Copyright (c) 2009 All rights reserved. http://works.bepress.com/wplummer Recent documents in William E. Plummer en-us Sun, 31 May 2009 13:09:41 PDT 3600 http://works.bepress.com/wplummer/2 http://works.bepress.com/wplummer/2 Mon, 07 Jul 2008 15:17:17 PDT Producers of domestic livestock strive to improve genetic influences in their herds. This requires identification, and propagation of animals that demonstrate desirable characteristics. The more animals available from which to select, the greater the opportunity to discover high-performance animals. Predetermination of the sex of offspring would provide a greater number of males or females from which to select the top individuals that will contribute the genetics to the next generation. Many attempts at sexing semen and identification of sex in preimplantation embryos have been mildly successful. However, recent advances in gene amplification enable investigators to use sex-specific probes to determine sex in only 1 cell removed from embryos. The biopsy method has had variable success in fresh embryos. However, manipulation of cryopreserved embryos reduces viability of the embryos (Bredbacka, 1998). Therefore, novel approaches to improve pregnancy rates may result in effective reproductive rates. One such approach is to vary the number of manipulated, cryopreserved embryos transferred into each recipient to increase the chances of successful pregnancy. The research performed identified the most successful techniques to biopsy and sex embryos using the mouse as a model animal. DNA from collected cells was amplified using polymerase chain reaction (PCR) or sex specific probes to determine sex. Secondly, the most effective techniques were applied to cattle embryos and survival rates in micromanipulated, cryopreserved embryos were determined. Finally, recipients were implanted with one or two embryos that sex had been previously determined. Pregnancy rates, including the incidence of twinning, were recorded. The hypothesis tested was: a single method for sexing bovine cryopreserved embryos can yield high accuracy and high pregnancy rates for the desired sex. William E. Plummer Articles http://works.bepress.com/wplummer/1 http://works.bepress.com/wplummer/1 Mon, 07 Jul 2008 15:16:43 PDT Depressed hog prices in 1998 and 1999 were due to not enough shackle space (kill capacity) and not to a glut of slaughter swine. However, many swine producers were put out of business in California. In 2000, market prices rebounded due to increased shackle space and reduced numbers of slaughter swine available as a result of the sellouts of the previous two years. The economic roller coaster ride emphasized the need for maximizing profit while streamlining operations. Increasing numbers of pigs per litter, and thereby reducing the cost per pig produced, is one aspect of streamlining. A significant step in improved litter efficiency would be to utilize platelet activating factor (PAF) in commercial swine operations. Platelet activating factor is involved in signal transduction within many of the body's physiological systems. Of primary interest in the reproductive system is PAF's enhancement of embryonic development, placental attachment and sperm functioning. The amount of embryo-derived PAF produced is correlated to pregnancy potential, since higher PAF levels lead to greater numbers of embryos developing to the blastocyst stage. It is produced by the embryos of various mammalian species, exerts significant effects upon the preimplantation embryo placental attachment, and perhaps maternal recognition of pregnancy and sperm functioning. Presently, only Professor John Diehl of the Animal and Veterinary Science Department at Clemson University, in collaboration with others, has published data to suggest that PAF is found in either male or female swine reproductive tracts. Most notably, PAF was found in the uterine luminal fluid (ULF), the developing filamentous embryo and the endometrium. William E. Plummer Articles