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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Utilization of early weaning and intrafollicular insemination as methods to improve the reproductive performance of cattle

Zezeski, Abigail Lee 30 January 2015 (has links)
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

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