The purpose of this study was to determine the influence of clinical mastitis on reproductive performance of high producing Jersey cows. Cows (n = 102) with clinical mastitis during the first 150 d of lactation were evaluated. Groups were balanced according to lactation number and days of lactation and sub-divided as follows: group 1, clinical mastitis before first artificial insemination (AI) (n = 48); group 2, clinical mastitis between first AI and pregnancy (n = 14); group 3, clinical mastitis after confirmed pregnancy (n = 40); and group 4, control cows (n = 103) with no clinical mastitis. No differences in reproductive performance were detected because of milk production or mastitis caused by Gram-positive or Gram-negative pathogens. The number of days to first AI was significantly greater for cows with clinical mastitis before first AI (93.6 d) than for all other groups (71.0 d). Artificial inseminations per conception were significantly greater for cows with clinical mastitis after first AI (2.9) than for cows with clinical mastitis before first AI (1.6), cows with no clinical mastitis, or cows with clinical mastitis after confirmed pregnancy (1.7). The number of days to conception for cows with clinical mastitis after first AI (136.6 d) was significantly greater than that for control cows and that for cows that developed clinical mastitis after confirmed pregnancy (92.1 d). Clinical mastitis during early lactation markedly influenced reproductive performance of Jersey cows.

The dairy farm environment and animals on the farm serve as important reservoirs of pathogenic and commensal bacteria that could potentially gain access to milk in the bulk tank via several pathways. Pathogenic gram-negative bacteria can gain access to bulk tank milk from infected mammary glands, contaminated udders and milking machines, and/or from the dairy farm environment. Contaminated raw milk when consumed by humans or fed to animals on the farm can result in gastroenteric infections in humans and animals and also provide an opportunity for organisms to colonize the farm environment. This scenario becomes much more complicated when pathogenic bacteria such as Salmonella, Shiga toxin-producing Escherichia coli, and commensal gram-negative enteric bacteria encode for antimicrobial resistance determinants. In recent years, the role of commensal bacteria as reservoirs of genetic determinants for antimicrobial resistance has come under closer scrutiny. Commensal bacteria in bulk tank milk can be a significant reservoir of antimicrobial determinants. Raw milk consumption can result in exposure to antimicrobial-resistant commensal gram-negative bacteria. This paper examines the prevalence and role of commensal gram-negative enteric bacteria in bulk tank milk and their public health significance.

The objective of the study was to determine if experimentally induced clinical mastitis before ovulation resulted in alterations of endocrine function, follicular growth, or ovulation. On d 8 (estrus = d 0), cows were challenged (TRT; n = 19) with Streptococcus uberis or were not challenged (control; n = 14). Forty-eight hours after induction of luteal regression on d 12, blood samples were collected to determine estradiol-17beta, LH pulse frequency, and occurrence of the LH surge. Ovaries were scanned to monitor follicular growth and ovulation. Cows with clinical mastitis (n = 12) had elevated rectal temperatures, somatic cell counts, and mammary scores. Estrus and ovulation occurred in 4 of 12 clinically infected cows and in all control cows. Cows that were challenged but did not develop clinical mastitis (n = 5) displayed estrus and ovulated. Due to differences in expression of estrus, cows were further subdivided for analyses into 4 groups: control, TRT-EST (infected cows that displayed estrus; n = 4), TRT-NOEST (infected cows that did not display estrus; n = 8), and NOMAS (cows that were inoculated but did not develop mastitis; n = 4). Ovulation rate was 100% for CON, NOMAS, and TRT-EST compared with 0% for TRT-NOEST cows. Size of the ovulatory follicle ("presumed" ovulatory follicle in TRT-NOEST cows) was similar for all groups. Frequency of LH pulses was decreased in TRT-NOEST compared with CON, TRT-EST, and NO-MAS. Estradiol-17beta increased over time in CON, NO-MAS, and TRT-EST cows, but did not increase in TRT-NOEST cows. Cows with clinical mastitis may exhibit estrus and ovulate normally or have disruptions in normal physiology including decreased LH pulsatility, absence of an LH surge and estrous behavior, suppressed estradiol-17beta, and failure to ovulate.

The purpose of this study was to evaluate the bulk tank milk (BTM) quality of 9 East Tennessee dairy farms and to determine its relationship with selected quality milk parameters. Bulk tank milk samples (n=1,141) were collected over a 42-mo period (June 2006 through November 2009) from farms, based on their preliminary incubation count (PIC) history. Parameters of BTM quality evaluated in this study included somatic cell count (SCC), standard plate count (SPC), PIC, laboratory pasteurization count (LPC), Staphylococcus spp. count, Streptococcus spp. count, and coliform count. Strong correlations between SPC and Streptococcus spp. counts (0.72) and between SPC and PIC (0.70) were found. However, moderate correlations were seen among other milk quality parameters. In addition, seasonal variations for some milk quality parameters were noted. For example, milk quality parameters such as SCC, SPC, LPC, and coliform count were significantly higher in summer, whereas Streptococcus spp. counts were significantly higher in winter. No seasonal variation in PIC or Staphylococcus spp. counts was observed. Summarizing, results from this investigation showed the importance of using several bacterial counts (SCC, SPC, PIC, LPC, Streptococcus spp. count, Staphylococcus spp. count, and coliform counts) as simultaneous indicators of milk quality.

Mastitis is a worldwide problem in dairy cows and results in reduced milk production, the culling of cows, and other economic losses. Bulk tank somatic cell count (BTSCC) over 200,000 cells/mL often indicates underlying subclinical mastitis in dairy herds. Several preventative measures that can be implemented to help improve the incidence of mastitis exist, but surveys find these practices not fully adopted by producers. The goal of this research was to analyze the farm and operator characteristics associated with BTSCC in dairy herds by analyzing a survey of dairy producers in the southeastern United States. We examined this region because it has experienced a decline in the number of dairy farms, dairy cows, and milk production over the past 2 decades. The southeast region is also associated with higher BTSCC levels than the national average. Dairy farms in Georgia, Mississippi, Kentucky, North Carolina, South Carolina, Tennessee, and Virginia were surveyed. Producers were asked questions about the BTSCC at which they take action to address BTSCC, the information sources they use to learn about and manage BTSCC, farm structure and management characteristics, and attitudinal variables associated with profitability, managerial control, and planning horizon. Least squares regression was used to determine how these factors were associated with BTSCC levels across the 7-state region. Concern over mastitis, financial consequences of mastitis, and increased previous-year BTSCC were associated with higher current BTSCC levels. Obtaining information about mastitis from veterinarians and extension personnel, taking action against mastitis at a BTSCC less than 300,000 cells/mL, and perceived ability to control processes and mastitis incidence were associated with reduced BTSCC. We found average BTSCC was lower in North Carolina and Virginia. These results suggest that proactive producers (i.e., those that perceive they can control BTSCC and seek information from reliable sources), were more likely to report lower BTSCC. As a result, it may be possible to achieve improved milk quality, evident from lowered BTSCC, across the region.