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SUMMARY: In the derivation of selection index weights it is typically assumed that population and economic parameters are known with certainty. In practice, however, estimates of selection index parameters must be used instead of the true parameters. It is shown that when errors in parameter estimates have asymmetrical effects on the efficiency of a selection index, the expected response from selection can be increased by biasing parameter estimates. In this way, the probability of making errors which result in large reductions in efficiency is reduced. A method of deriving optimum (biased) selection index weights when there is uncertainty in parameters is described. The method incorporates the error probability distributions of parameters estimated with uncertainty. In some examples, moderate (2-5%) increases in the expected response from selection occurred with uncertain heritability and economic weight estimates. Overall however, increases in selection response vary depending on the true index and are usually small (0 to .5 %) unless parameter estimates are extremely uncertain. Failure to account for uncertainty in unbiased parameters leads to over estimation of the value of selection. Applications of the method for both practical and theoretical purposes are discussed with specific reference to animal improvement programs. ZUSAMMENFASSUNG: Optimale Verzerrung von ungenau gesch?tzten Selektionsindex-Parametern Bei der Ableitung von Selektionsindex-Gewichten wird üblicherweise angenommen, da? die Populationsparameter und wirtschaftlichen Gewichte genau bekannt sind. In der praktischen Anwendung müssen jedoch Sch?tzwerte anstelle der wahren Parameter verwendet werden. über- und Untersch?tzungen der Parameter zeigen asymmetrische Effekte auf die Effizienz von Selektionsindices. Es wird gezeigt, da? der erwartete Selektionserfolg gesteigert werden kann, wenn verzerrte Parametersch?tzwerte verwendet werden. Dabei wird die Wahrscheinlichkeit von Fehlern, welche zu gro?en Effizienzverlusten führen, verringert. Es wird eine Methode zur Ableitung der optimalen (verzerrten) Selektionsindex-Parameter beschrieben. Die Methode berücksichtigt die Verteilung der Sch?tzfehler. In einigen Beispielen von ungenau gesch?tzten Heritabilit?ten und wirtschaftlichen Gewichten wurden bescheidene (2 bis 5%) Steigerungen des erwarteten Selektionserfolges gefunden. Im allgemeinen waren die erwarteten Effizienzsteigerungen jedoch klein (0 bis 0,5%), au?er bei Parametern mit extrem gro?en Sch?tzfehlern. Werden die Sch?tzfehler der im Selektionsindex verwendeten Parameter nicht berücksichtigt, wird der erwartete Selektionsfortschritt übersch?tzt. Praktische und theoretische Anwendungsm?glichkeiten werden diskutiert.  相似文献   
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The objective of this study was to investigate whether the occurrence of cryptorchidism in a litter is associated with the sex ratio in this litter. The analysis included for dog 1,339 litters of 4 different breeds, of which 12.8% had 1 and 3.1% had 2 cryptorchids, and for pig 119,920 litters of 14 different populations, of which 2.2% had 1 and 0.2% had 2 cryptorchids. The data were analyzed using the GLIMMIX procedure of SAS. In dog, the presence of cryptorchids in a litter does not affect litter size or the stillborn rate. In pig, litter size increases significantly with an increasing number of cryptorchids in a litter. The stillborn rate in pig is larger in litters with cryptorchids than in litters without cryptorchids. To characterize the imbalance of the sexes in a litter, the sex ratio, defined as the number of live males divided by the number of live offspring, and the sex difference, defined as the number of live males minus the number of live females, were used as dependent variables in the analyses. In both dog and pig, the presence of 1 or 2 cryptorchids in a litter clearly goes together with a shift in both the sex ratio and the sex difference in a litter, in favor of male offspring. Our results in dog and pig suggest a common underlying mechanism affecting both cryptorchidism and sex ratio, which may hold true in other mammals as well.  相似文献   
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Rat pups that are separated early from their mothers, at postnatal day 15, become hypothermic when subjected to physical restraint on postnatal day 30. Restraint of separated pups also elicits an unusually high incidence of gastric erosions, as well as insomnia and an increase in quiet wakefulness. If hypothermia during restraint is prevented, neither the erosions nor the behavioral responses occur. Rat pups separated at the customary age (postnatal day 22) do not become hypothermic during restraint, and the restraint of such pups is not associated with either gastric erosion or insomnia.  相似文献   
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Background

The ACTH stimulation test is used to evaluate the adrenocortical reserve. Recently, the availability of the synthetic ACTH formulation was limited, causing major problems in clinical practice.

Objectives

The objective of this study was to evaluate poststimulation peak cortisol concentrations and the duration of the stimulatory effect of a depot ACTH preparation in dogs.

Animals

Twenty‐two healthy dogs, 10 dogs with suspected hypoadrenocorticism (HA) and 15 dogs with suspected hyperadrenocorticism (HC).

Methods

Prospective study. An ACTH stimulation test using a synthetic depot tetracosactide, administered intramuscularly (5 μg/kg or at least 0.1 mL) was performed. Blood samples for determination of cortisol were taken immediately before and 1, 2, 3, 4, 6, and 24 hours after stimulation.

Results

Peak cortisol concentrations were reached after 2–4 hours in all dogs. Cortisol concentrations 1 hour after stimulation were >9 μg/dL in all healthy dogs and >5 μg/dL in all dogs in which HA was excluded. None of the dogs with HA showed a cortisol‐increase above the detection‐limit of the assay. After 6 hours, cortisol concentrations had decreased in the healthy and HC group and were back to baseline after 24 hours.

Conclusions and Clinical Importance

The depot formulation can be used in place of the short‐acting ACTH to evaluate the adrenocortical reserve. Blood for peak cortisol concentrations should be drawn 3 hours after stimulation in cases in which HC is suspected; in HA‐suspected cases, blood sampling can take place after 1 hour. As the stimulatory effect is gone after 24 hours, interference with other hormonal tests is unlikely after that time.  相似文献   
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Decreases of 40 percent in cardiac and respiratory rates occur during the first 12 to 16 hours after 2-week-old rat pups are separated from their mothers. These rates decrease without significant alteration in activity level and despite maintenance of body temperature, of nutrition by intubation, of an intact litter, and of the home cage nest.  相似文献   
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Molecular markers for the red grain color (R) loci controlling seed color and the polyphenol oxidase (Ppo‐A1) locus controlling polyphenol oxidase (PPO) activity in seed have recently been developed. These markers provided the opportunity to convert the hard red spring wheat cultivars Choteau and Hank to white‐seeded versions with high and low PPO levels, respectively. These sets of near‐isogenic lines provided material to test the effects of seed color and PPO activity on a range of end‐use quality traits. We tested recurrent parents Choteau and Hank, along with near‐isogenic derivatives with white seed, in two replicated trials in Bozeman, Montana, for end‐use quality parameters. The white‐seeded lines consisted of both high‐ and low‐PPO near‐isogenic lines. The primary impact of white seed was the production of whole wheat bread with a perceived sweeter taste relative to the red‐seeded lines. Noodle color was not consistently impacted by the level of PPO variation despite relatively large reductions in PPO level. The alleles for white seed color did not appear to impact agronomic traits. These results suggested that hard white low‐PPO hard spring wheat would be advantageous in terms of conferring brighter color to Asian noodles and a sweeter taste to whole wheat bread.  相似文献   
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