The production traits are based on three lactations,
and five regression coefficients per trait, as in the Canadian Test Day Model,
with regressions on Legendre polynomials of days in milk. A lactation length
of 365 days is assumed to be maximum. These allow the prediction of
yields for each day in milk, and also allow for different shapes of lactation
curves per animal. The predicted yields are expected amounts during an
average day for a healthy, non-pregnant, non-stressed, animal.
Production represents 105 different traits.
Each conformation trait is assumed to have a different
genetic value in each of the first three lactations, but the three genetic values
are correlated to each other at 0.80. This allows the genetic value for a
trait to either improve or to decline with age. Thus, there are a total
of 78 conformation traits.
|Conformation||Dairy Strength||Rump||Feet & Legs||Mammary System|
|Front||Chest||Body Depth||Loin||Pin Width|
|Rump Angle||Bone||Foot||Heel Depth||Rear Leg Side View|
|Rear Leg Rear View||Udder Depth||Texture||Median Suspensory||Fore Udder Attach.|
|Fore Teat Place.||Rear Attach Height||Rear Attach Width||Rear Teat Place.||Locomotion
|Angularity||Teat Length||Stature|| || |
There are eight fertility traits, and these are assumed to
be genetically the same throughout the life of the animal, but with age and
parity effects added for traits that observed more than once per cow.
The traits are the same as those in the Canadian fertility trait evaluation
|Age at first calving||Non return rate||No. of services|
|First service to conception||Gestation length||Calving to first service|
|Calving ease||Stillbirth|| |
Growth and Feed Traits
Weight and height are modelled by the Von Bertalanfy function
which has three parameters, A, B, and K. This function describes weight and
height at different ages throughout life. However, weights are affected by
lactation, pregnancy, heat, cold, and diseases. These are additional effects
that must be added or subtracted onto the expected weights. The effects differ
depending on the parity number. Height is not very variable during the life of the
animal, and once it reaches the mature value (i.e. the A parameter), then further
change should not occur. Dry matter intake (DMI) is very similar across animals from
birth to first calving, but there can still be individual variation.
Body condition score, (BCS), is observed only within lactations. BCS changes during
a lactation are assumed to be the same for all cows, just variation in the initial
BCS score. Eventually BCS could be modelled with the production traits when parameters
have been estimated.
|Weight A||Weight B||Weight K|
|Wt Change Lactation 1||Wt Change Lactation 2||Wt Change Lactation 3|
|Height A||Height B||Height K|
|DMI to 90d||DMI to 24m||DMI Lactation 1|
|DMI Lactation 2||DMI Lactation 3||BCS Changes|
|Milk Fever||Retained Placenta|| |
These are other traits with single values. The total
number of traits is 220.
|Feeding Temperament||Survival to 24m||Heat Stress|
|Survival||Milking Speed|| |