Genetic Evaluations in Canada
The calculation and publication of all dairy cattle genetic evaluations in
Canada is the responsibility of
Canadian Dairy Network (CDN).
This non-profit national organization is governed by an 8-member board of
directors, the majority being dairy producers. Member organizations include
all breed associations, milk recording agencies and artificial insemination
centres across Canada as well as Dairy Farmers of Canada.
Genetic Evaluations are provided by CDN for seven dairy breeds (Holstein,
Ayrshire, Jersey, Brown Swiss, Canadienne, Guernsey, and Milking Shorthorn).
All animals receive a genetic evaluation for a complete series of traits in
production, conformation, and Functionality.
All genetic evaluation calculations in Canada use a methodology called the
"animal Model”, which refers to the goal of estimating each animal’s genetic
merit. The genetic evaluation of each animal is based on contributions
from four possible sources: parents, performance, progeny and DNA
(genotype).
When an animal has no performance, no progeny or no DNA, we therefore rely
on the average of his parent to evaluate its genetic potential and calculate
its genetic merit or Parent Average. An animal’s Parent Average
continually evolves as the sire, dam and/or older ancestors in the pedigree
add performance data on themselves as well as on existing and new progeny.
The major contributing source of information for estimating an animal’s
genetic merit is the performance of their progeny. It is then an
"ultimate test” to know how good an animal is in transmitting its genetic
potential.
For cows, their performance (classification and production records) also
counts but at a lower extent. For animals that are genomically tested,
the DNA contribution is ADDED to the information available; it does not
replace any source of information. When information is added, reliability of
the genetic evaluation usually increases.
Reliability of Genetic Evaluations
The degree of certainty in calculating an Estimated Breeding Value (EBV) is
measured by "reliability”. It is defined as squared correlation between the
true and estimated breeding values of a trait. The level of reliability is a
function of heritability as well as the amount of the information available
on the trait.
Information from each animal’s DNA profile as an additional source of data
has significantly changed the landscape of genetic improvement programs and
strategies contributing to genetic evaluations. Effective August 2009,
official genetic evaluations in Canada for the Holstein breed include
genomic information in combination with traditional pedigree and progeny
performance data. The largest gains in accuracy of genetic evaluations are
realized for young bulls and heifers, which traditionally would only have a
Parent Average. The table below shows the average gain in LPI Reliability
(April 2013) for various sub-groups of animals in the Canadian Holstein
population.
Genetic Evaluations
| Sub-Group for Holstein Breed |
Average LPI Relability (%) |
|
Traditional |
Genomics |
Gain |
| 50K Young Bulls and Heifers (Born 2010-2012) |
38 |
70 |
32 |
| LD (3K or 6K) Heifers (Born 2011-2013 |
34 |
67 |
33 |
| LD Young Cows in 1stor 2nd Lactation |
50 |
69 |
19 |
| LD Foreign Cows with MACE in Canada |
42 |
69 |
27 |
| 1st Crop Proven Sires in Canada |
85 |
90 |
5 |
| Foreign Sires with MACE in Canada |
69 |
83 |
14 |
Lifetime Profit Index (LPI)
Canada has been selecting for a balanced breeding and the national index of
selection reflects the relative profitability that can be expected during
the lifetime of future daughters. Each breed has a different emphasis for
each trait but it always include three main sections known as Production,
Durability and Health & Fertility.
Interpretation of Genetic Evaluations
The main objective of genetic evaluations is to select the superior males
and females of each breed to be parents of the next generation. They are
identified and compared to a base reference group, which is considered the
breed average. The next table will help you to interpret the different
traits evaluated, their scale and the units they are expressed.
| Trait |
Interpretation |
Lifetime Profit
Index (LPI)
|
Expected relative lifetime profit of future progeny based on their
genetic potential for production, durability and health &
fertility.
Units and Scale- Holsteins:
Units: Points relative to breed average: ( 1800)
Scale: 0 to 3500 pts
|
Milk, Fat, and
Protein
Yields
|
Expressed as Estimated Breeding Values (EBVs). Expected yield of milk,
fat and protein during a 305-day lactation in a herd of average
management
Units and Scale- Holsteins:
Units: Kilograms
Scale: Milk: ± 2550 kg
Fat: ± 95 kg
Protein: ± 80 kg
More Information:
Calculated under the Canadian Test Day Model. Each cow 24-hr yields on
each monthly test are used.
|
Fat and Protein
Percentage
Deviations
|
Expected deviations from breed average for the % of fat and protein
during a 305-day lactation in a herd of average management.
Units and Scale- Holsteins:
Units: %
Scale: Holstein: Fat: ±0.80
Protein: ±0.50
|
Conformation
Traits
|
Expected relative superiority of first lactation daughters for each
type trait.
Units and Scale- Holsteins:
Average: 0
Range: -15 to +15
More Information:
Official classifications are used. All classifications and
reclassifications within 1st lactation are included to calculate those
indexes.
|
Somatic
Cell Score
|
Expected SCS of daughters during the first 3 lactations. Similar to
the other functional traits, higher RBV translates to lower Somatic
Cell Count and more resistance to mastitis.
Units and Scale- Holsteins:
Average: 100
Range: 85-115
More Information:
As of December 2018, proofs for Somatic Cell Score (SCS) are expressed
as Relative Breeding Values (RBV).
|
Lactation
Persistency
|
Expressed as a % of daughters’ expected daily milk yield at 280 days
in milk compared to day 60.
Units and Scale- Holsteins:
Average: 100
Range: 85-115
More Information:
Bulls with an above average proof have daughters with a flatter
lactation curve compared to bulls with daughters that have lower
average in daily milk yields after peak lactation.
|
| Herd Life |
Number of additional lactations that daughters are expected to last
due to reduced involuntary culling compared to the average bull,
independent of daughter production levels.
More Information:
Include a combination of true survival information (known later in
life) and a prediction of expected longevity (indirect herd life).
|
| Milking Speed |
% of first lactation daughters evaluated as "Average” or "Fast”.
|
Milking
Temperament
|
Expected % of first lactation daughters evaluated as "average”, "Calm”
or "Very Calm”.
More Information:
Each cow is evaluated during first 6 months of lactation by herd owner
as being "Very Slow”, "Slow”, "Average”, "Fast” or "Very Fast”.
|
| Calving Ability |
Helps to identify sires that increase the likelihood that their
progeny are born easily and alive.
More Information:
Includes : Calving Ease at 1st and later calvings, Calf survival at
1st and later calvings – for direct progeny of the sires.
|
Daughter
Calving Ability
|
Aims to reduce calving problems and increase the rate of calf
survival.
More Information:
Includes : Calving Ease at 1st and later calvings, Calf survival at
1st and later calvings – when daughters of these bulls calve.
|
Daughter
Fertility
|
Measurement of the expected fertility of a bull’s daughters evaluated
across all lactations.
More Information:
Include 4 traits: Age at 1st insemination of virgin heifers, the
56-day non-return rate for virgin heifers, interval between calving
and 1st insemination for cows and the 56-day non-return rate for cows.
|
Body
Condition
Score
|
Allows for selection to raise the average BCS at first calving and
when they are in peak production.
Units and Scale- Holsteins:
Average: 100
Range: 85-115
More Information:
This selection goal is expected to improve fertility, reduce the
incidence of disease, and lead to a longer productive life.
|
