical diseases in two dairy herds in Minnesota, USA

Our objectives were to identify associations between clinical or subclinical diseases and subsequent culling because of clinical Johne's disease (JD) or the detection of fecal shedding of Mycobacterium paratuberculosis (Map) after 305 days in milk (DIM). A total of 1297 cows from two Minnesota dairies were enrolled in the study. From study cows, fecal samples were obtained prior to calving (close-up period) and after at least 305 DIM or at the time of leaving the herd (sold/dead). Between 3 and 21 DIM, blood samples were obtained for serum betahydroxybutyrate (BHB) and serum total-protein testing. Body-condition score (BCS) was evaluated during the close-up period, between 3 and 21 DIM, and at the end of lactation. The diagnosis time (DIM) of clinical disease events (culling because of JD clinical signs, ketosis, lameness, mastitis, displacement abomasum, injury, metritis, milk fever, pneumonia, and retained placenta) was recorded. Sixty-six cows were culled because of JD clinical signs (CCDJ) with average DIM of 209. CCDJ was associated with event of pneumonia (n=131) (OR=3.0, 95% CI=1.0-6.0) and level of fecal shedding (light: OR=13.0, 95% CI=5.3-30.0; moderate: OR=34.0, 95% CI=13.0-89.0; heavy: OR=66.0, 95% CI=26.0-171.0). Detection of fecal shedding at the end of the lactation (n=79) was associated only with event of pneumonia (OR=2.0, 95% CI=1.0-4.0).     

Risk factors for clinical salmonellosis in Virginia, USA cattle herds

Veterinarians working in several Virginia, USA counties noticed an increase in clinical salmonellosis in cattle herds during 1994. We conducted a case–control study to identify potential risk factors for salmonellosis in cattle herds in this region. The potential impact of exposure to poultry-related factors was of particular interest because of the close proximity of poultry and cattle operations in this part of the state. Information was collected from 23 case farms and 23 control farms matched by herd veterinarian, type of enterprise (beef vs. dairy), and location. Faecal and environmental samples were collected during herd visits for bacteriologic culture.

Salmonella was isolated from 4.7% of 531 faecal, feed, water, and environmental samples collected. Salmonella Typhimurium was the serotype found most frequently in clinical cases in participating herds and from samples collected during study visits. Case herds had a higher percentage of study samples positive for Salmonella. Potential risk factors were screened using methods for pair-matched data and then analyzed in individual conditional logistic-regression models to estimate odds ratios with 95% profile likelihood confidence intervals. Significant factors included: the number of mature cows in the herd (OR=1.01; CI 1.00, 1.03), percent change in the number of mature cows during 1994 (OR=0.68; CI 0.11, 0.96), having calves usually born in a building rather than outdoors (OR=0.17; CI 0.01, 0.98), poultry manure spread on bordering property (OR=4.00; CI 1.00, 26.50), signs of rodents in cattle-housing or feed-storage areas (OR=2.75; CI 0.94, 9.92), and contact of wild geese with cattle or feed (OR=4.5; 1.16, 29.51).     

Effect of previous antimicrobial treatment on fecal shedding of Salmonella enterica subsp. enterica serogroup B in New York dairy herds with recent clinical salmonellosis

The association of herd- and sample-level factors with the isolation of Salmonella group B from cattle fecal samples was analyzed. Study farms were 65 dairy herds with a recent history of laboratory-confirmed clinical salmonella infections. Herds were visited once per month for three months to collect data and samples for bacteriological culture. Herd size varied widely from 34 to 3700 total cattle on the farm (median=370). Salmonella serogroup B was isolated from 270 of 2726 samples tested. The predominant serotypes identified were S. Typhimurium and S. Typhimurium var. Copenhagen. Logistic regression was used to analyze the relationship between potential risk factors and isolating Salmonella serogroup B. The only herd-level factor which was significantly associated with fecal shedding was total herd size (hundreds of cattle OR=1.09; 95% confidence interval (CI): 1.05, 1.14). The probability of a positive sample decreased substantially for longer intervals between the initial clinical case and sampling (interval in months OR=0.5; 95% CI: 0.3, 0.6). The presence of diarrhea increased the risk of shedding (OR=2.1; 95% CI: 1.4, 3.0). The effect of recent treatment with antimicrobial agents depended on age group. For heifers and cows, recent antimicrobial treatment increased the probability of isolating Salmonella (heifers OR=11.8; 95% CI: 2.9, 48.8; cows OR=4.1; 95% CI: 2.0, 8.4), but this effect was not statistically significant for calves before weaning. Among animals without recent antimicrobial treatment, preweaned calves were more likely to have positive samples than cows (OR=3.5; 95% CI: 1.8, 6.9; heifers OR=4.7; 95% CI: 2.3, 9.6).     

The effect of claw trimming on the hoof health of Swedish dairy cattle

A 2-year experiment on the effect of claw trimming on hoof health was performed in 77 Swedish dairy herds (3444 dairy cattle) selected on herd size, breed composition and membership in the official milk-recording scheme. In the autumn, cows within each herd were blocked according to breed, parity and stage of lactation and allocated to two treatments: autumn trimming (AT) or no autumn trimming (NAT). Outcome variables were claw measurements and prevalence of hoof lesions and lameness (measured at spring trimming) and the need for hoof treatments between scheduled trimmings. At spring trimming, NAT cows had longer and shallower claws than AT cows. The average net growth of the toe wall was greater for AT than for NAT cattle, with a marked variation between housing systems. Most hoof lesions present at AT had disappeared at the subsequent spring trimming. Controlled for clustering by herd-within-year and for the effects of individual-and herd-level covariates, AT cattle at spring trimmings had significantly lower odds of lameness (OR=0.66) and of haemorrhages of the sole or white-line (OR=0.86), sole ulcer (OR=0.59) and white-line fissure or double sole (OR=0.71)-but not of moderate-to-severe heel-horn erosion or dermatitis (OR=0.96). Acute hoof treatments between claw trimmings were more common in the NAT group (OR=2.02).     

Estimation of Neospora caninum seroprevalence in dairy cattle from Normandy, France.

An epidemiological study was conducted in Orne (France) on randomly selected dairy herds (42 herds including 1,924 cows and heifers, which were at least 15 months old). The aim was primarily to estimate the seroprevalence of Neospora caninum infection from two blood samples per cow, using an enzyme-linked immunosorbent assay (ELISA) for N. caninum (one positive result indicating infection). The second aim was to test the association between some individual and herd factors and N. caninum seropositivity with a logistic model including a random term effect. The prevalence was estimated at 5.6% (107 seropositive animals). At least 27 of the 42 herds had one seropositive cow or heifer. The intra-herd seroprevalence varied from 1.1 to 8% for 18 positive herds (66.7%). Dogs were present in 36 farms and 104 of the 107 seropositive animals were exposed to them. The factors associated with individual seropositivity were the presence of cats (OR = 0.17; P < 0.001), dogs (OR = 4.35; P = 0.02), rabbits and/or ducks (OR = 2.10; P = 0.04), long calving periods (12 months) (OR = 0.44; P = 0.007), tethered housing (OR = 2.50; P = 0.01), somatic cell counts (200-400 x 10(3) cells/mL) (OR = 0.24; P < 0.001) and pond water supply (OR = 2.43; P = 0.04). In conclusion, the animal and intra-herd seroprevalences were low in dairy cows from Normandy, France.     

Analysis of some factors affecting fertility levels in a high‐producing dairy herd in south‐western Japan

The present study aimed to know whether all cows have been showing declining fertility or only a proportion of cows are attributed to the declining fertility, and to describe factors affecting the level of fertility. A total of 131 cows calved from February 2005 to December 2007 in a dairy herd were examined. Fourteen cows were excluded from the study because of early culling. Of the remaining 117 cows, 47 (40%) conceived within 115 days postpartum after 1–3 artificial insemination (AI) (normal fertility cows), 42 (36%) conceived after 115 days postpartum following 1–3 AI or were culled after 1–2 (sub‐fertility cows/culled), and 28 (24%) were inseminated more than three times without detectable genital tract abnormalities (repeat breeders). Calving to conception interval in the normal fertility group was 72 + 3 days, while in the sub‐fertility/culled and repeat breeding groups the intervals were 170 + 8 and 259 + 16 days, respectively. Endometritis was the risk factor for sub‐fertility/culled (odds ratio (OR) = 3.76). Prolonged luteal phase (OR = 4.08), delayed first ovulation (OR = 6.02), and delayed corpus luteum formation after AI (OR = 8.55) were the risk factors for repeat breeding. In conclusion, 60% cows showed reduced fertility in a herd, while the other 40% had normal fertility. Uterine infection and some ovarian disorders contributed to reduced fertility.     

Leptospirosis: II. Investigation of clinical disease in dairy cattle in the Waikato district of New Zealand

Investigations were carried out in 1975, 1976 and 1977 in 16 dairy herds where leptospiral abortions were suspected and in five other herds where clinical disease was not present. Both Leptospira interrogans serovars pomona and hardjo were isolated from cattle in herds with leptospirosis, but only pomona was recovered from those that had aborted. There was no evidence that hardjo caused clinical disease in dairy cattle in the Waikato district. It was found that 73% of the cows that aborted and 19% of other animals in the same herds had microscopic agglutination test titres to pomona of 1:2,000 or greater. By contrast, only 2% of cattle in herds without clinical evidence of leptospirosis had such titres. One cow retained a titre of 1:2,000 or greater to pomona for 7 months; titres of this order had a shorter duration in other cows. Leptospiruria occurred in 50% of cows that had aborted and in 9% of in-contact cows in the same herds. Only 0.7% of cows had leptospiruria in the herds with no clinical disease. Ten of 35 cows shedding pomona still had leptospiruria one month later. It was concluded that clinical leptospirosis should be diagnosed by testing a sample of the herd, rather than just individual cows, because of the variability and persistence of leptospiruria and serological titres in cows with and without clinical signs. Although hardjo is common in cattle in the Waikato district, it was not found to cause abortion in cattle.     

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.