Udder Health Management Research Articles

Cross-Infection Between Cats and Cows: Origin and Control of Streptococcus canis Mastitis in a Dairy Herd

Group G streptococci in animals usually belong to the species Streptococcus canis and are most commonly found in dogs and cats. Occasionally, Strep. canis is detected in milk from dairy cows. An outbreak of Strep. canis mastitis in a dairy herd is described. Based on results from bacterial culture and ribotyping, a cat with chronic sinusitis was the most likely source of the outbreak. Subsequent cow-to-cow transmission of Strep. canis was facilitated by poor udder health management, including use of a common udder cloth and failure to use postmilking teat disinfection. Infected cows had macroscopically normal udders and milk, but significantly higher somatic cell counts than Strep. canis-negative herd mates. The outbreak was controlled through antibiotic treatment of lactating cows, early dry-off with dry cow therapy, culling of infected animals, and implementation of standard mastitis prevention measures. Cure was significantly more likely in dry-treated cows (87.5%) and cows treated during lactation (67%) than in untreated cows (9%). Whereas mastitis due to group G streptococci or Strep. canis in dairy cows is usually limited to sporadic cases of environmental (canine or feline) origin, this case study shows that crossing of the host species barrier by Strep. canis may result in an outbreak of mastitis if management conditions are conducive to contagious transmission. In such a situation, measures that are successful in control of Strep. agalactiae can also be used to control Strep. canis mastitis.

Use of partial budgeting to determine the economic benefits of antibiotic treatment of chronic subclinical mastitis caused by Streptococcus uberis or Streptococcus dysgalactiae

The economic effect of lactational antibiotic treatment of chronic subclinical intramammary infections due to Streptococcus uberis or Streptococcus dysgalactiae was explored by means of partial budgeting. Effects at cow level and herd level were modelled, including prevention of clinical mastitis episodes and the prevention of transmission of infections. Input variables for our deterministic model were derived from literature or based on 2002/2003 dairy prices and farming conditions in The Netherlands. Sensitivity analysis was used to examine the effect of uncertainty around input variables or changes in price estimates. On farms where pathogen transmission was prevented through proper udder health management, 3-d antibiotic treatment during lactation resulted in an average net profit of euro+11.62 over no treatment while 8-d antibiotic treatment had an average negative net result of euro-21.83. Sensitivity analysis showed that profitability depends on the probability of treatment-induced cure, pathogen transmission rates, culling rate, retention pay-off, and costs of antibiotic treatment. Three-day antibiotic treatment of chronic subclinical streptococcal mastitis is economically profitable over a range of input values for cure probabilities, transmission rates and losses due to culling. In contrast, 8-d lactational treatment is only profitable for very valuable animals, on farms where the risk of pathogen transmission is high and/or when the farmer is likely to cull a high percentage of cows with subclinical mastitis. Because bacterial flora, cow characteristics and management differ widely between farms, the economic outcome of lactational treatment of chronic subclinical streptococcal mastitis may be highly farm-dependent.

Milking Procedures and Udder Health Management on US Dairy Operations

Many recommendations relating to proper milking procedures and udder health management have been published, but adoption of these recommended practices on US dairy farms has not been determined. The National Animal Health Monitoring System's (NAHMS) Dairy 2002 Study included survey questions regarding these practices on dairy farms. The objective of this report is to describe current milking procedures and other management practices associated with udder health on U.S. dairy operations.

Analysis of an Outbreak of Streptococcus uberis Mastitis

An outbreak of Streptococcus uberis mastitis was described to gain insight into the dynamics of Strep. uberis infections at a herd level. Data were obtained from a longitudinal observational study on a commercial Dutch dairy farm with good udder health management. Quarter milk samples for bacteriological culture were routinely collected at 3-wk intervals from all lactating animals (n = 95±5). Additional samples were collected at calving, clinical mastitis, dry-off, and culling. During the 78-wk observation period, 54 Strep. uberis infections were observed. The majority of infections occurred during a 21-wk period that constituted the disease outbreak. The incidence rate was higher in quarters that had recovered from prior Strep. uberis infection than in quarters that had not experienced Strep. uberis infection before. The incidence rate of Strep. uberis infection did not differ between quarters that were infected with other pathogens compared with quarters that were not infected with other pathogens. The expected number of new Strep. uberis infections per 3-wk interval was described by means of a Poisson logistic regression model. Significant predictor variables in the model were the number of existing Strep. uberis infections in the preceding time interval (shedders), phase of the study (early phase vs. postoutbreak phase), and prior infection status of quarters with respect to Strep. uberis, but not infection status with respect to other pathogens. Results suggest that contagious transmission may haveplayed a role in this outbreak of Strep. uberis mastitis.

Evaluation of the California Mastitis Test for Screening Dairy Cows for Intramammary Infection at Calving

Udder health management programs at dry-off and during the dry period are essential to control and prevention of mastitis in dairy cattle. Knowledge of the prevalence of subclinical intramammary infection status at calving, and the specific pathogens involved, allows producers to evaluate effectiveness of these udder health programs. However, milk sampling and culturing all cows at the time of calving can be expensive and time consuming, and has not been widely adopted by the industry. California mastitis test (CMT) has not been recommended for use in recently fresh cows. This study examined the use of the CMT for selecting quarters in fresh cows for further bacteriological examination to identify the presence of intramammary infection. Cut-points for defining a positive CMT test and length of time post-calving were evaluated.

Ontario Bulk Milk Somatic Cell Count Reduction Program: Progress and Outlook

The objective of this study was to describe the results of the ongoing somatic cell count (SCC) reduction program in Ontario, Canada and to provide an outlook regarding the possible scenarios beyond the final stages of the current reduction program. The data were from all of the approximately 9500 farms in the province of Ontario during the last 10 yr and included monthly data for kilograms of milk sold, mean milk component measurements, and milk quality measurements (bulk milk SCC, plate loop count, and inhibitor presence).Four of five steps in the control program had a significant impact on the mean monthly bulk milk SCC. The total decrease in mean SCC that was attributable to the program was approximately 80 × 103 cells/ml. The monthly occurrence of inhibitor violations increased significantly. Cross-classification of the annual mean bulk milk SCC and the incidence of inhibitor violations indicated that the incidence specifically increased for farms with a relatively high bulk milk SCC. In 1994, bulk milk SCC increased, primarily because of farms that had a mean bulk milk SCC between 150 × 103 and 450 × 103/ml. The small relative contribution of farms with higher bulk milk SCC was due to their relatively low production and the small number of farms in those classes.The Ontario SCC reduction program was initially successful in the reduction of mean bulk milk SCC. Further reduction will require the active participation of farms with a relatively low bulk milk SCC. Not only is it necessary to penalize farms that exceed thresholds, but also an incentive to prevent farms with good udder health management from increasing bulk milk SCC is of great importance. The increase in inhibitor violations is of concern and requires further attention.