Optimization of reproductive efficiency of both beef and dairy herds is critical for sustainability and profitability. Two separate experiments were performed to test the reproductive outcomes following early weaning of beef heifers and intrafollicular insemination in dairy cows.
Early weaning is a proven way to induce precocious puberty in heifers. Heifers will experience more estrous cycles before breeding, which is associated with increased fertility. In this experiment, heifers were either subjected to early weaning and a high concentrate diet (EW; 106.5±3.4 days of age) or normal weaning (NW; 231.7±3.33 days of age) treatments. Despite no effect (P>0.15) of weaning treatment on age at puberty, EW heifers tended to have higher pregnancy rates than NW heifers. A progesterone clearance analysis revealed that EW heifers also have greater ability to metabolize progesterone. This altered progesterone metabolism could be a direct result of changes in metabolism caused by feeding a high concentrate diet after early weaning.
Pregnancy rates in cattle are often lower than desired. New reproductive advances are constantly developed to improve reproductive function. A recently described possible technique is intrafollicular insemination (IFI). The objective of the second experiment was to investigate whether IFI can cause fertilization. Abattoir ovaries with dominant follicles injected with semen and incubated overnight displayed sperm in close association with granulosa cells. When synchronized cows were subjected to IFI, no pregnancies resulted. While other studies have demonstrated success with IFI, it is still unknown if fertilization is possible within the follicle of the ovary. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/51235 |
| Date | 30 January 2015 |
| Creators | Zezeski, Abigail Lee |
| Contributors | Animal and Poultry Sciences, Rhoads, Michelle, Ealy, Alan D., Saacke, Richard G. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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