Status as of: 2015-09-22

Form GE

DESCRIPTION OF NATIONAL GENETIC EVALUATION SYSTEMS

Country (or countries)	United States of America	
Main trait group	Health (SCS)	
Breed(s)	AYS (RDC), BSW, GUE, HOL (B&W, R&W, SIM), JER, MSH (RDC); all breeds and crossbred cows evaluated together in a multibreed AM	
Trait definition(s) and unit(s) of measurement	SCS = log2 (SCC/100,000) + 3, where SCC is somatic cells per milliliter; lactation SCS is mean of TD SCS across first 305 days of lactation	
Method of measuring and collecting data	Collected by Dairy Herd Information Affiliates using ICAR-approved methods and quality certification standards administered by the Council on Dairy Cattle Breeding	
Time period for data inclusion	First calvings from 1984 and later; pedigree from birth years 1950 and later	
Age groups (e.g. parities) included	First 5 parities included	
Other criteria (data edits) for inclusion of records	Valid sire identification required; lactations from cows with >40 DIM and cows removed from the herd with >15 DIM included; TD by 90 DIM required	
Criteria for extension of records (if applicable)	Records with <305 days extended to 305 days using ST best prediction	
Sire categories	All sires (AI and NS) evaluated together	
Environmental effects, pre-adjustments 	Multiplicative adjustments for calving age and month as well as differing SD by parity; unequal variances across time, across herds, and across breeds adjusted to HOL base variance calculated from standardized records of first lactation cows that calved in 2007	
Method (model) of genetic evaluation	ST BLUP RP AM	
Environmental effects3 in the genetic evaluation model	Management group (flexible HYS, includes registry status for HOL) (F), parity × age (F), regression on inbreeding (F), regression on general heterosis (F),  PE (R), herd × sire interaction (R); released PTA includes regression coefficient multiplied by expected future inbreeding and coefficient of heterosis when mated to purebred as a post-processing step	
Adjustment for heterogeneous variance in evaluation model	Pre-adjustments for herd-year variance applied	
Use of genetic groups and relationships	Unknown parents grouped by birth year, breed, and, for HOL, separately for U.S. and foreign animals; unknown sires and dams of cows grouped separately, but unknown parents of bulls in a combined group; relationship matrix accounts for effects of inbreeding on Mendelian sampling variance	
Blending of foreign/Interbull information in evaluation	Foreign evaluations of parents not included	
Genetic parameters in the evaluation	See Appendix SM for h2 and genetic variance estimates; PE variance, 0.18; herd × sire interaction, 0.05; RP, 0.35	
System validation	Means and SDs for all variables calculated and examined overall; means for new bulls, changes for high bulls, largest changes, and key statistics for recent AI bulls checked; genetic trends for each breed validated by methods 1, 2, and 3	
Expression of genetic evaluations	PTA SCS; all-breed PTAs adjusted to within-breed bases as within-breed PTA = (all-breed PTA – breed mean) + phenotypic mean of 3	
Definition of genetic reference base
Next base change	Cows born in 2010 (stepwise, 5 years)

December 2019 (when base will be cows born in 2015)	
Calculation of reliability	Daughter equivalents from parents, progeny, and own records summed in an iterative process starting with REL from previous evaluation	
Criteria for official publication of evaluations	At least 10 daughters with a usable first-lactation record; Interbull evaluations reported as official in the U.S. if they include data from an additional country, the U.S. has no evaluation, or Interbull excludes U.S. data and Interbull evaluation has higher REL	
Number of evaluations/ publications per year	3 (April, August, December)	
Use in total merit index4	SCS receives 10% of total emphasis in lifetime net merit dollars (NM$, all breeds) and 5% of total emphasis in Total-Performance Index (TPI, HOL)	
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– 2129. 
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. 78:1843–1854.
VanRaden, P.M., and G.R. Wiggans. 1991. Derivation, calculation, and use of national animal model information. J. Dairy Sci. 74:2737–2746.
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. 90:2434–2441.
Cole, J.B., D.J. Null, and P.M. VanRaden. 2009. Best prediction of yields for long lactations. J. Dairy Sci. 92:1796–1810.
VanRaden, P.M., M.E. Tooker, J.R. Wright, C. Sun, and J.L. Hutchison. 2014. Comparison of single-trait to multi-trait national evaluations for yield, health, and fertility traits. J. Dairy Sci. (in press).	
Key organisation: name, address, phone, fax, e-mail, web site	Evaluation calculation and distribution:
 Council on Dairy Cattle Breeding
 One Town Center
 4201 Northview Drive,
 Suite 302
 Bowie, MD 20716
 Ph: 240 334 7744
 e-mail: joao.durr@cdcb.us
 web site: https://www.cdcb.us

Evaluation methodology:
Animal Improvement Program
Animal Genomics and Improvement Laboratory
Agricultural Research Service, U.S. Dept. of Agriculture 
10300 Baltimore Ave.
Bldg. 005, Room 306, BARC-West 
Beltsville, Maryland 20705-2350, USA
voice: 301-504-8334; fax: 301-504-8092 
e-mail: aipl.inquiry@ars.usda.gov
web site: http://aipl.arsusda.gov	

Form GE	Appendix SM

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

Country (or countries):	United States of America	
Main trait group:	Health (SCS)	
Breed(s):	AYS (RDC), BSW, GUE, HOL (B&W, R&W, SIM), JER, MSH (RDC)	

Trait	h2	Genetic
variance	Official proof
standardisation formulaa	
Milk Somatic Cell (SCS)	0.12	BSW SD = 0.39
GUE SD = 0.41
HOL SD = 0.40
JER SD = 0.38
RDC SD = 0.41	StandEval = PTA SCS + 3	
Clinical Mastitis	—	—	—	
a Expressed as follows:
StandEval = ((Eval − a)/b) × c + d, where a = mean of base adjustment, b = SD of base, c = SD of expression (include sign if scale is reversed), and d = base of expression.