Date of Award

5-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Animal and Veterinary Sciences

Advisor

Birrenkott, Glenn P

Committee Member

Overton , Michael W

Committee Member

Scharko , Patricia B

Committee Member

Parr , Boyd H

Abstract

Assessing pitfalls in reproductive efficiency of dairy cattle is often confounded by milk production, animal health, energy balance, and animal management practices, among others. Methods to reduce inefficiencies are classified in the following studies as maternal endocrine management, conceptus recognition, and uterine environment. The goal was to derive some insight into the mechanisms pre and post conception that can alter rates of pregnancy establishment. The initial study ascertained the ability to reduce progesterone (P4) dominance through additional PGF2-alpha (PGF) supplementation on efficiency of timed artificial insemination (TAI) in the Ovsynch® program. The single PGF animals received the standard Ovsynch® protocol (1X; n=19) while double PGF animals (2X; n=23) followed the same protocol but with a second PGF 12 h after the first. There was no difference in pregnancy rates associated with 1X versus 2X groups (P>0.05). Ovulation response (R) to the initial GnRH injection did increase the likelihood of having a functional CL at the time of initial PGF in both groups (P<0.05) and there was a positive correlation between follicular diameter at ovulation to the first GnRH in R cows with P4 values at PGF (P<0.05). Positive pregnancy diagnosis was influenced by P4 at breeding with values below 0.2 ng/mL increasing pregnancy success at TAI (P<0.05). Animals receiving the 2X treatment and in the R classification tended to have lower P4 at TAI (P=0.07). Research has well documented the reproductive and financial losses associated with failure of bovine pregnancy establishment. In a second study, the impact of trophoblastic vesicles (TV) on estrous cycle extension and pregnancy success when transferred in utero was assessed. Three pilot experiments with alterations in type and method of TV supplementation were conducted. There was no cycle extension for TVs transferred fresh or frozen in heifers and cows at both 7 and 14 d post estrus (P>0.05). Pregnancy rates to embryo transfer (ET) or on the cycle following a TV transfer were not higher in animals that received a TV (P>0.05). Numerically, for both experiments one and three, peak P4 was achieved more rapidly with TV supplementation (P>0.05, experiment 1; P=0.07, experiment 3). Uterine inflammation can negatively impact animal welfare, milk production and rebreeding capacity in dairy cattle. The objective of the final study was to investigate the relationship between prostaglandin E2 (PGE) in uterine flush fluid and systemic circulation on reproductive success in postpartum cows. Animals (n=32) were enrolled in a presynch program beginning at 35±3 DIM and followed by the Ovsynch® protocol at 60 d and TAI at70 d. They were then resynchronized and bred to a second TAI if open to the first with a final breeding to detected estrus if open to the second TAI. Uterine flush samples were collected prior to the first TAI and if checked open 35 d after first TAI or after detected estrus. Blood samples were collected for P4, PGE, and BioPRYN® analysis. P4 concentration exhibited no relationship to blood or uterine PGE (P>0.05) but were higher in pregnant animals beginning 14 d after breeding (P<0.05). Numerically, a reduced uterine PGE value increased the likelihood of pregnancy. Neither the PGE values in uterine flush fluid nor blood were significant predictors of pregnancy success (P>0.05). There was a high correlation between uterine PGE values and BioPRYN® optical density readings (P<0.05). Lastly, there was a strong correlation between bacterial IgG stimulation and services per pregnancy (P<0.05).

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