Status as of: May 1, 2007
 
Form GE

 

DESCRIPTION OF NATIONAL GENETIC EVALUATION SYSTEMS

 

Country (or countries)

United States of America

Main trait group1

Udder Health - Somatic Cell Score

 

Breed(s)

Holstein, Jersey, Brown Swiss, Guernsey, Ayrshire, Milking Shorthorn

All breeds and crossbred cows are evaluated together in a multi-breed animal model

Trait definition(s) and unit(s) of measurement2

Somatic Cell Score = log base 2 (SCC / 100,000) + 3; where SCC is somatic cells per milliliter. Lactation SCS is the average of test day SCS across the first 305 days of lactation.

Method of measuring and collecting data

Collected by Dairy Herd Improvement Associations using ICAR approved methods and Quality Certification standards administered by the Council on Dairy Cattle Breeding.

Time period for data inclusion

First calving 1984 and later plus pedigree from birth year 1950 and later.

Age groups (e.g. parities) included

First five parities are included.

Other criteria (data edits) for inclusion of records

Valid sire ID required. Lactations from cows >40 DIM and cows removed from the herd >15 DIM are included. TD by 90 DIM required.

Criteria for extension of records (if applicable)

Records < 305 d are extended to 305 d by best prediction.

 

Sire categories

All sires (AI and natural service) are evaluated together.

Environmental effects3, pre-adjustments

Multiplicative adjustments for age at calving, month of calving, and for differing SD by parity.

Method (model) of genetic evaluation3

ST BLUP Repeatability Animal Model.

Environmental effects3 in the genetic evaluation model

Fixed: management group (flexible herd-year-seasons), parity by age, regression on inbreeding, and regression on general heterosis. Random: permanent environment, and herd by sire interaction. HOL management group definition includes registry status. Published PTA includes expected future inbreeding (EFI) and coefficients of heterosis when mated to purebreds multiplied by the regression coefficients as a post-processing step.

Adjustment for heterogeneous variance in evaluation model

None.

Use of genetic groups and relationships

Unknown parents are grouped by year, breed, and, for Holsteins, separately for U.S. and foreign animals. Unknown sires and dams of cows are grouped separately, but unknown parents of bulls are in a combined group. Separate unknown parent groups are used for red and white or black and white Holsteins. The relationship matrix accounts for effects of inbreeding on Mendelian sampling variance.

Blending of foreign/Interbull information in evaluation

Foreign evaluations of parents are not included.

Genetic parameters in the evaluation

Heritability 12%, permanent environment variance 18%, herd by sire interaction 5%, repeatability 35%

System validation

Means and SD for all variables are calculated and examined overall. Means for new bulls, changes for high bulls, largest changes, and key statistics for recent AI bulls are checked. Genetic trends for each breed are validated by methods 1, 2, and 3.

Expression of genetic evaluations
If standardised (e.g. RBV), give standardisation formula in the appendix

PTA SCS.

All-breed PTAs are adjusted to within-breed bases as follows:

within-breed PTA = (all-breed PTA – breed mean)

A phenotypic mean of 3 is then added to PTA SCS.

Definition of genetic reference base

Next base change

Current base: cows born in 2000 (stepwise, 5 year).
February 2010 (when the base will be cows born in 2005).

Calculation of reliability

Daughter equivalents from parents and from progeny are summed by processing progeny from the youngest to oldest generation and then parents from oldest to youngest. Starting values for mate reliability are from the previous evaluation.

Criteria for official publication of evaluations

At least 10 daughters with usable first lactation record. Interbull evaluations are reported as official in the US if: they include data from an additional country; the US has no evaluation; or Interbull excludes US data and the Interbull evaluation has higher reliability than the US evaluation.

Number of evaluations / publications per year

Three, in February, May, and August of 2007, and in January, April, and August beginning 2008.

Use in total merit index4

Net Merit (all breeds): SCS receives 9% of the total emphasis.

TPI (Holsteins): SCS receives 5% of the total emphasis.

Anticipated changes in the near future

None

Key reference on methodology applied

· Schutz, M.M. 1994. Genetic evaluation of somatic cell scores for United States dairy cattle. J. Dairy Sci. 77:2113.

· Schutz, M.M., P.M. VanRaden, G.R. Wiggans, and H.D. Norman. 1995. Standardization of lactation means of somatic cell scores for calculation of genetic evaluations. J. Dairy Sci. 78:1843.

· VanRaden, P.M., M.E. Tooker, J.B. Cole, G.R. Wiggans, and J.H. Megonigal, Jr. 2007. Genetic evaluations for mixed-breed populations. J. Dairy Sci. 90:2434.

· VanRaden, P.M., and G.R. Wiggans. 1991. Derivation, calculation, and use of national animal model information. J. Dairy Sci. 74:2737.

Key organisation: name, address, phone, fax, e-mail, web site

Animal Improvement Programs Laboratory
USDA, Agricultural Research Service
Building 005, Room 306, BARC-West
10300 Baltimore Avenue
Beltsville, Maryland 20705-2350
U.S.A.
Tel: 301-504-8334 Fax: 301-504-8092
E-mail: wiggans@aipl.arsusda.gov
web site: http://aipl.arsusda.gov

 

1) Either: Production (e.g. milk, fat, protein), Conformation, Health (e.g. mastitis resistance, milk somatic cell, resistance to diseases other than mastitis), Longevity, Calving (e.g. stillbirth, calving ease), Female fertility (e.g. non-return rate, interval between reproductive events, number of AI’s, heat strength), Workability (e.g. milking speed, temperament), Beef production, Efficiency (e.g. body weight, energy balance, body conditioning score), or Other traits.

2) Indicate frequencies per category if the trait is categorical and specify transformation of data if practiced.

3) Use abbreviations for most common effects (see document with list of abbreviations at http://www-interbull.slu.se/service_documentation/General/list_of_abbreviations.rtf) and indicate random (R) or fixed (F).

4) Please give economic weights and indicate how they are expressed (preferably in genetic standard deviation units).

 

 

 

 

 

 Form GE                                                                                                             Appendix SM

 

Parameters for national genetic evaluations for udder health traits as provided to Interbull

 

Country (or countries):

USA

Main trait group:

Udder Health – Somatic Cell Score

Breed(s):

Holstein, Jersey, Brown Swiss, Guernsey, Ayrshire, Milking Shorthorn

 

Trait

h2a

Genetic

variancea

official proof

standardisation formulab

Milk Somatic Cell:

 

.12

BSW (.43)2

GUE (.46)2

HOL (.44)2

JER (.41)2

RDC (.43)2

 

StandEval = PTASCS + 3

 

Breed means for converting from the all-breed base to the within-breed bases will be updated on the AIPL web site. March 2007 estimates were:

BSW PTA = all-breed PTA + .06

GUE PTA = all-breed PTA – .03

HOL PTA = all-breed PTA + 0.01

JER PTA = all-breed PTA – .09

MSH PTA = all-breed PTA + .04

RDC PTA = all-breed PTA + 0.08

Clinical Mastitis:

 

 

 

 

a    If repeated records are treated as separate traits, provide heritability estimates and genetic variances separately for each trait, as well as for all traits pooled, i.e. for the trait submitted to Interbull.

b    Expressed as follows:
StandEval=((eval-a)/b)*c+d where a=mean of the base adjustment, b=standard deviation of the base, c=standard deviation of expression (include sign if scale is reversed), and d=base of expression.