Objectives

The objectives of the study were primarily:

• to compare the performance of the Red Maasai and Dorper breeds and their various crosses in terms of productivity under high disease risk
• to study genetic sources of variation among lambs within the two breeds and their crosses

In this example we shall consider the first objective but just look at weaning weight as the performance variable. We shall determine the effect of breed and other factors or covariates on weaning weight. Weaning of lambs took place on a single day each year when the average age of the lambs was 3 months. However, dates of birth varied and so weaning weight will, to some extent, have been influenced by the age of the lamb on that day.

In Case Study 4 we shall study the genetic variation expressed among offspring from different rams and ewes.