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The objective of this study was to probe the contribution of streptococci to the microbial quality of raw milk. Over a 5-month period, bulk tank milk samples from 48 New York State dairy farms were analyzed qualitatively for bacterial ecology and quantitatively for total bacterial, streptococcal, staphylococcal, and gram-negative bacterial counts. Linear regression analysis was used to determine the contribution of differential counts to total bacterial counts. Streptococci, staphylococci, and gram-negative bacteria accounted for 69, 3, and 3% of total bacterial count variability, respectively. Randomly selected Streptococcus isolates from each bulk tank milk sample were identified to species by means of the API 20 STREP identification system. The most commonly identified streptococcal species were Streptococcus uberis, Aerococcus viridans, and Streptococcus agaiactiae, which were detected in 81, 50, and 31% of 48 bulk tank samples, respectively. For five herds, S. uberis isolates from bulk tank milk and individual cows were characterized by PvuII ribotyping. A farm-specific dominant ribotype was found in each bulk tank sample, and that ribotype was isolated from at least one cow within each herd of origin. Bacteriological and strain typing data indicate that control of streptococci, specifically mastitis-causing species, is important for improvement of the microbial quality of raw milk in New York State. [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate the effects of different types of clinical mastitis (CM) on the probability of conception in New York State Holstein cows. Data were available on 55,372 artificial inseminations (AI) in 23,695 lactations from 14,148 cows in 7 herds. We used generalized linear mixed models to model whether or not a cow conceived after a particular AI. Independent variables included AI number (first, second, third, fourth), parity, season when AI occurred, farm, type of CM (due to gram-positive bacteria, gramnegative bacteria, or other organisms) in the 6 wk before and after an AI, and occurrence of other diseases. Older cows were less likely to conceive. Inseminations occurring in the summer were least likely to be successful. Retained placenta decreased the probability of conception. Conception was also less likely with each successive AI. The probability of conception associated with the first AI was 0.29. The probability of conception decreased to 0.26, 0.25, and 0.24 for the second, third, and fourth AI, respectively. Clinical mastitis occurring any time between 14 d before until 35 d after an AI was associated with a lower probability of conception; the greatest effect was an 80% reduction associated with gram-negative CM occurring in the week after AI. In general, CM due to gramnegative bacteria had a more detrimental effect on probability of conception than did CM caused by gram-positive bacteria or other organisms. Furthermore, CM had more effect on probability of conception immediately around the time of AI. Additional information about CM (i.e., its timing with respect to AI, and whether the causative agent is gram- The objective of this study was to estimate the effects of different types of clinical mastitis (CM) on the probability of conception in New York State Holstein cows. Data were available on 55,372 artificial inseminations (AI) in 23,695 lactations from 14,148 cows in 7 herds. We used generalized linear mixed models to model whether or not a cow conceived after a particular AI. Independent variables included AI number (first, second, third, fourth), parity, season when AI occurred, farm, type of CM (due to gram-positive bacteria, gram-negative bacteria, or other organisms) in the 6 wk before and after an AI, and occurrence of other diseases. Older cows were less likely to conceive. Inseminations occurring in the summer were least likely to be successful. Retained placenta decreased the probability of conception. Conception was also less likely with each successive AI. The probability of conception associated with the first AI was 0.29. The probability of conception decreased to 0.26, 0.25, and 0.24 for the second, third, and fourth AI, respectively. Clinical mastitis occurring any time between 14 d before until 35 d after an AI was associated with a lower probability of conception; the greatest effect was an 80% reduction associated with gram-negative CM occurring in the week after AI. In general, CM due to gram-negative bacteria had a more detrimental effect on probability of conception than did CM caused by gram-positive bacteria or other organisms. Furthermore, CM had more effect on probability of conception immediately around the time of AI. Additional information about CM (i.e., its timing with respect to AI, and whether the causative agent is grampositive or gram-negative bacteria, or other organisms) is valuable to dairy personnel in determining why some cows are unable to conceive in a timely manner. These findings are also beneficial for the management of mastitic cows (especially those with gram-negative CM) when mastitis occurs close to AI. [ABSTRACT FROM AUTHOR]

Naturally occurring cases of bovine clinical mastitis (CM) were studied among J5 vaccinates and controls on 3 commercial dairy farms. Milk production change and reproductive performance following CM were compared between the 2 groups. Among 306 controls and 251 vaccinates, there were 221 new cases of CM affecting 120 cows; 437 lactations never had a case of CM. Environmental pathogens made up 90% (159/176) of etiologic agents isolated. Change in daily milk production following CM was associated with J5 vaccination, days in milk (DIM) at onset of CM, and herd effect as well as each 2-way interaction between the 3 factors. The adjusted daily milk for 21 d following CM was 7.6 kg greater among J5 vaccinates than controls; however, this protective effect of vaccination waned with increasing DIM at onset of CM. A mixed linear model with autoregressive order 1 [AR(1)] correlation structure estimated the daily milk production of any cow (whether or not she had CM) on a given DIM. Cows with CM caused by nonagalactiae streptococci, Staphylococcus aureus, Escherichia coli, or Klebsiella lost significant daily milk production for the entire lactation relative to nonmastitic cows. Another mixed linear model for only coliform CM cases (E. coli, Klebsiella, and Enterobacter) within the first 50 DIM showed milk loss for 21 d following coliform CM to be significantly less for J5 vaccinates than for controls, by 6 to 15 kg per day. Cows were significantly less likely to become pregnant if they had CM caused by E. coli (42% pregnant) or Streptococcus spp. (38% pregnant), whereas 78% (342/437) of cows with no mastitis conceived. Days open (number of days from calving until pregnancy) averaged 131 d for cows with no CM and 162 d for cows that had at least one case of CM. Days until conception, days until last breeding, days open, times bred, and percentage of cows pregnant by 200 DIM were not changed with J5 vaccination. Nonetheless, an important benefit of the use of J5 bacterin appears to be reduction of the loss of daily milk production following CM, whether all cases or only those caused by coliform bacteria were considered. [ABSTRACT FROM AUTHOR]

This study was designed to explore the relationship between cow and udder cleanliness scores and the risk of isolation of Klebsiella spp. from lower hind legs and teat ends, respectively. The distribution of Klebsiella species was compared among isolates from teat ends, legs, and cases of clinical mastitis obtained from 2 dairy farms in New York State, with 850 and 1,000 cows, respectively. Farms were visited twice approximately 4 wk apart in August and September 2007 to obtain cleanliness scores and swabs from legs and teats. Isolates of Klebsiella clinical mastitis from each farm were collected from July through October 2007. Two studies were conducted. In the first study, whole-cow cleanliness of a purposive sample of 200 lactating cows was scored using a 4-point scale, and swabs were taken from their lower hind legs. In the second study, udder cleanliness of a separate convenience sample of 199 lactating cows was scored in the milking parlor, and swabs were taken from their teat ends before and after premilking udder preparation. Prevalence of Klebsiella spp. on legs and teat ends before udder preparation was 59 and 60%, respectively. Logistic regression was used to explore the association between isolation of Klebsiella spp. and cleanliness scores. Cow cleanliness scores and udder cleanliness scores were not associated with detection of Klebsiella on legs and on teats before udder preparation, respectively. After udder preparation, 43% of previously Klebsiella positive teat end samples remained positive, with significant differences between farms and months. Teats from dirty udders were significantly more likely to test positive for Klebsiella after udder preparation than teats from clean udders. The proportion of Klebsiella pneumoniae and Klebsiella oxytoca isolates was similar for isolates from teat end swabs and clinical mastitis cases, supporting the notion that the presence of Klebsiella on teat ends may lead to opportunistic intramammary infections. Udder cleanliness scores could be used as a management tool to monitor the risk of exposure to Klebsiella spp. on teat ends. [ABSTRACT FROM AUTHOR]