RESUMO
The underlying physical principles of magnetic resonance (MR) imaging are discussed. MR imaging system components are described, and system performance criteria are discussed and demonstrated. Examples of image quality variables are shown, and measurement techniques and apparatus are given.
Assuntos
Espectroscopia de Ressonância Magnética , Humanos , Espectroscopia de Ressonância Magnética/métodos , Modelos EstruturaisRESUMO
One-hundred sixty-four gilts were artificially inseminated (AI) with frozen-thawed boar semen and, of these, 78 were immediately bred by a vasectomized boar after AI. The farrowing rate and litter size were 37.2 and 7.2 for mated gilts and 38.4 and 7.5 for control gilts, respectively. Mating by a vasectomized boar did not improve fertility or litter size.
RESUMO
The synthetic progestogen, allyl trenbolone, was fed daily to 60 gilts at 15 mg/gilt for 18 days. Sixty-eight gilts that came into estrus the same week as treated gilts served as controls. Gilts were checked for estrus twice daily and were artificially inseminated with frozen semen or bred by natural service. All but two treated gilts returned to estrus between 4 and 7 days after withdrawal of allyl trenbolone (mean = 5.6; SD = .82). The farrowing rate among gilts inseminated with frozen semen was significantly lower than that among gilts bred by natural service (52.5 vs 89.6%). The farrowing rate among synchronized gilts was similar to that among untreated gilts (70.7 vs 73.5%). Average total and live litter sizes at birth and litter size at weaning were significantly smaller for untreated gilts inseminated with frozen semen than for synchronized gilts inseminated with frozen semen or those of untreated gilts bred by natural service. Average litter size for synchronized gilts bred by natural service was not significantly larger than that for synchronized gilts inseminated with frozen semen or that of untreated gilts bred by natural service.
