Breeding values

Test-day-model

A Multi-Lactation Test Day Animal Model (MTDAM) was introduced by VIT in 1996 to estimate breeding values for somatic cell score and in 1998 for milk production traits. The main advantages of using a Test Day Animal Model instead of a Lactation Animal Model are

• Using the original yield observation (test day record) as yield information for evaluation, thus optimum correction of environmental effects on herd test day level. 
• Cows get earlier an EBV with the first test day records.
• All daughters of a sire having at least one test day record are included in evaluations, thus a possible bias from selection effects is avoided.

Data base

Test day records of cows with first lactation initiated since 1990 are considered in the genetic evaluation. All official test day records are included, if

• Age of calving is: 20 - 40, 30 - 56 and 44 - 75 month for lactations 1, 2 and 3, respectively
• Test day: 5. - 325. day after calving

Base of Breeding Values

The "BV base 2000" recommended by INTERBULL is used to adjust the level of breeding values within breed. That means the average breeding value of all cows of the same breed born in 1995 is set to zero, and the breeding values of all animals are expressed in relation to their base. (GH: Germ. Holstein; GRH: Germ. Red Holstein; GRC: Germ. Red Cattle)
The difference between the breed bases for yield traits are calculated from all cows born in 1995.
GH - GRH: BVmilk-kg: +472 kg BVfat-kg: +17,7 kg BVprotein-kg: +12,8 kg
GRH - GRC: BVmilk-kg: +521 kg BVfat-kg: - 5,5 kg BVprotein-kg: + 8,0 kg

The relative breeding values (RZ…) are standardised to a yearly rolling basis with a mean of 100 and a genetic standard deviation of 12 points. The base shifts in June and comprises the currently proven bulls of a breed (at present the test bulls born in 1991-1993).