Pig breeding is generally conducted among many herds, so EBV comparisons across populations are necessary. Genetic connectedness is required for reliable between-farmanimal EBV comparisons.Five quantitative overall connectedness measures among populations have been proposed so far,coefficient of connectedness(γ*), coefficient of determination (CD) and overall indices of precision, connectedness rating, number of direct genetic links between subpopulations due to common sires and dams (GLt), and average genetic covariance (AGC) are reviewed and theirproperties are discussed in this paper. It is recommended to use AGC at present for measuring genetic connectedness between herds. 相似文献
A variety of powerful techniques to control the position and velocity of neutral particles has been developed. As examples of this new ability, lasers have been used to construct a variety of traps, to cool atoms to temperatures below 3 x 10(-6) kelvin, and to create atomic fountains that may give us a hundredfold increase in the accuracy of atomic clocks. Bacteria can be held with laser traps while they are being viewed in an optical microscope, and organelles within a cell can be manipulated without puncturing the cell wall. Single molecules of DNA can now be stretched out and pinned down in a water solution with optical traps. These new capabilities may soon be applied to a wide variety of scientific questions as diverse as precision measurements of fundamental symmetries in physics and the study of biochemistry on a single molecule basis. 相似文献
1. The effects of dietary penicillin on the urease activities of small intestine, large intestine, caecum and their contents, liver and kidney in chickens fed a diet containing 5 g/kg protein plus urea were examined.
2. About 0.88 of the total urease activity determined was observed in intestinal contents, of which 0.95 of the activity was accounted for by caecal contents, 0.05 by colo‐rectal contents and none by small intestinal contents. Intestinal tissues (caecum included), liver and kidney accounted for 0.03, 0.06 and 0.02, respectively, of the total urease activity.
3. Dietary penicillin decreased urease activity to 0.17 in caecal contents and to 0.05 in colo‐rectal contents of the corresponding control values (P< 0.01). The urease activity of caecal tissue was lowered by penicillin to half that of control activity (P < 0.05) but none of the activities of other tissues were affected.
4. It is concluded that, even when the urease activity is stimulated by dietary urea, 20 mg/kg dietary penicillin can strikingly lower it in the caecum, where most of the urease activity in the chicken body is to be found. 相似文献