National Livestock Breeding Center
Incorporated Administrative Agency

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Detailed Dairy Cattle Evaluation Information

2017/05/24

Genetic evaluation for production traits

Milk, fat, protein and SNF (Solids Non-Fat) yields were evaluated using a single-trait multiple-lactation test-day model. Fat, protein and SNF percentages are evaluated indirectly from yield trait evaluations. Milk records of dairy cows have been accumulated since 1974 in Japan through the DHIP. The data editing criteria are:
  • For cows:
    • holstein,
    • sires known,
    • supervised milking ( A4 or AT( milking frequency is twice or thrice time per day)) or automatic milking,
    • 18 to 35 months of age at first calving,
    • 30 to 55 months of age at second calving,
    • 42 to 75 months of age at third calving,
    • all test day records between 6 and 305 DIM for first three lactations,
    • at least one contemporary record must exist in the herd-milking frequency-test day subclass and herd-test year-parity subclass.


The evaluation models for production yield traits are:

y = HTDT + ΣBM・w +ΣPA・w + Σhyp・v +Σpe・z + Σu・z + e

where,
y :
yields of milk, fat, protein or SNF on test day (pre-adjustment for heterogeneous variance),
HTDT :
fixed effects of herd-test day- milking freaquency,
BM :
fixed regression coefficients for regional block( 2 blocks) - calving month,
PA :
fixed regression coefficients for parity - age at calving,
pe :
random regression coefficients of cow for permanent environment effects,
hyp :
random regression coefficients of herd-year of test-parity,
u :
random regression coefficients of additive genetics,
pe :
random regression coefficients of cow for permanent environment effects,
e :
random residuals,
w :
Legendre polynomial with five parameters intercept, φ1(t), φ2(t), φ3(t), φ4(t) and exp(-0.05t) on DIM(t),
v :
Legendre polynomial with five parameters intercept and φ1(t) on DIM(t),
z :
Legendre polynomial with three parameters 1, φ1(t) and φ2(t) on DIM(t)

At least four generations from recorded cows are identified using all available pedigree information. Unknown or unidentified parents are grouped into random genetic groups of phantom parents. Heritability are assumed as following.


Tabe: Heritabilities for production trait in Japan
Traits 1st Lactation 2st Lactation 3st Lactation Combined
Milk 0.433 0.382 0.362 0.500
Fat 0.405 0.387 0.377 0.498
SNF 0.360 0.333 0.335 0.429
Protein 0.386 0.342 0.330 0.448



Genetic evaluations for 7 production traits are expressed as EBV ( Estimated Breeding Value ) , but EBVs for example FAT % EBV, are calculated indirectly from yield EBVs with the following formula:

EBV(F%) = ((EBV(Fkg) + Fbase) / (EBV(Mkg) + Mbase)) - (Fbase / Mbase)) * 100
  • where,
    • Fbase, Mbase:
    • the average fat and milk yields (kg) of the cows born in the genetic base year,
    • Mkg, Fkg:
    • Milk(kg), and Fat (kg),
    • F%:
    • Fat(%).
SBV (Standardized Breeding Value) is also calculated for bulls based on means and standard deviations of bull EBV.
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