Research Projects for 2009
ME08306-03 Stokes, M.
Improvement of silage quality and its utilization by dairy cows
Many silage additives are marketed with very little
scientific evidence to support their efficacy. Effects of many additives can be
determined in small-scale silos but these may not truly represent farm silo conditions.
We will construct pneumatic packers for laboratory and small-scale silos to make
laboratory data more representative of farm-scale ensilage. Commercial silage additives
will then be evaluated to provide useful information to producers.
ME08308-08 Bayer, R.,
D. Bouchard
Health Problems in the Stock of the American Lobster
Lobster mortality in shipment and live storage is becoming more
of an economic problem. Shrinkage of over 20% have been reported. The goal of this project
is to find the cause of the lobster mortalities and try to reduce them.
ME08315-07 Causey, R.
Acquired immunity or innate resistance; how does the equine uterus eliminate bacteria?
Uterine infections continue to be a serious cause of infertility
in horses, and were recently assessed as among the most common complaints treated by equine
practitioners. Maine has a large equine industry, which is expected to grow with the advent
of slot machine revenues. As a result, horse prices will increase, but the opportunity cost
of infertility will therefore also increase. It is therefore important for the Maine equine
industry to improve fertility in their brood mare population, in order to keep pace with
increased horse prices. Previous research has shown that Streptococcus zooepidemicus is
the most commonly isolated organism from uterine infections, but represents a very diverse
group of organisms. What is not yet understood is how such variation affects pathogensis of
disease, or effectiveness of treatments. A critical piece of the puzzle that is still missing
is an understanding of how the immune response to Streptococcus zooepidemicus influences protection
against infection. Would the immune response protect against one strain or many strains?
Do non-immune defenses against disease, e.g., mucociliary clearance, also protect against infection?
The objectives of this research are designed to address these questions.
ME08319-08MRF Weber, J.
Methods to increase reproductive efficiency in cattle
Owners of commercial dairy herds cannot efficiently produce calves because a high
percentage of milking cows do not have consistent estrous cycles for much of early lactaion.
This project focuses on the development of methods that effectively synchronize estrous
in postpartum beef and dairy cows by decreasing the period of time over which estrous
detection is required, thus facilitating the use of timed artificial insemination.
ME08898-08 A.
Lichtenwalner, D. Bouchard
Mastitis resistance to enhance dairy food safety
(alternative approaches to mastitis control in dairy animals)
Mastitis continues to be a major economic risk, capable of devastating the small or
large dairy operation. Prevention and control have relied on hygiene during and between
milkings, antibiotic treatment or teat sealants during the dry period, antibiotic treatment
of clinically detectable mastitis, and culling of seriously affected cattle. Due to human health
concerns, dairy farmers follow strict regulations, and are encouraged to avoid exogenous
chemicals or drugs. To reduce the need for antibiotics, both innate and adaptive immune responses
can be activated in the mammary gland. In innate immunity, the role of "normal flora" on the skin
and mucosal surfaces can be vital: "good" bacteria can kill, or simply outcompete, pathogens.
That normal flora, if augmented following each disruption by milking, might help form a defense
against pathogens. This project will evaluate normal flora of the teat skin, and attempt to
augment innate defenses by enhancing that flora between milkings. As well, we will question
whether that flora can increase innate host cellular defenses against pathogens. In general,
candidates for use as probiotics should be capable of colonizing the site, must have
antimicrobial properties, and not be potentially pathogenic. Lactobacilli produce bacteriocidal
substances (bacteriocins) and acidify the local microenvironment, suggesting their use to enhance
innate defenses. The somatic cell count (SCC) of milk samples reflects a variety of cells that are
shed into the lumen of the mammary gland during lactation: epithelial cells, neutrophils, and
other cells involved with immune defenses, such as macrophages. High SCC values are associated with
infection, but a lower average SCC may actually be associated with a higher incidence of mastitis
due to coliforms, or environmental organisms. An optimal number or composition of SCC may exist in
the healthy cow's milk, and the activation status of these cells may determine the outcome of
infection with pathogens. Innate defenses may be triggered by pathogen-associated molecular patterns
(PAMPS) which are perceived by cellular receptors called PRR; pattern recognition receptors.
The toll-like receptors (TLR) form a family of PRR. Between the 13 known vertebrate TLR, it is
thought that essentially all pathogens can be recognized. Work with intestinal epithelial cells
suggests that expression of TLRs are modulated by intestinal microbial flora. Modulation of TLR on
the mammary epithelial cell component of the SCC may be a way of detecting up- or down-regulation of
the innate immune system of the udder. Expression of TLR or of other innate mechanisms may be
modulated by the presence of a probiotic, as occurs in the gut. If true, then a probiotic teat dip
will be an active way of protecting the teat end, versus the passive protection via disinfectants
such as iodine. Enhancing innate immunity will reduce mastitis, reducing losses from an estimated
11% of total US milk production.
