The amount of information available on other traits which are related to the trait of interest, i.e. the birthweight and 200 day weight will influence the 400 day weight of an animal. The number of animals within a recorded group, the more the better To simplify selection decisions these values have been combined into a multi-trait selection index, known as the Calving Value Index. This is an overall assessment of the economic value of an animal's effect on calving, designed to help producers select easy-calving bulls. The calving value is presented as a cash value per head, representative of the bull's genetic ability. As a bull passes on half his genes to the next generation the value must be halved.
Positive values mean increased profits, negative values mean a reduction in profits.
Selecting a bull using the figures Comparing two Charolais bulls. If avoiding difficult calvings is an important consideration, Bull A's progeny will be easier to calve compared to Bull B, as denoted by a 7 difference in the Calving Values. Also the EBV's for Bull A are less likely to fluctuate in the future, when compared with Bull B, as the accuracy values for comparable EBV's are higher for Bull A than Bull B. Higher accuracy means more confidence can be placed on the information. Society Indexes Additional to EBV's and accuracy several breed societies, the Limousin, Charolais, Simmental and Aberdeen Angus have introduced a Society Index Line. The main aim of the Index Line is to simplify the BLUP data so that it is easy to determine whether an animal is above or below breed average for each trait.