Ann Dunnington and Paul Siegel assembled 61 Power Points to illustrate selection for growth. They describe a real-life long-term experiment selecting meat-type chickens at 8 weeks of age for 27 generations, simultaneously both for small and for large body weight. At the same time, a control unselected population was included for comparison to look for long-term trends over the 27 years of this trial. In addition to body weight, a number of other measurements such as age at sexual maturity, feed intake, and egg weight were made looking for correlated responses. Readers are led through the logic for the experimental design, results, analyses, discussion, and summary and conclusions, as if the reader were a partner in the experiment. At each stage of this research, readers are asked questions and led through discussions to help them understand the research.
While this file uses chickens to illustrate the process of selection, the principles apply equally to other classes of animals. For example, one might reflect upon the concern about dwarfism in cattle when in the mid-1900’s beef cattle were selected for compact conformation.
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