Recipient Organization
OREGON STATE UNIVERSITY
(N/A)
CORVALLIS,OR 97331
Performing Department
Animal and Rangeland Sciences
Non Technical Summary
Uterine infections during the period after calving, or the postpartum period, are a significant problem to dairy producers. Dairy cows are particularly susceptible to develop uterine infections because of conditions associated with housing and production. Bacterial infections, such as endometritis, metritis and pyometra, occurring within 28 days postpartum affect 10 to 50% of cows annually. Fertility is reduced in cows with uterine infections because of abnormal reproductive cycles, lower conception rates (20% lower than healthy cows), and longer days open (an average of 30 days longer than healthy cows). The cost of days open beyond 100 days has been estimated to be as much as $5.40/day for the dairy cow. Depending on the uterine infection incidence one uses to calculate cost to Oregon dairy producers on a state-wide basis, income loss is estimated to range between $2 million to 10.1 million annually. During pregnancy, the uterus is a sterile environment, but during calving and the early postpartum period, bacteria from the cow's environment can colonize the uterus, causing infection. It is known that uterine susceptibility to bacterial infection is higher when the ovarian hormone progesterone is high and is lower when the ovarian hormone estrogen and the uterine hormone prostaglandin F2a (PGF2a) are high. These findings, though important, have not aided in the development of new methods of prevention and treatment of uterine infections. Significant research effort has been directed towards studying the pathogenic microorganisms that cause uterine infections. However, despite this research, preventative practices and new treatment strategies have not been developed, and the incidence of uterine infection has not changed significantly in cattle over the previous 30 years. New knowledge in this area is a necessary first step towards development of new and practical methods for preventing uterine infections and novel therapeutic regimes not requiring antibiotics for treatment. Preliminary work conducted in our laboratory examined plasma neutrophil (a class of white blood cell) numbers in dairy cows following a single injection of either PGF2a (specifically, the pharmaceutical product, Lutalyse) or saline (Control). Lutalyse caused the number of circulating neutrophils to rise significantly within one hour after administration and remain elevated for four hours thereafter. Results from this experiment suggest that Lutalyse, a drug commonly used to synchronize the estrous cycle in cattle, can also recruit neutrophils into the cow's plasma. This effect of Lutalyse may be used to construct a preemptive strategy that counters the development of uterine infections in dairy cattle. Based on these observations, we are proposing to evaluate a treatment strategy using Lutalyse to reduce the development of uterine infections. Expected outcomes and impacts include a change in knowledge, where the results of this basic research will be published in a scientific journal, and a potential change in conditions in better and less expensive animal health.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Uterine infections during the period after calving are a significant problem to dairy producers. Fertility is poorer in cows with uterine infections and in Oregon this reduced fertility can contribute to an income loss estimated to reach as high as $10 million annually. Uterine susceptibility to bacterial infection varies depending on which ovarian hormone is dominating the cow's physiology at the time. Susceptibility is greater when progesterone is high and lower when estrogen and the uterine hormone prostaglandin F2a (PGF2a)are high. White blood cells, in particular neutrophils and macrophages, are the first line of defense against uterine infections but little is known about how these cells respond to reproductive hormones. Preliminary experiments conducted in our laboratory investigated the effect of a single injection of either PGF2a (the pharmaceutical product, Lutalyse) or saline on plasma neutrophil numbers in dairy cows. Lutalyse caused the number of circulating neutrophils to increase within one hour after administration and remain elevated for four hours thereafter. Numbers of neutrophils decreased by eight hours but were still greater than the number observed prior to Lutalyse injection. These data suggest that Lutalyse, a drug commonly used in dairies to synchronize estrus, recruits neutrophils into the cow's plasma. This property of Lutalyse may be used to create a preemptive strategy that counters the development of uterine infections in dairy cattle. Therefore, the objective of the proposed research is to evaluate the effects of a Lutalyse injection protocol on uterine bacterial load and neutrophil numbers in postpartum dairy cows. Expected outputs: Activities - conducting and analyzing experiments in the research project and teaching and mentoring graduate students; Events - presenting the results of the research at scientific societal conferences and training graduate students in this research; Products - graduating students with master's or doctoral degrees.
Project Methods
Forty-eight postpartum cows will be randomly assigned to four treatments: 1) saline (5 ml; im) on Days 0 or 1 and 14 postpartum (where Day 0 = day of calving), 2) saline (5 ml; im) on Days 14 and 28 postpartum, 3) Lutalyse (25 mg/5 ml; im) on Days 0 or 1 and 14 postpartum and 4) Lutalyse (25 mg/5 ml; im) on Days 14 and 28 postpartum. On the day of the second injection (Day 14 or 28), the cow's uterus will be sampled for uterine bacterial load using a double guarded swab (Time 0). Twenty-four h after the first swab, a second uterine swab will be collected (Time 24). To provide an assessment of the uterine neutrophil population, a guarded CytoBrush will be passed into the uterus immediately following the uterine swabbing at Times 0 and 24. The CytoBrush will be rolled onto a microscope slide to create a cell smear and neutrophils will be counted. Cows will receive their second injection following completion of the uterine swabbing and CytoBrush procedures at Time 0. Blood samples (10 ml) will be drawn by coccygeal venipuncture at Times 0 and 24 to assay plasma progesterone concentrations. Serial dilutions will be made from the original uterine sample and 100 ul will be plated onto each side of a Blood Agar/MacConkey's Agar bacteriological culture biplate. Colony counts on the blood agar side provide the total number of pathogenic bacteria and counts from the MacConkey's agar side provide the number of E.coli. All cows on experiment will be evaluated daily for evidence of uterine infections, e.g., vaginal discharge, fever, etc. Differences between Times 0 and 24 in the total numbers of bacteria, E. coli and neutrophils and plasma progesterone will be analyzed by analysis of variance (ANOVA) for a 2 x 2 factorial design. Sources of variation in the ANOVA include Treatment regimen (Days 0 and 14, Days 14 and 28), Injection (saline, Lutalyse) and the Treatment X Injection interaction. If significant effects are observed in the ANOVA, differences between means will be evaluated by Fisher's least significant differences procedures. Observational data or the number of cows observed with uterine infections will be analyzed for differences due to treatment using Chi-square procedures. Efforts will include adding this information into material used for formal classroom and laboratory instruction and outreach. If this research demonstrates a difference due to Lutalyse treatment in reducing uterine bacterial loads and infections and increasing the uterine neutrophil population it can be easily implemented with relatively little cost. Lutalyse is commonly used in dairy operations to synchronize estrous cycles for artificial insemination and a single dose costs approximately $2.85. It is anticipated that the results of this experiment will be published in a format accessible to dairy producers for information, and if successful, application. The success and merit of the study will be evaluated by tracking the number of times the publication reporting this research is cited in the scientific literature.