Randy T. Dingwell

Microbiological quality of bulk tank raw milk in Prince Edward Island dairy herds

The objectives of this study were to evaluate microbiological quality of bulk tank milk in Prince Edward Island, to evaluate correlation among milk quality criteria, and to determine seasonal effects on milk quality parameters. Bulk tank raw milk quality was evaluated on all Prince Edward Island dairy herds (n = 235) over a 2-yr period (March 2005 to March 2007). Biweekly total aerobic (TAC), preliminary incubation (PIC), laboratory pasteurization, and coliform (CC) counts were determined using a Petrifilm culture system. Additionally, bulk tank somatic cell count was determined weekly. The mean and median values were 12.8 x 10(3) and 4.9 x 10(3) cfu/mL for TAC, 29.6 x 10(3) and 13 x 10(3) cfu/mL for PIC, 87 and 12 cfu/mL for laboratory pasteurization count, 21 and 5 cfu/mL for CC, and 218 x 10(3) and 187 x 10(3) cells/mL for somatic cell count. There was moderate correlation (0.57) between TAC and PIC. All other correlation coefficients were low (<0.26). Correlation results suggest that a single quality parameter could not predict others used in this study. Seasonal data indicate that 1) in general, all counts tended to be low in winter, 2) the CC and somatic cell count were always high in summer, and 3) TAC tended to be high during summer.

Evaluation of the California Mastitis Test to Determine Udder Health Status of Early Lactation Dairy Cows

Summary Quarter milk bacteriology results of samples collectedwithin the first week of calving were used to calculate thetest characteristics of the California Mastitis Test (CMT)that estimate the udder health status of fresh dairy cows.Over 1,200 quarters were both cultured and had a CMTperformed. The overall sensitivity and specificity of theCMT was 68.8% and 71.5%, respectively. Using a cutpointof any CMT reaction as a positive test, and examining theresults by various days in milk, the highest sensitivity andspecificity occurred at day four (82.4% and 80.6%,respectively). The CMT has the potential to be useful toolfor monitoring udder health in fresh cows. Introduction The dry period is a time in the lactation cycle toeliminate existing and prevent new intramammary infections(IMI). A major goal of dry cow management programs is tohave as few quarters infected with mastitis-causingpathogens as possible at the next calving. Increased interesthas occurred recently in novel dry cow managementstrategies that would help prevent new IMI from occurringin the dry period, such as external and internal teat sealers.These new strategies offer promise in helping to reduce therate of new IMI above what can be achieved by conventionaldry cow antibiotic therapy alone. Dry cow antibiotictherapy generally does not persist into the late dry period,and is ineffective against gram-negative organisms.However, whatever dry cow udder health managementprogram is used, new IMI are still likely to occur in the dryperiod. Thus, emphasis should be placed on identifyinginfected cows early after calving as part of mastitis controlin dairy herds.Identifying and eliminating IMI in early lactation mayhave significant economic benefits. Preventing clinicalmastitis in early lactation, decreasing the amount ofdiscarded milk, and reducing bulk milk somatic cell countare some of the benefits. Bacteriological culture of milksamples is the standard method for identifying subclinicalIMI. However, the logistic and financial considerationsinvolved with sampling all fresh cows have precluded thistechnique from being widely adopted. The CaliforniaMastitis Test (CMT) is arguably the only reliable cowsidescreening test for subclinical mastitis that can easily beapplied.Most recent studies evaluating the CMT have looked atidentifying IMI in the first 10 days of lactation, and alsodescribing changes in somatic cell counts (SCC) during thatsame time. It was determined that the optimal strategy toselect infected quarters for bacteriological culture was 3 dayspost-calving. Similar work in the Netherlands has supportedthose findings. These studies also have demonstrated thatindividual cow SCC declines more rapidly than thepreviously suggested 2 weeks. Furthermore, other studieshave begun to evaluate specific diagnostic and treatmentprotocols for early fresh cows based on the results of aCMT. It seems that the CMT has the potential to be a rapidand cost-effective cowside test for fresh cows. Thus, thepurpose of this study was to evaluate the ability of theCMT to determine the udder health status of dairy cowswithin the first week of calving, using a large number ofcows in various herds.

Association of cow and quarter-level factors at a dry off and new intramammary infections in the dry period

Data from 300 cows and 1,178 quarters were analyzed to determine factors associated with new intramammary infections (IMI). Teatends that were cracked and teats that did not close during the dry period were 1.7 and 1.8 times more likely to develop new IMI, respectively. The level of milk production on the last day of lactation significantly influenced new IMI and teat canal closure. More (P<0.05) cows (36%) producing

Impact of milk production and important management factors on the process of dry-off in lactating dairy cows

21 kg of milk developed new IMI than cows (18%) producing less. When milk production was 21 kg or higher, teat canals were 1.8 times more likely to remain open.; Dairy Day, 2002, Kansas State University, Manhattan, KS, 2002;

Prevalence of contagious mastitis pathogens in bulk tank milk in Prince Edward Island

A study of 250 cows located in Canada and the United States revealed the rate of new mammary infections was 9.9% during the dry period. Average milk production on the day prior to dry-off was 13.2 ± 7.2 kg. The odds of a cow developing a new infection was three times greater if the cow was producing more than 5 kg of milk. After 6 weeks of the dry period, 25% of the teats still remained open. This research will serve as the foundation to investigate and implement management strategies prior to dry-off that might improve the overall udder health of dairy cows.