Systemic and local bactericidal potentiality in late lactation Holstein-Friesian cows following a combined antibiotics and Enterococcus faecium SF68 dry-cow treatment.

Antibiotic dry-cow treatment contributes a major part to the total use of antibiotics in dairy herds. Enterococcus faecium strain SF68 (SF68) was of human origin but has been authorized in EU as probiotic feed additive. In the present study, one of the front and rear quarters of twelve late lactation Holstein-Friesian cows were infused once with a commercial antibiotic dry-cow formula (antibiotics quarter) on the first milk-stasis day (d 1), when the contrallateral quarters were infused with 5 x 10(8)-CFU SF68 plus half-dose antibiotic dry-cow formula (SF68/antibiotics quarter) meanwhile. Gelatinase level and cellular reactive oxygen species (ROS) production capacity were measured for blood and quarter secretion. The results showed that the count of blood total leukocytes minorly decreased on d 3 only but the microscopic somatic cell count (MSCC) continuously increased up to d 7, especially in SF68/antibiotics quarters. Plasma level of gelatinase A remained similar up to d 7 but gelatinase B was not detectable in plasma throughout the study. The level of gelatinase A in quarter secretion increased up to d 7 but gelatinase B increased even more drastically, especially in SF68/antibiotics quarters. The ROS production capacity of blood leukocytes increased temporarily only on d 3, but that of milk cells continuously increased up to d 7, especially in SF68/antitiotics quarters. Overall, late lactation Holstein-Friesian cows were systemically adaptable to the combined antibiotics and SF68 dry-cow treatment, while the local bactericidal potentiality in mammary gland was actively responsive to additional SF68 intramammary treatment.

Intramammary infusion of an Enterococcus faecium†SF68 preparation promoted the involution of drying off Holstein cows partly related to neutrophil-associated matrix metalloproteinase 9.

A problem for dairy cows following milk stasis is to cope with a high risk of intramammary infection and there is a need to initiate an extensive renewal of secretory modules in mammary glands so that milk production in next lactation may be optimized. We recently reported that ultrasonicated Enterococcus faecium SF68 (SF68) is compatible with cow mammary glands and an enhancer of innate immunity during the immediate post-milk stasis period. The current study further examines the concomitant effect of ultrasonicated SF68 on mammary tissue remodeling. Four Holstein cows each received intramammary infusions of regular antibiotic dry-cow formula (positive control) and two different doses of SF68 in different quarters. Analyses of individual quarter secretion samples showed faster neutrophil infiltration, earlier modifications in protein composition, including caseins and lactoferrins, as well as more prompt elevation of the specific unit of 92-kDa matrix metalloproteinase 9 (MMP9) in SF68-infused quarters compared to the positive controls. Intramammary infusion of ultrasonicated SF68 seems able to accelerate the regression of mammary synthetic capacity and potentiate the breakdown of glandular extracellular matrix, indicating a more efficient mammary gland involution. Correlation analyses imply that the ability of ultrasonicated SF68 to induce faster neutrophil chemotaxis and the associated MMP9 release is partly responsible.

Ultrasonicated Enterococcus faecium SF68 enhances neutrophil free radical production and udder innate immunity of drying-off dairy cows.

Proper dry cow management is critical not only for subsequent milk production and fertility but also for mastitis control. A phenomenon of immunosuppression was commonly observed in transition cows, an example being the high susceptibility of the mammary gland during early the dry period to new infectious agents. Polymorphonuclear neutrophils (PMN) play important defence roles in the mammary gland of newly dried cows. One of the bactericidal mechanisms of PMN is through producing reactive oxygen species (ROS), which can be efficiently quantified by chemiluminescence (CL) assay. In the current study, the potential of intramammary application of a commercial Enterococcus faecium SF68 (SF68) product to enhance the local innate immunity of newly dried mammary glands was evaluated based on the CL assay. The preliminary experiments in vitro indicated virtual dose-responsiveness of ROS generation from three different cell preparations, bovine blood PMN, bovine blood PMN pre-conditioned with cow milk, and the post-diapedesis model somatic cells from cow milk, on their exposure to phorbol 12-myristate 13-acetate (PMA), viable SF68, and ultrasonicated SF68, but not dry-heated SF68. Because ultrasonication treatment was found to profoundly enhance the immunogenicity of SF68 in vitro, in the following animal trial, single infusion of either 5 or 10×107 original cfu of ultrasonicated SF68 was randomly applied to the front quarters and phosphate-bufferedsaline (PBS) applied to the rear quarters of each of the four experimental cows on the first day of milk stasis. The results showed that within the first post-infusion week, ultrasonicated SF68 induced a faster and greater (P<0·05) recruitment of PMN into mammary lumen with no apparent local or systemic inflammatory sign. Meanwhile, ultrasonicated SF68 also induced a greater (P<0·05) ROS production in response to PMA challenge by in situ somatic cells of mammary secretion. Taken together, ultrasonicated SF68 modulated ROS generation of bovine neutrophils, and would be a potential enhancer of udder innate immunity in drying-off dairy cows. More thorough work is warranted.

Modifications of the defense and remodeling functionalities of bovine neutrophils inside the mammary gland of milk stasis cows received a commercial dry-cow treatment.

An appropriate length of milk stasis between two consecutive lactations of dairy cows is crucial for sustainable milk production. This dry period of cows allows extensive remodeling and sufficient cell renewal in mammary gland. Nevertheless, early dry period is one of the most risky stages in cow lactation cycle to intramammary infection. Dry-cow treatment through teats is, therefore, widely practiced at the commencement of milk stasis. Neutrophils are the most abundant cellular components in cow mammary secretion during early dry period, which in turn attribute to the meanwhile elevation of somatic cell counts and matrix metalloproteinase-9 (MMP-9) level. This study used bovine peripheral neutrophils as a cell model to examine the mode of modifications in their defense and remodeling functionalities after infiltration into mammary gland during early dry period. Results indicate a dose-dependent suppression of phorbol 12-myristate 13-acetate-stimulated free radical production and induction of MMP 9 degranulation in bovine peripheral neutrophils exposure to the d 7-dry secretion of cows received dry cow treatment at d 0 in milk stasis. Meanwhile, an enhancement of plasminogen activation and TNF-α shedding on bovine peripheral neutrophils were also observed. These two cellular events might be involved in the functional modifications on infiltrated neutrophils during early dry period. In conclusion, the opposite trend of modifications in the defense and matrix remodeling functionalities of neutrophils inside the mammary gland of cows at early dry period reflect the collaboration of infiltrated neutrophils for promoting extensive glandular remodeling at minimum compromise of local defense during the acute involution period without apparent disturbance by dry cow treatment.