Master of Science, The Ohio State University, 2021, Animal Sciences
Mastitis is a key challenge for the dairy industry. Defined as inflammation of the
mammary gland, mastitis is most commonly caused by a bacterial intramammary
infection (IMI). A large proportion of dairy heifers have an IMI prior to calving and
beginning their first lactation. An infection during this time is expected to be deleterious
to the growth and development of the mammary gland (quarter), diminishing future
milk production and producer profitability. The objectives of these works were to
describe the effects an IMI has on primigravid heifer mammary secretions, determine if
prepartum administration of an internal teat sealant (ITS) in heifers reduced the odds of
IMI at calving, and determine if administration of ITS earlier (75 vs 35 days prepartum)
differentially affected the odds of IMI at calving. A total of 270 heifers were utilized.
Aseptic secretion samples were obtained from one quarter of every heifer at 75 days
prepartum and another quarter of every heifer at 35 days prepartum. Immediately
following sampling, the designated quarter was administered ITS. The other 2 quarters
of every heifer were not interfered with prior to calving. After calving, each quarter of
every heifer was sampled. Both prepartum secretion as well as colostrum samples were
bacterially cultured to determine quarter infection status and the somatic cell count
(SCC) was enumerated. Prepartum secretion samples were scored based on viscosity as
thick or thin. At 75 days prepartum, 26% of quarters had an IMI, and 28% were infected
at 35 days prepartum. Uninfected secretion samples were 133.2 (95% confidence
interval (CI): 16.8 - > 999.9) times more likely to be thick compared to samples infected
with a major pathogen, and 14.3 (95% CI: 8.5 - 24.1) times more likely to be thick
compared to samples infected with non-aureus staphylococci (NAS). Secretion SCC was
elevated when an IMI was present within the quarter; quarters with an IMI caused b (open full item for complete abstract)
Committee: Benjamin Enger (Advisor); Jessica Pempek (Committee Member); Craig Zimmerly (Committee Member)
Subjects: Animal Sciences