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- Author or Editor: Yrjo T. Grohn x
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Summary
Association between individual cumulative milk yield and various reproductive disorders in 56,772 Finnish Ayrshire cows belonging to 5,912 herds in 80 communities was studied. All cows delivered calves between September 1985 and September 1986.
Five logistic regression models were fitted, 1 for each outcome disorder of interest: early metritis, late metritis, silent heat, ovarian cyst, and other infertility. Cumulative individual 37-day milk yield was used in the early metritis model, and cumulative individual 60-day milk yield was used in the other models, on the basis of median days in milk when these disorders developed. Cumulative 305 - day herd milk yield, parity, calving season, presence or absence of other disorders, and community were also included in the models. Point estimates from the models represented odds ratios for the likelihood of having the outcome disorder.
Lactational incidence risks for the 5 reproductive disorders studied were: early metritis (2.4%), late metritis (1.1 %), silent heat (5.4%), ovarian cyst (6.6 %), and other infertility (2.1 %). The risk of early metritis decreased with increasing 37-day milk yield. The risk of silent heat, ovarian cyst, and other infertility increased with increasing 60-day milk yield; 60-day milk yield had no effect on late metritis. The 305-day herd milk yield increased the risk of early metritis, ovarian cyst, and other infertility; it had no effect on late metritis or silent heat.
Parity had an effect on all disorders, except late metritis. Cows that delivered calves during the colder, darker seasons of the year had a higher risk of reproductive disorders than did those that delivered calves at other times of the year. A number of other disorders, reproductive and otherwise, were significant predictors of development of the outcome disorders.
Summary
A total of 21 calves were inoculated IV with 1 of the following isolates of bovine viral diarrhea virus (BVDV); CD87 (n = 10), NY-1 (n = 3), NADL (n = 5), or were sham-inoculated with virus-free medium (n = 3). Subsequent to inoculation, platelet counts were monitored to detect differences between noncytopathic (CD87, NY-1) and cytopathic (NADL) isolates in their ability to induce thrombocytopenia. Platelet count decrease throughout infection was statistically analyzed by comparing the slope of the line drawn from the count on the day of infection to the lowest count achieved by that calf. Significant difference was observed in the CD87-inoculated calves and in the NY-1-inoculated calves, compared with those of the same control group. Significant difference was not observed in the slope of platelet count decrease between the cytopathic NADL-infected calves and control-group calves. The data indicate that noncytopathic BVDV isolates may more easily induce thrombocytopenia than do cytopathic isolates in immune-naive, immunocompetent calves; acute infection with 1 cytopathic BVDV isolate (NADL) did not induce thrombocytopenia. In addition, although each calf seroconverted, virus was rarely isolated from mononuclear cells obtained from calves with cytopathic infections. At some point after infection, virus was always isolated from each of the calves undergoing noncytopathic infections, and occasionally, transient association of noncytopathic BVDV antigen with platelets was observed during these infections.
Abstract
Objective—To develop a mathematical model to simulate infection dynamics of Mycobacterium bovis in cattle herds in the United States and predict efficacy of the current national control strategy for tuberculosis in cattle.
Design—Stochastic simulation model.
Sample—Theoretical cattle herds in the United States.
Procedures—A model of within-herd M bovis transmission dynamics following introduction of 1 latently infected cow was developed. Frequency- and density-dependent transmission modes and 3 tuberculin test–based culling strategies (no test-based culling, constant [annual] testing with test-based culling, and the current strategy of slaughterhouse detection–based testing and culling) were investigated. Results were evaluated for 3 herd sizes over a 10-year period and validated via simulation of known outbreaks of M bovis infection.
Results—On the basis of 1,000 simulations (1,000 herds each) at replacement rates typical for dairy cattle (0.33/y), median time to detection of M bovis infection in medium-sized herds (276 adult cattle) via slaughterhouse surveillance was 27 months after introduction, and 58% of these herds would spontaneously clear the infection prior to that time. Sixty-two percent of medium-sized herds without intervention and 99% of those managed with constant test–based culling were predicted to clear infection < 10 years after introduction. The model predicted observed outbreaks best for frequency-dependent transmission, and probability of clearance was most sensitive to replacement rate.
Conclusions and Clinical Relevance—Although modeling indicated the current national control strategy was sufficient for elimination of M bovis infection from dairy herds after detection, slaughterhouse surveillance was not sufficient to detect M bovis infection in all herds and resulted in subjectively delayed detection, compared with the constant testing method. Further research is required to economically optimize this strategy.
Abstract
Objective—To assess seasonal variation in prevalence of Listeria monocytogeneson ruminant farms and identify management practices associated with ruminant listeriosis and fecal shedding of L monocytogenes.
Study Design—Case-control study.
Sample Population—2,056 samples of feces, feed, soil, and water from 24 case farms with listeriosis and 28 control farms without listeriosis.
Procedure—Samples were collected and evaluated via bacterial culture for L monocytogenes. Univariate associations between farm management practices and listeriosis and fecal shedding of L monocytogenes were assessed. Multivariate models were developed to identify farm management practices associated with listeriosis and fecal shedding of L monocytogenes.
Results—The prevalence of L monocytogeneson cattle, goat, and sheep farms was seasonal, especially in fecal samples, with peak prevalence in winter. Although the prevalence of L monocytogenes in feedstuffs from small-ruminant farms also peaked during winter, the bacterium was detected at a constant rate in cattle farm feedstuffs throughout the year. Farm management practices, animal health and hygiene, and feedstuff quality and storage were associated with ruminant listeriosis and fecal shedding of L monocytogenes.
Conclusions and Clinical Relevance—Results suggest that the prevalence of L monocytogenes on ruminant farms is seasonal, management practices are associated with ruminant listeriosis and fecal shedding of L monocytogenes, and the epidemiologic features of listeriosis differ in cattle versus small ruminants. Awareness of risk factors may be used to develop control measures to reduce animal disease and introduction of L monocytogenes into the human food chain. (J Am Vet Med Assoc 2005;227:1808–1814)
Objective
To describe causes of death, mortality, and morbidity from nonrespiratory diseases in dairy calves.
Design
Prospective observational cohort study.
Animals
Convenience sample of 410 dairy heifers born between January and December 1990 in 18 southwestern New York herds.
Procedure
Heifers were examined weekly by a veterinary clinician during the first 3 months of life and all disease conditions were recorded.
Results
Crude risks for diarrhea, umbilical infection, and umbilical hernia were 28.8, 14.2, and 15.1%, and the median ages at first diagnoses were 2, 1, and 3 weeks, respectively. Mean durations of umbilical infection and umbilical hernia were 3.7 and 6.7 weeks, respectively. Crude mortality was 5.6%. Case-fatality risks were 12.8% for diarrhea during the first week of life, 5.1% for diarrhea after the first week of life, and 0% for umbilical infection and umbilical hernia. Diarrhea was diagnosed by the caretaker or the clinician; umbilical conditions were diagnosed by the clinician. The primary cause of death was diarrhea in 43%, pneumonia in 24%, septicemia in 10%, and other single causes in the rest of the 21 necropsied calves.
Clinical Implications
The high incidence and somewhat long duration of umbilical infection, the finding that diarrhea was the primary cause of death, and the high case-fatality risk for diarrhea during the first week of life suggested that calf caretakers need training in the prevention and treatment of these conditions. (J Am Vet Med Assoc 1996:208:2043-2046)
Objective
To describe the incidence of respiratory tract disease in dairy calves and to compare antibody titers and microbial isolates from transtracheal wash samples between calves with and without respiratory tract disease (cases and controls, respectively).
Design
Prospective observational cohort study, with matched case-control substudy.
Animals
410 dairy heifers; in substudy, 105 cases and 59 controls from the same population.
Procedure
Calves were examined weekly by a veterinarian during the first 3 months of life. Blood samples were collected for serologic testing at the first visit for each calf and during acute and convalescent periods for cases. Transtracheal wash samples also were obtained during the acute period from cases and controls.
Results
Incidence and case-fatality risk for clinician-diagnosed pneumonia were 25.6 and 2.2%, respectively. Mycoplasma sp and Pasteurella multocida together were isolated from 29% of cases and 11% of controls, and Mycoplasma sp alone from 7% of cases and 30% of controls (both P ≤ 0.05). From postcolostral to acute-phase serum samples, Mycoplasma dispar titers increased 1.3-fold among cases, compared with 0.7-fold among controls; from acute- to convalescent-phase samples, Μ dispar titers increased 2.4-fold among cases, compared with 5.6-fold among controls (both P ≤ 0.005).
Clinical Implications
Results of this study suggested a synergistic effect between Mycoplasma sp and P multocida and a possible initiative role of Μ dispar in the development of respiratory tract disease. Postcolostral total IgG values and antibody titers were not significantly different between cases and controls, implying that other factors have an important role in the development of respiratory tract disease. (J Am Vet Med Assoc 1996;208:2035-2042)
Abstract
Objective—To determine the duration of fecal shedding of and serologic response to Salmonella spp after natural infection in dairy calves and characterize Salmonella organisms recovered from these herds.
Design—Longitudinal study.
Animals—Calves from 2 dairy herds (A and B) in the northeast United States that were identified at the beginning of a Salmonella outbreak.
Procedures—Fecal samples were collected twice per week (herd A) or once per week (herd B); blood samples were collected for serologic testing once per week in both herds. Bacteriologic culture of fecal samples was performed, and Salmonella isolates were characterized by serotype, pulsed-field gel electrophoresis (PFGE) pattern, and antimicrobial resistance profile.
Results—All Salmonella isolates from herd A were serovar Typhimurium var Copenhagen, had the same PFGE pattern, and were resistant to at least 9 antimicrobials. All isolates from herd B were Salmonella Typhimurium, represented 2 PFGE patterns, and were susceptible to all antimicrobials evaluated. The estimated duration of fecal shedding was 14 days in herd A and 9 days in herd B. Few calves were seropositive for antibody against Salmonella lipopolysaccharide within the first week after birth (0 of 20 in herd A and 13 of 79 in herd B) or seroconverted (6 in herd A and 4 in herd B). Fecal shedding was more common in calves that seroconverted, but overall, there was not a strong association between seropositivity and fecal shedding of Salmonella organisms.
Conclusions and Clinical Relevance—Although the herds differed in serologic response and Salmonella subtype, the duration of fecal shedding among calves was similar between herds.
Abstract
Objective—To determine the radiographic methods that best predict the development of osteoarthritis in the hip joints of a cohort of dogs with hip dysplasia and unaffected dogs.
Animals—205 Labrador Retrievers, Greyhounds, and Labrador Retriever-Greyhound crossbred dogs.
Procedure—Pelvic radiography was performed when the dogs were 8 months old. Ventrodorsal extendedhip, distraction, and dorsolateral subluxation (DLS) radiographs were obtained. An Orthopedic Foundation for Animals-like hip score, distraction index, dorsolateral subluxation score, and Norberg angle were derived from examination of radiographs. Osteoarthritis was diagnosed at the time of necropsy in dogs ≥ 8 months of age on the basis of detection of articular cartilage lesions. Multiple logistic regression was used to determine the radiographic technique or techniques that best predicted development of osteoarthritis.
Results—A combination of 2 radiographic methods was better than any single method in predicting a cartilage lesion or a normal joint, but adding a third radiographic method did not improve that prediction. A combination of the DLS score and Norberg angle best predicted osteoarthritis of the hip joint or an unaffected hip joint. All models that excluded the DLS score were inferior to those that included it.
Conclusions and Clinical Relevance—A combination of the DLS score and Norberg angle was the best predictor of radiographic measures in 8-month-old dogs to determine whether a dog would have normal or osteoarthritic hip joints. (Am J Vet Res 2003;64:1472–1478)
