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in Journal of the American Veterinary Medical Association

Summary

For efficient disease management in dairy production, the influence of disease prevention strategies on farm profitability must be known. A survey of mastitis control practices, milking machine function and maintenance, and cow environmental conditions was conducted with 406 dairy producers on the Michigan Dairy Herd Improvement-somatic cell counting program responding. These survey data, in conjunction with Dairy Herd Improvement production data, were used to develop a model estimating the marginal value products of mastitis control practices. Lost milk production associated with increased somatic cell count was calculated for each herd. Mastitis control practices, milking machine function and maintenance, and cow environmental conditions were used as independent variables in an analysis of covariance model with lost milk production as the dependent variable. Variables significant in explaining changes in production from increased somatic cell count were the use of teat dip, use of sanitizer in the wash water, milking cow bedding, summer nonlactating cow housing, summer calving locations, type of regulator, alternating pulsation, and rolling herd average milk production. The marginal value product (change in revenues received) from the use of iodine, chlorhexidine, and quaternary ammonium-type teat dips were $13.79, $16.09, and $22.17/cow/year, respectively, and these changes were statistically significant. However, sanitizer in the wash water was associated with a decrease in production. Management practices that have previously been shown to be economical and did not appear in the final model included nonlactating cow therapy and single-use paper towels.

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in Journal of the American Veterinary Medical Association

Summary

An epidemiologic model of Pseudorabies virus (PRV) in swine was developed. This model was used to project future herd-to-herd disease transmission under alternative eradication or control programs over 20 years (1993 to 2012). With current PRV eradication program funding, it was projected that prevalence would be 23% in higher-risk states in the United States, 10% in moderate-risk states, and 1% in lower-risk states. Increased funding for the PRV eradication program was projected to reduce PRV prevalence substantially.

Productivity and economic impacts of PRV also were estimated for the average size farrow-to-finish operation. These impacts included mortality for preweaning, nursery, growing/finishing, and breeding hogs; market weights and number of market hogs sold; farrowing rates, number of live pigs per litter, and number of litters per sow-year. Profitability was estimated to be $6/cwt less for PRV-in-fected herds than for uninfected herds.

Aggregate effects of PRV eradication programs were estimated by use of economic welfare analysis. For all PRV eradication program alternatives analyzed, consumers were the major beneficiaries of the program because of reduced prices and increased consumption of pork. Estimates of the value of economic welfare impacts under the current program with an assumed parallel supply-curve shift were determined: consumers gained $336.5 million; producers gained $35.9 million; government expenditures were $197.1 million; and the benefit/cost ratio of the program was 1.89. Economic welfare measures were projected to increase substantially with increased PRV eradication program funding. Economic welfare measures also were estimated under other assumptions.

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in Journal of the American Veterinary Medical Association

Summary

Supplementation of selenium and vitamin E to enhance disease resistance in dairy cattle has become common, particularly to prevent periparturient reproductive disorders and mastitis. To establish reference values for serum vitamin E and selenium concentrations in postparturient dairy cattle and to determine whether serum concentrations of these micronutrients varied with season and stage of lactation, cows from a stratified random sample of 50 herds were studied for 1 year. Blood samples were collected from each of the 50 study herds twice, from the 10 most recently parturient cows or from 10% of the herd, whichever was greatest. Mean concentration of vitamin E and selenium was 2.55 μg/ml and 78.12 ng/ml, respectively. Vitamin E concentrations were significantly (P < 0.05) higher during the summer and fall than during the winter and spring. Selenium concentrations were significantly (P < 0.05) lower during the summer and fall than during the winter and spring. Herd, season of blood sample collection, and time since parturition were significant (P < 0.02) in explaining variation in vitamin E and selenium concentrations.

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in Journal of the American Veterinary Medical Association

Summary:

Various nutrious nutritional-supplement gels are being marketed for use in veterinary medicine. This study was designed to determine whether serum calcium, phosphorous, or magnesium concentrations were different between cows given a gel containing calcium chloride as its active ingredient (treated) and cows given inert carrier gel (control). The study revealed a significant (P < 0.01) increase in serum total calcium concentration within 5 minutes of administration of a calcium gel given to cows within 1 hour of parturition. Serum total calcium concentration had returned to baseline value by 24 hours after calcium gel administration. Serum inorganic phosphorus concentration also increased significantly (P < 0.05) after treatment. Significant changes in serum magnesium concentrations were not detected.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare serologic testing with slaughter evaluation in assessing effects of subclinical infection on average daily weight gain (ADG) in pigs.

Design—Cohort study.

Animals—18 cohorts (30 to 35 pigs/cohort) of pigs on 7 farms.

Procedure—Blood samples were collected, and pigs were weighed at 8, 16, and 24 weeks of age. Sera were tested for antibodies to porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), transmissible gastroenteritis virus (TGEV), pseudorabies virus, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae. At slaughter, skin, nasal turbinates, lungs, and liver were examined. Associations between ADG and results of serologic testing and slaughter evaluation were examined by use of multiple linear regression.

Results—Pathogens that had a significant effect on any given farm during any given year and the magnitude of that effect varied. However, at 16 and 24 weeks of age, a higher antibody titer was consistently associated with a lower ADG. Mean differences in ADG between seropositive and seronegative pigs were 18 g/d (0.04 lb/d) for SIV, 40 g/d (0.09 lb/d) for PRRSV, 38 g/d (0.08 lb/d) for M hyopneumoniae, and 116 g/d (0.26 lb/d) for TGEV. Of the evaluations performed at slaughter, only detection of lung lesions was consistently associated with a decrease in ADG.

Conclusions and Clinical Relevance—Results suggest that subclinical infection with any of a variety of pathogens commonly found in swine herds was associated with a decrease in ADG. Serologic testing was more effective than slaughter evaluation in assessing the impact of subclinical infection on ADG in these pigs. (J Am Vet Med Assoc 2000;217:888–895)

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in Journal of the American Veterinary Medical Association

Summary

A hospital-based case-control study was conducted to evaluate and compare risk factors for abomasal volvulus (av) and left displaced abomasum (lda) in cattle. Medical record abstracts were derived from 17 North American veterinary schools by the Veterinary Medical Data Program for all cattle admitted between Jan 1, 1977 and Dec 31, 1986, and for those with a diagnosis of av or lda. From a total of 108,956 individual cattle records, 1,036 cases of av and 7,695 cases of lda were identified, with a ratio of LDA to AV cases of 7.4 to 1. In-hospital mortality was 23.5% for av and 5.6% for lda.

Age, breed, gender, and season each had significant (P < 0.05) effects on risk for av and lda. Risk for av and lda increased with increasing age, with greater risk in cattle aged 4 to 7 years. Dairy cattle were at higher risk of developing av (adjusted odds ratio, 36.4) and lda (adjusted odds ratio, 95.2) than were beef cattle. The odds of AV in Brown Swiss cattle were significantly (P < 0.0001) lower, and the odds of lda in Guernsey cattle were significantly (P < 0.0001) higher than those in Holstein cattle. Female cattle were also at higher risk of developing av (adjusted odds ratio, 3.3) and lda (adjusted odds ratio, 29.1) than were male cattle. The odds of av and LDA varied considerably throughout the year, with the lowest number of cases observed in autumn. Seasonal development of AV differed significantly (P < 0.0001) from that of LDA, with the odds of av and lda being highest in January and March, respectively.

The medical records for all cattle with av and lda examined at the teaching hospital over a 10- and 5-year period, respectively, were reviewed, and the time interval since parturition, as well as the existence and nature of concurrent disease, were recorded. Proportionately fewer cases of av than lda developed during the first 2 weeks after parturition (28.3% of av cases vs. 57.0% of lda cases). Concurrent disease existed in 30.4% of av cases and 53.6% of LDA cases, with the rates of concurrent disease differing significantly (P < 0.0001) between the 2 groups. The mis-classification rate for data generated at the teaching hospital was estimated to be 6.5% for av and 5.3% for lda.

On the basis of the findings of this study, we hypothesize that: abomasal atony is a prerequisite for av and lda; existence of an abdominal void immediately after parturition facilitates development of AV and lda; normal rumen volume provides a moderately effective barrier against lda; risk of lda does not increase appreciably with advancing pregnancy; and the direction of abomasal displacement (av or lda) after abomasal atony and dilation is influenced principally by rumen volume.

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in American Journal of Veterinary Research

Summary:

A stratified random sample of 50 Ohio dairy herds, monitored for 1 year between March 1988 and May 1989, was used to estimate the component costs of clinical mastitis per cow-year overall and by organism, the component costs of an episode of clinical mastitis overall and by organism, and the incidence of clinical mastitis by organism. Each herd was visited monthly by a veterinarian who conducted on-farm interviews and completed standardized data-collection forms designed to elicit economic information about the on-farm costs of clinical mastitis and mastitis prevention. Producers collected milk samples prior to treatment of clinical mastitis cases. Culturing methods allowed identification of 18 specific mastitis pathogen classifications. Annual costs estimated were on a per cow-year and clinical episode basis. The monthly mean population of cows monitored was 4,068. Mastitis prevention cost $14.50/cow-year, whereas the cost incurred by producers because of clinical cases of mastitis was $37.91. Organisms prevalent in the cows’ environment caused the most costly types of mastitis. Disregarding contaminated samples and episodes for which no milk samples were taken, mastitis for which 2 organisms were isolated accounted for 35.5% of costs of clinical mastitis, followed by cases for which Escherichia coli (21.3%) was isolated, cases for which culturing yielded no growth (8.6%), and cases for which esculin-positive Streptococcus spp (6.4%), Klebsiella spp (5.7%), esculin-negative CAMP-negative Streptococcus spp (5.1%), Enterobacter spp (4.8%), coagulase-negative Staphylococcus spp (4.1%), coagulase-positive Staphylococcus spp (3.0%), S agalactiae (2.5%), and Bacillus spp (1.2%) were isolated. Other categories of classification each accounted for < 0.5% of costs. Mean cost per clinical episode was $107.11. Mean incidence of clinical mastitis was 38.74 cases/100 cowyears. Mixed infections had the highest incidence (mean, 4.80 cases/100 cow-years), followed by cases with no growth (2.96), E coli (2.10), esculin-positive Streptococcus spp (1.94), coagulase-negative Staphylococcus spp (1.60), esculin-negative CAMP-negative Streptococcus spp (1.25), coagulase-positive Staphylococcus spp (1.04), Enterobacter spp (0.36), and Klebsiella spp (0.27).

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in Journal of the American Veterinary Medical Association

Summary:

A cross-sectional study of 1,032 dairy herds in Ohio was conducted to determine the prevalence of the major contagious pathogens of mastitis (Streptococcus agalactiae and Staphylococcus aureus) and the use of common mastitis control measures.

Herd owners were surveyed by mail concerning their use of mastitis control measures. The survey focused on treatment of nonlactating cows, postmilking teat dipping, culling practices, milking machine maintenance, treatment for clinical mastitis, and premilking hygiene practices. Nearly 90% of questionnaires were returned.

The prevalence of Streptococcus agalactiae and Staphylococcus aureus was determined by use of bulk-tank milk samples. Most herds (n = 802) met the criteria for classification into 1 of 4 groups: (1) Free of contagious pathogens, as determined by inability to isolate coagulase positive staphylococci (cps) and esculin-negative camp positive streptococci (encps) from 3 bulk-tank milk samples, (2) cps, but not encps, isolated from at least 1 sample (3) encps, but not cps, isolated from at least 1 sample, (4) both encps and cps isolated from at least 1 sample. The number of herds in which both encps and cps were isolated was low; therefore, these herds were grouped with herds in which encps alone was isolated for the evaluation of mastitis control practices related to herd pathogen status.

Herd somatic cell count (scc) was determined using Dairy Herd Improvement Association data by calculating the geometric mean scc from individual cow test day scc. Twelve months of scc data from 741 herds were included in this study.

Contagious pathogens were not isolated from bulk-tank milk from most herds, nevertheless cps was isolated from bulk-tank milk from a large proportion of herds (45.4%, 364/802). From the mail survey, it was determined that a high proportion of herd managers teat dipped all cows after milking (90.5%, 838/926) and treated all nonlactating cows (83.8%, 776/926). The other mastitis control practices were not as widely adopted in this group of dairy managers. When the adoption of mastitis control practices were related to the results of the bulk-tank survey, numerous groups of herds could be identified. Group-1 had the highest proportion of herds adopting the surveyed practices, groups 3 and 4 represented the lowest proportion of herds in which all the surveyed practices were adopted, and group 2 had essentially the same profile for adoption of the surveyed practices as group 1. This latter observation in conjunction with the observation that groups 1 and 2 had similar distributions of herd scc suggested that the role of the mastitis control program surveyed in our study may be to control the impact of cps, but it may not be effective in eliminating cps. Another trend was that managers of herds without contagious pathogens were more likely to use a teat dip prior to milking than farms with either contagious pathogen, and this was the 1 management variable that distinguished herds without contagious pathogens from herds with cps.

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in Journal of the American Veterinary Medical Association