Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: Ynte H. Schukken x
  • Refine by Access: Content accessible to me x
Clear All Modify Search

Abstract

Objective

To determine antibody titer against bovine respiratory syncytial virus (BRSV) in dairy calves on farms and to investigate whether passively acquired antibody titers differ in calves born in various seasons.

Sample Population

Serum samples from 129 colostrum-fed replacement calves in 8 dairy herds.

Procedure

A standard ELISA was used to determine BRSV-specific antibodies in serum samples obtained monthly, and antibody titers for calves born in various seasons were compared.

Results

BRSV-specific antibody titer in colostrum-fed dairy calves decreased to undetectable values at 3 to 4 months old. Calves born in winter generally had lower titers, compared with those for calves born in other seasons (P< 0.05). Titers in calves born in seasons other than winter did not differ.

Conclusions and Clinical Relevance

Calves born in winter generally have lower BRSV-specific antibody titers, which may be caused by generally lower antibody titers in colostrum or by factors influencing colostrum intake. (Am J Vet Res 1999;60:1098-1101)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine sources and amounts of variation in a kinetics ELISA (KELA) and results of culture of fecal samples for Mycobacterium avium subsp paratuberculosis (MAP) in repeated tests of individual cows.

Animals—112 cows on 6 commercial dairy farms in New York.

Procedure—A nonrandom longitudinal study was conducted from January 2001 to March 2002. A KELA was performed monthly, and MAP culture was performed bimonthly. Cow- and herd-level data were collected. The KELA and culture results were analyzed by use of models that corrected for clustering within herds and repeated measures on cows.

Results—Cows of second or higher lactation had increased KELA values, compared with values for first-lactation cows. Cows had lowest KELA values during the first 15 days in milk; KELA values increased until 60 days in milk and then stabilized. Moderate and heavy shedders had significantly higher KELA values than culture-negative cows, and KELA values of shedders progressively increased over time. On average, the KELA value was significantly increased 132 days after a cow was first detected to be a moderate shedder and 236 days after a cow was first detected to be a low shedder.

Conclusions and Clinical Relevance—Analysis suggests that KELA results vary on a cow-level on the basis of lactation number and stage of lactation. High KELA values indicate heavy fecal shedding, but the KELA is not useful in identifying low and moderate shedders that can require up to 236 days to have a significant increase in KELA value. (Am J Vet Res 2003;64:479–484)

Full access
in American Journal of Veterinary Research

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.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify management factors associated with veterinary usage by organic and conventional dairy farms.

Design—Prospective case-control study.

Sample—292 farms.

Procedures—Organic farms in New York, Oregon, and Wisconsin were matched to conventional farms on the basis of location and herd size. During a single herd visit, a questionnaire was administered, information about animal disease incidence and number of veterinarian visits in the preceding 60 days was collected, and forms to record similar information during the 60 days after the visit were left for the herd manager to complete. For analysis, conventional herds were classified as either grazing or nongrazing. Multiple correspondence analysis was used to assess relationships among management factors and selected outcomes for frequency of veterinary usage.

Results—Intensive management practices were closely associated with frequent veterinary usage. Generally, organic management practices were associated with less frequent veterinary usage than were conventional management practices. Conventional grazing practices were associated with intermediate veterinary usage (more than organic practices but less than intensive practices), whereas conventional nongrazing practices were associated with frequent veterinary usage. Cost of routinely scheduled veterinarian visits/45 kg (100 lb) of milk produced/y was greater for small farms than that for large farms.

Conclusions and Clinical Relevance—Results suggested that management intensiveness was more closely associated with frequency of veterinary usage than was organic status; therefore, veterinarians should characterize farms by factors other than organic status when investigating which farms are most likely to use their services. Economic factors substantially affected routine veterinary usage on small farms.

Full access
in Journal of the American Veterinary Medical Association

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)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To determine relative impact of genetic, common-litter, and within-litter factors on puppy mortality.

Animals

2,622 Boxer puppies of 413 litters born during a 14-month period.

Procedure

For each puppy, pedigree was determined, and litter in which it was born was registered. Overall mortality and mortality per specific cause of death were analyzed by use of a model that included an additive genetic effect, common-litter effect, within-litter effect, and regression of mortality on inbreeding coefficient. Relative importance of the effects was determined from estimates of the variance in mortality explained by each factor.

Results

22% of the puppies died before reaching 7 weeks old. Stillbirth was the most frequent cause of death, followed by infection. Most observed differences were attributable to within-litter factors, which explained 67% of the variance in death attributable to infection and ≤ 96% of the variance in death attributable to asphyxia. Common-litter factors were more important than additive genetic factors. Variance attributed to common-litter factors ranged from 2% for cheiloschisis, palatoschisis, or cheilopalatoschisis to 30% for death attributable to infection, and variance attributed to additive genetic factors ranged from 0% for asphyxia to 14% for euthanatized because of white color. Inbreeding coefficient had a significant effect on death attributable to infection, which increased 0.26% for each percentage increase of inbreeding.

Conclusions and Clinical Relevance

Additive genetic factors have less impact on preweaning mortality than common-litter factors, which in turn have less impact than within-litter factors. Mortality attributable to infection increases significantly with increases in inbreeding. (Am J Vet Res 1999;60:1106-1110)

Free access
in American Journal of Veterinary Research