Estimated Breeding Values (EBVs)

An Estimated Breeding Value (or EBV) is a prediction of an animal's genetic merit for a particular trait relative to other animals in the same population. PIGBLUP combines all the information on the trait recorded on the animal and its relatives.

The PIGBLUP system can calculate EBVs for:

Average Daily Gain (ADG)	Carcase Fat
Feed Conversion Ratio	%Lean Meat
Gain in Test Period	Number Born Alive (NBA)
Backfat P2 (BF)	21 Day Litter Weight
Carcase Muscle	IGF1 trait (PrimeGRO)

Examples

ANIM ID	ADG	BF	NBA
841103	+28.0	-0.6	+0.2
841104	0	+1.0	-0.2

For the first boar, the EBVs are:

ADG : 28.0 grams
BF : 0.6mm
NBA : 0.2 pigs/litter

If these two boars are mated to two groups of sows with similar EBVs, the expected average progeny difference in performance is half the difference in the boars EBVs.

+14 grams/day faster growth of progeny from boar 841103
0.8mm leaner carcases of progeny from boar 841103
+0.2 pigs/litter more from daughters of boar 841103

The boars contribute only half of the progenies genetic makeup, the other half will come from the mates.Because the EBVs of the two goups are similar, in this example, their EBVs can be ignored.

Notes

The point of interest with EBVs is the difference between animals once EBVs have been calculated rather than the absolute value of the EBV itself.
Comparisons across herds are not possible using PIGBLUP EBVs, unless genetic linkage exists and data has been analysed jointly.

What makes PIGBLUP EBVs so good?

PIGBLUP's Estimated Breeding Values (EBVs) are better than EBVs obtained by other less advanced methods because BLUP makes better use of all the recorded information in assessing the genetic merit of all animals. In calculating a pig's EBV for a trait such as average daily gain (ADG), PIGBLUP takes into account not only the pig's phenotype (its own recorded ADG) but also information from all its known relatives, past and present, and measurements on related traits, such as backfat.

PIGBLUP removes recorded biases introduced by environmental (non-genetic) factors.

PIGBLUP therefore offers pig breeders a better decision making tool for the culling and selection of animals.

PIGBLUP

Uses information from all known relatives, past and present, to calculate a pig's EBV.
Uses the additional information from other associated traits.
Removes most of the biases introduced by systematic environmental influences such as:
- age difference
- management differences if recorded
- litter effects
- parity effects
- effects of selection itself
- preferential mating

Calculates average EBVs over time so genetic trends can be assessed.
Combines genetic, economic, production and marketing information into a single $EBV index.
Assists the breeder in "tightening up" the total breeding operation.

This gives breeders the capability to compare the genetic merit of all pigs on the farm and evaluate the genetic progress in the herd.

How are EBVS used?

Having obtained performance records and EBVs on a number of traits, the next issue is how much emphasis to place on each of the traits in the breeding program. For instance should breeders pick the animal with the highest value for gain, or the lowest value for backfat? How do you combine these EBVs into a single value upon which to base selection decisions? In PIGBLUP the EBVs produced are combined into a $INDEX, a single customised selection index which uses economic, production and marketing data supplied by the breeder. This combination determines the economic worth of the basic EBVs for that animal by assessing costs and returns. These indexes are themselves also EBVs but are more valuable because they now contain genetic and economic information for a number of traits.