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Summary

A clinical field trial was undertaken to determine the influence of an intramammary device (imd) on environmental mastitis and production. On 4 central California dairies, 200 Holstein first-lactation cows were randomly assigned to 2 groups. Cows in the treatment group were fitted with an imd, and cows in the control group were not. The incidence of clinical mastitis for the 2 groups was determined during the study period. Bacteriologic monitoring at intervals over 2 lactations (lactation 2 and through 60 days of lactation 3) was used to determine the incidence of subclinical infection. In addition, data were collected to determine whether the groups differed in milk production, butterfat production, postmilking and test-day somatic cell counts, and reproductive efficiency. Total milk production and butterfat production over the 2 lactation periods did not vary significantly between the groups. Also, the groups did not differ in calving-to-conception interval, duration of lactation, calving interval, and calving-to-first service interval. Cows with imd were significantly less likely to develop clinical mastitis (5% vs 13%) than control cows. The imd did not appear to affect subclinical infection rates (minor pathogens only) except at day 300 of lactation 2 and at day 10 of lactation 3, when prevalence was greater in the cows with imd. The minor pathogens were predominately (80%) coagulase-negative staphylococci. It was unusual to have coagulase-negative staphylococci in the same quarter at 2 consecutive samplings, prompting the speculation that during lactation, the duration of coagulase-negative staphylococci infection is short (resolves without intervention). However, new infections developed in other quarters, thus maintaining a consistent quarter prevalence throughout the lactation. The imd induced a significant increase in postmilking somatic cell count, compared with results from control cows, and test-day somatic cell count had a more modest increase in cows with imd, compared with previous studies.

Free access
in Journal of the American Veterinary Medical Association

Objective

To monitor effects that improvements in housing facilities would have on herd performance. Financial measures were calculated to estimate whether improvements resulted in an improved financial status for the farm.

Design

Prospective, observational study.

Animals

160-cow dairy herd.

Procedure

Farm visits were conducted from 1990 to 1994. Areas for improvement were identified, and changes were recommended. Herd production and farm financial records were analyzed before, during, and after adoption of recommended changes.

Results

After improving facilities, somatic cell count was somewhat constant, but tended to decrease during the last 16 months of the study. During the last 8 months of the study, incidence for clinical cases of mastitis decreased to 3.3% per month. Reproductive variables improved dramatically after implementing use of a bull for breeding. Subjective evaluation of cow comfort and lameness indicated apparent improvements in each area. However, milk production remained fairly constant from January 1991 through December 1994.

Review of the farm's financial status revealed that costs of production increased from 1990 through 1993, but decreased in 1994. Slow financial response to improvements were attributed to a large decrease in milk price in 1991 and a poor crop harvest in 1993. Thus, although progress was made toward financial stability, approximately 55% of the farm's assets (determined on a market-basis value) were represented by debt.

Clinical Implications

It is important to monitor financial status when managing complex health problems that involve several aspects of a farm's operation. (J Am Vet Med Assoc 1996;209:1406–1410)

Free access
in Journal of the American Veterinary Medical Association

Objective

To determine associations between subclinical Mycobacterium paratuberculosis infection and milk production, milk components, and somatic cell counts of dairy cattle.

Design

Cross-sectional epidemiologic survey.

Animals

23 dairy herds in Wisconsin containing 1,653 adult cows were studied. The herds had above average milk production and a history of bovine paratuberculosis in the herd within the previous 12 months.

Procedure

All adult cows in the herds were tested for paratuberculosis by use of an absorbed ELISA. Milk yield, fat, protein, and somatic cell count data were retrieved electronically from Dairy Herd Improvement Association records.

Results

147 ELISA-positive and 1,506 ELISA-negative cows were identified. ELISA-positive cows had a mature-equivalent milk production of 376 kg (829 lb)/lactation less than that for ELISA-negative herdmates. Significant difference was not found in lactation average percentages of fat and protein, or somatic cell count linear score. When comparing ELISA-positive and -negative cow's current mature equivalent milk with all previous lactations, significant difference was found only from the immediate-preceding lactation. When this difference was examined by parity group, significant difference was confined to cows in the second lactation.

Clinical Implications

Subclinical paratuberculosis infections, as determined by ELISA, are associated with a 4% reduction in milk yield and add to the already substantial costs of clinical M paratuberculosis infection in the dairy industry. (J Am Vet Med Assoc 1996;208:1872-1876)

Free access
in Journal of the American Veterinary Medical Association

Objective

To use an on-farm recording form to quantify the effect of specific management practices on apparent prevalence of Mycobacterium paratuberculosis in dairy cattle herds.

Design

Epidemiologic survey.

Animals

26 commercial Wisconsin dairy farms.

Procedures

An instrument was developed on the basis of literature review and expert interviews to quantify on-farm management practices associated with increased apparent prevalence of M paratuberculosis. On-farm visits were conducted to assess how specific management practices were conducted. Apparent prevalence of M paratuberculosis infection was measured for all animals > 20 months old on all farms, using a commercial ELISA. Regression analysis was used to identify management variables that were significantly associated with apparent prevalence of M paratuberculosis.

Results

Regression analysis (R 2 = 0.90) identified that high scores for environmental conditions, newborn calf care, grower calf care, bred heifer care, and manure handling were significantly associated with M paratuberculosis apparent prevalence in Wisconsin dairy herds.

Clinical Implications

Environmental conditions, newborn calf care, grower calf management, bred heifer management, and manure handling factors may serve as a prioritized checklist for instructing owners and managers where to place emphasis in changing management practices to limit M paratuberculosis prevalence. Likewise, the factors identified as having low association with apparent prevalence may be de-emphasized in control programs, allowing dairy managers to focus time and finances on more effective components of an M paratuberculosis control program. (J Am Vet Med Assoc 1996;208:1877-1881)

Free access
in Journal of the American Veterinary Medical Association

Summary

Body condition scoring (using a 5-point scale with quarterpoint divisions) was performed on 66 Holstein dairy cows that began their second or later lactation in August, September, or October 1988. Cows’ body condition was scored beginning on postpartum day 4 (± 1) and subsequently at postpartum days (± 1) 18, 32, 46, 60, 73 and 87. Blood samples were obtained on the same dates. Reproductive health examinations were conducted by 1 of 2 veterinarians beginning at postpartum day 21. Reproductive performance was evaluated in relation to body condition score and serum urea nitrogen and cholesterol concentrations.

Number of days to first recorded signs of estrus and first breeding were not related to body condition score at calving, amount of condition loss, cumulative 80-day milk yield, or 305-day fat corrected milk yield. Cows that calved with body condition score ≥ 3.50 required more days to conceive. Cows losing > 0.75 points of condition had longer days of conception. Body condition score at calving and amount of condition lost were not related to services per conception or diagnosis of follicular cyst.

Cumulative 80-day milk yield was not related to days to conception or services per conception. Cows that produced = the mean 305-day milk yield required more services and had longer days to conception than cows that produced < the mean 305-day milk yield. Cows with diagnosis of ovarian follicular cysts had greater cumulative 80- and 305-day milk yields than did cows that were not diagnosed with follicular cysts.

Cows conceiving with ≤ 2 services did not differ in average daily milk production, body condition score, or serum urea nitrogen concentration from cows conceiving with > 2 services, but cows that conceived with ≤ 2 services had higher serum cholesterol values than did cows requiring more services.

Free access
in American Journal of Veterinary Research

Summary

Body condition scoring (using a 5-point scale with quarter-point divisions) was performed on 66 Holstein dairy cows that began their second or later lactation in August, September, or October 1988. Body condition was scored, beginning on postpartum day 4(± 1) and subsequently at postpartum days (± 1) 18, 32, 46, 60, 73, and 87. Blood samples were obtained on the same dates. Kilograms of milk produced per cow was measured daily. Body condition score and changes in body condition score were evaluated in relation to daily milk production, cumulative 80- day milk yield, and serum urea nitrogen and cholesterol concentrations.

Average daily milk production during week 1 was indicative of cumulative 80-day production, but not of 305- day milk yields. Cows that calved with body condition score ≥ 3.50 did not differ in average daily milk production, cumulative 80-day milk yield, or 305-day milk yield, compared with cows that calved with body condition score < 3.50. Cows that calved with body condition score ≥ 3.50 lost more condition than did cows that calved with body condition score < 3.50. Body condition score at calving and amount of body condition loss interacted with the rate of change in daily milk production.

Serum urea nitrogen concentration did not differ for cows grouped by cumulative 80-day milk production or for cows grouped by amount of condition loss. Serum cholesterol values were higher than previously reported values and increased directly with milk production. Serum cholesterol values were inversely related to condition loss, but changes in cholesterol concentration were not related to condition loss.

Free access
in American Journal of Veterinary Research