Introduction

The genetic potential of the AI sires is evaluated on basis of their offspring within the framework of the program called progeny-test. The data is collected on the farm by technicians in three visits:  a first visit at birth, a second one when the animal is approximately 14 months of age, and finally with the linear classifications of the adult cows.

 

At Birth,
the indexes concern :

  • The zootechnical traits  :
    • Conformation (scale from 1 to 9 – from lightly muscled tot hyper muscled) ;
    • Gestation length (in days) ;
    • Birth weight (estimated in kg). 

Even if the gestation length and the birth weight are recorded in full blood Belgian Blue cattle, they remain reliable indications of the calving ease when used in crossbreeding programs.

  • The functional traits  :
    • Ability to drink (scale from 1 to 3 – from bad to good) ;
    • Vitality (Hardiness) (scale from 1 to 3 – from bad to good) ;
    • Death rate (cases reported at the moment of the visit, whatever the cause is) ;
    • Defects at the forelegs. For this trait, only the male calves are taken into account seeing the strong influence of the sex on their incidence ;
    • Straight hocks / bent hocks: These traits are not anomalies but belong to the normal variation of the hock’s angle. A more detailed assessment of this criterion is performed within the context of the linear classification ;
    • Mouth defects:  presence or not of protruding tongue, deviation of the lower jaw, prognathism. These anomalies are not lethal and many cases cure naturally.

The genetic evaluations carried out for the second visit take in account the following traits :

  • The zootechnical traits  :
    • Conformation (scale from 1 to 9 – from lightly muscled tot hyper muscled) ; :
    • Weight (in kg estimated via the measure of the thoracic perimeter )
    • Height  (in cm)
    • Combined index « weight-conformation ».
  • The functional traits  :
  • Death rate (cases reported at the moment of the visit, whatever the cause is)
  • Defects at the forelegs (deviation, sagged knee, fetlock forelegs…).
  • Defects at the rear legs (deviation, fetlock rear legs,)
  • Straight hocks / bent hocks. A more detailed assessment of this criterion is performed within the context of the linear classification
  • Mouth defects: presence or not of deviation of the lower jaw, prognathism, brachygnathism.

 

For the linear score, the indexes are carried out on basis of 23 traits, noted on a linear scale varying from 0 to 50.  (For more information, see the webpage “selection and testing programmes).

Linear score : meaning of a low or high index

Character

Low Index

High Index

Height

Smaller

Taller

Length

Shorter

Longer

Chest width

Narrower

Wider

Pelvis width

Narrower

Wider

Shoulder muscling

Less developed

More developed

Top muscling

Less developed

More developed

Rib

Flat

Round

Skin

Thicker

Thinner

Rump

Less sloping

More sloping

Pelvis lengh

Shorter

Longer

Tail set

Less promineny

More prominent

Thighs : side view

Less rounded

More rounded

Thighs : rear view

Less bulging

More bulging

Bone structure

Thicker

Thinner

Shoulder bone

Prominent

Smooth

Top line

Concave

Convex

Fore legs

Turned-in feet

Turned-out feet

Rear legs

Turned-in feet

Turned-out

Hocks

Less bent

Bent

General aspects

Average

Good


See « selection and test program ».

 

Interpretation of the indexes

The breeding values obtained from the genetic evaluation procedure are expressed into the unit measure of the trait.  To facilitate the use of those results, they are converted in a standardised index with an average of 100 and a standard deviation of 10.  Their interpretation is the following: an index value of 100 indicates that the sire belongs to the average population for this trait. An index higher than 100 indicates that the animal is higher than the average population.  That does not always mean “better”: it depends on the trait (e.g.: defects, mortality…).

The notion of standard deviation allows locating the animal in the population for a particular trait: 68 % of the evaluated animals have an index between 90 and 110.  And 95 % have an index between 80 and 120.  An index higher than 120 indicates that the animal is amongst the 2,5 % best animals of the population for that trait.

The calculated index in the genetic evaluations is only an estimation of the “true” genetic value of an animal.  That’s why each index is associated with a precision (reliability or R2), which indicates the confidence we can have in the index. 
Remind that, a prediction error (Err Pred) is associated with a given reliability (Table below).

 

Er Pred Er Pred Er Pred
50 7,07 80 4,47 97 1,73
60 6,32 90 3,16 98 1,41
70 5,48 95 2,24 99 1,00

 

Légende

The genetic evaluation results which are available via this research software have been calculated in December 2007 for the 1st visit and in July 2007 for the second one and the linear score.

To assess the sire’s position for each trait separately colour codes are used.  Here is their signification:

    INDEX
  strongly improver for this trait min. 20 points above / below the average
  improver for this trait 10 to 19 points above / below the average
  in the average for this trait 0 to 9 points above / below the average
  unfavourable for this trait 10 to 19 points above / below the average
  strongly unfavourable for this trait min. 20 points above / below the average

 

Most indexes express favourable characteristics when they are high (except the gestation length, defects and mortality).  However, for some criteria, it is better to have indexes close to the average.  For the linear score, these criteria are: the top line, the forelegs, the rear legs and the hocks).  The objective of the birth weight was chosen to stabilize it.

In order to define a more current average, the sire potential has been assessed on basis of females present in farms, which have characteristics recorded in genetic evaluation and which are born in 2005. The indexes have been adapted in order to take this average into consideration for each criterion. Consequently, an index of 100 is more representative of the average of the present population. 

The ECONOMICAL INDEX calculated on the base of the 2nd visit figures is now called
“WEIGHT-CONFORMATION INDEX”. Nowadays, an economical index should indeed take more factors than the weight and the conformation into account.
The tables below show the correspondence between functional indexes and defects expected frequencies (%) of the sire offspring.

Publishing criteria

The Indexes are considered as « official » when they reach a precision threshold. This one must reach 0.50 for all the criteria of 1st and 2nd visits. 
Concerning the linear score the precision threshold must reach 0,70 for the partial score “muscling”.
Moreover, the sires must have at least 10 calves born in minimum 2 different herds.

 

Correspondence

The tables show the correspondence between functional indexes and defects expected frequencies (%) of the sire offspring as well as the difference for the zootechnical indexes (expressed in the unit of the trait) produced by a 10 points variance.

 

See " index et pedigree "