A follow-up study was performed to describe characteristic physiological alterations by means of computer tomography, direct chemical analysis and histology of the liver, and blood biochemical parameters during conventional force-feeding of Landes geese. 30 birds were exposed to an 18-day long force-feeding. Sampling was performed at the start and during force-feeding (7th, 11th, 14th, 18th days). Computer tomographic data were plotted in 3D histograms, effectively indicating the volumetric development and the fat deposition of the liver. Applying the so-called fat index, a saturation process was found for the hepatic fat content. Histological sections indicated the appearance of microvesicular fat forms in the hepatocyte cytoplasm, which first turned to a total fatty infiltration, later changing to a macrovesicular form with progressing inflammation; membrane damage was not visualized. In blood metabolites triglyceride, total and HDL cholesterol and uric acid increased measurably, while creatinine concentration decreased. Alanine aminotransferase, aspartate aminotransferase activities increased strongly, while that of lactate dehydrogenase only slightly. Based on the results of macroscopic and microscopic imaging techniques and blood biochemical parameters, a comprehensive follow-up study was performed, elucidating still unknown processes during force-feeding of geese.

Plasma levels of testosterone (T), 17-β-estradiol (E2), progesterone (P4), dehydroepiandrosterone (DHEA), corticosterone (B), thyroxine (T4) and triiodothyronine (T3) were monitored during postnuptial and the prenuptial molt in domestic goose (Anser anser domesticus) in both sexes. 1. At the beginning of postnuptial molt (when the old, worn dawny-, and cover feathers' loss starts) in ganders, the levels of T, E2, P4 decrease while DHEA and B significantly increase. The elevated levels of T4 and low T3 concentrations characteristic of the last phase of the reproduction, remain unchanged. In layers, similar changes were observed, however, B decreases. 2. In the early phase of outgrowth of wing and cover feathers, plasma levels of T, E2 and P4 are low. Elevated B, DHEA and T4 concentrations decrease in ganders, while in layers DHEA increases and B and T4 levels remain unchanged. T3 increases in both sexes. 3. The subsequent intensive outgrowth period of wing- and cover feathers both in ganders and in layers is characterized by very low levels of T, E2, DHEA and T4, but P4 increased, and T3 concentration remain high. 4. At the end of postnuptial molt - when the outgrowth of dawny, cover-, and wing feathers stops - very low T, E2, P4, DHEA and T4 levels and and high T3 plasma levels were found in both sexes. Fast increase of plasma B was detected in ganders, while in geese, B concentration remain high. 5. During prenuptial molting (outgrowth of contour and tail feathers) low E2, P4 and T4, increasing T and DHEA, but very high T3 and B plasma concentration were measured in ganders. In layers, very low T, E2, P4, DHEA and T4 levels, and very high B and T3 levels were found. 6. At the beginning of the fall-winter sexual repose (postmolting stage) T, E2, P4, DHEA and T4 levels increase, T3 and B declines in both sexes. 7. In the subsequent phase of fall-winter period (preparatory stage) there is a further increase in T, P4 and T4, a fast increase of B and a decrease of E2, DHEA and T3 in ganders. In layers, T, P4 and DHEA decrease, B increases and the T4 and T3 do not change. 8. At the beginning of reproduction high T level, unchanged DHEA, slightly declined P4, and decreased E2, T4, T3 and a strong decline of B concentrations occur in ganders. In layers, T is further increased, E2 and P4 shows high levels, and, at the same time DHEA and T3 remain unchanged, while B and T4 decrease.

-Commercial geese (Gray Landes) were examined by means of high-resolution spiral computer tomography in order to follow their liver development in vivo. Three ganders were scanned six times before, within and after a force-feeding period. 3D images of the liver were reconstructed from the 2D transverse slices with segmentation and rendering methods. The changes in the external surface, the volume of the liver and also the characteristic Hounsfield values were determined. The livers of another 70 ganders were examined by CT, then by direct chemical analysis (days 0, 13, 18, 19, 20 and 21 of force-feeding). To estimate the chemical composition of the tissue, prediction equations were developed based on the pixel frequency distributions. With partial least squares (PLS) regression, the ether extract and crude protein content could be estimated with R 2 = 0.97 and R 2 = 0.96 accuracy, respectively. Data analysis was complemented with serial blood serum measurements characteristic of liver steatosis. The method applied may be a unique possibility to study the real geometrical relations of liver development and also to describe the qualitative changes of tissue composition during the force-feeding period in vivo, with special regards to selection purposes. goose liver / computerized tomography / liver yield / liver composition Résumé -Études in vivo du développement du foie d'oie par tomographie. Le développement du foie des oies (Landaise grise) a été examiné « in vivo » par tomographie spirale à haute résolution (CT). Les coupes ont été préparées sur six jours différents, avant, pendant et après le gavage, sur trois jars. Les images en trois dimensions (3D) ont été reconstituées à partir des images en 2D, par l'ajustement selon la méthode d'ajustement par segments. La modification de la surface externe et du volume du foie ont été définies par les valeurs Hounsfield. Outre les foies des trois jars, 70 jars ont été encore examinés par la même méthode (CT), ensuite des analyses chimiques directes ont été réalisées aux jours 0, 13, 18, 19, 20 et 21 du gavage. La composition chimique du foie a été estimée par la création d'équations de régression en fonction de la division de fréquence des pixels. A l'aide d'équations des moindres carrés la teneur en graisse et en protéines du foie ont été prédites avec une bonne précision (R 2 = 0,97 et 0,90, respectivement). L'analyse du développement de la stéatose hépatique a été complétée par la mesure des caractéristiques sanguines. La méthode de tomographie « in vivo » donne la possibilité unique de caractériser les corrélations géométriques réelles au cours du développement du foie et de décrire les modifications qualitatives dans la composition du tissu pendant l'engraissement par gavage. Cette méthode pourrait être utilisée en sélection.foie gras / oie / tomographie / rendement / composition