Detailed Dairy Cattle Evaluation Information
2017/03/16
Genetic evaluation for calving ease
The trait of calving ease is evaluated by sire threshold models. Calving ease of cow is classified into two categories : easy or difficult calving. Sire evaluation for calving ease is expressed as ETA for percentage of difficult births in heifers, and are shown as sire calving ease(SCE) and daughter calving ease(DCE). The data have been collected through DHIP since 1986.

The genetic evaluation of calving ease is estimated by the first calving data. If a bull with less than 15 data of first calving, ETA calving ease of the bull are estimated by the best prediction (BP) method. The BP calculation contains covariance among ETA calving ease from all calving, EBV of milk, fat, stature, body depth, fore udder attachment, rear udder height and rear udder width, and ETA calving ease from first calving.

Data editing criteria for calving ease evaluation is :

sire of cow is known and Holstein,
sire of calf is Holstein or beef cattle,
insemination date is known and gestation length from 261 to 299 days,
18 to 35 months of age at first calving,
sex of the calf identified,
single calf (exclude stillbirth data),
at least one contemporary record in the herd-year subclass.

The evaluation model for calving ease is:
y = hy + BM + A + X + SB + MB + f1 + sc + sd + e

where,
y :
records of calving ease assumed normal distribution,
hy :
random effects of herd-year to account for the effect of management groups on a record,
BM :
fixed effects of calving month by regional block,
A :
fixed effects of age at calving,
X :
fixed effects of sex-breed of calf,
SB :
fixed effects of sire birth year groups,
MB :
fixed effects of MGS birth year groups,
f1 :
fixed effects of cross-breed,
sc :
random additive genetic effects of the sire of calf,
sd :
random additive genetic effects of the sire of dam,
e :
random residuals.

In calving ease evaluation, pedigree information among bulls is used, and sire and MGS of bulls within four generations of recorded cows are identified.

Direct heritability : 0.06
Maternal heritability : 0.03