(new) Chapter 5.11.2 Examples of common environmental effects

In Table 2 you see an example of common environmental effects on a number of traits in sows of two different breeds. This common environmental effect represents the effect of being raised in the same litter until weaning. You see that the effect is largest on the leg score of the animals. Possibly this can have something to do with the milk composition of the sow that may have affected the growth and development of the bones. But this would be speculation. What the table also shows is the size of the effect of taking this common environment into account or not when estimating the heritability for the traits. As explained earlier, this is because of the environmental effect of sharing the same litter. But it is also because it is difficult to disentangle the environmental effect of sharing that same litter from the fact that the animals in the litter were related. This makes it difficult to have accurate estimates of the variances due to the additive genetic and common environmental effects.

Table 2. Examples of heritabilities without (h²) and with (h^2*) taking the common environmental effect (c²) into account for two different breeds of pigs.