2006 8th World Congress on Genetics Applied to Livestock Production (1) Trait Selection When Culling U.S. Holsteins H.D. Norman, J.L. Hutchison, J.R. Wright, and M.T. Kuhn Animal Improvement Programs Laboratory Agricultural Research Service, USDA, Beltsville, MD, USA

2006 8th World Congress on Genetics Applied to Livestock Production (2) Changes in trait selection More traits available for selection Assignment of economic weights in genetic indexes − Economic information on benefits and costs associated with traits − Estimation of phenotypic and genetic relationships among traits

2006 8th World Congress on Genetics Applied to Livestock Production (3) Objectives Determine emphasis currently placed on different yield and fitness traits when culling during the first 3 parities Document trends in trait emphasis when culling over the last 20 years

2006 8th World Congress on Genetics Applied to Livestock Production (4) Data Yield (milk, fat, true protein), somatic cell score, days open, dystocia score, and conformation records U.S. Holsteins that 1st calved between January 1982 and October 2000 by 36 months of age Dairy Herd Improvement herds on test for 1600 days after cow’s 1st calving date Identified sires Calving intervals of 270 to 650 days

2006 8th World Congress on Genetics Applied to Livestock Production (5) Models Yield and somatic cell score Y = H + S + e Days open and dystocia score Y = A + C + H + S + e Final score and linear type traits Y = A + D + H + S + e Y = traitA = age group H = herd-calving seasonC = calendar month S = survival groupD = lactation stage e = residual

2006 8th World Congress on Genetics Applied to Livestock Production (6) Defining survival groups 1st-parity analysis − Cows with 1st parity only − Cows with 1st and 2nd parities only − Cows with 1st, 2nd, and 3rd parities only − Cows with 4 parities or more Alternate 1st-parity analysis − Cows with 1st parity only − Cows with 2 parities or more

2006 8th World Congress on Genetics Applied to Livestock Production (7) Defining survival groups 2nd-parity analysis − Cows with 1st and 2nd parities only − Cows with 3 parities or more 3rd-parity analysis − Cows with 1st, 2nd, and 3rd parities only − Cows with 4 parities or more

2006 8th World Congress on Genetics Applied to Livestock Production (8) Differences in 1st-parity milk yield (kg) by survival group Year of 1st calving Parities survived 22 23 4 Differences in 1st-parity milk yield (kg) by survival group

2006 8th World Congress on Genetics Applied to Livestock Production (9) Year of 1st calving Parities survived 22 23 44 1987−0.37−0.26−0.34− −0.41−0.32−0.39− −0.51−0.39−0.48− −0.62−0.49−0.59− −0.58−0.46−0.56− −0.34−0.23−0.32− −0.34−0.24−0.33−0.44 Differences in 1st-parity somatic cell score by survival group

2006 8th World Congress on Genetics Applied to Livestock Production (10) Year of 1st calving Parities survived 22 23 44 1982−20−19−17− −18−14−15− −20−16−18− −24−18−22− −29−21−28− −37−29−35− −43−34−41−52 Differences in 1st-parity days open by survival group

2006 8th World Congress on Genetics Applied to Livestock Production (11) Year of 1st calving Parities survived 22 23 44 1987−0.13−0.11 − −0.10 −0.09− −0.11−0.10 − −0.13−0.10−0.12− −0.12−0.09−0.12− −0.10−0.07−0.10− −0.12−0.09−0.11−0.16 Differences in 1st-parity dystocia score by survival group

2006 8th World Congress on Genetics Applied to Livestock Production (12) Year of 1st calving Parities survived 22 23 4 Differences in 1st-parity final score by survival group

2006 8th World Congress on Genetics Applied to Livestock Production (13) Results for other parities 2nd-parity differences within 15% of 1st-parity differences except for days open and dystocia score − Less difference in survivor advantage for days open over time compared with 1st parity − Differences for dystocia score about half those for 1st parity 3rd-parity differences similar to those for 1st and 2nd parities

2006 8th World Congress on Genetics Applied to Livestock Production (14) Trait emphases* (%) during 1st-lactation culling Year of 1st calving Fat yield True protein yield Somatic cell score Days open Dystocia score Final score …−23−8… …−20− −23−22− −26−24− −26−30− −31−61− −33−74−1533 *Relative to 100% for milk yield (on standardized trait basis)

2006 8th World Congress on Genetics Applied to Livestock Production (15) Conformation trait emphases during 1st- lactation culling Relative to 100% for final score Body traits received more emphasis during 1980s (22 to 32%) than during recent years (1 to 20%) Udder trait emphasis has remained consistent (40 to 64%) Emphasis on udder depth had greatest increase (from 13 to 41%) Emphasis on feet and legs increased slightly Emphasis on dairy form decreased (from 50 to 23%)

2006 8th World Congress on Genetics Applied to Livestock Production (16) Trait emphases* (%) during 2nd-lactation culling Year of 1st calving Fat yield True protein yield Somatic cell score Days open Dystocia score …−61− …−58− −59−61− −64−65− −66−70− −70−112− −75−115−19 *Relative to 100% for milk yield (on standardized trait basis)

2006 8th World Congress on Genetics Applied to Livestock Production (17) Trait emphases* (%) during 3rd-lactation culling Year of 1st calving Fat yield True protein yield Somatic cell score Days open Dystocia score …−70− …−66− −62 − −66−57− −63−58− −73−93− −79−100−17 *Relative to 100% for milk yield (on standardized trait basis)

2006 8th World Congress on Genetics Applied to Livestock Production (18) Conclusions Relative emphasis among traits when culling has remained reasonably consistent since 1982 regardless of parity Protein yield received nearly the same emphasis as milk yield Emphasis on fat yield was slightly lower than on milk yield (72 to 91%)

2006 8th World Congress on Genetics Applied to Livestock Production (19) Conclusions Increased emphasis being placed on lower somatic cell score in later parities Culling emphasis on days open has increased, and clearly more given for later parities Culling emphasis on dystocia score was low relative to milk yield (7 to 19%) Emphasis on final score when culling was low relative to milk yield (22 to 38%)

2006 8th World Congress on Genetics Applied to Livestock Production (20) Application Knowledge from this study could be useful for: Selection by artificial-insemination organizations of bulls to progeny test or to retain in active service consistent with trait priority of dairy producers Development of culling-decision software with index-style culling guide Optimal genetic gains at minimal cost

2006 8th World Congress on Genetics Applied to Livestock Production (21) Acknowlegments Tom Lawlor, Holstein Association USA, for providing Holstein conformation data.