Analysis of a long-term selection experiment with an exponential model.

UNLABELLED: ZUSAMMENFASSUNG: Analyse eines Langzeitselektionsversuchs mittels eines exponentiellen Modells Für die Analyse von Langzeitselektionsexperimenten wird ein exponentielles Modell vorgestellt. Dieses Modell basiert auf der Idee der "realisierten Heritabilität" una liefert Parameter, die als die Schlüsselparameter für die Beschreibung von Langzeitselektionsexperimenten betrachtet werden können: Gesamterfolg, maximaler Selektionserfolg je Generation, Halbwertzeit. Außerdem liefert es die "realisierte h(2) -Funktion". Die Anwendung dieses Modells wurde demonstriert, bei Nutzung der Daten eines Langzeitselektionsexperimentes, in dem Mäuse über 84 Generationen auf hohe Körpermasse selektiert wurden. Das geschätzte Selektionsplateau für die Körpermasse am 60. Lebenstag betrug 43.6 g und lag damit um 21.3 g (96 %, 7.7 phänotypische bzw. 12.8 genetische Standardabweichungen oder um das 18fache des maximalen Selektionserfolges) über dem Ausgangswert. Die Halbwertzeit betrug 15-16 Generationen (= 0.15 Ne). Zum Selektionsbeginn betrug die realisierte Heritabilität 0.361 während sie zum Ende auf 0.0004 fiel. Während sich die genetische Varianz von 2.8 auf 0.016 g(2) verringerte, erhöhte sich die phönotypische Varianz von 7.7 auf 39 g(2) , größtenteils als Skaleneffekt. Der Variationskoeffizient für das Selektionsmerkmal betrug im Mittel 11.5 % und zeigte nur eine geringfügige Erhöhung während des Experimentes. Die Anwendbarkeit und der Nutzen des Auswertungsmodells für einige Typen von Langzeitselektionsexperimenten wird diskutiert. SUMMARY: An exponential model is presented for the analysis of long-term selection experiments. This model is based on the idea of "realised heritability" and it provides parameters which can be considered as the key parameters for the description of long-term selection experiments, such as the total response, the maximal response per generation and the half-life. In addition it provides the "realised h(2) -function". The application of this model is demonstrated, using as an example the data of a long-term selection experiment in which mice were selected for 84 generations on body weight at 60 days. The estimated selection limit for body weight at 60 days was 43.6 g and therefore 21.3 g (96 %, 7.7 phenotypic and 12.8 genetic standard deviations or 18 times the maximal response per generation) over the starting value. The half-life time was 15 to 16 generations (= 0.15 Ne). At the beginning of this experiment the realised heritability was 0.361 and decreased to 0.0004 at the end. While the genetic variance declined from 2.8 to 0.016 g(2) , the phenotypic variance increased from 7.7 to 39 g(2) , partly as a scale effect. The mean coefficient of variation for the selected trait was about 11.5% and showed only a small increase during the experiment. The usefulness of the application of the presented model for the analysis of some types of long-term selection experiments is discussed.

Correct equations for comparing models in diallel analysis.

SUMMARY: Correct equations are given to express the parameter estimates of four models for complete diallels as a function of the parameter estimates in the model of Eisen et al. (1983). In recent literature these equations have been partly incorrect. ZUSAMMENFASSUNG: Korrekte Gleichungen für den Vergleich von Modellen in der Diallelanalyse Für die Darstellung der Parameterschätzwerte von vier Modellen für vollständige Diallele als Funktion der Parameterschätzwerte des Modells von Eisen et al. (1983), die in der Literatur teilweise fehlerhaft erfolgte, werden korrekte Formeln angegeben.

[The effect of nutritional factors on the ruminal mucosa. 3. Condition of the mucosa after infusion of propionic acid, acetic acid and butyric acid]. / Untersuchungen über den Einfluss von Ernährungsfaktoren auf die Pansenschleimhaut

Three non-lactating cows (Deutsches Schwarzbuntes Rind) with large ruminal fistulas were fed coarsely structured food. Within a trial period of 21 weeks infusion periods lasting 3 weeks alternated with equally long control periods (K). During the 3 infusion periods, 8.4 mMol of propionic acid (P), 14.8 mMol of acetic acid (E) and 4,5 mMol of butyric acid (B) per kg liveweight per day were administered through the fistula, the total quantity being 19 litres of solution. In the periods K1...4 the ruminal fluid contained an average of 68 Mol% E, 19 Mol% P, 13 Mol% B (maximum of 10.25 mMol free fatty acids (FFS) per 100 ml, minimum pH 6.4). In the course of the 10 hrs of infusion the Mol percentages of the particular acids infused increased to 27% P (maximum of 11.14 mMol FFS per 100 ml, minimum pH 6.4) or 79% E (maximum of 12,99 mMol FFS per 100 ml, minimum pH 6.0 (5.5)) or 25% B (maximum of 10.34 mMol FFS per 100 ml, minimum pH 6.0 (5.5)). Infusions of E and B had the most pronounced effect on the ruminal mucosa compared with the K periods. All fatty acids increased the process of keratinization and decreased the size of cell nuclei in the stratum basale. As specific effect, P infusions produced a thickening of the lamina propria; B infusions caused a thickening of the stratum germinativum (proliferative effect) while e infusions led to a drastically reduced thickness of villi (antiproliferative effect) due to reductions in the stratum germinativum and the lamina propria. According to the morphological situation high specific mucosal function is suggested during the B-period. The mucosa appeared quite normal during all periods investigated, with the exception of the E period, where hyperkeratosis, atrophy and necrosis were observed in 34% of the sample. Changes in the state of the mucosa appeared as early as 1 week after the beginning of the respective trial periods. Keratin consolidation was the primary cause for chemically induced keratosis. The development of hyperkeratosis seemed to be favoured if low pH values occurred in the rumen in combination with small amounts of metabolites inducing proliferation, both representing synergistic factors.