IMPROVING REPRODUCTIVE PERFORMANCE OF CATTLE THROUGH THE DEVELOPMENT OF NOVEL MANAGEMENT STRATEGIES AND TECHNOLOGIES
MetadataShow full item record
Masello Souza, Magdalena
The objectives of the studies presented in Section I were to evaluate insemination dynamics, time to pregnancy, and profitability of replacement dairy heifers managed with first service programs that relied primarily on insemination at detected estrus (AIE), timed-artificial insemination (TAI), or a combination of both. The objectives of the experiments presented in Section II were; to develop and validate a tool integrating a disposable fluorescence-based lateral flow immunoassay (LFIA) coupled with a portable imaging device to determine the reproductive status of cows based on circulating progesterone (P4) concentration; to test the efficacy of intravaginal (IVG) administration of prostaglandin-F2_ (PGF) to induce corpus luteum (CL) regression; and to develop and validate an electronically-controlled hormone delivery device for reproductive control of cattle. The studies presented in Section I demonstrated that a reproductive management strategy designed to submit all heifers to TAI reduced time to first AI and time to pregnancy when compared with a strategy that relied primarily on AIE after induction of estrus with PGF treatments. The program that combined AIE and TAI resulted in intermediate performance. In spite of greater reproductive cost, programs that used TAI in combination with AIE or solely TAI reduced rearing cost and generated more revenue during first lactation, which translated in numerically greater cash flow under fixed or simulated market conditions. The first experiment of Section II demonstrated that the developed LFIA system can accurately predict the presence of a functional CL (i.e., P4 ≥ 1 ng/mL) using bovine plasma samples. Additional improvements of this assay may lead to the development of a rapid, low-cost, cow-side tool for determination of reproductive status of cattle. The other experiments presented in Section II demonstrated that two IVG treatments of PGF 12 hours apart resulted in similar luteal regression risk, estrus expression, ovulatory response to GnRH, and pregnancy per AI compared with that observed after a single intramuscular dose of PGF. Further, we demonstrated that the current IVG prototype device for hormone delivery can be programmed to automatically release PGF for successful induction of luteal regression in cattle. Once optimized, the developed IVG device may be an alternative too to the needle-injection methods presently used to synchronize ovulation of cows.
Giordano, Julio O.
Nydam, Daryl Van; Gavalchin, Jerrie; Erickson, David
Ph. D., Animal Science
Doctor of Philosophy
Attribution-NonCommercial-NoDerivatives 4.0 International
dissertation or thesis
Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivatives 4.0 International